TWI708673B - Injection molding apparatus and method of controlling same - Google Patents

Abstract

A method of controlling a melt pressure of an injection molding apparatus is provided. The method includes establishing a melt pressure profile having a plurality of setpoints.

Description

Injection moulding equipment and its control method

The systems and methods described below are generally related to the field of injection molding systems.

Injection molding is commonly used to manufacture parts made of fusible materials, such as thermoplastic polymers. In order to facilitate the injection molding of these parts, a solid plastic resin is introduced into a hot barrel containing a reciprocating screw. The heat and the reciprocating screw cooperate to promote the melting of the plastic and inject the molten plastic into the mold cavity to form a desired shape. Generally speaking, the controller has multiple set points, each set point defining the desired melt pressure for a unique time during the molding cycle. For each set point, the controller commands the reciprocating screw to operate in such a way that the melt pressure converges to the desired melt pressure for the time defined by the set point. However, the controller will maintain the desired melt pressure based on the previous set point until the desired melt pressure based on the next set point is achieved. In other words, the pressure curve of the set point follows a stepwise defined function. Therefore, the controller tries to make the melt pressure reach the set point immediately (for example, within the duration of a sample), which causes the internal melt pressure of the injection molding unit to suddenly increase to the desired internal melt pressure, and the molded part The integrity of the product is adversely affected.

According to one embodiment, a method of controlling the melt pressure of an injection molding equipment is provided. The method includes receiving a melt pressure profile. The melt pressure curve includes a plurality of set points, each of which defines the desired melt pressure of the injection molding equipment. The melt pressure curve extends between each set point. Each set point is separated from other set points by a time period defining at least a part of the injection molding process during which the thermoplastic material is injected into the cavity (e.g., during initial injection, during filling, during packaging During, during storage and/or during any decompression after filling, encapsulation or storage). The method further includes measuring the melt pressure curve at one or more time intervals between the set points. Each of the one or more time intervals and set points are separated by time, and each of the one or more time intervals defines the desired melt pressure of the injection molding equipment. At each of the one or more time intervals, the injection molding equipment is controlled based on the desired melt pressure defined by the melt pressure curve at each of the one or more time intervals. For at least two immediately adjacent set points, the desired melt pressure at each of the one or more time intervals between the set points and the desired melt pressure at each of the at least two immediately adjacent set points Body pressure is different.

According to another embodiment, a method of establishing a melt pressure curve of an injection molding equipment is provided. The method includes specifying a plurality of set points, the set points each defining a desired melt pressure of the injection molding equipment. Each set point is separated from the other set points by a time period defining at least a part of the injection molding process during which the thermoplastic material is injected into the mold cavity. The method further includes specifying one or more desired melt pressures between each of the set points and specifying one or more sampling time intervals for the melt pressure curve. The sampling interval is separated by time. For at least two immediately adjacent set points, the expected melt pressure at each of the one or more sampling time intervals between the set points is different from the expected melt pressure at at least two immediately adjacent set points.

According to another embodiment, the injection molding equipment includes a heat barrel, a reciprocating screw, a power unit Element, clamping unit, nozzle and control system. The reciprocating screw is placed in the heat barrel and is configured to reciprocate relative to the heat barrel. The power unit is operatively coupled with the reciprocating screw and is configured to promote the reciprocating movement of the reciprocating screw relative to the hot barrel. The clamping unit is for the mold. The clamping unit is associated with the heat barrel. The nozzle is arranged at one end of the hot barrel and is configured to distribute the contents of the hot barrel to the clamping unit. The control system communicates with the power unit and is configured to facilitate the operation of the reciprocating screw. The control system has a melt pressure curve stored on it. The melt pressure curve includes a plurality of set points, each of which defines the desired melt pressure of the injection molding equipment. The melt pressure curve extends between each set point. Each set point is separated from the other set points by a time period defining at least a part of the injection molding process during which the thermoplastic material is injected into the mold cavity. The control system is configured to sample the melt pressure curve at one or more time intervals between set points, and at each of the one or more time intervals, based on The desired melt pressure defined by the melt pressure curve at the time interval controls the operation of the reciprocating screw. For at least two immediately adjacent set points, the expected melt pressure at each of the one or more time intervals between the set points is different from the expected melt pressure at at least two immediately adjacent set points.

10: Injection molding equipment

12: Injection molding unit

14: Funnel

16: Hot barrel

18: Reciprocating screw

20: nozzle

22: power unit

24: Thermoplastic pellets

26: Melting thermoplastic materials

28: Mould

30: The first mold part

32: The second mold part

34: Mould cavity

36: Clamping unit

38: Gate

40: control system

42: Melt pressure sensor

43: Cavity pressure sensor

44: Screw control

46: PID controller

48: data storage area

50: Melt pressure curve

52: main controller

60: Melt pressure curve

62: The first level part

63: The first vertical part

64: second level part

65: second vertical part

66: The third level part

67: third vertical part

68: The fourth level part

70: sudden increase

72: Undershoot

150: Melt pressure curve

C: Control signal

E: Error signal

G: PID control algorithm

P: set point

P0 to P5: set point

P0 to P18: set point

Pa1 to Pa4: set point

S1: signal

S2: signal

T1 to T5: time period

V1 to V4: Time interval

It is believed that certain embodiments will be better understood based on the following description and drawings, in which: Figure 1 is a schematic diagram depicting an injection molding equipment according to an embodiment; Figure 2 is a diagram depicting the control of the injection molding equipment of Figure 1 System block diagram; Fig. 3 is a block diagram depicting the PID controller of the control system of Fig. 2; Fig. 4 is a graph of an exemplary melt pressure curve depicting the relationship between the desired melt pressure and time according to one embodiment ; Figure 5 is a curve of the conventional melt pressure curve depicting the relationship between the desired melt pressure and time Figure; and Figure 6 is a graph of an exemplary melt pressure curve depicting the relationship between the desired melt pressure and time according to another embodiment.

This application is non-provisional and claims the rights and interests of US Provisional Application No. 62/210,514 filed on August 27, 2015. Priority application US 62/210,514 is incorporated herein by reference.

The embodiments disclosed herein are generally about systems, machines, products, and methods for manufacturing products by injection molding, and more specifically, about systems, machines, products, and injection molds with a substantially constant pressure by low pressure Method of making products.

As used herein, in terms of the melt pressure of thermoplastic materials, the term "low pressure" means a melt pressure of about 6000 psi and below 6000 psi near the nozzle of an injection molding machine.

As used herein, with regard to the melt pressure of a thermoplastic material, the term "substantially constant pressure" means that the deviation from the baseline melt pressure does not cause a meaningful change in the physical properties of the thermoplastic material. For example, "substantially constant pressure" includes (but is not limited to) pressure changes that do not cause a meaningful change in the viscosity of the molten thermoplastic material. In this regard, the term "substantially constant" includes a deviation of approximately 30% from the baseline melt pressure. For example, the term "substantially constant pressure of about 4600 psi" encompasses pressure fluctuations in the range of about 6000 psi (30% over 4600 psi) to about 3200 psi (30% below 4600 psi). The melt pressure is considered to be substantially constant as long as the melt pressure does not fluctuate more than 30% from the listed pressure.

In conjunction with the views and examples of FIGS. 1 to 4 and 6 (in the whole view, the same numbers indicate the same or corresponding elements), FIG. 1 shows an injection molding apparatus 10 for manufacturing molded plastic parts. The injection molding apparatus 10 may include an injection molding unit 12, which includes a funnel 14, a heat cylinder 16. Reciprocating screw 18 and nozzle 20. The reciprocating screw 18 may be placed in the heat barrel 16 and configured to reciprocate relative to the heat barrel 16. The power unit 22 may be operatively coupled with the reciprocating screw 18 to promote the power reciprocating movement of the reciprocating screw 18. In some embodiments, the power unit 22 may include a hydraulic motor. In some embodiments, the power unit 22 may include an electric motor controlled by an electric servo. The thermoplastic pellets 24 can be placed in the funnel 14 and fed into the heat barrel 16. After entering the heat barrel 16, the thermoplastic pellets 24 may be heated (for example, heated to between about 130° C. and about 410° C.) and melted to form the molten thermoplastic material 26. The reciprocating screw 18 can reciprocate in the heat barrel 16 to drive the molten thermoplastic material 26 into the nozzle 20. In an alternative embodiment, the injection molding unit may be a plunger-type system having a plunger (not shown) disposed in a thermal cylinder (eg, 16) and configured to move linearly relative to the thermal cylinder.

The nozzle 20 may be associated with a mold 28 having first and second mold portions 30, 32 that cooperate to form a mold cavity 34. The clamping unit 36 can support the mold 28 and can be configured to move the first and second mold parts 30, 32 between a clamping position (not shown) and a release position (Figure 1). When the first and second mold parts 30 and 32 are at the clamping positions, the molten thermoplastic material 26 can be supplied from the nozzle 20 to the gate 38 defined by the first mold part 30 and located in the cavity 34. When the cavity 34 is filled, the molten thermoplastic material 26 may be in the form of the cavity 34. When the cavity 34 is sufficiently filled, the reciprocating screw 18 can be stopped and the molten thermoplastic material 26 is allowed to cool in the mold 28. After the molten thermoplastic material 26 is cooled and solidified, or at least partially solidified, the first and second mold parts 30, 32 can be moved to their released positions so that the molded part is removed from the mold 28. In one embodiment, the mold 28 may include a plurality of mold cavities (eg, 34) to increase overall productivity.

The clamping unit 36 can apply a clamping force in the range of about 1000 P.S.I. to about 6000 P.S.I. during the molding process to keep the first and second mold parts 30, 32 at the clamping position Together. To support these clamping forces, in some embodiments, the mold may be formed of a material with a surface hardness of more than about 165 BHN to less than 260 BHN, but a material with a surface hardness of BHN exceeding 260 can be used, as long as the material can be easily processed , Discussed further below. In some embodiments, the mold 28 may be a 101-type or 102-type injection mold (eg, "ultra-high-yield mold").

The injection molding apparatus 10 may include a control system 40 that performs signal communication with various components of the injection molding apparatus 10. The control system 40 may be in signal communication with a melt pressure sensor 42 located in the nozzle 20, at or near the nozzle 20, and with a cavity pressure sensor 43 located near the end of the cavity 34.

The melt pressure sensor 42 may facilitate (directly or indirectly) the detection of the actual melt pressure (eg, measured melt pressure) of the molten thermoplastic material 26 located in, at or near the nozzle 20. The melt pressure sensor 42 may or may not be in direct contact with the molten thermoplastic material 26. In one embodiment, the melt pressure sensor 42 may be a pressure transducer, which responds to the melt pressure at the nozzle 20 to transmit an electrical signal to the input of the control system 40. In other embodiments, the melt pressure sensor 42 may facilitate monitoring of any of a variety of other or alternative characteristics of the molten thermoplastic material 26 at the nozzle 20 that may indicate melt pressure, such as temperature, viscosity, and/or flow rate. If the melt pressure sensor 42 is not located in the nozzle 20, logic, commands, and/or executable program instructions can be used to set, configure, and/or program the control system 40 to provide appropriate correction factors to evaluate or calculate the nozzle 20 The value of the measured feature. It should be understood that sensors other than melt pressure sensors can be used to measure any other characteristics of the molten thermoplastic material 26, screw 18, barrel, or the like known in the art, such as temperature, viscosity, Flow rate, strain, velocity, etc., or any other characteristic or characteristics indicative of any of these characteristics.

The cavity pressure sensor 43 can facilitate (directly or indirectly) the detection of the nozzle 20, the nozzle The melt pressure of the molten thermoplastic material 26 at or near the nozzle 20. The pocket pressure sensor 43 may or may not be in direct contact with the molten thermoplastic material 26. In one embodiment, the cavity pressure sensor 43 may be a pressure transducer, which transmits an electrical signal to the input end of the control system 40 in response to the cavity pressure in the mold cavity 34. In other embodiments, the pocket pressure sensor 43 can facilitate monitoring of any of a variety of other or alternative features of the thermoplastic material 26 or mold 28 that can indicate pocket pressure, such as, for example, the strain of the molten thermoplastic material 26 and/ Or flow rate. In one of these embodiments, the cavity pressure sensor 43 may be a strain gauge. If the cavity pressure sensor 43 is not located in the cavity 34, logic, commands, and/or executable program instructions can be used to set, configure, and/or program the control system 40 to provide appropriate correction factors to evaluate or calculate the mold The value of 28 measured characteristics.

The control system 40 can also be in signal communication with the screw control part 44. In one embodiment, when the power unit 22 is a hydraulic motor, the screw control member 44 may include a hydraulic valve associated with the reciprocating screw 18. In one embodiment, when the power unit 22 is an electric motor, the screw control member 44 may include an electric controller associated with the reciprocating screw 18. In the embodiment of FIG. 1, the control system 40 can generate a signal, and the signal is transmitted from the output end of the control system 40 to the screw control member 44. The control system 40 can control the injection pressure in the injection molding apparatus 10 by controlling the screw control element 44, and the screw control element 44 controls the injection rate by the injection molding unit 12. The control system 40 may command the screw control 44 to advance the reciprocating screw 18 at a rate that maintains the desired melt pressure of the molten thermoplastic material 26 in the nozzle 20.

This signal from the control system 40 to the screw control part 44 can be generally used to control the molding process, so that changes in material viscosity, mold temperature, melt temperature and other changes affecting the filling rate are taken into consideration by the control system 40. Adjustments can be made by the control system 40 immediately during the molding cycle, or corrections can be made in subsequent cycles. In addition, several signals from multiple cycles can be used as The basis for the control system 40 to adjust the molding process. The control system 40 can be connected to the melt pressure sensor 42 and/or the pocket pressure sensor 43 and/or the screw control member 44 via any type of signal communication known in the art.

Referring now to FIG. 2, the control system 40 can include a PID controller 46 and a data storage area 48. The PID controller 46 may be a feedback controller that facilitates the control of the melt pressure of the injection molding unit 12 (eg, at the nozzle 20) to a set point that represents the desired melt pressure of the injection molding unit. As shown in the exemplary feedback block diagram of the PID controller 46 in FIG. 3, a set point P may be provided as a signal S1, which is compared with a signal S2 from the melt pressure sensor 42 indicating the actual melt pressure. An error signal E is generated and provided to the PID control algorithm G, which generates a control signal C that commands the screw control 44 to advance the reciprocating screw toward the rate at which the melt pressure converges as indicated by the set point P 18.

During the molding cycle, the melt pressure of the injection molding unit 12 can be changed by providing the PID controller 46 with different set points. In one embodiment, the different set points provided to the PID controller 46 may correspond to different phases of the molding cycle. For example, to initiate the initial injection phase, PID controller 46 may be provided with a set point that causes the melt pressure to increase enough to cause thermoplastic pellets 24 to begin to melt and distribute the melt to nozzle 20. When the melt pressure is increased enough to start filling the cavity 34, the PID controller 46 can be provided with a set point that initiates the filling phase at a pressure suitable for filling the cavity 34 properly. When the cavity 34 is almost filled (e.g., the filling is complete), the PID controller 46 may be provided with a set point to be reduced enough to initiate the packaging phase and maintain a substantially constant melt pressure during the storage phase.

The PID controller 46 may be provided with a plurality of set points to facilitate effective control of the melt pressure of the injection molding unit 12 during each molding cycle. The specific set point provided to the PID controller 46 can be selected to enhance the performance of the molten thermoplastic material 26 throughout each molding cycle and can be visually manufactured Depending on the specific molded part. The set point for the molded part can be determined through empirical analysis and/or theoretical analysis. The set point can be provided by any of a variety of sources. In one embodiment, as shown in FIG. 2, a plurality of set points can be provided by the data storage area 48 on the control system 40 board. In other embodiments, multiple set points may be provided by remote sources, such as the Internet or cloud-based storage devices.

The PID controller 46 can establish the melt pressure curve 50 from a plurality of set points provided to the PID controller 46 (FIG. 2). In one embodiment, the PID controller 46 may establish the melt pressure curve 50 by substantially linearly interpolating the desired melt pressure value between each of the set points. An example of such a melt pressure curve is shown in FIG. 4. In this example, the melt pressure curve 50 is represented as a graph depicting a variety of different set points P0 to P5 over time. Each of the set points P0 to P5 can be separated from the other set points P0 to P5 by the corresponding time period T1 to T5. The melt pressure curve 50 is shown to extend substantially linearly between the set points P0 to P5.

Still referring to FIG. 4, the PID controller 46 may be configured to sample the pressure curve 50 at different time intervals (shown as vertical hash marks) to facilitate control of the melt pressure of the injection molding unit 12. In particular, the PID controller 46 can control the melt pressure of the injection molding unit 12 at each time interval based on the desired melt pressure defined by the melt pressure curve 50 at the time interval. In one embodiment, the PID controller 46 may compare the melt pressure value at the time interval with the current actual melt pressure of the injection molding unit 12 (eg, from the melt pressure sensor 42). If there is a deviation between the actual melt pressure and the desired melt pressure, the PID controller 46 can adjust the actual melt pressure of the injection molding unit 12 (for example, by controlling the advance rate of the reciprocating screw 18) to make the actual melt The body pressure converges toward the desired melt pressure. For example, if the actual melt pressure of the injection molding unit 12 exceeds the desired melt pressure at a predetermined time interval, the PID controller 46 can control the operation of the reciprocating screw 18 to reduce the actual melt pressure. pressure. If the actual melt pressure of the injection molding unit 12 is less than the desired melt pressure at a predetermined time interval, the PID controller 46 can control the operation of the reciprocating screw 18 to increase the actual melt pressure. The PID controller 46 may maintain the melt pressure to converge toward the desired melt pressure until the pressure curve 50 is sampled at the next time interval. It should be understood that although the time periods T1 to T5 are shown to be between about 5 mS and 20 mS, the set point can have any suitable duration. It should also be understood that although the melt pressure curve is shown to take samples every approximately 1 mS, any of a variety of different sampling rates can be used.

The melt pressure curve 50 is shown to rise substantially linearly between the set points P0 and P1 and remains substantially horizontal between the set points P1 and P2. The melt pressure curve 50 is shown to decrease substantially linearly between the set points P2 and P3 and remains substantially horizontal between the set points P3 and P4. The melt pressure curve 50 further shows a substantially linear decrease between the set points P4 and P5. For the rising or falling part of the melt pressure curve 50 (for example, P0 to P1, P2 to P3, or P4 to P5) (for example, immediately adjacent to the set point), at each time interval located at the set point and between the set points The desired melt pressure below is different from the desired melt pressure at each of the immediately adjacent time intervals between the set points (see, for example, time intervals V1 and V2). For example, for the set points P2 and P3, the desired melt pressure at each time interval between the set points P2 and P3 and the set points P2 and P3 and the immediate time interval between the set points ( For example, the expected melt pressure is different under each of the time intervals between P2 and P3.

For the portion of the melt pressure curve 50 that remains substantially horizontal between set points (e.g., P1 and P2 and P3 and P4) (e.g., immediately adjacent to the set point), the expected melt pressure at each time interval and the The expected melt pressures at the immediate time intervals between their set points (eg, P1 and P2 and P3 and P4) are substantially the same. For example, for the set points P1 and P2, the expectations at the time intervals between the set points P1 and P2 and between the set points P1 and P2 The melt pressure is substantially the same as the desired melt pressure at the immediate interval between their set points. For set points P3 and P4, the expected melt pressure at each time interval located at the set points P3 and P4 and between the set points P3 and P4 and the immediate time interval between their set points (Figure 4 The above is the time interval V3 and the time interval V4 respectively) The expected melt pressures are substantially the same. It should be understood that although the melt pressure curve 50 has been described as sampling the melt pressure curve 50 at each time interval between all set points, any combination of time intervals can still be sampled between each of the set points, such as only Some of the set points or various consecutive time intervals between set points. It should also be understood that time intervals can be separated by substantially the same amount of time or different amounts of time.

By sampling the slope of the melt pressure curve 50 between the set points (for example, between P0 and P1, between P2 and P3, and between P4 and P5), the PID controller 46 can gradually change the injection mold The actual melt pressure of the control unit 12 is controlled so that it closely follows the melt pressure curve 50. An exemplary graph of actual melt pressure is shown as a dashed line on FIG. 4. Therefore, compared with the conventional injection molding unit, the actual melt pressure of the injection molding unit 12 can be less sensitive to sudden increase/undershoot, which can promote the consistency, repeatability and quality of the molded parts. It should be understood that the melt pressure curve 50 can be implemented in the control system 40 as a data table with the expected melt pressure specified for each time interval. During operation, the control system 40 can look up the desired pressure for the current time interval and can accordingly generate commands to control the actual melt pressure. It should also be understood that any of a variety of suitable algorithms can be used to calculate the melt curve (e.g., in real time). In one example, the algorithm may be a curve fitting algorithm, such as linear interpolation, polynomial curve, simple fitting curve, geometric fitting curve, or any other curve fitting method known in the art. In other examples, any other suitable algorithm can be used to calculate the melt pressure curve.

The conventional controller can establish a melt pressure curve by providing multiple set points to the conventional controller 60, as shown in Figure 5. The melt pressure curve 60 is represented as a graph depicting a stepwise definition of multiple different set points Pa1 to Pa4 over time. Each of the set points Pa1 to Pa4 can be separated from the other set points by time. The melt pressure curve 60 is shown to be composed of a first horizontal portion 62, a second horizontal portion 64, a third horizontal portion 66, a fourth horizontal portion 68, and a first vertical portion 63, a second vertical portion 65 and a third vertical portion 67 . The first vertical portion 63 may extend between the first horizontal portion 62 and the second horizontal portion 64. The second vertical portion 65 may extend between the second horizontal portion 64 and the third horizontal portion 66. The third vertical portion 67 may extend between the third horizontal portion 66 and the fourth horizontal portion 68. Each of the first vertical portion 63, the second vertical portion 65, and the third vertical portion 67 indicates the position at which a large change in melt pressure is expected (for example, almost immediately within the duration of a time interval). This large change can cause the conventional controller to try to reach the desired melt pressure as quickly as possible, thereby causing a sudden increase and/or undershoot of the actual melt pressure relative to the desired melt pressure. An exemplary graph of actual melt pressure is shown as a dashed line on FIG. 5. The sudden increase and undershoot are displayed at 70 and 72 respectively.

An alternative embodiment of the melt pressure curve 150 is shown in FIG. 6. The melt pressure curve 150 may be similar to the melt pressure curve 50 shown in FIG. 4. However, the melt pressure curve can have more set points (P0 to P18). The interpolation between each of their set points may be curvilinear and non-linear, making the melt pressure curve substantially curvilinear. It should be understood that any of a variety of different melt pressure curves can be used to achieve the specific performance of the injection molding unit 12.

It should also be understood that the PID controller 46 can be implemented in hardware, software, or any combination of the two. It should also be understood that the control system 40 can be any control configuration with one or more controllers that implement actual melt pressure control. In addition, the control system 40 may include other controllers, such as the main controller 52, which may perform other functions for the injection molding equipment.

The foregoing descriptions of the embodiments and examples are presented for the purposes of illustration and description. It's not It is intended to be exhaustive or restrict the form. According to the above teaching, many modifications can be made. Some of their modifications have been discussed and others will be understood by those familiar with the technology. The embodiments are selected and described to illustrate various embodiments. Of course, the scope is not limited to the examples or embodiments described herein, but it can be used in a variety of applications and equivalent devices by those skilled in the art. To be precise, therefore, the category is intended to be defined by the scope of the patent application attached here. In addition, for any method claimed and/or described, whether or not the method is described in conjunction with a flowchart, it should be understood that unless the context otherwise dictates or requires, any clear steps in the execution of the method Neither implied ordering implies that these steps must be performed in the order shown and can be performed in a different order or simultaneously.

The dimensions and values disclosed herein should not be construed as strictly limited to the precise values stated. In fact, unless otherwise stated, each of the dimensions is intended to mean both the stated value and the functionally equivalent range surrounding the stated value. For example, the size disclosed as "40mm" is intended to mean "about 40mm".

Unless expressly excluded or otherwise restricted, each document cited in this article, including any cross-references or related patents or applications, and any patent applications or patents for which this application claims priority or rights, shall be in full The way of reference is incorporated into this article. The citation of any document does not admit that it is the prior art of any invention disclosed or claimed herein or that it alone or in combination with any other references teaches, shows or discloses any such invention. In addition, if any meaning or definition of a term in this document contradicts 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 present invention have been illustrated and described, it will be obvious to those skilled in the art that various other changes can be made without departing from the spirit and scope of the present invention And modify. Therefore, it is intended to cover all such changes and modifications within the scope of the present invention in the scope of the attached patent application.

10‧‧‧Injection molding equipment

12‧‧‧Injection molding unit

14‧‧‧Funnel

16‧‧‧Hot barrel

18‧‧‧Reciprocating screw

20‧‧‧Nozzle

22‧‧‧Power Unit

24‧‧‧Thermoplastic pellets

26‧‧‧Melted thermoplastic material

28‧‧‧Mould

30‧‧‧The first mold part

32‧‧‧Second mold part

34‧‧‧Mould cavity

36‧‧‧Clamping unit

38‧‧‧Gate

40‧‧‧Control System

42‧‧‧Melt pressure sensor

43‧‧‧Cavity pressure sensor

44‧‧‧Screw Control Parts

Claims (21)

A method for controlling the melt pressure of an injection molding equipment, the method comprising: receiving a melt pressure curve, the melt pressure curve including a plurality of set points, each of the plurality of set points is defined on a time limit point The desired melt pressure of the injection molding equipment, wherein (i) each of the plurality of set points is separated from at least one other set point of the plurality of set points for a period of time, which defines at least one injection molding process A portion of the time period during which the thermoplastic material is injected into the mold cavity; and (ii) the pressure curve includes each of the plurality of set points; for at least two adjacent set points Use a curve fitting algorithm to define the desired melt pressure value of the injection molding equipment between the at least two adjacent set points; at each of the plurality of set points Time-defined point, via a PID controller according to the desired melt pressure value at each of the plurality of set points to control the injection molding equipment; and between the at least two adjacent set points or In a plurality of intervals, the injection molding equipment is controlled by a PID controller according to the desired melt pressure value defined by the curve fitting algorithm used in the interval, wherein one of the at least two adjacent set points is the first A first desired melt pressure of a set point is different from a second desired melt pressure of one of the at least two adjacent set points, and the first and second set points are adjacent. The method of claim 1, wherein for the at least two adjacent set points, the curve fitting algorithm is substantially the same as the curve fitting algorithm used for at least two other adjacent set points. The method of claim 1, wherein the curve fitting algorithm is a linear interpolation method. The method of claim 1, wherein the curve fitting algorithm is a curve interpolation method. As in the method of claim 1, wherein at least two immediately adjacent set points are separated by about 10 milliseconds. The method of claim 5, wherein each or more intervals between the at least two adjacent set points are separated by about one millisecond. The method of claim 1, wherein controlling the injection molding device via the PID controller based on the desired melt pressure further includes: receiving, at the PID controller, an actual melt pressure value from a pressure sensor, The pressure sensor is associated with the thermal barrel of the injection molding equipment and is configured to measure the melt pressure of the thermal barrel; the measured melt pressure of the thermal barrel is compared with the The expected melt pressure in each of the one or more time intervals is compared by the PID controller; and if the measured melt pressure is different from that in each of the one or more time intervals If there is a deviation between the expected melt pressure under one of them, the operation of the injection molding equipment is adjusted so that the measured melt pressure converges toward the expected melt pressure. The method of claim 7, wherein adjusting the operation of the injection molding equipment includes controlling a reciprocating screw disposed inside the heat barrel. The method of claim 8, wherein controlling the reciprocating screw includes controlling a hydraulic valve associated with the reciprocating screw. The method of claim 7, wherein adjusting the operation of the injection molding equipment includes controlling a plunger disposed inside the heat barrel. The method of claim 1, wherein one or more intervals between the at least two adjacent set points are a plurality of intervals between the at least two adjacent set points, and between the at least two adjacent set points The desired melt pressure of one of the first intervals of the plurality of intervals between adjacent set points and the second interval of one of the plurality of intervals between the at least two adjacent set points It is desired that the melt pressure is different, wherein the first interval is immediately adjacent to the second interval. An injection molding equipment, comprising: a heat barrel; a reciprocating screw, which is arranged in the heat barrel and configured to reciprocate relative to the heat barrel; a power unit, which is operable with the reciprocating The screw is coupled and configured to promote the reciprocating movement of the reciprocating screw relative to the hot barrel; a clamping unit for the mold, the clamping unit is associated with the hot barrel; a nozzle, which is arranged on the One end of the heat cylinder and is configured to move the inside of the heat cylinder The contents are distributed to the clamping unit; a control system that communicates with the power unit and is configured to facilitate the operation of the reciprocating screw via a PID controller, the control system having a melt stored thereon The melt pressure curve includes a plurality of set points, each of the plurality of set points defines the desired melt pressure of the injection molding equipment at a defined point in time, (i) the plurality of set points The set points are each separated from at least one other set point of the plurality of set points for a period of time that defines at least a portion of the injection molding process during which the thermoplastic material is injected into the mold cavity, and (ii) The pressure curve includes each set point of the plurality of set points, and the control system is configured to: align the melt pressure curve at one or more time intervals between the set points Take a sample; for one or more intervals between at least two adjacent set points, use a curve fitting algorithm to define the desired melt pressure of the injection molding equipment between the at least two adjacent set points Value; at each of the plurality of set points of the time defined point, the injection molding equipment is controlled according to the desired melt pressure value at each of the plurality of set points; and in the at least two phases In one or more intervals between adjacent set points, the injection molding equipment is controlled according to the desired melt pressure value defined by the curve fitting algorithm used in the interval, wherein the at least two adjacent set points One of the first set points and one of the first desired melt pressures is different from one of the second set points of the at least two adjacent set points and one of the second desired melt pressures, the first and second set points being Adjacent. The injection molding equipment of claim 12, which further includes a melt pressure sensor communicatively coupled with the control system, the melt pressure sensor being configured to detect the actual measurement of the thermal cylinder Melt pressure, wherein at each of the one or more time intervals, the control system is further configured to: compare the measured melt pressure of the hot barrel to the desired melt pressure Compare; and if there is a deviation between the measured melt pressure and the desired melt pressure, adjust the operation of the injection molding equipment so that the measured melt pressure converges toward the desired melt pressure. The injection molding apparatus of claim 12, wherein the control system includes a data storage area for storing a plurality of set points of the melt pressure curve thereon. The injection molding apparatus of claim 12, which further includes a mold disposed in the clamping unit. The injection molding apparatus of claim 12, wherein the power unit is a hydraulic system. The injection molding apparatus of claim 16, wherein the hydraulic system includes a hydraulic valve. The injection molding apparatus of claim 12, wherein the power unit is an electric system. The injection molding apparatus of claim 18, wherein the electrical system includes an electrical server. The injection molding apparatus of claim 12, wherein the curve fitting algorithm is a linear interpolation method. The injection molding apparatus of claim 12, wherein the one or more time intervals between the at least two adjacent set points are a plurality of time intervals between the at least two adjacent set points , And between the desired melt pressure at one of the first intervals between the at least two adjacent set points and the plurality of time intervals between the at least two adjacent set points The desired melt pressure is different for a second interval, wherein the first interval is immediately adjacent to the second interval.

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