US20080029397A1

US20080029397A1 - Hot embossing tooling with integrated heating/cooling fluid channels and method

Info

Publication number: US20080029397A1
Application number: US11/498,681
Authority: US
Inventors: Robert E. Szokolay
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-08-02
Filing date: 2006-08-02
Publication date: 2008-02-07

Abstract

An electroformed tool has an integrated base with channels contacting the tool with heating and cooling fluids flowing through the channels during injection molding or hot embossing. A blank base is machined with a network of interconnected open channels on a top surface and end flow through passageways communicating with the channels. The tool is used as an electrode to erode the top surface of the blank base using plunge electro discharge machining by lowering the uneven deposit on the bottom of the electroformed tool down onto the top surface of the blank base in the electro discharge machining environment to form a top contoured surface to mate with the uneven deposit on the non-embossing side of the substrate. The tool and base are sealed together.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to injection molding tooling and hot embossing tooling used in injection molding and hot embossing micro- and nano-structures, and in particular to enhanced injection molding or hot embossing tooling formed with an attached base with flow through channels for hot and cold fluid, the top of the base being shaped by electro-discharge machining to mate with the uneven bottom surface of the electroformed plate and the method of forming the tooling.
2. Description of Related Art including Information Disclosed Under 37 CFR 1.97 and 1.98
In injection molding and hot embossing of micro/nano-structures, electroforming is frequently employed as a technique for producing tooling. Often, this is the only practical method for replicating structures of such small feature sizes, with sufficient fidelity. Unfortunately, this presents a problem, as the backsides of electroforms are inherently non-uniform and hence typically require extensive post-plating machining to planarize the back surface of the electroformed tool. This is necessary, in order to facilitate heat exchange between the tool, and the platen against which it is mounted.
Heating and cooling means are typically integrated into this platen in order to regulate the temperature of the tooling at the tool/plastic interface, where molding/embossing takes place. Quicker, more responsive control of the tool temperature is expected to facilitate better replication fidelity, and allow for minimization of process cycle times.
Prior art tooling does not adequately address the problem of minimizing the time involved in the operation while maximizing heating and cooling efficiency of the tooling.
What is needed is hot embossing and injection molding tooling formed by a rapid process of attaching a blank to an electroform without having to planarize the back surface of the electroform, the blank having integrated flow-through channels attached as part of the tooling for a quicker, more responsive temperature control with heating and cooling to be facilitated by passing a heat exchange medium (fluid) through the integrated channels in the embossing/molding die.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a device and method for hot embossing and injection molding tooling formed by a rapid process of attaching a blank to an electroform without having to planarize the back surface of the electroform by using electro-discharge machining (EDM) to quickly shape the top of the blank to conform precisely to the back surface of the electroform and then attaching the electroform and blank together as integrated hot embossing or injection molding tooling, the blank having integrated flow-through channels attached as part of the tooling for a quicker, more responsive temperature control with heating and cooling to be facilitated by passing a heat exchange medium (fluid) through the integrated channels in the embossing/molding tooling or die to fit within existing limited space in hot embossing and injection molding equipment.
Another object of the present invention is to provide a method for creating a molding/embossing tool with integrated cooling/heating channels, without the necessity of planarizing the electroform's uneven deposit on the non-embossing side to prevent damage to the electroformed tool.
One more object of the present invention is to seal and cure the electroformed tool to the blank base using a liquid-tight structural adhesive or to interconnect the electroformed tool and blank base using screws and sealing them together with a sealant, such as a silicone based adhesive, to allow for higher maximum temperatures to extend the application of the device to plastics with higher glass transition temperatures or such as ceramic-metallic-epoxy sealants which can be used for sealing for even higher temperature applications.
In brief, an electroformed tool has an integrated base with channels contacting the electroform with heating and cooling fluids flowing through the channels during injection molding or hot embossing. A blank base is machined with a network of interconnected open channels on a top surface and flow through passageways communicating with the channels. The electroform is used as an electrode to erode the top surface of the blank base using plunge electro-discharge machining by lowering the uneven contour on the bottom of the electroformdown onto the top surface of the blank base in the electro-discharge machining environment to form a top contoured surface to mate with the uneven contour on the non-embossing side of the electroform. The electroform and base are sealed together.
A primary advantage of the present invention is that it provides for a quicker, more responsive temperature control in an electroformed tool by integrating fluid channels in direct contact with the electroform with heating and cooling to be facilitated by passing a heat exchange medium (fluid) through the integrated fluid channels.
A related advantage of the present invention is that it provides an electroformed tool with integrated liquid heating and cooling channels which fits within existing limited space in hot embossing and injection molding equipment.
Another advantage of the present invention is that it provides a rapid process of attaching a blank to an electroform, and eliminates the need to planarize the back surface of the electroform.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other details of my invention will be described in connection with the accompanying drawings, which are furnished only by way of illustration and not in limitation of the invention, and in which drawings:

FIG. 1 is a perspective view of the blank base of the invention showing the top channels and the end flow through openings;

FIG. 2 is a side view of the blank base of FIG. 1;

FIG. 3 is a top plan view of the blank base of FIG. 1;

FIG. 4 is an end view of the blank base of FIG. 1;

FIG. 5A is a side view of the blank base of FIG. 1 and the electroformaligned with the top of the blank base showing the top embossing side of the electroform to function as an embossing surface and an uneven contour on a non-embossing bottom side of the electroform left as a by-product of electroforming;

FIG. 5B is a side view of the blank base and the electroform aligned with the top of the blank base of FIG. 5A showing the beginning of the process of using the electroform as an electrode to erode the top surface of the blank base using plunge electro-discharge machining to form a contoured surface to mate with the uneven conyour of the non-embossing side of the electroform;

FIG. 5C is a side view of the blank base and the electroformaligned with the top of the blank base showing the completion of the process of using the electroformas an electrode to erode the top surface of the blank base using plunge electro-discharge machining to form a contoured surface to mate with the uneven contour on the non-embossing side of the electroform;

FIG. 5D is a side view of the blank base of FIG. 5C and the uneven contour of the bottom of the electroformaligned with the contoured top of the blank base;

FIG. 5E is a side view of the contoured blank base and the electroformsecured together with the uneven contour of the bottom of the electroformmating with the contoured top of the blank base to form an electroformed tooling device with integral heating and cooling fluid channels for use in injection molding and hot embossing.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1-5, an electroformed tooling device 20 with integral heating and cooling fluid channels for use in injection molding and/or hot embossing is shown in various stages of fabrication.
In FIGS. 5A-5E, an electroform10 with an embossing surface and an uneven contour 12 on the bottom non-embossing side left as a by-product of electroforming.
In FIGS. 1-4 and 5A, a blank base 21 comprises a block of metal with a smooth flat bottom surface 25, a top surface 22 having a network of open channels 23 in the top surface, and one or more surfaces each having an opening 24A and 24B therein communicating with the network of open channels to allow fluid to flow into a first opening, such as the end opening 24A and flow through the network of open channels 23 and flow out a second opening, such as the end opening 24B. The machining of the blank base comprises milling, drilling, grinding and turning techniques. The channels are so arranged, that the area in which they are contained is smaller than the projected area of the electroformed tool.
In FIGS. 5C-5E, the top surface 22 of the blank base 21 further comprising a an electro-discharge machined contoured surface 22A to mate with the uneven deposit 12 on the bottom non-embossing side of the substrate.
In FIG. 5E, the electroformed tool 10 and the blank base 21 with the contoured top 22A are interconnected by a means of securing the electroformed tool 10 to the blank base 21 with the non-embossing side 12 contacting and mating with the mating contoured top surface 22A of the blank base to form an electroformed tool with integral heating and cooling channels 23 so that hot and cold fluid flowing through the blank base network of open channels 23 contacts the electroformed tool to alternately heat and cool the electroformed tool during use in injection molding and hot embossing processes to manufacture items such as microfluidic devices, optical reflectors or molds, holograms or other precision formed articles.
The means of securing the electroformed tool 10 to the blank base 21 may comprise a liquid-tight structural adhesive which is cured to bind them together or the means of securing the electroformed tool 10 to the blank base 21 may comprise a threaded fastener and a sealant for a watertight device, preferably, but not limited to, a silicon based adhesive sealant for use in high temperatures, ceramic-metallic-epoxy sealants for even higher temperatures or other securing means to bind them together with a watertight fit.
A method of making an electroformed tooling device 20 with integral heating and cooling fluid channels for use in injection molding and hot embossing comprises the steps illustrated in FIGS. 5A-5B.
In FIG. 5A, a first step comprises forming an electroformed tool 10 by electroforming from a structured substrate to plate electrodeposited metal 13 to fom the embossing side of the tool to function as an embossing and molding surface while leaving an uneven conture 12 on a non-embossing side of the electro-deposit left as a by-product of electroforming.
A second step comprises machining a block of metal to form a blank base 21, shown in FIGS. 1-4 and 5A. The blank base 21 comprises a smooth flat bottom surface 25, a top surface 22 having a network of open channels 23 in the top surface, and one or more surfaces having an end opening 24A and 24B therein communicating with the network of open channels 23 to allow fluid to flow into a first opening, such as the end opening 24A, and flow through the network of open channels 23 and flow out a second opening, such as the end opening 24B. The fluid could flow in either direction from one opening to the other.
The machining of the blank base comprises conventional milling, drilling, grinding and turning techniques. The finished blank base 21 has a series of deep grooves 23, milled from above, with the flat top surface 22, left undisturbed, between the grooves 23. This pattern of grooves and top surface, when sealed off in subsequent steps, forms the cooling/heating fluid channels. The openings 24A and 24B are drilled, through one or more surfaces of the blank base 21, intersecting the channels 23.
In FIGS. 5B and 5C, a third step comprises using the electroformed tool 10 as an electrode to erode the top surface 22 of the blank base 21 using plunge electrodischarge machining to erode the top surface to form a top contoured surface 22A to mate with the uneven deposit 12 on the non-embossing side of the electroform 10 by lowering the uneven contour 12 on the bottom of the electroformed tool 10 down onto the top surface 22 of the blank base 21 in the electro-discharge machining environment. The top contoured surface 22A of the blank base 21 should not be as deep as the pre-milled cooling/heating channels 23, so as not to completely block those channels after subsequent interconnecting of the electroformed tool 10 and the blank base 21.
In FIGS. 5D and 5E, a fourth step comprises interconnecting the electroformed tool 10 and the blank base 21 by a means of securing the electroformed tool to the blank base with the non-embossing side 12 of the electroform 10 contacting the mating top contoured surface 22A of the blank base to form an electroformed tool with integral heating and cooling channels 23 so that hot and cold fluid flowing through the blank base network of open channels 23 contacts the electroformed tool 10 to alternately heat and cool the electroformed tool during use in injection molding and hot embossing processes.
The electroformed tool 10 may be adhered to the blank base 21 using a liquid-tight structural adhesive and the structural adhesive cured or alternately screwed to the blank base 21 and adhered to the blank base 21 using a sealant, preferably a silicon based adhesive sealant for use of the device in high temperatures, or otherwise secured with the bottom non-embossing side uneven deposit 12 of the electroformed tool 10 mating with the top contoured surface 22A of the blank base 21 so that hot and cold fluid flowing through the channels 23 directly contacts the electroformed tool 10 to heat and cool the tool during injection molding and hot embossing processes.
If the bottom 25 of the blank base 21 is not parallel to the top embossing surface of the electroformed tool 10, then the method further comprises the step of planarizing the bottom surface 25 of the blank base to parallel the substrate top embossing surface so that the electroformed tooling device 20 with integral heating and cooling fluid channels 23 fits properly in the equipment used for injection molding or hot embossing. The planarizing may be accomplished by grounding, turning, or fly cutting the bottom surface 25 of the blank base 21.
It is understood that the preceding description is given merely by way of illustration and not in limitation of the invention and that various modifications may be made thereto without departing from the spirit of the invention as claimed.

Claims

1. An electroformed tooling device with integral heating and cooling fluid channels for use in injection molding and/or hot embossing, the device comprising:

an electroform, an electroformed tool comprising electrodeposited metal which has been plated from a structured substrate on an embossing side to function as an embossing surface and an uneven contour on a non-embossing side of the electroform left as a by-product of electroforming;

a blank base comprising a smooth flat bottom surface, a top surface having a network of open channels in the top surface, and one or more surfaces having openings therein communicating with the network of open channels to allow fluid to flow into a first opening and flow through the network of open channels and flow out a second opening, the top surface further comprising a an electro discharge machined contoured surface to mate with the uneven deposit on the non-embossing side of the substrate;

wherein the electroformed tool and the blank base are interconnected by a means of securing the electroformed tool to the blank base with the non-embossing side of the electroform contacting and mating with the mating top contoured surface of the blank base to form an electroformed tool with integral heating and cooling channels so that hot and cold fluid flowing through the blank base network of open channels contacts the electrodeposit to alternately heat and cool the electroformed tool during use in injection molding and/or hot embossing processes.

2. The device of claim 1 wherein the means of securing the electroformed tool to the blank base comprises a liquid-tight structural adhesive.

3. The device of claim 1 wherein the means of securing the electroformed tool to the blank base comprises a threaded fastener and a sealant for a watertight device.

4. The device of claim 3 wherein the sealant comprises a silicon based adhesive sealant for use in high temperatures.

5. The device of claim 3 wherein the sealant comprises a ceramic-metallic-epoxy sealant for use in high temperatures.

6. A method of making an electroformed tooling device with integral heating and cooling fluid channels for use in injection molding and/or hot embossing, the method comprising:

a first step of fabricating an electroform, a tool by electroforming from a structured substrate to create an embossing side of the electroform to function as an embossing and molding surface while leaving an uneven deposit on a non-embossing side of the electroform left as a by-product of electroforming;

a second step of machining a metal blank base comprising a smooth flat bottom surface, a top surface having a network of open channels in the top surface, and one or more surfaces having an opening therein communicating with the network of open channels to allow fluid to flow into a first opening and flow through the network of open channels and flow out a second opening;

a third step of using the electroform as an electrode to erode the top surface of the machined blank base using plunge electro-discharge machining to form a contoured surface to mate with the uneven contour of the non-embossing side of the electroform by lowering the uneven contour of the non-embossing side of the electroform onto the top surface of the blank base in the electro discharge machining environment;

a fourth step of interconnecting the electroformed tool and the blank base by a means of securing the electroformed tool to the blank base with the non-embossing side of the electroform contacting the mating top contoured surface of the blank base to form an electroformed tool with integral heating and cooling channels so that hot and cold fluid flowing through the blank base network of open channels contacts the electroform to alternately heat and cool the electroformed tool during use in injection molding and hot embossing processes.

7. The method of claim 6 wherein the electroform is adhered to the blank base using a structural adhesive and the structural adhesive is cured.

8. The method of claim 6 wherein the electroform is screwed to the blank base by a threaded fastener and the electroform is adhered to the blank base using a sealant for a watertight device.

9. The method of claim 8 wherein the electroform is adhered to the blank base using a silicon-based adhesive sealant for use in high temperatures.

10. The method of claim 8 wherein the electroform is adhered to the blank base using a ceramic-metallic-epoxy sealant for use in high temperatures.

11. The method of claim 6 further comprising the step of planarizing the bottom surface of the blank base to parallel the top embossing surface of the electroformed tool.

12. The method of claim 6 wherein the machining of the blank base comprises milling, drilling, grinding and turning techniques.