TWI686284B - Method of injection molding using one or more external sensors as a virtual cavity sensor - Google Patents

Abstract

A injection molding method involves measuring, using at least one external sensor, a change in a parameter of a mold side of a mold cavity, approximating a condition within the mold cavity based on the change in the parameter, such as pressure within the mold cavity or flow front position, and comparing the approximated condition to a trigger point. If the approximated condition equals or exceeds the trigger point, activating a virtual cavity sensor having an optimal pre-defined pressure-time curve, and upon activation, the virtual cavity sensor tracks an approximated condition calculated from the change in parameter measurements measured by the at least one external sensor over time. In an embodiment, results of the approximated parameter tracking can be used in conjunction with an optimal pre-defined pressure-time curve.

Description

Injection molding method using one or more external sensors as virtual cavity sensors

This application is generally about injection molding, and more specifically, to using external sensors to estimate conditions (such as pressure or melting in injection molds) on the exterior of the mold surface adjacent to the parting line of the mold Method of fluid flow front position), and depending on the situation, if the estimated condition hits or exceeds the trigger point, other calculations and/or adjustments to the injection molding process are performed, thereby using the external sensor and the virtual cavity sensor as pressure Part of the control system.

During injection molding, molten thermoplastic material flows into the cavity of the mold through one or more gates. The pressure in the cavity is a crucial vector, because insufficient pressure may produce improperly formed parts, and excessive pressure may cause damage to the mold. The pressure at the front of the melt flow provides overall information related to the injection molding process by, for example, calculating the speed of filling the cavity and the length of time that the molded part may take to cool in the cavity. Some injection molding processes aim to make the melt flow front follow a specific pressure pattern over time to optimize the injection molding process. For example, some injection molding processes maintain the pressure of the gas pressure in the cavity and the pressure at the front of the melt flow in order to produce the final product where internal stresses (which will otherwise lead to undesirable shrinkage, dents, and warpage) are completely eliminated. Pressure balance between the two, when the molten thermoplastic material moves into the cavity of the mold, the air pressure in the cavity will be based on the mold cavity. He shape varies. For the injection molding system, in order to determine whether the desired pressure/time curve is correctly tracked, it is important to determine the immediate pressure at the front of the melt flow, and if a deviation from the pressure/time curve is identified , An adjustment is made to correct the pressure at the front of the melt flow.

Ideally, the sensors used to measure the pressure in the mold cavity and at the front of the melt flow will be indirect, easy to install, and inexpensive. Direct sensors, such as those placed in the mold cavity, can leave undesirable marks on the surface of the part. For example, despite the increased requirements for injection molded parts with a high gloss finish, direct sensors positioned in the mold cavity have a tendency to damage the high gloss finish of the part. Therefore, it is better to connect the sensor not in the cavity. Some current indirect sensors include a parting line sensor, an ejector pin sensor (ejector pin sensor) or a fixed pin sensor (static pin sensor), and an ultrasonic sensor. Disadvantageously, these indirect sensors cannot always be placed at the optimal location. Sometimes, in order to process so that the sensors can be installed, the mold equipment needs to go through downtime, and can be expensive. The strain gauge sensors currently used to indirectly measure the pressure in the mold cavity suffer from the same problem. For example, strain gauge sensors have been used in conjunction with molding equipment that has ejector sleeves or long heart pins, but not all injection molding equipment is configured to include ejector sleeves or long heart pins.

Embodiments within the scope of the present invention relate to the use of external sensors to estimate conditions during the injection molding process, such as the pressure in the mold cavity or the location of the melt flow front. Strain gauge sensors are the main types of external sensors discussed, but other external sensors capable of detecting half-mode movement can achieve the same purpose and are within the scope of the present invention. For example, microwave sensors, x-ray sensors, ultrasonic sensors, barometric pressure sensors, air temperature sensors, Subsurface temperature sensors can replace the strain gauge sensors described and depicted below. In addition, other types of external gauge sensors can be used instead of strain gauge sensors, such as inductive sensors, electronic sensors, mechanical sensors, wireless sensors, and fiber optic sensors.

Embodiments within the scope of the present invention relate to the use of strain gauge sensors to estimate conditions during the injection molding process, such as pressure in the mold cavity or at the location of the melt flow front. In many molds, there is a direct correlation between the internal cavity pressure and the strain change measured by one or more strain gauges located on the outside of the mold. In such molds, external strain gauges can be used instead of direct sensors to monitor and adjust the internal cavity pressure. In the remaining molds, there is no direct correlation between the internal cavity pressure and the strain changes measured by one or more strain gauges located on the outside of the mold. However, there is still a direct correlation between the position of the melt flow front in the mold cavity and the strain change measured by one or more strain gauges located on the outside of the mold. Use strain gauge sensors and virtual cavity sensors as part of the pressure control system to sense the parameters in the mold cavity, such as the pressure in the mold cavity or the position of the melt flow front, and if the parameter hits or exceeds the trigger point or Range, then adjust the injection molding process. In an embodiment within the scope of the present invention, at least one strain gauge sensor is mounted on the outside of the mold, such as the outside of the mold plate of the stacked mold, which is adjacent to the parting line between the two mold sides The parting line defines one or more cavities of the injection molding system. In some embodiments of the invention, two strain gauge sensors are used, one adjacent to the parting line of the mold and close to the nozzle reaching the cavity, and the other adjacent to the parting line of the mold and when molten thermoplastic material When injected into the cavity, it is located downstream of the nozzle.

The strain gauge sensor is studied by measuring the surface strain on the mold surface that occurs during the standard injection molding process. In a typical injection molding apparatus, a cavity is formed between two mold sides, which are joined together by pressing or clamping units under pressure. because Thus, along the parting line of the mold, the pressing or clamping unit applies a closing force. When the molten thermoplastic material is injected into the cavity, the molten thermoplastic material exerts an opening force along the parting line of the mold. Ideally, the opening force applied by the molten thermoplastic material is less than the closing force applied by the clamping unit. If the opening force exceeds the closing force, the die side is forced to separate and overflow or leakage of molten thermoplastic material occurs. The strain gauge sensor placed on the outside of the mold surface adjacent to the parting line of the mold can sense the change in surface strain that occurs on the mold surface over time due to the closing force and the opening force.

In response to changes in surface strain, the strain gauge sensor emits electrical signals typically in the range of -10 volts to 10 volts. The signals emitted by the strain gauge sensors are received and used by the controller to estimate one or more conditions in the mold, such as the pressure in the mold cavity or the position of the melt flow front. In a specific mold where the length of the flow channel is larger than the thickness of the molded part, that is, a mold with a high L/t ratio, the melt flow front can be estimated based on the signal emitted by the strain gauge sensor pressure. These approximate values can be applied to adjust the injection molding process. For example, the amount of pressure in the cavity can be estimated and compared to the maximum allowable cavity pressure to ensure that excess cavity pressure does not cause damage to the cavity.

In some embodiments within the scope of the present invention, if the condition calculated by the controller hits or exceeds the trigger point, the strain gauge sensor as part of the pressure control system can adjust the operation of the injection molding system to Reduce or restore the sensed or another parameter to a level within the desired range. In addition to one or more strain gauge sensors, the pressure control system of the present invention also includes a virtual pocket sensor, which can be implemented in the form of a set of instructions (eg, software programs) that are stored in non-temporary Machine-readable media and executed by one or more general-purpose or special-purpose processors. The virtual pocket sensor can read data from machine-readable memory, and in some cases write data to machine-readable memory, The memory stores data representing the best pre-defined pressure-time curve, which corresponds to the parts made by the injection molding process and the materials forming the parts. The predefined pressure-time curve is defined by an equation or relationship where time is an independent variable and pressure is a dependent variable. In some embodiments, the pre-defined pressure-time curve is a parabolic curve that approaches an asymptote at a maximum set pressure to achieve mold cavity. In some embodiments where the controller estimates the internal mold pressure based on the change in strain, the virtual pocket sensor compares the instantaneous pressure estimated by the reading of the strain gauge over time with the best predefined pressure-time curve to determine the injection Whether the molding process is working as expected. Combined with other information available from injection molding equipment, such as how far the screw injects the molten thermoplastic material into the cavity, the virtual cavity sensor can measure the viscosity of the molten thermoplastic material and the filling percentage of the cavity. In the event that the real-time data estimated from the strain gauge sensor readings does not follow the best predefined pressure-time curve, the virtual pocket sensor system can guide the injection molding equipment to take corrective actions, such as by changing The advancing rate and/or advancing force of the screw injecting additional molten thermoplastic material is to increase the pressure at the front of the melt flow or in the cavity of the mold.

The term "flow front" refers to when the molten polymeric material advances from the nozzle or gate of the mold cavity (that is, the point where the molten polymer material is introduced into the mold cavity) toward and eventually to the position where the filling of the mold cavity ends, as defined in the mold cavity The front edge of the injection of molten polymeric material is experienced by the surface of the mold.

In some embodiments where the controller determines the position of the melt flow front based on the change in strain, when it is realized that the strain sensor data indicates that the melt flow front reaches a certain position in the mold cavity, the virtual cavity sensor system may Guided injection molding equipment takes actions guided by a predefined pressure-time curve, such as increasing or adjusting the screw advance rate and/or propulsion force to ensure that the mold is properly filled, or even actuating a part of the mold.

An example of a part of the actuation mold that can be implemented when the melt flow front reaches a predetermined position in the mold cavity is continuous molding, which is discussed in detail on June 30, 2015 and is called "Sequential Coining" In US Patent Application No. 62/186,722, said application is incorporated herein by reference.

The term "flow-filled mixing" is defined as the area of a part of the mold that forms the feature of the part to be molded, which is particularly susceptible to any one or more of the various problems that complicate the molding of the part or makes the molded part less May have one or more defects or reduced mechanical properties, such as transient filling, warpage, dents, embrittlement, overflow, voids, unfilled, weak (for example, low tensile strength, torsional strength and/or circumferential strength) , High stress concentration, low modulus, reduced chemical exposure resistance, premature fatigue, uneven shrinkage, and discontinuities in color, surface texture, opacity, translucency, or transparency. Non-exhaustive examples of flow-fill mixing are: position and transitions in the mold used to form ribs, bumps or corners, and obstacles in the mold (such as heart-shaped pins) (such as changes in the thickness of the parts to be molded, which may It is a sudden stepped thickness change or a progressive thickness change, such as a decreasing area). These may involve a transition from a relatively thick area to a relatively thin area, and then revert to a relatively thick area, and may involve one or more thickness changes. For the purposes of the present invention, a transformation that is of particular interest is the living hinge, which is usually a relatively thin area of one of the molded parts, which allows a part of the part (such as the flip of the lid) to rotate relative to the rest of the part. When the term flow-fill mixing is used herein, the area of a component affected by a specific mix is expected to be located at a specific location, along the area, or downstream of the specific location or area, and therefore, flow-fill mixing need not be limited to the specificity of mold shape changes Position, but can extend beyond, that is, downstream of such a position.

Use data from one or more external sensors, such as strain gauge sensors, to melt The measurement of the position of the flow front can also be used to determine the position of the melt flow front relative to the flow filling and mixing in the cavity. The indication that the melt flow front has reached a predetermined position relative to the flow filling and mixing can serve as a part of starting or stopping heating of the mold cavity, such as a signal of a limited duration of the area of the mold cavity in the vicinity of induction heating of the flow filling and mixing, while the melt The flow front passes through or along the flow filling and mixing, such as the US patent application for "Injection Molding with Localized Heating in Flow Challenge Regions" filed on September 3, 2014 As mentioned in case No. 62/045,373, said application is incorporated herein by reference.

10: Injection molding equipment

12: Injection system

14: clamping system

16: Thermoplastic pellets

18: funnel

20: Heating barrel

22: Reciprocating screw

24: molten thermoplastic material

25: first die side

26: Nozzle

27: Second mold side

28: mold

30: Gate

32: mold cavity

34: Pressing or clamping unit

36: Screw control

50: controller

51: Virtual pocket sensor

52: First strain gauge sensor/First strain gauge/Strain gauge sensor

53: Second strain gauge sensor/strain gauge sensor

54: Wire

56: Wired connection

125a: first die side

127c: Second mold side

127d: Second mold side

132a: mold cavity

132b: Mold cavity

132c: Mold cavity

132d: mold cavity

133: Board

135a: core

135b: core

135c: core

135d: core

137: Board

154: Strain gauge sensor

210: Injection molding equipment

224: molten thermoplastic material

230: Gate

232: Mold cavity

256: Strain sensor

258: Traditional cavity sensor

300: Method

302: Step

304: Step

306: Step

308: Step

310: Step

312: Step

Although this specification concludes by specifically pointing out and clearly claiming the scope of the patent application regarded as the subject matter of the present invention, Xianxin's present invention will be more fully understood from the following description in conjunction with the accompanying drawings. For the purpose of showing other components more clearly, some of the drawings may be simplified by omitting selected components. Except when an explicit description can be made in the corresponding written description, the omission of elements in some drawings does not necessarily indicate the presence or absence of specific elements in any of the exemplary embodiments. All drawings are not necessarily drawn to scale.

Fig. 1 shows semi-schematically an injection molding apparatus constructed in accordance with the present invention, in which two strain gauge sensors are located on the outer surface of the mold side adjacent to the parting line between the mold sides, the first strain gauge senses The sensor is located on the first mold side near the nozzle that reaches the mold cavity, and the second strain gauge sensor is located on the second mold side downstream of the nozzle; Figure 2 shows the stacking of the multi-cavity injection molding system A mold, which includes a pair of plates defining two mold sides, at least one of which has a strain gauge sensor on its outer surface located on a parting line adjacent to the mold sides, which is shown in Before any force is applied to the cavity; FIG. 3 shows the stacking mold of the multi-cavity injection molding system shown in FIG. 2 when a clamping unit (not shown) applies a closing force immediately before injecting molten thermoplastic material into the mold cavity or at the beginning of injection Figure 4 shows the cavity, core and first and second mold sides present in the stacked mold of the multi-cavity injection molding system shown in Figure 3.

FIG. 5 shows the plate surrounding the cavity and the first mold side in the stacked molds of the multi-cavity injection molding system shown in FIGS. 3 to 5.

6A to 6B show the plate surrounding the cavity and the plate surrounding the core in the stacked molds of the multi-cavity injection molding system shown in FIGS. 3 to 5.

FIGS. 7A to 7B show the stacked molds of the multi-cavity injection molding system shown in FIGS. 3 to 6 when a clamping unit (not shown) applies a closing force and an opening force is applied when molten thermoplastic material is injected into the cavity FIG. 8 graphically shows that when the injection molding system can be controlled based on the feedback from the strain gauge to achieve the desired pressure-time curve, the parabolic pre-defined pressure that can be utilized by the virtual cavity sensor system of the present invention − A graph of the time curve; Figure 9 shows a double-layer stacked injection molding apparatus using a strain gauge sensor and multiple mold cavities; and Figure 10 shows the use of readings from the strain gauge sensor for adjusting the internal melt pressure (IMP) is a flowchart of an exemplary method, which may be implemented in, for example, the controller of FIG.

Referring to the drawings in detail, FIG. 1 shows an exemplary injection molding apparatus 10 (eg, injection mold 101 or "ultra-high-yield mold", 102) for manufacturing thermoplastic parts having a high volume. Category (medium to high yield mold) or category 103 (medium yield mold)). The injection molding apparatus 10 generally includes an injection system 12 and a clamping system 14. The thermoplastic material may be introduced into the injection system 12 in the form of thermoplastic pellets 16. The thermoplastic pellets 16 may be placed in a hopper 18, which feeds the thermoplastic pellets 16 into the heating barrel 20 of the injection system 12. After feeding into the heating barrel 20, the thermoplastic pellets 16 can be pushed to the end of the heating barrel 20 by a push rod, such as a reciprocating screw 22. The heating of the heating barrel 20 and the extrusion of the thermoplastic pellets 16 by the reciprocating screw 22 cause the thermoplastic pellets 16 to melt, forming a molten thermoplastic material 24. The molten thermoplastic material is usually processed at a temperature of about 130°C to about 410°C.

The reciprocating screw 22 urges the molten thermoplastic material 24 toward the nozzle 26 to form an injection of thermoplastic material that will be injected into the cavity 32 of the mold 28 through one or more gates. Molten thermoplastic material 24 may be injected via gate 30, which directs molten thermoplastic material 24 to mold cavity 32. The mold cavity 32 is formed between the first mold side 25 and the second mold side 27 of the mold 28 and the first mold side 25 and the second mold side 27 are combined together by a pressing or clamping unit 34 under pressure. The pressing or clamping unit 34 applies a clamping force during the molding process, which exceeds the force applied by the injection pressure acting on the two mold halves 25, 27, thus when the molten thermoplastic material 24 is injected into the cavity 32 So that the first mold side 25 and the second mold side 27 are combined together. In a typical high-variable-pressure injection molding machine, a pressure of 30,000 psi or more is usually applied because the clamping force is directly related to the injection pressure. To support these clamping forces, the clamping system 14 may include a mold frame and a mold base.

After the injection of molten thermoplastic material 24 is injected into the cavity 32, the reciprocating screw 22 stops moving forward. The molten thermoplastic material 24 is in the form of a cavity 32 and the molten thermoplastic material 24 is cooled in the mold 28 until the thermoplastic material 24 solidifies. After the thermoplastic material 24 is cured, the pressing unit 34 releases the first mold side 25 and the second mold side 27, and the first mold side 25 and the second mold side 27 are separated from each other, and the final part can be ejected from the mold 28. The mold 28 may include a plurality of mold cavities 32 to increase the overall yield. The shapes of the cavity of the plurality of mold cavities may be the same, similar or different from each other. (Plurality of mold cavities can be regarded as mold aristocrats).

The controller 50 is in communication with the first strain gauge sensor 52 and the screw control 36. The first strain gauge 52 is located on the outer surface of the first mold side 25 near the parting line between the first mold side 25 and the second mold side 27 and in the vicinity of the nozzle 26. The controller 50 may include a microprocessor (or another suitable processing unit, or several such units), non-transitory memory, and one or more communication links. The controller 50 is also optionally connected to a second strain gauge sensor 53 which is located in the second mode close to the parting line between the first die side 25 and the second die side 27 The side 27 is on the outer surface and located downstream of the nozzle 26. Although two strain gauge sensors are used in the embodiment depicted in FIG. 1, other embodiments within the scope of the present invention may use only one strain gauge sensor or may use more than two strain gauge sensors Device. In addition, embodiments within the scope of the present invention may use strain gauge sensors located elsewhere on the die side.

The strain gauge sensors 52 and 53 sense the surface strain of the mold, as discussed in more depth according to FIGS. 2 to 4. The data from the strain gauge sensors 52 and 53 can be communicated to a processor that calculates changes in the surface strain of the mold. The electrical signals from the strain gauge sensors 52, 53 can travel along one or more electrical paths, such as wires 54 (depicted in solid lines in FIG. 1), with an intensity ranging from 0 volts to 10 volts. The controller 50 may be connected to the screw control 36 via a wired connection 56. In other embodiments, the controller 50 may communicate with the screw control 36 via a wireless connection, a mechanical connection, a hydraulic connection, a pneumatic connection, or known in the art to those skilled in the art. Any other type of communication connection is connected to the screw control 36.

The controller 50 can use the surface strain changes calculated by the information provided by the first strain gauge sensor 52 and the second strain gauge sensor 53 to estimate conditions such as the length and molding of the flow channel in the mold cavity or in particular The thickness of the part is relatively large. In a specific mold, the pressure at the melt flow front of the molten thermoplastic material 24 or the position of the melt flow front. These approximations can then be used to adjust the injection molding process. For example, the amount of pressure in the cavity 32 can be estimated and compared to the maximum allowable cavity pressure to ensure that excess cavity pressure does not cause damage to the cavity 32. If the amount of pressure in the mold cavity 32 is estimated to be dangerously close to the maximum allowable mold cavity pressure or even exceed a safe threshold far below the maximum allowable mold cavity pressure, the controller 50 may direct the screw control 36 to stop the injection of molten thermoplastic material . Other approximations can be used to control the molding process so that changes in material viscosity, mold temperature, melt temperature, and other changes that affect the filling rate can be used to cause the controller 50 to adjust the injection molding system. These adjustments can be made immediately during the molding cycle or can be corrected in subsequent cycles. In addition, the approximation can be averaged over multiple cycles and then used to make the controller 50 make adjustments to the molding process.

In addition, the controller 50 communicates with a virtual pocket sensor 51, which is implemented in the form of a program or a set of software instructions. However, more generally, the virtual pocket sensor can be implemented in hardware (eg, in the form of an application specific integrated circuit (ASIC)), firmware, software, or any suitable combination thereof. In the present invention, the term "virtual cavity sensor" may refer to a module that measures a process variable, such as a pressure value, without directly measuring the process variable. The strain gauge sensors 52 and 53 and the virtual cavity sensor 51 together form a pressure control system that generates data related to the strategic control of the pressure in the mold cavity 32. As used herein, the term "pressure control system" refers to any suitable group of components that can include software implementation components and hardware implementation components that generate signals indicative of conditions in the mold cavity based on signals indicative of another process variable.

For example, if based on the surface strain information provided by the first strain gauge sensor 52 and the second strain gauge sensor 53, the processor associated with the controller 50 determines that the pressure in the mold cavity exceeds the trigger point (or If it exceeds the predetermined acceptable range), the virtual cavity sensor 51 signals the controller to adjust the screw control 36 to return the pressure in the mold cavity to a level lower than the trigger point (or within a predetermined acceptable range). As another example, if based on the surface strain information provided by the first strain gauge sensor 52 and the second strain gauge sensor 53, the processor associated with the controller 50 determines that the melt flow front has advanced beyond the trigger point (It can be related to the filling percentage of the mold), then the virtual cavity sensor 51 signals the controller to adjust the screw control 36 to return the pressure in the mold cavity to a predetermined acceptable final pressure or range, which may involve reducing The pressure avoids overfilling the mold cavity and therefore prevents undesirable flash.

2 to 7 show a stacked multi-cavity injection molding system using strain gauge sensors 154. FIG. As shown in FIG. 3, the stacked multi-cavity injection molding system has mold cavities 132 in the first mold side 125 and complementary mold cores 135 in the second mold side 127. The stacked multi-cavity injection molding system depicted in FIGS. 2 to 7 has a total of four mold cavities 132 (132a, 132b, 132c, 132d) in the four first mold sides 125 (125a, 125b, 125c, 125d) ) And four mold cores 135 (135a, 135b, 135c, 135d) in the four second mold sides 127 (127a, 127b, 127c, 127d), but the mold cavity 132 or the second in the first mold side 125 One or more of the cores 135 in the mold side 127 are omitted from FIGS. 3 to 5 to make other elements visible in the drawings. A stacked multi-cavity injection molding system within the scope of the present invention may have more than four or less than four cavity 132 in the first mold side 125 and more than four or less than four in the second mold side 127的之模芯135.

As shown in FIG. 4, the mold cavities 132 a, 132 b, 132 c, and 132 d are surrounded by the plate 133. As shown in FIG. 5, the core 135 in the second mold side 127 is surrounded by the plate 137. Depicted in Figures 2 to 7 In an embodiment, the strain gauge sensor 154 is located on the outside of the plate 133 and is adjacent to the parting line of the mold between the plate 133 and the plate 137. In other embodiments within the scope of the present invention, more than one strain gauge sensor 154 may be used, and one or more strain gauge sensors may be placed on the board 133, the board 137, and the first mold side 125 Either one or on the second die side 127. The strain gauge sensor 154 is located near the corner of the board 133 in FIGS. 2 to 7. However, in some embodiments, the strain gauge sensor 154 can be placed near the middle of the plate 133. Due to the force acting on the mold cavity 132, the strain change experienced by the strain gage 132 is greater than that by a guide pin (leader pin) ) The corners of the supported plates are large. In some embodiments, it is determined whether to place the strain gauge sensor 154 or the plate 133 or 137 based on which plate experiences more strain, which is made of a material with less rigidity, is thinner or has more wear The effect of a board whose hardness is reduced through its cut. In some embodiments, the plate 137 experiences more strain and therefore becomes the main location of the strain gauge sensor 154. In some embodiments, interfering components or features, such as cooling channel connections, may affect the position of the strain gauge sensor 154. In some embodiments where the mold has more than one parting line, the strain gauge sensor 154 may be placed closest to the parting line that more directly experiences the opening force generated by the injection of molten thermoplastic material, in some embodiments In this, the parting line is the parting line from which the molded part is pushed out. If possible, place the strain gauge sensor where there is a direct correlation between the internal cavity pressure and the strain gauge reading of the strain gauge. Such locations are most likely to exist in simple molds. If there is no such location, in the case of a complex mold where the load is transferred to multiple parts, it is more likely that the strain gauge sensor is placed between the position of the melt flow front and the strain change reading of the strain gauge. The position of direct correlation. The trial and error method can be used to determine the optimal position of the strain gauge. By drawing the measurement results obtained by the strain gauge when filling the mold cavity, each mold will have a unique or near-unique mark that can be mapped. Various signs on the map, such as peaks, most Low points, valleys, local minimums, or local maximums may indicate, for example, the position of the melt flow front. The strain gauge sensors described in this application include the strain gauge sensors 52, 53, and 154 depicted in FIGS. 1 to 4, which can be selected from a variety of commercially available strain gauge sensors. For example, in embodiments within the scope of the present invention, the Kistler "surface strain sensor" model 9232A or Rocktest Telemac's "surface mounted strain gauge" model SM-5A or SM-5B will be studied. The strain gauge sensor is designed to be fast and easy to install because it may have an anchor block that can be welded to the injection molding device or that can be screwed in the surface of the injection molding device.

FIG. 2 shows the stacked multi-cavity injection molding system before any force is applied to the cavity 132 when the injection molding system is in the open condition. In the absence of an external force to the plate 133, the base having a thickness X _1. Likewise, plate 133 has an inherent baseline strain in its construction, which may be zero. The strain gauge sensor 154 detects strain based on the sensed baseline strain of the plate 133, for example, με ₁ .

FIG. 6A shows the mold cavity 132 under the closing force applied by the pressing or clamping unit (not depicted). Under the closing force, the shape of the plate 133 changes slightly. For example, the thickness of the plate 133 (previously X ₁ ) changes from the amount ΔX to the new thickness X ₂ . The strain in plate 133 also changes. The strain gauge sensor 54 detects strain in response to this change, for example με ₂ . In general, the closing force causes compressive strain. However, this may not always be the case, depending on the specific injection molding equipment used and the position of the strain gauge sensor 154. Therefore, the strain change detected by the strain gauge sensor 154 over time may be positive or negative, or the system of the present invention may operate based on the absolute value of the strain change over time. 6B is an enlarged view of the portion of FIG. 6A with a strain gauge sensor.

7A shows the closing force applied by the pressing or clamping unit (not depicted) and the mold cavity 132 under the opening force applied by the thermoplastic molten material when it is injected into the mold cavity 132. The plate 133 responds to the combination of forces. For example, the thickness of the plate 133 (when no force is applied to the mold cavity 32 of the X ₁ and the cavity 132 when a closing force is applied to only X ₂₎ the amount of change to the new thickness △ X X _3. The displacement caused by adding the opening force to the closing force also causes a change in the surface strain, and the strain gauge sensor 154 detects the strain in response to this change, for example με ₃ . Generally speaking, the opening force causes relaxed tensile strain. However, this may not always be the case, depending on the specific injection molding equipment used and the position of the strain gauge sensor 154. Therefore, the strain change detected by the strain gauge sensor 154 may be positive or negative. Depending on where the strain gauge sensor 154 is located, the strain gauge sensor 154 can detect changes in tensile strain or changes in compressive strain. The virtual cavity sensor is activated, and the preset trigger point of the virtual cavity sensor 51 such as that depicted in FIG. 1 usually appears as depicted in FIG. 7A, when the mold cavity 132 experiences both an opening force and a closing force, because This is the time period during which the molten thermoplastic material is actually being injected into the cavity 132 to form the part during the injection molding process. 7B is an enlarged view of the portion of FIG. 7A with a strain gauge sensor.

FIG. 8 depicts the best predefined pressure-time curve that can be used by the virtual pocket sensor 51. The independent (horizontal) axis represents time, and the related (vertical) axis represents pressure. The origin is a preset trigger point, which may occur at or near when molten thermoplastic material begins to enter the cavity 32, 132, or 232 and exerts an opening force that can be detected by the strain gauge sensor. In some embodiments, the best predefined pressure-time curve is parabolic, where the asymptote is located at the maximum pressure set when the part is fully formed. In some embodiments, the pressure-time curve is defined by the following two variables: 1) the time to fill the mold cavity to 75%, and 2) the maximum pressure setting. In some embodiments, the virtual pocket sensor 51 compares the instantaneous pressure estimated by the strain gauge sensor readings over time with the best predefined pressure-time curve to determine whether the injection molding process is performing as As expected. In combination with other information available from the injection molding equipment 10 or 210, such as measured by a mechanism connected to the screw 22, the reciprocating screw 22 rows In the near and far extent, the virtual cavity sensor 51 can measure the viscosity of the molten thermoplastic material 24 or 224 and the filling percentage of the cavity 32, 132 or 232. The virtual pocket sensor 51 can guide the injection molding apparatus 10 in the case where the real-time data estimated by the readings of the strain gauge sensors 52, 53, 154 or 256 indicate that the best predefined pressure-time curve is not followed Or 210 takes corrective action, such as by injecting additional molten thermoplastic material 24 or 224 to increase the pressure at the front of the melt flow or in the mold cavity 32, 132, or 232. An exemplary method of taking the corrective action will be discussed below with reference to FIG. 10. In other embodiments, the virtual cavity sensor 51 determines whether the position of the melt flow front has reached or passed through the trigger position in the mold cavity 32, 132 or 232, which can match the mold cavity 32, 132 or 232, and can guide the injection molding apparatus 10 or 210 to take actions guided by the best predefined pressure-time curve, such as increasing (or decreasing) the injection rate of additional molten thermoplastic material 24 or 224 to increase (or Reduce) the pressure at the front of the melt flow or in the cavity 32, 132 or 232; activate one or more local heating elements to heat or actuate one or more regions of the cavity 32, 132, 232 One part (for example, to achieve molding). In the example discussed above, in addition to measuring the estimated pressure, the virtual pocket sensor 51 also causes the injection molding apparatus 10 or 210 to take corrective action. In another embodiment, the virtual cavity sensor 51 only generates a signal indicating the pressure in the cavity, and another component is determined in view of the output of the virtual cavity sensor 51 and other signals or preset values that may exist Whether to guide the injection molding apparatus 10 or 210 to take corrective action. This component is implemented as part of the controller 50 of FIG. 1, for example. More generally, functions related to the use of strain gauge sensor readings to estimate pressure, compare readings with predefined curves, and determine whether corrective actions should be taken can be assigned to the controller 50, virtual pocket sensor 51, etc. in any suitable manner in.

9 shows an alternative configuration of the injection molding apparatus 10 depicted in FIG. In FIG. 6, the injection molding apparatus 210 has a two-layer stacked molding configuration. There are multiple mold cavities 232 and can be mutually Stacked. To accommodate the stacked configuration, molten thermoplastic material 224 flows through two gates 230 into cavity 232. A plurality of strain sensors 256 may be used at or near the parting line of the injection molding apparatus 10. Compared to having only a single cavity 232 equipped with a strain sensor, the benefit of having multiple strain sensors 256 in multiple cavity 232 is that the virtual cavity sensor 51 (depicted in FIG. 1) can determine the mode The fill percentage of each of the holes 232. This is important because in a specific molding configuration, some cavity 232 can be filled earlier or later than other cavity 232, so that the filling percentage of a single cavity 232 does not necessarily indicate the filling of all multiple cavity 232 percentage. In addition, a conventional cavity sensor 258 may be present in the mold cavity 232. These conventional pocket sensors 258 may provide the controller 50 (depicted in FIG. 1) with information that can be used to initiate specific changes to the injection molding process, which are not controlled by the virtual pocket sensor 51. In addition to the conventional cavity sensor 258, one benefit of having a plurality of strain gauge sensors 256 in the injection molding apparatus 210 is that the specific cavity 232 is not filled with melt due to downtime for maintenance of the cavity 232 In the case of a thermoplastic material 224, the conventional cavity sensor 258 does not provide any measurement of a given cavity 232. However, the strain gauge sensor 256 located on the mold cavity 232 still provides information that can be used to determine, for example, whether the shutdown mold cavity 232 experiences strain changes that can cause a pressure level to damage the mold cavity 232.

FIG. 10 shows an exemplary method 300 for adjusting the injection melt pressure (IMP) when a thermoplastic material is injected into the cavity 32 (see FIG. 1). The controller 50 can implement this method to dynamically adjust the signal supplied to the screw control member 36 via, for example, a wired connection 56.

The method 300 starts at step 302, where an initial value of IMP is obtained. At step 304, the measurement results from the strain gauge sensor (eg, strain gauge sensor 52) are obtained. In some embodiments, measurement results from multiple strain gauge sensors are received at step 304. Measure approximate cavity pressure using measurements from one or more strain gauge sensors (step 306) force. For example, the virtual pocket sensor 51 may implement steps 304 and 306.

Subsequently, at step 308, the adjusted value of IMP is determined using the approximate pocket pressure measured at step 306. For this purpose, the controller 50 and/or the virtual pocket sensor 51 may receive from the operator (e.g., "adjust the IMP by N units in response to the detection of each M unit falling in the pocket", from An indication of a suitable mapping in a predefined lookup table or any other suitable according to a certain formula. At step 310, the adjustment value is added as feedback to the current IMP value to execute the feedback loop control process.

If it is determined at step 312 that certain predefined conditions have been met, such as the strain gauge measurement results providing data indicating that the melt flow front has reached the end of filling or another predetermined location in the cavity, then the method 300 is completed. Otherwise, the flow returns to step 304 to wait for a new reading from the strain gauge sensor. For example, the timing of re-executing step 304 may be pre-configured or controlled by the operator. By way of example only, new readings from strain gauge sensors can be received continuously or almost continuously. When these terms are used in this document, they include every millisecond, every two milliseconds, every three milliseconds, every four milliseconds, every Five milliseconds or any other increment of time division that may be needed from the beginning of filling to the end of filling, the time division is suitable for strain measurement, the results of their measurements and data points that meet predetermined or expected pressure and time values Compare and adjust IMP to work to offset any deviations. Readings can be taken in increments of equal or unequal time during filling or during specific time intervals while filling the mold cavity.

Part or all of any of the embodiments disclosed herein can be combined with part or all of other injection molding embodiments known in the art, including those described below.

Embodiments of the present invention can be used with embodiments directed to injection molding at low constant pressure, such as those filed on May 21, 2012, entitled "Under Low Constant Pressure Apparatus and Method for Injection Molding at Low Constant Pressure" (Applicant Case No. 12127) and disclosed in US Patent Application 13/476,045 published as US 2012-0294963, said application The case is incorporated by reference.

The embodiment of the present invention can be used together with an embodiment for pressure control, such as the "Alternative Pressure Control for a Low Constant Pressure Injection Molding Equipment" filed on May 21, 2012. Constant Pressure Injection Molding Apparatus)” (Applicant Case No. 12128), which is currently disclosed in US Patent Application 13/476,047 of US 8,757,999, which is incorporated herein by reference.

The embodiment of the present invention can be used together with an embodiment for a non-naturally balanced feeding system, such as the "Non-naturally balanced feeding system for injection molding equipment (Non -Naturally Balanced Feed System for an Injection Molding Apparatus)" (Applicant Case No. 12130), which is now disclosed in US Patent Application 13/476,073 of US 8,911,228, which is incorporated herein by reference.

Embodiments of the present invention may be used with embodiments directed to injection molding at low, substantially constant pressure, such as those filed on May 21, 2012, entitled "Low, Substantially Constant Pressure Injection "Method for Injection Molding at Low, Substantially Constant Pressure" (Applicant Case No. 12131Q) and disclosed in US Patent Application 13/476,197 published as US 2012-0295050, which is cited by reference Incorporated in this article.

Embodiments of the present invention may be compatible with injection molding at low, substantially constant pressure The examples are used together, and the example is applied for on May 21, 2012, and is entitled "Method for Injection Molding at Low, Substantially Constant Pressure" (Applicant's case No. 12132Q) and disclosed in US Patent Application 13/476,178 published as US 2012-0295049, which is incorporated herein by reference.

The embodiment of the present invention can be used together with an embodiment for a co-injection process, such as the application filed on February 22, 2013, called "High Thermal Conductivity Co-Injection Molding System" )" (Applicant case number 12361) and disclosed in US Patent Application 13/774,692 published as US 2013-0221572, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to moldings that accompany simplified cooling systems, such as those filed on February 12, 2013, entitled "Simplified Evaporative Cooling System or Simplified Cooling with Exotic Cooling Fluid Injection Mold Having a Simplified Evaporative Cooling System or a Simplified Cooling System with Exotic Cooling Fluids" (Applicant Case No. 12453M), which is now disclosed in US Patent Application 13/765,428 of US 8,591,219. The application is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments for molding thin-walled parts, such as the method of "substantially constant pressure injection molding for thin-walled parts" filed on August 31, 2012. And Apparatus (Method and Apparatus for Substantially Constant Pressure Injection Molding of Thinwall Parts)" (Applicant Case No. 12487D), which is now disclosed in US Patent Application 13/601,514 of US 8,828,291, which is cited by reference Incorporated in this article.

The embodiment of the present invention can be used together with an embodiment for molding with a fail-safe mechanism, such as the application "Injection Mold With Fail with a fail-safe pressure mechanism" filed on November 8, 2012. Safe Pressure Mechanism) (Applicant Case No. 12657) and disclosed in US Patent Application 13/672,246 published as US 2014-0127338, which is incorporated herein by reference.

The embodiment of the present invention can be used together with an embodiment for high-yield molding, such as the "Method for Operating a High Productivity" filed on November 20, 2012, entitled "Method for Operating a High Productivity" Injection Molding Machine)" (Applicant Case No. 12673R) and disclosed in US Patent Application 13/682,456 published as US 2013-0221575, which is incorporated herein by reference.

The embodiments of the present invention can be used together with an embodiment for molding a specific thermoplastic material, such as the method of molding a composition called "Thermoplastic Polymer and Hydrogenated Castor Oil", which was applied on November 20, 2013 ( Methods of Molding Compositions of Thermoplastic Polymer and Hydrogenated Castor Oil)" (Applicant Case No. 12674M) and disclosed in US Patent Application 14/085,515 published as US 2014-0145374, which is incorporated herein by reference in.

The embodiment of the present invention can be used together with an embodiment for a runner system, such as the one filed on November 21, 2013, entitled "Reduced Size Runner for an injection mold system (Reduced Size Runner for an Injection Mold System)" (Applicant Case No. 12677M) and disclosed in US Patent Application 14/085,515 published as US 2014-0141117, which is incorporated herein by reference.

The embodiment of the present invention can be used with an embodiment directed to a mobile molding system, such as the "Low Constant Pressure Injection Molding System with Variable Position Molding Cavity" filed on May 13, 2014 (Low Constant Pressure Injection Molding System with Variable Position Molding Cavities)" (applicant case number 12896) and disclosed in US Patent Application 14/275,944 published as US 2014-0335219, which is incorporated by reference In this article.

The embodiment of the present invention can be used with an embodiment directed to an injection mold control system, such as an injection molding machine filed on February 10, 2014, entitled "In consideration of changes in material properties during injection molding operations and Methods (Injection Molding Machines and Methods for Accounting for Changes in Material Properties During Injection Molding Runs)" (Applicant Case No. 13020), which is now disclosed in US Patent Application No. 14/176,505 of US 8,980,146. The way of quotation is incorporated herein.

The embodiment of the present invention can be used with an embodiment directed to an injection mold control system, such as an injection molding machine filed on July 31, 2014, entitled "In consideration of changes in material properties during injection molding operations and Method (Injection Molding Machines and Methods for Accounting for Changes in Material Properties During Injection Molding Runs)" (Applicant Case No. 13021M) and disclosed in US Patent Application No. 14/448,648 published as US 2015-003518. Incorporated by reference.

The embodiment of the present invention can be used with an embodiment directed to an injection mold control system, such as an injection molding machine filed on July 31, 2014, entitled "In consideration of changes in material properties during injection molding operations and Method (Injection Molding Machines and Methods for Accounting for Changes in Material Properties During Injection Molding Runs)” (Applicant Case No. 13022) and disclosed in US Patent Application 14/448,726 published as US 2015-0115491, which is incorporated by reference Into this article.

Embodiments of the present invention may be used with embodiments directed to the use of injection molding to form overmolded products, such as those filed on December 19, 2014, entitled "Method for Forming Overmolded Products ( Methods of Forming Overmolded Articles)" (Applicant Case No. 13190) and disclosed in US Patent Application 14/577,310 published as US 2015-0174803, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to controlling the molding process, such as those issued on March 17, 1998, entitled "Method and Equipment for Injecting Molten Materials into Mold Cavities ( Method and Apparatus for Injecting a Molten Material into a Mold Cavity) (Applicant Case No. 12467CC) is disclosed in US Patent 5,728,329, which is incorporated herein by reference.

The embodiment of the present invention can be used together with an embodiment directed to controlling the molding process, such as the "Injection Control System" granted on February 10, 1998 (Applicant Case No. 12467CR ) Is disclosed in US Patent 5,716,561, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to molded preforms, such as "Plastic Article Forming Apparatus and Methods for Using the Same" (Applicant No. 13242P) is disclosed in US Patent Application 61/952281, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to molded preforms, such as "Plastic Article Forming Apparatus and Methods for Using the Same" (Applicant No. 13243P) is disclosed in US Patent Application 61/952283, which is incorporated herein by reference.

The embodiment of the present invention can be used with an embodiment for a brazing feeding system, such as "Feed System for an Injection Molding Machine" (Applicant Case No. 13488P ) Is disclosed in US Patent Application 62/032,071, which is incorporated herein by reference.

The embodiment of the present invention can be used with an embodiment for a non-brazing feed system, such as "Feed System for an Injection Molding Machine" (Applicant Case No. 13498P) is disclosed in US Patent Application 62/042,577, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments of heated molds for injection molding machines, such as "Injection Molding with Localized Heating in Flow Challenge Regions" "(Applicant Case No. 13509P) is disclosed in US Patent Application 62/045,373, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to retrofitting injection molding machines, such as the US patent entitled "Retrofitted Injection Molding Machines" (Applicant Case No. 13553P) It is disclosed in the application 62/053,499, which is incorporated herein by reference.

Embodiments of the invention can be used with embodiments for continuous injection molding, the Examples of implementation are disclosed in US Patent Application 62/084,778 entitled "System and Method for Continuous Injection Molding" (Applicant Case No. 13638P), which is cited by reference Is incorporated into this article.

The embodiment of the present invention can be used with an embodiment for continuous co-injection molding, which is called "Co-Injection with Continuous Injection Molding" (Applicant Case No. 13639P ) Is disclosed in US Patent Application 62/084,787, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to injection molding accompanied by molding, such as in US Patent Application 62/186,722 named "Sequential Coining" (Applicant Case No. 13935P) As disclosed, the application is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to injection molding control, such as "Method of Injection Molding with Constant-Velocity Flow Front Control" (Applicant case number 13936P) is disclosed in US Patent Application 62/186,739, which is incorporated herein by reference.

Embodiments of the present invention can be used with embodiments directed to injection molding under specific device conditions, such as "Injection Molding with a Leaking Check Ring" (Applicant No. 13957P) is disclosed in US Patent Application 62/192,616, which is incorporated herein by reference.

The dimensions and values disclosed herein should not be understood to be strictly limited to the precise numerical values described. In fact, unless stated otherwise, each such dimension is intended to mean both the stated value and the functionally equivalent range surrounding that stated value. For example, the size revealed as "40mm" It means "about 40mm".

Unless expressly excluded or otherwise restricted, each document cited in this document, including any cross-references or related patents or applications and any patent applications or patents in which this application claims priority or interest, is in full text The way of quotation is incorporated herein. The citation of any document does not admit that it is the prior art of any invention disclosed or claimed herein or teaches, indicates or discloses any such invention alone or in combination with any other reference. In addition, in the event that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to the term in this document shall prevail .

Although specific embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended to cover all such changes and modifications within the scope of the present invention within the scope of the accompanying patent application.

10: Injection molding equipment

12: Injection system

14: clamping system

16: Thermoplastic pellets

18: funnel

20: Heating barrel

22: Reciprocating screw

24: molten thermoplastic material

25: first die side

26: Nozzle

27: Second mold side

28: mold

30: Gate

32: mold cavity

34: Pressing or clamping unit

36: Screw control

50: controller

51: Virtual pocket sensor

52: First strain gauge sensor/First strain gauge/Strain gauge sensor

53: Second strain gauge sensor/strain gauge sensor

54: Wire

56: Wired connection

Claims (15)

A method for injection molding a thermoplastic material, the method comprising: using at least one strain gauge sensor (52) to measure a strain change in a mold side of a mold cavity (32); estimating the mold cavity based on the strain variation At least one of the pressure or the melt flow front position; compare the pressure or melt flow front position in the estimated cavity with the trigger point that occurs at or near the point when the molten thermoplastic material begins to enter the mold When an opening force that can be detected by the strain gauge sensor is applied; if the pressure in the estimated mold cavity or the melt flow front position is equal to or exceeds the trigger point, the virtual cavity sensor (51) is activated; When activated, the virtual cavity sensor tracks the pressure in the estimated cavity calculated from the strain change measurement results, and the tracking result of the pressure in the estimated cavity is the best predefined pressure- Time curve for comparison, the strain change measurement result is measured by the at least one strain gauge sensor over time, the best pre-defined pressure-time curve is close to the maximum set pressure to achieve the mold cavity Parabolic curve of asymptote. The method of claim 1, wherein when activated, the virtual pocket sensor causes the controller (50) to perform actions including at least one of: increasing the extrusion rate of the molten thermoplastic material; decreasing the extrusion of the molten thermoplastic material Pressure rate; increase the injection force of molten thermoplastic material; reduce the injection force of molten thermoplastic material; actuate part of the cavity; The heating element in the cavity. As in the method of claim 1, the method further includes: wherein, if the comparison of the tracking result of the pressure in the estimated cavity with the optimal predefined pressure-time curve indicates that the optimal predefined is not followed Pressure-time curve, then adjust the injection molding process. The method of claim 3, wherein adjusting the injection molding process includes injecting additional molten thermoplastic material. The method of claim 3, wherein adjusting the injection molding process includes increasing the extrusion rate of the molten thermoplastic material. The method of claim 3, wherein adjusting the injection molding process includes reducing the injection rate of the molten thermoplastic material. The method of claim 3, wherein adjusting the injection molding process includes increasing the injection force of the molten thermoplastic material. The method of claim 3, wherein adjusting the injection molding process includes reducing the injection force of the molten thermoplastic material. The method of claim 1, wherein when activated, the virtual pocket sensor determines The viscosity of the molten thermoplastic material entering the cavity. The method of claim 1, wherein when activated, the virtual cavity sensor measures the percentage of the mold cavity that has been filled with molten thermoplastic material. As in the method of claim 1, the method includes: using at least one conventional cavity sensor to measure a change in mold cavity pressure in the mold cavity. The method of claim 1, the method comprising: measuring strain changes in the plurality of mold sides of the plurality of mold cavities using a plurality of strain gauge sensors; and wherein when activated, the virtual cavity sensor The percentage of mold cavities that have been filled with molten thermoplastic material is determined for each of the plurality of mold cavities. As in the method of claim 12, the method includes using at least one conventional cavity sensor to measure the cavity pressure in each of the plurality of cavity. The method of claim 13, the method comprising: ensuring that by using the at least one strain gauge sensor, none of the mold cavity pressures measured by the at least one conventional cavity sensor exceeds the maximum mold cavity pressure. The method of claim 1, wherein the trigger point occurs when the die side experiences both an opening force and a closing force.

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