WO2022123295A1

WO2022123295A1 - Method and system for adjusting a slot die used for making an extruded article

Info

Publication number: WO2022123295A1
Application number: PCT/IB2020/061687
Authority: WO
Inventors: Robert A. Yapel; Pentti K. Loukusa; Jennifer L. Trice; William J. Kopecky; Paul C. THOMAS; Gregory D. Kostuch; Derek J. Dehn
Original assignee: 3M Innovative Properties Company
Priority date: 2020-12-09
Filing date: 2020-12-09
Publication date: 2022-06-16
Also published as: JP2023553100A; EP4259414A1; MX2023006851A

Abstract

Provided are methods of operating a slot die having an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, and at least one of a group consisting of: a choker bar and a flexible die lip. The choker bar or the flexible die lip shape can be manipulated by applying, with a force application mechanism, forces that are generally parallel to the width of the slot die. Further provided are methods of operating and purging a slot die, where at least a portion of the applicator slot is blocked with one or more deckles to reduce an effective width of the applicator slot.

Description

METHOD AND SYSTEM FOR ADJUSTING A SLOT DIE USED FOR MAKING AN EXTRUDED ARTICLE

Field of the Invention

The invention relates to slot dies, along with assemblies, systems, and methods related thereof.

Background

Generally, slot dies include die lips that form an applicator slot. The width of the applicator slot can extend along the width of a moving web or the width of a roller that receives an extrudate, such as a film. As used herein, with respect to slot dies and components of slot dies, “width” refers to the cross-web (or cross-roller) dimension of a slot die and its components. In this regard, an applicator slot of a slot die extends along the width of the slot die.

Slot dies are commonly used to form extrusions, coatings, and other extruded articles. As an example, slot dies can be used in slot die coatings to apply a liquid material to a moving flexible substrate or “web.” There are many variations in techniques for slot die coatings. As one example, coating materials can be at room temperature or a controlled temperature. When a coating material temperature is elevated to ensure that the coating material is melted or liquefied for processing, this is often referred to as “hot melt" coating. In other examples, a coating material can include solvent diluents. Solvents can be water, organic solvents, or any suitable fluid that dissolves or disperses components of a coating. Solvents are typically removed in subsequent processing such as by drying. A coating can include single or multiple layers, and some slot dies may be used to apply multiple layers simultaneously. A coating can be a continuous coating across the width of the die or instead be comprised of strips, with each strip extending across only a portion of the width of the die and being separated from adjacent strips.

Slot dies are also used to form extrusions, including thin-film extrusions or other extrusions. In some examples, extrusions can be extrusion coatings and applied to a web substrate, a process which may be referred to as extrusion coating. In other examples, the extruded material forms a film or web directly. An extruded film might be subsequently processed by length orienting or tentering operations. As with coating, the extrudate might comprise a single layer or multiple layers.

The thickness of an extrudate, such as a film or coating, is dependent upon, among other factors, the flow rate of the extrudate through the slot die. In one example, a slot die can include an adjustable choker bar within the flow path that can be used to locally adjust the flow rate of the extrudate through the slot die to provide a desired choker bar height profile. A slot die can also include a flexible die lip that can be used to adjust the local height of the applicator slot (or “slot height”) to control the flow rate of the extrudate from the applicator slot to provide a desired extrudate thickness profile.

A slot die may include a plurality of actuators spaced along the width of the applicator slot in order to manipulate the thickness profile. For example, each actuator can be configured to provide a local positional adjustment of a choker bar or flexible die lip.

After starting an extrusion process using a slot die, the cross-web profile of an extrudate can be measured. Each actuator may then need to be individually adjusted to provide a desired thickness profile, such as a uniform thickness, for the extrudate across the width of the applicator slot.

Summary

This disclosure includes techniques for manipulating die lip or choker bar shape by applying forces that are generally parallel to the width of the die and where the associated force application mechanism is largely contained within the flexible die lip or restrictor/choker bar. Such forces parallel to the width of the die can be provided by an omni-directional expansion or contraction such as caused by localized heating or cooling of the die lip or choker bar. For example, the flatness of a die lip can be manipulated by expanding the metal near the die lip, which causes the shape of the die lip to change between the discrete control points. This technique is analogous to the die having muscles that can flex between the positioning devices.

These techniques can be used in combination with the conventional means of adjustors to advantageously adjust the die slot between the conventional die slot control element locations themselves, thus improving the spatial resolution of extruded uniformity control. In a first aspect, a method for operating a slot die is disclosed. The slot die includes: an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, and at least one of a group consisting of a choker bar and a flexible die lip. The method comprises manipulating the choker bar or flexible die lip shape by applying, with a force application mechanism, forces that are generally parallel to the width of the die.

In a second aspect, a method for operating a slot die is provided, wherein the slot die includes: an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, at least one of a group consisting of: a choker bar and a flexible die lip, and a plurality of actuators spaced along the width of the slot die, wherein each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot, wherein the method comprises: determining a setting for a force application mechanism to locally expand or contract the choker bar or the flexible die lip of the slot die along a direction generally parallel to the width of the slot die, thereby adjusting a cross-web slot height profile where the force application mechanism engages with the choker bar or flexible die lip; and engaging the force application mechanism with the choker bar or the flexible die lip based on the determined setting.

In a third aspect, a method for operating a slot die is provided, wherein the slot die includes: an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, at least one of a group consisting of: a choker bar and a flexible die lip, and a plurality of actuators spaced along the width of the slot die, wherein each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot, wherein the method comprises: blocking a portion of the applicator slot with a deckle to reduce an effective width of the applicator slot; predicting, with a controller, a set of discrete settings from a plurality of discrete settings based on a pre-selected cross-web slot height profile for an unblocked zone of the applicator slot, the prediction based on a known correlation between the set of discrete settings and a cross-web slot height profile of the extrudate; and setting a position of each actuator according to the predicted set of discrete settings for the adjustment of the slot die, wherein the actuators are fixed over blocked zones of the applicator slot and dynamic over unblocked zones of the applicator slot during operation of the slot die.

In a fourth aspect, a method for making an extruded article is provided, the method comprising: operating a slot die according to an aforementioned method; and extruding through the applicator slot of the slot die an extrudate to obtain the extruded article.

In a fifth aspect, a method for purging a slot die is provided, wherein the slot die includes: an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, a choker bar or a flexible die lip extending along the width of the slot die; a plurality of actuators spaced along the choker bar or a flexible die lip, each operable to adjust a height of the applicator slot at its respective location to provide a local adjustment of fluid flow through the applicator slot; and one or more deckles blocking a portion of the applicator slot to reduce an effective width of the applicator slot; wherein the method comprises manipulating the choker bar or the flexible die lip shape by applying forces with the plurality of actuators to obtain a target cross-web slot height profile, the actuators being fixed over a blocked zone of the applicator slot and being dynamic over an unblocked zone of the applicator slot; and selectively enlarging the cross-web slot height profile along the unblocked zone of the applicator slot with the plurality of actuators, while tapering down the degree of enlargement along a transition zone between the unblocked zone and the blocked zone.

In a sixth aspect, a system is provided comprising: a slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, and at least one of a group consisting of: a choker bar and a flexible die lip, and a force application mechanism operatively coupled to the choker bar or flexible die lip; and a controller configured to set a position of each actuator according to one of a plurality of discrete settings to operate the slot die, wherein the controller is configured to manipulate the choker bar or the flexible die lip shape by applying, with the force application mechanism, forces that are generally parallel to the width of the slot die.

In a seventh aspect, a system is provided, comprising a slot die and a controller The slot die includes an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, a choker bar or a flexible die lip extending along the width of the slot die; a plurality of actuators spaced along the choker bar or a flexible die lip, each operable to adjust a height of the applicator slot at its respective location to provide a local adjustment of fluid flow through the applicator slot; and one or more deckles blocking a portion of the applicator slot to reduce an effective width of the applicator slot. The controller is configured to manipulate the choker bar or the flexible die lip shape by applying forces with the plurality of actuators to obtain a target cross-web slot height profile, wherein the actuators are fixed over a blocked zone of the applicator slot and dynamic over an unblocked zone of the applicator slot; and selectively enlarge the cross-web slot height profile along an unblocked zone of the applicator slot with the plurality of actuators, while tapering down the degree of enlargement along a transition zone between the unblocked zone and the blocked zone.

The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

of the Drawings

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

FIGS. 1 A-1B illustrate a slot die including a choker bar with a plurality of actuators, each actuator operable to adjust a height of the fluid flow path at its location.

FIG. 2 illustrates a slot die including an adjustable rotary rod with a plurality of actuators connected to the rotary rod, each actuator operable to adjust the local position of the rotary rod at its location and thereby adjust the local height of the applicator slot.

FIG. 3 illustrates a slot die including a flexible die lip with a plurality of actuators connected to the flexible die lip, each actuator operable to adjust the local position of the flexible die lip at its location and thereby adjust the local height of the applicator slot.

FIG. 4 illustrates an actuator assembly including a position sensor and a controller for selecting the position of the actuator assembly based on the output of the position sensor. FIG. 5 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a preselected cross-web profile of the extrudate.

FIG. 6 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a preselected die cavity pressure during operation of the die.

FIG. 7 is a flowchart illustrating techniques for purging a slot die by increase the height of the fluid flow path adjacent each of the actuators while continuing to operate the die.

FIG. 8 is a flowchart illustrating techniques for purging a slot die by substantially closing fluid flow path adjacent each of the actuators while continuing to operate the die.

FIG. 9 illustrates a strip coating including a pattern created by repeatedly adjusting actuator position settings in a slot die.

FIG. 10 illustrates an extrudate including a pattern created by repeatedly adjusting actuator position settings in a slot die.

FIGS. 11 A-l ID illustrate an example of a user interface for a slot die controller.

FIG. 12 illustrates techniques retrofitting a slot die with a set of actuator assemblies.

FIGS. 13-22 relate to techniques for manipulating die lip shape by applying forces that are generally parallel to the width of the die and where the force application mechanism is largely contained within the flexible die lip or restrictor/choker bar in accordance with the techniques disclosed herein.

Detailed Description

As used herein, the terms “preferred” and “preferably” refer to embodiments described herein that can afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention. As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements.

It is noted that the term “comprises”, and variations thereof do not have a limiting meaning where these terms appear in the accompanying description. Moreover, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably herein. Relative terms such as left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and, if so, are from the perspective observed in the particular drawing. These terms are used only to simplify the description, however, and not to limit the scope of the invention in any way.

Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described relating to the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Where applicable, trade designations are set out in all uppercase letters.

FIGS. 1A and IB illustrate a slot die 10. Slot die 10 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 10. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between rotary rod 12, which is mounted to upper die block 2, and die lip 13 of lower die block 3. Because slot die 10 includes rotary rod 12 at its applicator slot, slot die 10 may be referred to as a rotary rod die.

Slot die 10 includes a choker bar 11 that extends across the width of the fluid flow path within slot die 10. As one example, the width of the fluid flow path within slot die 10 at choker bar 11 may be approximately the same as the width of applicator slot 6 such that choker bar 11 extends along the width of applicator slot 6. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 10. In some example, mounting bracket 9 may be segmented, e.g., mounting bracket 9 may include separate structures for each actuator assembly 200. Each actuator assembly 200 is operable to adjust a height of the fluid flow path at its respective location along the width of slot die

10 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of choker bar 11 within the fluid flow path of the extrudate within slot die 10.

During operation of slot die 10, an extrudate enters slot die 10 at fluid flow path entry 5 and continues through the fluid flow path of slot die 10, including die cavity 4 until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool. One or more additional processes may be performed to the extrudate downstream of roller 7. While not germane to this disclosure, such processes include, but are not limited to, stretching, coating, texturing, printing, cutting, rolling, and laminating. In some processes, production release liners can be removed and release liners added, or one or more additional layers (such as a laminated transfer tape) can be added. Curing steps could also occur, such as exposure to e-beam, an oven, or an ultraviolet (UV) chamber.

As shown in FIG. IB, slot die 10 includes a set of actuator assemblies 200 mounted on a common mounting bracket 9. Five actuator assemblies 200 are shown, but different numbers of actuator assemblies are also possible. Each actuator assembly 200 is attached to, or otherwise engaged with, choker bar 11 and actuator assemblies 200 are spaced along a width of choker bar 11. Each of the actuators is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of choker bar 11 within the fluid flow path within slot die 10.

As discussed in further detail with respect to FIG. 4, each of actuator assemblies 200 can include a motor that drives a linear actuator. Each of actuator assemblies 200 can also include a precision sensor, such as a linear variable differential transformer (LVDT) or a linear encoder, that detects position movements of the output shaft of the linear actuator. The output shafts of linear actuator assemblies 200 are spaced along the width of choker bar

11 such that each linear actuator assembly 200 is operable to adjust the local position of the choker bar. As discussed in further detail below, the positions of each linear actuator are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 10 by adjusting the overall cross-sectional area of the fluid flow path adjacent to the choker bar 11 within slot die 10. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features. As referred to herein, references to the position of an actuator or actuator assembly are intended to more specifically refer to the relative positioning of the actuator output shaft.

FIG. 2 illustrates slot die 20. Slot die 20 includes adjustable rotary rod 22 with a plurality of actuator assemblies 200 connected to rotary rod 22. Each actuator assembly 200 is operable to adjust the local position of rotary rod 22 at its location and thereby adjust the local height of applicator slot 6. Some aspects of slot die 20 are similar to those of slot die 10 and are discussed in limited detail with respect to slot die 20. Components of slot die 20 that have the same reference numeral as components in slot die 10 are substantially similar to the like-numbered component of slot die 10.

Slot die 20 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 20. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between adjustable rotary rod 22, which is mounted to upper die block 2 and die lip 13 of lower die block 3. Because slot die 20 includes an adjustable rotary rod 22 at its applicator slot, slot die 20 may be referred to as a rotary rod die.

Slot die 20 differs from slot die 10 in that the height of applicator slot 6 is controlled by actuator assemblies 200, which connect to rotary rod 22. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 20. Each actuator assembly 200 is operable to adjust a height of the fluid flow path at its respective location along the width of slot die 20 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of rotary rod 22. While only one actuator assembly 200 is shown in FIG. 2, slot die 20 includes a set of actuator assemblies 200 spaced along the width of rotary rod 22 and slot die 20 and, similar to the arrangement of actuator assemblies 200 as shown in FIG. IB.

During operation of slot die 20, an extrudate enters slot die 20 at fluid flow path entry 5 and continues through the fluid flow path of slot die 20, including die cavity 4, until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool. One or more additional processes may be performed to the extrudate downstream of roller 7, as described above with respect to FIGS. 1 A and IB.

Each of actuator assemblies 200 is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of rotary rod 22. As discussed in further detail below, the positions of each actuator assembly 200 are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 20 by adjusting the overall cross-sectional area of applicator slot 6. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features.

While slot die 20 does not include a choker bar, in other examples, a slot die with an adjustable rotary rod may also include an adjustable choker bar, like choker bar 11 of slot die 10. The position of such a choker bar may be locally controlled by a set of actuators, just as with choker bar 11 of slot die 10.

FIG. 3 illustrates slot die 30. Slot die 30 includes flexible die lip 32 with a plurality of actuator assemblies 200 connected to flexible die lip 32. Each actuator assembly 200 is operable to adjust the local position of flexible die lip 32 at its location and thereby adjust the local height of applicator slot 6. Some aspects of slot die 30 are similar to those of slot die 10 and slot die 20 and are discussed in limited detail with respect to slot die 30. Components of slot die 30 that have the same reference numeral as components in slot die 10 and slot die 20 are substantially similar to the like-numbered components of slot die 10 and slot die 20.

Slot die 30 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 30. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between die lip 34, which is part of upper die block 2, and flexible die lip 32 of lower die block 3.

Slot die 30 differs from slot die 10 in that the height of applicator slot 6 is controlled by actuator assemblies 200, which connect to flexible die lip 32. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 30. Each actuator assembly 200 is operable to adjust a height of the fluid flow path at its respective location along the width of slot die 30 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of flexible die lip 32. While only one actuator 220 is shown in FIG. 3, slot die 30 includes a set of actuator assemblies 200 spaced along the width of flexible die lip 32and slot die 30 and, similar to the arrangement of actuator assemblies 200 as shown in FIG. IB.

During operation of slot die 30, an extrudate enters slot die 30 under pressure at fluid flow path entry 5 and continues through the fluid flow path of slot die 30, including die cavity 4, until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool.

In other examples, slot die 30 may be used with a different configuration of rollers. For example, the extrudate may form a curtain that drops onto a downstream roller, in this case referred to as a casting wheel, that can be temperature controlled. In other examples, an extrudate curtain may drop vertically or traverse horizontally (or any angle) into a nip of two rollers for subsequent processing. This is often used in both film extrusion and extrusion coating operations.

One or more additional processes can be performed to the extrudate downstream of roller 7, as previously described with respect to FIGS. I A and IB.

Each of actuator assemblies 200 is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of flexible die lip 32. As discussed in further detail below, the positions of each actuator assembly 200 are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 30 by adjusting the overall cross-sectional area of applicator slot 6. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features.

While slot die 30 does not include a choker bar, in other examples, a slot die with a flexible die lip may also include an adjustable choker bar, like choker bar 11 of slot die 10. The position of such a choker bar may be locally controlled by a set of actuators, just as with choker bar 11 of slot die 10.

FIG. 4 illustrates an assembly including actuator assembly 200, zero-backlash coupler 240 and controller 300. As shown in FIGS. 1A-3, actuator assembly 200 may be used in a slot die to provide a local adjustment of a fluid flow path of the slot die, e.g., by adjusting the height of an applicator slot as with slot dies 20, 30 or by adjusting the height of a fluid flow path within the slot die as with slot die 10.

Actuator assembly 200 includes motor 210, linear actuator 220, which is coupled to motor 210, and position sensor 230. As one example, motor 210 may be a stepper motor. The output shaft (not shown) of motor 210 is mechanically coupled to linear actuator 220. Sensor 230 senses the position of linear actuator 220. For example, sensor 230 may be a LVDT sensor or a linear encoder. Sensor 230 is secured to output shaft 222 of linear actuator 220 with clamp 232 and precisely measures the relative position of output shaft 222 of linear actuator 220. In other examples, the sensor 230 might measure the output coupler 240, die actuator linkage 252, flexible die lip 32, rotary rod 22, or choker bar 11. As one example, actuator assemblies that are suitable for use as actuator assemblies 200 are available from Honeywell International Incorporated of Morristown, New Jersey.

Controller 300 receives position inputs from both motor 210 and sensor 230. For example, motor 210 may be a stepper motor and may provide an indication of the number of “steps” the stepper motor has taken from a known reference position of the stepper motor. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. Controller 300 provides instructions to motor 210 to drive output shaft 222 of actuator 220 to a preselected position. For example, controller 300 may monitor the position output shaft 222 of actuator 220 with sensor 230 while operating motor 210 in order to position output shaft 222 of actuator 220 according to a preselected position. In some examples, controller 300 may control a set of actuator assemblies 200, either simultaneously or sequentially. For example, controller 300 may control each of the actuator assemblies 200 in slot die 10, as shown in FIG. IB.

In slot dies 10, 20, 30, output shaft 222 of actuator 220 can be advantageously connected to die actuator linkage 252 by zero-backlash coupler 240. Zero backlash coupler 240, in this example, includes two halves that screw together: bottom half 242 and top half 244. Bottom half 242 is directly attached to die actuator linkage 252 with a screw. In addition, zero backlash coupler 240 includes a stacked protrusion assembly that bolts onto the end of output shaft 222 of actuator 220. The stacked protrusion assembly includes two metallic discs 246 surrounding an insulative disc 248. As one example, insulative disc 248 may comprise a ceramic material. Bottom half 242 and top half 244 combine to encircle the stacked protrusion assembly, including metallic discs 246 and insulative disc 248, bolted onto the end of output shaft 222 of actuator 220. Once top half 244 is securely screwed to bottom half 242, output shaft 222 of actuator 220 is effectively connected to zero-backlash coupler 240 and die actuator linkage 252.

Zero-backlash coupler 240 functions to thermally isolate actuator assembly 200 from the slot die. In particular, insulative disc 248 significantly limits the metal-to-metal contact path between output shaft 222 of actuator 220 and die actuator linkage 252. This helps protect actuator assembly 200 from the damaging heat of a slot die. For example, slot dies commonly operate at temperatures in excess of 300°F (149°C), whereas the components of actuator assembly 200, including motor 210 and sensor 230 may experience limited functionality or even permanent damage when subjected to temperatures to in excess of 130°F (54°C). For this reason, zero-backlash coupler 240 may function to keep the temperature of actuator assembly 200 at 130°F (54°C) or less. In some examples, metallic discs 246 may also be formed from nonmetallic materials such that there is no metal-to- metal contact between output shaft 222 of actuator 220 and die actuator linkage 252. Such examples further thermally isolate actuator assembly 200 from the slot die housing. In a further example, the surface area of the coupler 240 can be chosen to dissipate heat to keep the temperature of the actuator assembly 200 at 130°F (54°C) or less. This might be used independently or in combination with the insulative disc 248. In further examples, active thermal control can be used cool to zero-backlash coupler 240, output shaft 222 or actuator assembly 200. Suitable examples of active thermal control include convective air flow, circulating liquid and thermo-electron devices.

In contrast to slot-die designs that utilize differential bolts as actuation mechanisms, zero-backlash coupler 240 couples the output shaft 222 of actuator 220 to die actuator linkage 252 with limited or no backlash. Whereas as a differential bolt mechanism may have a backlash of more than one-hundred micrometers, zero-backlash coupler 240 may provide almost no backlash, such as less than ten micrometers, or even less than five micrometers, such as about three micrometers. In a slot die utilizing a set of differential bolts to control applicator slot width or choker bar position, the relatively large backlash of each differential bolt means that adjusting the position of one differential bolt may change the height of the fluid flow path at other bolts. For this reason, the absolute position of the choker bar may never be known while operating the extrusion die. In contrast, in slot dies 10, 20, 30 the position of output shaft 222 of actuator 220 directly corresponds to the local position of choker bar 11 (for slot die 10), rotary rod 22 (for slot die 20) and flexible die lip 32 (for slot die 30). For this reason, slot dies 10, 20 and 30 facilitate repeatable, precise positioning not available in slot dies utilizing differential bolts as actuation mechanisms.

FIG. 5 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a preselected cross-web profile of the extrudate. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 5 are described with respect to slot die 10 (FIGS. 1 A-1B), actuator assembly 200 (FIG. 4) and controller 300 (FIG. 4). In different examples, the techniques of FIG. 5 may be utilized for strip coating, a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a waterbased coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.

First, a slot die, such as slot die 10, is obtained (step 502). The slot die includes an applicator slot extending along a width of the slot die and a plurality of actuators spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot.

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 504). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210.

Using fluid dynamics and a digital model of slot die 10, such as a solid model of slot die 10, controller 300 predicts a set of discrete settings from the plurality of discrete settings corresponding to a preselected cross-web profile (step 506). In different examples, controller 300 may retrieve the preselected cross-web profile from a non-transitory computer readable medium or may receive the preselected cross-web profile from a user input.

In different examples, the predicted setting may correspond to measurements from sensor 230 and/or discrete positions settings for motor 210. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. For this reason, controller 300 may predict settings for an actuator assembly 200 based on measurements from sensor 230 and may operate motor 210 to locate output shaft 222 according to the predicted setting rather than directly driving motor 210 to a number of steps corresponding to the predicted position.

In a slot die including a plurality of actuator assemblies, such as actuator assemblies 200, each actuator assembly including a measurement instrument, such as sensor 230, each measurement instrument is configured to provide a local measurement of the slot die, the local measurement corresponding to the height of the fluid flow path at the location of the respective measurement instrument. When a controller, such as controller 300, positions each of the actuators, e.g., according to the set of discrete settings, the controller may monitor the local measurements from the measurement instruments. The controller may then, for each of the actuators, adjusting the relative position of the actuator until the actuator provides the absolute height of the fluid flow path at the respective location of the actuator defined by the set of discrete settings.

Fluid dynamics, fluid properties of the extrudate, and a digital model of a die allows controller 300 to predict discrete setting for the actuators of slot die 10. In many applications, it is desirable to provide a consistent thickness of an extrudate across the entire width of the die. As another example for strip coating controller may predict discrete setting for the actuators of slot die 10 to predict a set of discrete settings from the plurality of discrete settings corresponding to a preselected strip width.

Modeling of an extrudate flowing through a die may incorporate many aspects of the die itself including applicator slot width, a distance from the manifold cavity to the exit of the applicator slot, and a slot height, which is the narrow dimension of the applicator slot between the two parallel surfaces defining the slot itself. One fundamental issue in attaining the uniformity of the flow, and critical uniformity of the coated product, is the ability to construct a die with the best possible uniformity of the die slot height. The sensitivity is greater than linear, which means that variations in slot height are magnified in extrudates. Modeling the flow may use of any appropriate models characterizing fluid rheology. For example, modeling the flow may include finite element analysis or may more directly rely on one or more equations. As one example, for a power law fluid, the relationship between flow in the slot and the slot geometry is given by the equation:

(Equation 1)

In Equation 1, Q/W is the flow per unit width, B is the slot height, P is pressure, L is the slot length (corresponding to the die width), n is the power law index and K is the coefficient for power law viscosity. A Newtonian constant viscosity fluid has n=l and K is then the numerical viscosity.

As another example, slot uniformity can be characterized by the uniformity of the walls of the slot. If each slot has a Total Indicated Runout of 2t, then the percent uniformity of the flow from the slot is then:

(Equation 2)

For a constant viscosity (Newtonian) fluid, this means that the coating uniformity goes as the cube of the slot height (B). This relationship is shown as Equation 3.

(Equation 3)

Equation 3 may not be directly used to predict slot settings because Equation 3 may not account for all details including details related to the extrusion flows, materials, and to the die design itself. However, Equation 3 demonstrates the importance for providing a precisely tuned height across the width of the die. In particular, Equation 3 demonstrates that any variations in the height of the fluid flow path are magnified in the resulting crossweb profile of the extrudate.

Equation 1 may, for example, be used to predict a die slot change because, according to the techniques disclosed herein, the position of the actuator, and by inference the slot height B, is known in combination with the desired extrudate target thickness, the current measured extrudate thickness. Previously, knowing the absolute position of the slot height during an extrusion process has not be possible, e.g., due to the backlash in differential bolts. Using the known target extrudate thickness and the measured extrudate thickness profile, Equation 1 can predict an appropriate die slot change. For example, as we know by inference the relationship between slot height profile and extrudate thickness profile from the known slot height profile and the measured extrudate thickness profile and can thus predict a slot height profile that would obtain the target thickness profile.

Assuming that other elements of the flow path are of less importance, for a Newtonian fluid, the predicted slot height corresponding to actuator “i”, B, ’ is calculated as shown in Equation 4.

(Equation 4)

For a more generalized Power Law fluid, Equation 4 may be represented as Equation 5.

Bi' = (Equation 5)

For purposes of illustration, the fluid mechanical predictions can include the geometric circumstances of the die. For a flexible die lip such as flexible die lip 32 in FIG. 3, the slot height may be better approximated by considering converging or diverging slots with a nominal fixed slot at the hinge point. Assuming the hinge point slot remains constant, then Equation 6 applies.

(Equation 6)

According to the fluid mechanics lubrication approximation:

(Equation 7)

This results in Equation 8. Equation 9 represents Ci for Equation 8.

(Equation 9) These closed form examples are useful, but it is clear that one may extend the model to include every conceived detail of the mechanical, thermal, and fluid dynamical process details. The better the predictive model, the more rapid the techniques disclosed herein will converge to the best operating condition for the desired extrudate profile.

Equations 1-9 are merely exemplary, and any number of equations may be used to predict the settings for actuator assemblies 200 in slot die 10 corresponding to a preselected cross-web profile. For example, predicting the optimal settings for actuator assemblies 200 in slot die 10 may include modeling heat transfer and thermal dissipation throughout slot die 10 and the extrudate. Such predictive modeling may include prediction of the mechanical deflections of the die assembly and mechanical elements due to thermal and flow induced forces. As previously mentioned, such models may rely upon finite element analysis, or may use more general equations to predict the settings for actuator assemblies 200 in slot die 10 corresponding to the preselected cross-web profile.

Once controller 300 predicts the settings for actuator assemblies 200 in slot die 10 corresponding to the preselected cross-web profile, slot die 10 is operated by passing an extrudate through the fluid flow path and out applicator slot 6 with the actuator assemblies 200 positioned according to the set of predicted settings (step 508).

During the operation of slot die 10, controller evaluates the cross-web profile of the extrudate after it exits the applicator slot according to measurements of the extrudate (step 510). For example, controller 300 may receive inputs from a sensor that directly measures thicknesses of the extrudate at multiple cross-web locations. As one example, a beta radiation thickness gauge may be used to measure the thicknesses of the extrudate during operation of a slot die. For strip coating, controller 300 may receive inputs from a sensor that directly measures strip width and/or thickness of individual strips. Using the evaluation of the cross-web profile, fluid dynamics and the digital model of the die, controller 300 then determines whether adjustments to the predicted set of discrete settings may provide a crossweb profile of the extrudate after it exits the applicator slot that more closely matches the preselected cross-web profile.

If controller 300 determines that adjustments to the predicted set of discrete settings may provide a cross-web profile of the extrudate after it exits the applicator slot that more closely matches the preselected cross-web profile, the controller predicts an improved set of discrete settings from the plurality of discrete settings corresponding to the preselected cross-web profile (step 512). While continuing to operate the slot die by passing the extrudate through the fluid flow path and out the applicator slot, controller 300 repositions the actuators according to the improved predicted set of discrete settings (step 514). Steps 510, 512 and 514 may be repeated until controller 300 determines that the predicted set of settings cannot be improved and/or at periodic intervals to maintain a desired cross-web profile. A set of discrete settings (step 514) can be saved as a recipe for future retrieval and use at a future time minutes, hours, or years later when similar materials, extrusion or coating properties, and processing conditions are required.

FIG. 6 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a preselected die cavity pressure. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 6 are described with respect to slot die 10 (FIGS. IA -IB), actuator assembly 200 (FIG. 4) and controller 300 (FIG. 4). In different examples, the techniques of FIG. 6 may be utilized for a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die an extrusion replication die, a vacuum contact die, or other slot die.

First, a slot die, such as slot die 10, is obtained (step 602). The slot die includes an applicator slot extending along a width of the slot die and a plurality of actuators spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot.

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 604). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210.

Using fluid dynamics and a digital model of slot die 10, such as a solid model of slot die 10, controller 300 predicts a set of discrete settings from the plurality of discrete settings corresponding to a preselected die cavity pressure (step 606). In different examples controller 300 may retrieve the preselected die cavity pressure from a non-transitory computer readable medium or may receive the preselected die cavity pressure from a user input. In different examples, the predicted setting may correspond to measurements from sensor 230 and/or discrete positions settings for motor 210. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. For this reason, controller may predict settings for an actuator assembly 200 based on measurements from sensor 230 and may operate motor 210 to locate output shaft 222 according to the predicted setting rather than directly driving motor 210 to a number of steps corresponding to the predicted position.

Fluid dynamics, known fluid properties of the extrudate, and a digital model of a die allows controller 300 to predict discrete setting for the actuators of slot die 10. Modeling of an extrudate flowing through a die may incorporate many aspects of the die itself including applicator slot width, a distance from the manifold cavity to the exit of the applicator slot, and a slot height, which is the narrow dimension of the applicator slot between the two parallel surfaces defining the slot itself.

Any number of equations may be used to predict the settings for actuator assemblies 200 in slot die 10 corresponding to a preselected die cavity pressure. For example, predicting the optimal settings for actuator assemblies 200 in slot die 10 may include modeling heat transfer and thermal dissipation throughout slot die 10 and the extrudate. As previously mentioned, such models may rely upon finite element analysis, or may use more general equations to predict the settings for actuator assemblies 200 in slot die 10 corresponding to the preselected die cavity pressure.

Once controller 300 predicts the settings for actuator assemblies 200 in slot die 10 corresponding to the preselected die cavity pressure, slot die 10 is operated by passing an extrudate through the fluid flow path and out applicator slot 6 with the actuator assemblies 200 positioned according to the set of predicted settings (step 608).

During the operation of slot die 10, controller measures the die cavity pressure within die cavity 4 (step 610) or at a suitable measurement point in flow path, which may occur before or after fluid flow path entry 5. For example, controller 300 may receive inputs from a sensor that directly measures die cavity pressure within die cavity 4. Using the measured die cavity pressure, fluid dynamics and the digital model of the die, controller 300 then determines whether adjustments to the predicted set of discrete settings may provide a die cavity pressure that more closely matches the preselected die cavity pressure. If controller 300 determines that adjustments to the predicted set of discrete settings may provide a die cavity pressure that more closely matches the preselected die cavity pressure, the controller predicts an improved set of discrete settings from the plurality of discrete settings corresponding to the preselected die cavity pressure (step 612). While continuing to operate the slot die by passing the extrudate through the fluid flow path and out the applicator slot, controller 300 repositions the actuators according to the improved predicted set of discrete settings (step 614). Steps 610, 612 and 614 may be repeated until controller 300 determines that the predicted set of settings cannot be improved and/or at periodic intervals to maintain a desired die cavity pressure.

In some examples, the techniques of FIG. 6 may be combined with the techniques of FIG. 5. For example, controller 300 may seek to provide a cross-web profile with a consistent slot height, while also maintaining a preselected die cavity pressure. In such examples, controller 300 may use the same fluid dynamics and a digital model of the die discussed with respect to FIG. 5 and FIG. 6 to determine settings for actuator assemblies 200 that will provide both a certain cross-web profile and a preselected die cavity pressure. In one example, the pressure control enables control of a die arranged to coat strips or precise width. Further, the pressure control can be accomplished where a sensor to detect strip width in communication with controller 300 is utilized to select the die pressure control. A set of discrete settings (step 514) can be saved as a recipe for future retrieval and used at a future time that could be minutes, hours, or years later when similar materials, extrusion or coating properties, and processing conditions are required.

FIG. 7 is a flowchart illustrating techniques for clearing a slot die by increasing the height of the fluid flow path adjacent each of the actuators while continuing to operate the die. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 7 are described with respect to slot die 10 (FIGS. 1 A, IB), actuator assembly 200 (FIG. 4) and controller 300 (FIG. 4). In different examples, the techniques of FIG. 7 may be utilized for a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.

First, a slot die, such as slot die 10, is obtained (step 702). The slot die includes an applicator slot extending along a width of the slot die and a plurality of actuators spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot.

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 704). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210. Controller 300 then positions each of the actuators with the controller according to a set of discrete settings selected from the plurality of discrete settings (step 706), and slot die 10 is operated by passing an extrudate through the fluid flow path and out applicator slot 6 with the actuator assemblies 200 positioned according to the set of discrete settings (step 708).

Next, a defect in a profile of the extrudate after the extrudate flows out of the applicator slot is observed, e.g., either by controller 300 or by a user. As discussed in conjunction with Equation 3, any small disturbance to the flow in the die slot will result in a disruption to the flow of liquid emitted from the die slot, thus affecting the cross-web uniformity of the extrudate or coating. Often, such disturbances are associated with gels or particulates getting caught in the die slot itself. In coating, this flow blockage results in a streak, or if wider, a band in the coating. In film extrusion, this results in undesirable die lines. For this reason, it is desirable to allow the impurity to pass through the die.

In order to allow the impurity to pass through the die, once the defect in the profile of the extrudate after the extrudate flows out of the applicator slot is observed, controller 300 increases the height of the fluid flow path adjacent each of the actuator assemblies 200 while continuing to pass the extrudate through the fluid flow path and out the applicator slot (step 710). For example, controller 300 may operate actuator assemblies 200 in unison or sequentially to increase the height of the fluid flow path through slot die 10.

After increasing the height of the fluid flow path adjacent each of the actuators to allow the disturbance to clear the die, while continuing to pass the extrudate through the fluid flow path and out the applicator slot, controller repositions each of the actuators with the controller according to the original set of discrete settings, i.e., the most recent set of adjusted settings prior to the purge operation, to resume operating the slot die with the actuators positioned according to the original set of discrete settings (step 712). In some examples, the repositioning of the actuators according to the original set of discrete settings may occur within thirty minutes, such as less than fifteen minutes, less than five minutes, less than two minutes or even less than one minute, of increasing the height of the fluid flow path adjacent the actuators.

FIG. 8 is a flowchart illustrating techniques for purging a slot die by substantially closing the fluid flow path adjacent each of the actuators while continuing to operate the die. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 8 are described with respect to slot die 10 (FIGS. 1 A, IB), actuator assembly 200 (FIG. 4) and controller 300 (FIG. 4). In different examples, the techniques of FIG. 8 may be utilized for a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.

First, a slot die, such as slot die 10, is obtained (step 802). The slot die includes an applicator slot extending along a width of the slot die and a plurality of actuators spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot.

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 804). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210. Controller 300 then positions positioning each of the actuators with the controller according to a set of discrete settings selected from the plurality of discrete settings, and slot die 10 is operated by passing an extrudate through the fluid flow path and out applicator slot 6 with the actuator assemblies 200 positioned according to the set of discrete settings (step 806).

Next, either a user or controller 300 decides to interrupt the extrusion process through slot die 10. Accordingly, controller 300 substantially closes the fluid flow path adjacent each of the actuator assemblies 200 (step 808). For example, controller 300 may operate actuator assemblies 200 in unison or sequentially to substantially the fluid flow path through slot die 10.

Stopping flow of the extrudate through slot die 10 can be undesirable; e.g., it may take significant time on start-up to each equilibrium temperatures of slot die 10 and the extrudate. In addition, for a heated extrudate, stopping the flow may undesirably lead to thermal degradation of the stagnant material in the flow system. For this reason, a slot die, such as slot die 10, can include a purge valve (not shown in the figures). The extrudate may continue to flow through the slot die once by purging the extrudate from the purge valve while the fluid flow path is substantially closed (step 810). For example, the purge valve may operate as a pressure relief valve and may open automatically once controller 300 substantially closes the fluid flow path adjacent each of the actuator assemblies 200 due to increased pressure within die cavity 4. In other examples, the purge valve may be actively opened, either by controller 300 or an operator.

After substantially closing the fluid flow path adjacent each of the actuator assemblies 200, while continuing to purge the extrudate from the purge valve, once ready to resume operations, controller 300 repositions each of the actuators according to the original set of discrete settings (step 812). In addition, the purge valve is closed, either automatically or manually to resume operation of the slot die (step 814). In some examples, the repositioning of the actuators according to the original set of discrete settings to resume operating the slot die with the actuators positioned according to the set of discrete settings may occur within thirty minutes, such as less than fifteen minutes, less than five minutes, less than two minutes or even less than one minute, of substantially closing the fluid flow path.

FIG. 9 illustrates a strip coating 900, which includes strips 904 that form a strip pattern created by repeatedly adjusting actuator position settings in a slot die. Strips 904 were extruded simultaneously from a single die, such as slot die 10 along direction 902. In particular, strip coating 900 provides strips 904 having varying widths.

A slot die, such as slot die 10 may be operated to produce strips 904 by positioning each of the actuators with the controller according to a first set of discrete settings selected from the plurality of discrete settings and by passing an extrudate through the fluid flow path and out the applicator slot with the actuators positioned according to the first set of discrete settings. Then, while passing the extrudate through the fluid flow path and out the applicator slot, controller 300 may change the positions of the actuators with the controller to create strips having varying widths.

For example, controller 300 may cycle between a series of sets of discrete settings including the first set of discrete settings such that the varying widths of strips 904 provide a substantially repeating pattern, such as that shown in FIG. 9. Controller 300 can continue to change the position of the actuators while passing the extrudate through the fluid flow path and out the applicator slot to create varying widths in the extrudate for a period in excess of ten minutes, such as a period in excess of thirty minutes, a period in excess of one hour, a period in excess of three hours or even a period in excess of twelve hours.

FIG. 10 illustrates extrudate 910 including a pattern created by repeatedly adjusting actuator position settings in a slot die. Extrudate 910 was extruded from a die, such as slot die 10 along direction 912. As shown in FIG. 10, lighter sections represent relatively thicker portions of the patterned product and darker sections represent relatively thinner portions of the patterned product. In particular, extrudate 910 includes a series of ridges that extend at an angle across a width of extrudate 910.

A slot die, such as slot die 10, may be operated to produce extrudate 910 by positioning each of the actuators with the controller according to a first set of discrete settings selected from the plurality of discrete settings and by passing an extrudate through the fluid flow path and out the applicator slot with the actuators positioned according to the first set of discrete settings. Then, while passing the extrudate through the fluid flow path and out the applicator slot, controller 300 may change the positions of the actuators with the controller to create patterned features in the extrudate.

In some examples, controller 300 may selects randomized settings from the plurality of discrete settings such that the patterned features in the extrudate are randomized pattern features. The randomized settings selected by the controller conform to preselected specifications for the randomized pattern features, for example, such preselected specifications may represent an average extrudate thickness, a standard deviation of product thickness or other product profile specification.

In other examples, controller 300 may cycle between a series of sets of discrete settings including the first set of discrete settings such that the patterned features in the extrudate are a substantially repeating pattern, such as that shown in FIG. 10. Controller 300 may continue to change the position of the actuators while passing the extrudate through the fluid flow path and out the applicator slot to create patterned features in the extrudate for a period in excess of ten minutes, such as a period in excess of thirty minutes, a period in excess of one hour, a period in excess of three hours or even a period in excess of twelve hours. Controller 300 may retrieve the first set of discrete settings and preselected specifications for the pattern features from a non-transitory computer readable medium. In other examples, controller 300 may receive the first set of discrete settings and preselected specifications for the pattern features from a user input.

FIGS. 11 A-l ID illustrate an example user interface 920 for a slot die controller. User interface 920 may interact with controller 300 to control operations of a set of actuator assemblies to control the operation of a slot die. As indicated in FIG. 11A , user interface 920 includes indications of a selected slot die operation program 924, die temperature 926 and die pressure 928. User interface 920 also include a set of selectable buttons that control operations of the die as well as corresponding cancel button, which allow a user to cancel the selection of one of the selectable buttons in the event that a selectable button was inadvertently activated. Selectable button 930 is configured to initiate a purge operation, such as the techniques disclosed herein with respect to FIG. 8. Selectable button 932 is configured to initiate a slot-clearing operation, such as the techniques disclosed herein with respect to FIG. 7. Selectable button 934 is configured to resume operation of the slot die according to the previous settings after a purge operation or a slot-clearing operation.

FIG. 11 A also illustrates profile tab 940. Selection of profile tab 940 displays a graph including an indication of an extrudate product profile measured across a width of the extrudate product. The chart also displays an actuator number relative to the width of the extrudate product. In addition, profile tab 940 includes a scroll bar 942, which may be used to view the extrudate product profile at different times. However, as shown in FIG. 11 A, scroll bar 942 is in the most forward position, such that profile tab 940 displays the current extrudate product profile and not a historical record of the extrudate product profile.

FIG. 1 IB illustrates slot height tab 950. Selection of slot height tab 950 displays a graph including an indication of slot height across a width of the die. The chart also displays an actuator number relative to the width of the slot height. In addition, slot height tab 950 includes a scroll bar 952, which may be used to view the slot height at different times. However, as shown in FIG. HB , scroll bar 952 is in the most forward position, such that slot height tab 950 displays the current extrudate product profile and not a historical record of the extrudate product profile. Slot height tab 950 further includes selectable button, which may be used to save the current actuator settings for later retrieval. FIG 11C illustrates auto-select average setpoint tab 960. Selection of auto-select average setpoint tab 960 displays a chart including the actuator position associated with each actuator of the slot die, the actual current height of the die slot corresponding to each actuator position, and the measured extrudate thickness by weight and height. In addition, auto-select average setpoint tab 960 includes a selectable update setpoint button 964. Selection of selectable update setpoint button 964 causes the controller to calculate new setpoints that will limit variability in the product profile. The new setpoints are then displayed in the chart of auto-select average setpoint tab 960. Selectable button 966 allows a user to then change the position of the actuators according to the calculated new setpoints.

FIG. 1 ID illustrates auto-select pressure tab 970. Selection of auto-select pressure tab 970 displays a chart including the actuator position associated with each actuator of the slot die, the actual current height of the die slot corresponding to each actuator position, and the measured extrudate thickness by weight and height. In addition, auto-select pressure tab 970 includes a selectable update setpoint button 974. Selection of selectable update setpoint button 974 causes the controller to calculate new setpoints according to the pressure indicated in the “set new pressure box” 978. The new setpoints are then displayed in the chart of auto-select pressure tab 970. Selectable button 976 allows a user to then change the position of the actuators according to the calculated new setpoints.

FIG. 12 illustrates techniques for retrofitting a slot die with actuator assemblies, such as a set of actuator assemblies 200 (FIG. 4). In different examples, the techniques of FIG. 12 may be utilized for a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.

First, a slot die is obtained (1202). The slot die includes an applicator slot extending along a width of the slot die and a plurality of actuation mechanisms spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuation mechanisms is operable to adjust a height of the fluid flow path at its respective location to provide an adjustment of fluid flow through the applicator slot. The slot die may be operated using the plurality of actuation mechanisms to control a height of a fluid flow path across a width of the slot die. In different examples, the actuation mechanisms include one or more of the following: thermally adjustable bolts, differential bolts, piezo-electric actuators, pneumatic actuators; and/or hydraulic actuators. In one example, the actuation mechanisms include thermally-adjustable bolts and the technique for retrofitting a slot die with thermally- adjustable bolts may include evaluating the cross-web profile of the extrudate after it exits the applicator slot and adjusting the relative position of one or more of the actuation mechanisms with its respective thermally-adjustable bolt such that the cross-web profile of the extrudate after it exits the applicator slot more closely conforms to a preselected crossweb profile.

In one exemplary actuation mechanism, the applicator slot can be adjusted by applying a pressing load or tensile load to a flexible die lip using a lever supported by a rotating shaft as a fulcrum, along with an operating rod displaced in an axial direction by the body of the slot die. Rotational force of the lever is converted into a force in the axial direction of the operating rod, and the force in the axial direction becomes a pressing load or a tensile load exerted on the flexible die lip. The lever directly can apply a force to the operating rod at the point of action of the lever.

In another example, thermally adjustable bolts automatically regulate the applicator slot using a plurality of adjusting pins, coupled to respective thermoelements disposed on a flexible die lip. The thermoelements can be controllable by the controller in to adjust the applicator slot through the action of mechanical force applied to the flexible die lip by the corresponding adjusting pin through expansion or contraction of the thermoelements. As a further option, the actuation mechanism can include providing at least two adjusting pins and/or thermoelements that are simultaneously adjusted.

Further aspects of the foregoing, along with other variants, are described in U.S. Patent No. 9,700,911 (Nakano) and PCT Patent Publication No. WO 2019/219724 (Colell et al.).

Next, the actuation mechanisms are removed from the die housing (1204). A plurality of actuator assemblies, such as actuator assemblies 200, are installed in place of the actuation mechanisms (1206). Each actuator assembly in the plurality of actuator assemblies is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot. Next, a controller, such as controller 300, is obtained and a communication link is formed between each actuator assembly and the controller (1208). The controller is configured to set the position of each actuator assembly according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210.

Using fluid dynamics and a digital model of the slot die, controller 300 predict a set of discrete settings from the plurality of discrete settings corresponding to a preselected die cavity pressure. In different examples, controller 300 may retrieve the preselected die cavity pressure from a non-transitory computer readable medium or may receive the preselected die cavity pressure from a user input.

In different examples, the predicted setting may correspond to measurements from sensor 230 and/or discrete position settings for motor 210. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. For this reason, controller may predict settings for an actuator assembly 200 based on measurements from sensor 230 and may operate motor 210 to locate output shaft 222 according to the predicted setting rather than directly driving motor 210 to a number of steps corresponding to the predicted position.

Fluid dynamics, known fluid properties of the extrudate, and a digital model of a die allows controller 300 to predict discrete settings for the actuator assemblies. Modeling of an extrudate flowing through a die may incorporate many aspect of the die itself including applicator slot width, a distance from the manifold cavity to the exit of the applicator slot, and a slot height, which is the narrow dimension of the applicator slot between the two parallel surfaces defining the slot itself.

Any number of equations may be used to predict the settings for the actuator assemblies, and the predicted settings may correspond to, e.g., a preselected cross-web profile and/or a preselected die cavity pressure. For example, predicting settings for the actuator assemblies may include modeling heat transfer and thermal dissipation throughout the slot and the extrudate.

Once controller 300 predicts the settings for actuator assemblies 200 in slot die 10 corresponding to the preselected die cavity pressure, the slot die is operated by passing an extrudate through the fluid flow path and out the applicator slot with the actuator assemblies positioned according to the set of predicted settings (1212). FIGS. 13-20 illustrates techniques for manipulating die lip shape by applying forces that are generally parallel to the width of the die and where a force application mechanism is provided and largely contained within the flexible die lip or restrictor/choker bar in accordance with the techniques disclosed herein.

Flatness of coating and extrusion dies during processing is critical to product quality. Die lips can be manipulated by differential bolts, heated bolts, or piezoelectric devices. Another alternative is through actuator assemblies, such as actuator assemblies 200. In all cases, these devices are intended to control the die lip globally by pushing or pulling at discrete locations. In all of these cases, the pushing/pulling is done in a direction generally orthogonal to width of the die. In accordance with the present disclosure, the die lip shape is instead manipulated by applying forces that are generally parallel to the width of the die and where a force application mechanism is provided that is largely contained within the flexible die lip or restrictor/choker bar. For example, the flatness of the die lip can be manipulated by expanding the metal near the die lip, which causes the shape of the die lip to change between the discrete control points, as shown in FIG. 13. This technique is analogous to the die having muscles that can flex between the positioning devices. The slot die profiles shown in FIG. 13 illustrate how varying amounts of expansion in the flexible die lip, with vertical notches (i.e., saw cuts) in the flexible die lip, can be quantified to enable precise tuning of slot die profile. An expanded version of this chart shall be visited later in FIG. 17.

These techniques can be used in combination with the conventional means of adjustors to advantageously adjust the die slot between the conventional die slot control element locations themselves, thus improving the spatial resolution of extruded uniformity control. In one example, this allows attenuating the effect of pressure deflection on the flexible die lip or internal restrictor/choker bar between the conventional adjustors to attain improved extruded uniformity.

The provided techniques provide a force application mechanism that extends or reacts to enable localized deflection of the die lip or choker bar. Exemplary force application mechanisms include piezoelectric devices, heated elements, mechanical devices, pneumatic devices, and hydraulic devices. In one example, application of bolt torque via a shoulder bolt element is used to expand the metal in the vicinity of the threads and change the profile at the lip of the die. In a further example, this shoulder bolt also serves as a spindle for actuator assemblies of the die, such as actuator assemblies 200. In another example, localized cooling or heating of the lip at points along the lip would contract the metal in the vicinity and change the profile at the die lip.

The techniques disclosed herein could be utilized as a sole adjusting means for a “fixed slot” type die, which does not include the aforementioned conventional adjusters.

In a further example, the techniques disclosed herein can be used to create a coating die with a “built in” pressure mitigating shape such as by grinding the die with force elements that when removed and the die assembled, create the desired pressure mitigating shape. Alternatively, this same strategy can be used to simply create a “flat” die slot upon assembly of the die.

The pressure mitigating shape can be based on pre-determined forces or actuator settings, either of which can be provided automatically, semi-automatically, or manually. In exemplary embodiments, the aforementioned pre-determined forces are parallel to the width of the slot die, and locally expand or contract the choker bar or flexible die lip parallel to the width of the slot die. The setting for the force application mechanism can be automatically determined, for instance, based on a target cross-web slot height profile average across the width of the slot die.

As discussed above, any small disturbance to the flow in the die slot will result in a disruption to the flow of liquid emitted from the die slot, thus affecting the cross-web uniformity of the coating or extruded sheet.

Extrusion dies typically have a flexible die lip so that the slot can be adjusted to improve the uniformity of the extruded film. Several techniques are used to flex the lip including differential bolts, thermal bolts, piezoelectric devices and actuators, as described previously. In all of these cases, the pushing/pulling is done in a direction generally orthogonal to width of the die. Spacing of the devices used to move the lip varies from around an inch (2.54 centimeters) to as much as 2.75 inches (7 centimeters). Between the devices, it is critical to have a smooth, continuous surface on the die lip since it is difficult to affect these interstitial areas by activating the movement devices. It is generally desirable to provide fine spatial resolution of extruded uniformity control. However, the spatial resolution is limited by the number of actuators that can be adjacently placed along the width of the die. In the techniques disclosed herein, the spatial resolution of the adjustable die (e.g., flexible lip or choker bar types) can be essentially doubled. Further, pressure deflection between the conventional adjustors is a fundamental limitation for all adjustable dies. To make the lip or choker bar adjustable, it must be flexible. However, making the flexible lip or choker bar resist undesirable pressure deflection in the spans between adjusters requires making it stiffer — directly at odds with the need to make it adjustable. By means of this disclosure, the die lip can remain more flexible, important to enable the extruded flow uniformity adjustment, while also directly mitigating the effects of pressure deflection between the conventional actuators.

Force application mechanisms capable of pushing and pulling a flexible lip or choker bar are generally engaged with the lip or choker bar. This may be provided, for example, by a threaded connection. In some examples, the threaded connection includes a shoulder bolt. As disclosed herein, lip profile can be manipulated by controlling the shoulder bolt torque. Tightening or torqueing the bolt causes the material around the threads to be compressed and when the expansion occurs near the lip, it can be used to change the die lip profile. This may be particularly useful when combined with actuator assemblies 200.

In a further example, the techniques of this disclosure may be used to create a coating die with a “built in” pressure-mitigating shape. Precision die lip adjustment can be done using several methods, including mechanical bolts which rely on threaded engagement, thermal bolts which locally heat the lip and adjust lip position via thermal expansion, piezoelectric devices which are moved electrically, actuators which use stepper motors to push the lip or combinations of these. The intent of the adjustment mechanism in all of these is to move the lip at discrete locations, which are aligned with the device, which are typically spaced from 2.5 cm to 7 cm apart. The shape of the die lip between the devices is uncontrolled but does react to the movement of the device, both with and without the effect of the die pressure.

In accordance with the techniques disclosed herein, the shape of the die lip is intentionally manipulated by controlling the attachment of the pushing device. In the case of a mechanical actuator which pushes a spindle, the spindle is threaded into the die lip. This would also be true for thermal bolts and differential bolts, singly or in combination with piezoelectric devices. If desired, it is possible to use two or more thermal bolts disposed in the choker bar or flexible die lip to provide non-uniform thermal expansion along the choker bar or flexible die lip. Piezoelectric devices and thermal bolts have limited extension, so they are often combined with differential bolts for coarse adjustment.

FIG. 14 illustrates an enlarged view of a flexible die block 1300 with bolts 1302 serving as force application mechanisms attached to the flexible die lip 1304. This die was fabricated from a precipitation hardening stainless steel commonly referred to as 15-5 PH (obtained under the trade designation “UNS SI 5500” from Crucible Materials Corporation, Syracuse, NY). The bolts 1302 can connect to one or more actuator assemblies, such as actuator assemblies 200. As shown, the flexible die lip includes a plurality of regularly- spaced notches 1306 to facilitate bending of the flexible die lip 1304 as the metal expands.

FIG. 15 illustrates an interferometer plot (using a laser interferometer provided by ZYGO Corporation, Middlefield, CT) of the die lip shown in FIG. 14 without the spindles attached to the die lip, whereas FIG. 16 illustrates an interferometer plot of the die lip shown in FIG. 14 with the spindles attached to the die lip. In these figures, the dashed line represents a slot die parting line, while the downward pointing arrows in FIG. 16 show the actuator spindle locations.

In the case of actuators, which due to their physical size are spaced at a distance of 2.5 inches (6.4 centimeters), there can optionally be one or more notches machined into the lip to facilitate locally flexing the choker bar or flexible die lip. The threaded connection of the device into the die lip causes movement of the lip between the primary positioning devices. An example of this is shown in FIGS. 15 and 16 for a test die with five actuators. FIG. 15 shows the profile near the lip edge without spindles attached and FIG. 16 shows a similar plot with the spindles attached and torqued to 35 ft-lbs. (47 newton-meters). Data was collected using the interferometer, on the top die surface, near the slot exit. Here, the torque applied to the threaded connection, working against the shoulder of the bolt, causes compressive stress in the material in the vicinity of the threads. This effectively “pushes away” from the threaded connection and causes the material between the positioning devices to effectively expand, therefore changing the profile between the positioning devices. Increasing the torque can increase this effect, as discussed below.

The die shown in FIG. 13 has fifteen actuators and measurements were taken at each actuator as well as the mid and quarter points. Initially, the spindles were left loose and the die profile was measured. Then, the spindles were torqued to various levels. The profile is shown in FIG. 17. The vertical lines at integer positions on the plot represent the location of spindles and the amplitude each curve represents the variation between the actuators. The solid line labeled “Loose” represents the profile of the die lip without the spindles. Each of the other series in the plot represents increasing torque. It can be seen that the variation is increasing with the level of torque applied to the spindles. FIG. 18 shows the linear relationship between the variation between actuators and the applied torque. FIG. 18 plots the spindle torque relative to the average deviation between actuators and illustrates the effect of spindle torque on slot profile.

In order to produce a flat film or coating, it may be necessary to control the uniformity of the die slot. One technique of improving the flatness would be to grind the surface of the die slot after installing the spindles, which could eliminate the variation seen in FIG. 17. However, depending on the material being coated or extruded, there are different levels of die cavity pressure, which will account for variation between the positioning devices. As mentioned previously, it has typically been difficult to control the position of the die lip at locations between the positioning devices. This variability can become significant, especially when the spacing of the positioning devices increases, as is the case with actuators, and with relatively high die pressure. Finite element modeling can be used to predict the die lip profile with the effect of the positioning devices and the die cavity pressure.

FIG. 19 shows the lip profile for the test die shown in FIG. 14, with a representative cavity pressure applied. The variation between actuators is found to be around 77 millionths of an inch (i.e., 1.96 micrometers). The direction of the deflection is opposite of the direction of the deflection due to torque, which combines to make the die lip profile more uniform. So, based on the relationship between average deviation and torque shown in FIG. 18, one could choose 35 ft-lbs. (or 47 newton-meters) of torque on the spindles to exactly counteract the pressure induced die slot deflection.

Differential thermal expansion can also be used to compensate for pressure induced die slot deflection. In an actual example, Table 1 below characterizes the oscillation of crossweb slot height profile at three locations along the applicator slot. These measurements demonstrate that it can be possible to substantially remove the “waviness” of the cross-web slot height profile through judicious application of heat to a die lip segment to induce thermal expansion at the die lip segment. In this example, heat was applied using electrically-resistive heat tape wrapped around the die lip segments. Heat could also be applied to actuator spindles near to where the actuator spindles attach to the flexible die lip.

TABLE 1.

Notably, the desired temperature for the die lip segment can be either higher or lower than that of the die, depending on the level of heat input. If the temperature in the vicinity of the die lip segment is lower than that of the remainder of the die, it is possible to invert the peaks and valleys observed in the cross-web slot height profile of the applicator slot. This is shown in FIG. 20.

It should be noted that in these embodiments, the control of the die lip profile is described as being a function of the bolt torque. However, based on the theorized mechanism of control, any method of applying a controlled expansion, or even contraction of the material in the vicinity of the die lip would be expected to have a similar effect. This could include mechanical, thermal or electrical methods. In addition, the example here implies expansion radially away from the axis of the spindle, but this could be in any direction, for example parallel to the die lip.

In a further example, the techniques disclosed herein can be used to create a coating die with a “built in” pressure mitigating shape such as by grinding the die with force elements (and associated forces) that when removed and the die assembled, create the desired pressure mitigating shape. Suppose, for example, fluid pressure normally deflects the die shape by 1.27 micrometers in the spans between actuators, but the required spindle torque with a shoulder bolt feature induces a deflection of 2.54 micrometers. In this case, the coating die can be ground with shoulder bolts at a lower torque level that, when removed, would result in a non-flat shape. However, when the spindles with shoulder bolt feature are inserted and torqued to their specification, the desired 1.27 micrometer deflection mitigates the pressure effects, resulting in a desired flat shape.

This strategy can also be used for die elements that do not include shoulder bolt spindle attachments for actuators. For example, if the actuator attachment does not induce the deflection as a shoulder bolt does, then elements could be added for use in the grinding process only to deflect the die lip or choker bar so that when they are removed, the lip includes the desired shape profile to resist pressure deflection.

In examples above, the control of the die lip profile is described as being a function of the bolt torque. However, based on the theorized mechanism of control, any method of applying a controlled expansion, or even contraction of the material in the vicinity of the die lip can have a similar effect. Useful force application mechanisms include mechanical, thermal or electrical methods, piezo electric devices, heated elements, mechanical devices, pneumatic devices, and hydraulic devices. In addition, the example here implies expansion radially away from the axis of the spindle, but this could be in any direction, for example parallel to the die lip. The techniques disclosed herein include the fabrication strategies to induce a desired flow slot shape, means suitable as a “die set-up" such as spindle torque as discussed above, and fully controllable means of adjusting the die lip profile shape on-line during the extrusion or coating process itself.

There are instances in which it can be desirable to reduce the effective width of the applicator slot. This can be sought, for example, when manufacturing a film that has a transverse dimension significantly less than the overall width of the slot die. To make such a film using the same slot die, it can be convenient to insert one or more deckles into the applicator slot to block flow of extrudate along at least a portion of the applicator slot. The deckles are generally tightly clamped between opposing die lips to prevent the deckles from falling out during operation of the slot die.

In some cases, a deckle can also function as a shim that changes the slot height of the applicator slot in its neutral, or rest, position. This neutral position is the position of the flexible die lip or choker bar when not being flexed open or closed by a force application mechanism.

In the predictive control scheme described above, it can be a technical challenge to incorporate such deckles into the extrusion process, since the actuators are configured to dynamically adjust fluid flow through the applicator slot using a choker bar or flexible die lip based on incoming extrudate thickness (i.e., caliper) data and would not normally recognize the presence of a deckle. This problem can be overcome by a process known as “freezing,” in which at least some actuator settings are assigned fixed values during operation of the slot die and do not change even as other actuator settings are iteratively corrected during operation of the die.

For the sake of clarity in the passages below, “blocked zones” refer to those areas along the width of the slot die that are aligned with the deckle, where extrudate cannot pass through the applicator slot. “Unblocked zones” refer to those areas along the width of the slot die that are not aligned with the deckle, where extrudate can pass through the applicator slot. Deckles preferably have a thickness similar to that of the applicator slot in its neutral position to avoid creating a discontinuity in slot height between the blocked and unblocked zones.

In an exemplary process, at least a portion of the applicator slot of the slot die is blocked with a deckle to reduce an effective width of the applicator slot, and the slot die is operated with at least some actuator settings being fixed over a blocked zone of the applicator slot and at least some actuator settings being dynamic over an unblocked zone of the applicator slot. To provide continuity between neighboring the actuator positions, the control scheme preferably constrains the assigned actuator settings such that the die lip or choker bar slot height profile over a blocked zone and that over a neighboring unblocked zone converge to the same value where the blocked and unblocked zones come together.

Preferably, the convergence of cross-web slot height profile where the blocked and unblocked zones come together is a monotonic convergence. In some instances, the convergence is not a monotonic convergence, but a sinusoidal convergence. Even where the convergence is sinusoidal, however, it is preferable that the actuator settings in the vicinity of at the transition point between the blocked and unblocked zones are automatically or semi-automatically constrained by the controller to reduce the amplitude of oscillation relative to the cross-web profile that would be obtained in absence of such constraints.

Deckles can be used even if the actuators are not engaged to a die lip. For example, one could use a plurality of actuators that engage a choker bar across the full width of the die slot, even when a portion of the applicator slot is blocked with one or more deckles at the die exit. With the deckles present, the precise configuration of the choker bar would not control the flow in the blocked slot areas, but would nonetheless exert some influence as a result of bending interactions (i.e., convolutions) with unblocked areas along the die slot.

In the above control scheme where actuators are engaged to a choker bar, the actuators corresponding to blocked zones of the slot are simply locked into a fixed position (“freeze mode”). This fixed position can be determined based on a cross-web slot height profile average only along unblocked zones of the applicator slot. As described below, other control modes are possible.

In a second control mode, the actuator settings are predictively programmed to arrive at a fixed target slot position over the blocked zones of the slot (“freeze slot mode”). Here, actuators are not frozen but rather manipulated by the controller, based for example on fluid physics calculations, to arrive at a fixed slot profile. In some embodiments, this is an iterative process, where actuator settings can be adjusted more than once to converge on the desired fixed slot profile.

In a third control mode, the choker bar along the blocked zones ride along with the adjacent outer portion of the open die slot (“slave mode”). In other words, the actuators over the blocked zone become the “slave” of the last actuator in the unblocked zone.

In one embodiment, this freeze slot mode can be accomplished by manipulating the fluid physics in the freeze slot actuator zones. Suppose, for example, Actuator #1 and #2 are frozen, while the segment of applicator slot corresponding to Actuator #3 is not blocked and yields good caliper data. In this case, the average caliper measurement over the unblocked actuator zone can be substituted for the non-existent caliper data in the blocked Actuator zones (i.e., Actuator #1 and #2).

Mathematically, this result can be achieved using matrix methods described in PCT Patent Publication No. WO 2012/170713 (Secor et al.) as follows: ttarget ⁼ Unfrozen Average Caliper (assuming a flat caliper profile)

Define, tj ^target B

simplifying to B₂ = B₂

As shown above, the matrix methods will hold the slot constant by manipulating the actuator positions to account for their convolution interaction.

Adjusting the relative position of Freeze Slot 1 or Freeze Slot 2 compared to Actuator 3, can be achieved by: (1) suspending the automated fluid physics control; (2) adjusting the positions of Actuators #1 and/or #2 as desired; and then (3) resuming the automated fluid physics control. The result is that Actuator #1 and #2 remain as Slaves, but their positions are defined relative to new starting points accounted for in the adjusted slot height Bi

In the “freeze mode” above, the location at which actuators with fixed settings transition to actuators with dynamic settings can be advantageously adjusted by an operator based on the application at hand. This transition location can be made relative to the position of one or more deckles within the applicator slot. For example, the aggressiveness of the freeze can be tailored according to the following three options (in these descriptions, “z” represents actuator number):

(1) Freeze Option A: Freeze to (i+1) when the deckle is past z (most aggressive)

(2) Freeze Option B: Freeze to (z+7) when deckle is past (i+0.5) (moderately aggressive)

(3) Freeze Option C: Freeze to (z) when deckle is past z (least aggressive)

The above options assume that a deckle is installed on the left side (low actuator number side) of the die. The same principles would apply in mirror image on the opposite side (high actuator number side) if deckles are installed on both sides of the die.

A significant technical challenge in deckling an applicator slot when actuators are subject to the control schemes above comes from the tendency for the controller to overcompensate for the abrupt change in slot height profile where the blocked and unblocked zones come together. This can produce undesirable “kinks” in the slot height profile, artifacts from a sinusoidal convergence. Left uncorrected, this phenomenon can produce a “W” or “M” shape in the slot height profile as shown in the dotted lines in FIGS. 21 and 22, respectively. In these figures, Actuators #l-#10 and #26-#35 were frozen, while the remaining Actuators #11-#25 were not. To mitigate or prevent the phenomenon described above, the predicted actuator settings near to where this transition occurs may be further adjusted to provide for a monotonic convergence between the cross-web slot height profile along the unblocked zone and the cross-web slot height profile average over the blocked zone. In various embodiments, this adjustment can be made manually, automatically, or semi-automatically. The idealized result of this adjustment is represented by the solid lines in FIGS. 21 and 22, with actual slot profile values represented by the bar chart. In the illustrative example of FIG. 21, a monotonic convergence was achieved for the deckle boundary on the left side of the chart but not on the right side, where an undesirable kink remained in the slot height profile.

When purging a slot die that has one or more deckles installed, the issue of continuity again arises, particularly in configurations where the actuators are engaged to a flexible die lip. When the flexible die lip clamps down on the deckle, the actuator positions along the deckle are essentially fixed. A traditional purge in which all actuators fully open the applicator slot would cause the deckles to fall out. Yet, even fully opening the applicator slot only along the unblocked zones is also problematic because it would require a discontinuity (or a fracture) in the flexible die lip.

To resolve this dilemma, the controller can send instructions to the actuators to automatically or semi-automatically enlarge the cross-web slot height profile along an unblocked zone of the applicator slot, while tapering down the degree of enlargement along a transition zone between the unblocked zone and the blocked zone. The transition zone can extend over three, four, or even more than four consecutive actuators. This solution enables the applicator slot to be purged, while providing for a smooth transition of slot height profile between the blocked and unblocked zones of the applicator slot.

The techniques described in this disclosure, such as techniques described with respect to controller 300, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various examples of the techniques may be implemented within one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in controllers, user interfaces or other devices. The term “controller” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

When implemented in software, the functionality ascribed to the systems and controllers described in this disclosure may be embodied as instructions on a computer- readable storage medium such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic media, optical media, or the like. The instructions may be executed to cause one or more processors to support one or more examples of the functionality described in this disclosure. Various examples have been described in the foregoing passages. These and other examples are within the scope of the claims that follow.

Further, all cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

CLAIMS: What is claimed is:

1. A method for operating a slot die, the slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, and at least one of a group consisting of: a choker bar and a flexible die lip, wherein the method comprises: manipulating the choker bar or the flexible die lip shape by applying, with a force application mechanism, forces that are generally parallel to the width of the slot die.

2. The method of claim 1, wherein the forces that are generally parallel to the width of the slot die expand a metal of the flexible die lip or the choker bar.

3. The method of claim 1 or 2, wherein the forces that are generally parallel to the width of the slot die are selected to create a pressure mitigating shape.

4. The method of any one of claims 1-3, wherein the slot die further includes the choker bar, wherein the slot die further includes plurality of actuators spaced along the width of the slot die, wherein the plurality of actuators are engaged with the choker bar along the width of the choker bar, and wherein each actuator is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of a choker bar within the fluid flow path.

5. The method of any one of claims 1-4, wherein the slot die further includes plurality of actuators spaced along the width of the slot die, wherein each actuator in the plurality of actuators is operable to adjust a height of the applicator slot at its respective location to provide a local adjustment of fluid flow through the applicator slot.

42

6. The method of claim 5, wherein the slot die further includes the flexible die lip on one side of the applicator slot, and wherein the plurality of actuators is operable to control the height of the applicator slot by moving the flexible die lip.

7. The method of claim 6, wherein the flexible die lip includes a plurality of notches to facilitate locally flexing the choker bar or flexible die lip.

8. The method of any one of claims 1-7, wherein the forces that are generally parallel to the width of the slot die either contract or expand a metal forming the flexible die lip.

9. The method of any one of claims 1-8, further comprising: grinding the slot die while applying the forces that are generally parallel to the width of the slot die; and removing the forces that are generally parallel to the width of the slot die after grinding the slot die such that the slot die assumes a pressure mitigating shape.

10. The method of any one of claims 1-9, wherein the force application mechanism comprises a heated element, piezoelectric device, mechanical device, shoulder bolt element, pneumatic device, or hydraulic device.

11. A method for operating a slot die, the slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, at least one of a group consisting of: a choker bar and a flexible die lip, and a plurality of actuators spaced along the width of the slot die, wherein each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot, wherein the method comprises: determining an actuator setting to locally expand or contract the choker bar or the flexible die lip of the slot die along a direction generally parallel to the width of the slot die, thereby adjusting a cross-web slot height profile where the plurality of actuators engage with the choker bar or flexible die lip; and

43 engaging the plurality of actuators with the choker bar or the flexible die lip based on the determined actuator setting. The method of claim 11, wherein the choker bar or flexible die lip includes a plurality of notches extending generally parallel to a fluid flow direction to facilitate locally flexing the choker bar or flexible die lip. A method for operating a slot die, the slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, at least one of a group consisting of: a choker bar and a flexible die lip, and a plurality of actuators spaced along the width of the slot die, wherein each actuator in the plurality of actuators is operable to adjust a height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot, wherein the method comprises: blocking a portion of the applicator slot with a deckle to reduce an effective width of the applicator slot; predicting, with a controller, a set of discrete settings from a plurality of discrete settings based on a pre-selected cross-web slot height profile for an unblocked zone of the applicator slot, the prediction based on a known correlation between the set of discrete settings and a cross-web slot height profile of the extrudate; and setting a position of each actuator according to the predicted set of discrete settings for the adjustment of the slot die, wherein the actuators are fixed over blocked zones of the applicator slot and dynamic over unblocked zones of the applicator slot during operation of the slot die. The method of claim 13, wherein the height profile along unblocked zones of the applicator slot converges to a height profile average over the blocked zone of the applicator slot where the unblocked and blocked zones of the applicator slot come together.

44 A method for making an extruded article, the method comprising: operating a slot die according to the method of any one of claims 1-14; and extruding through the applicator slot of the slot die an extrudate to obtain the extruded article. A method for purging a slot die, the slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, a choker bar or a flexible die lip extending along the width of the slot die; a plurality of actuators spaced along the choker bar or a flexible die lip, each operable to adjust a height of the applicator slot at its respective location to provide a local adjustment of fluid flow through the applicator slot; and one or more deckles blocking a portion of the applicator slot to reduce an effective width of the applicator slot; wherein the method comprises manipulating the choker bar or the flexible die lip shape by applying forces with the plurality of actuators to obtain a target cross-web slot height profile, the actuators being fixed over a blocked zone of the applicator slot and being dynamic over an unblocked zone of the applicator slot; and selectively enlarging the cross-web slot height profile along an unblocked zone of the applicator slot with the plurality of actuators, while tapering down the degree of enlargement along a transition zone between the unblocked zone and the blocked zone. The method of claim 16, wherein the height profile along unblocked zones of the applicator slot converges to a height profile average over a blocked zone of the applicator slot where the unblocked and the blocked zones of the applicator slot come together. A system comprising: a slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, at least one of a group consisting of: a choker bar and a flexible die lip, and a force application mechanism operatively coupled to the choker bar or flexible die lip; and a controller configured to set a position of each actuator according to one of a plurality of discrete settings to operate the slot die, wherein the controller is configured to manipulate the choker bar or the flexible die lip shape by applying, with the force application mechanism, forces that are generally parallel to the width of the slot die. A system comprising: a slot die including an applicator slot extending along a width of the slot die, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die, a choker bar or a flexible die lip extending along the width of the slot die; a plurality of actuators spaced along the choker bar or a flexible die lip, each operable to adjust a height of the applicator slot at its respective location to provide a local adjustment of fluid flow through the applicator slot; and one or more deckles blocking a portion of the applicator slot to reduce an effective width of the applicator slot; and a controller configured to manipulate the choker bar or the flexible die lip shape by applying forces with the plurality of actuators to obtain a target cross-web slot height profile, wherein the actuators are fixed over a blocked zone of the applicator slot and dynamic over an unblocked zone of the applicator slot; and selectively enlarge the cross-web slot height profile along an unblocked zone of the applicator slot with the plurality of actuators, while tapering down the degree of enlargement along a transition zone between the unblocked zone and the blocked zone.