Injection molding control device

Abstract

Provided is an injection molding control device that controls an injection molding machine having a pressurizing member which pressurizes a molten resin in a cavity formed between a plurality of molds, a pressurization drive mechanism which moves the pressurizing member, and a pressure detector which detects a pressure of the molten resin, said injection molding control device comprising: a pressure setting unit that sets a set value of the pressure of the molten resin; a pressure control unit that controls an operation of the pressurization drive mechanism so as to bring a detection value of the pressure detector closer to the set value by the pressure setting unit; and a movement adjustment unit that performs movement adjustment control for adjusting the operation of the pressurization drive mechanism such that a frictional force generated by movement of the pressurizing member acts in a direction to increase the pressure of the molten resin.

Description

Injection molding control device

[0001] The present disclosure relates to an injection molding control device.

[0002] In an injection molding machine, pressure holding control can be performed to pressurize the molten resin in the cavity to a constant pressure and compensate for the shrinkage when the resin hardens. As a typical example, a configuration that holds the pressure of the molten resin by adjusting the position of the screw can be adopted (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 11-70553

[0004] For pressure holding, it is necessary to pressurize the molten resin by moving a pressurizing member such as a screw toward the cavity in accordance with the shrinkage accompanying the cooling of the molten resin in the cavity. Usually, the pressure of the molten resin is maintained at about 50 MPa to 100 MPa by pressure holding control. Therefore, the mechanism for moving the pressurizing member for pressure holding consumes a lot of energy. Thus, a technique capable of reducing the energy consumption for pressure holding is desired.

[0005] An injection molding control device according to an aspect of the present disclosure is an injection molding control device that controls an injection molding machine having a pressurizing member that pressurizes molten resin in a cavity formed between a plurality of molds, a pressurizing drive mechanism that moves the pressurizing member, and a pressure detector that detects the pressure of the molten resin, and includes a pressure setting unit that sets a set value of the pressure of the molten resin, a pressure control unit that controls the operation of the pressurizing drive mechanism so that a detection value of the pressure detector approaches the set value of the pressure setting unit, and a movement adjustment unit that performs movement adjustment control to adjust the operation of the pressurizing drive mechanism so that a frictional force generated by the movement of the pressurizing member acts in a direction to increase the pressure of the molten resin.

[0006] It is a schematic diagram showing the configuration of an injection molding machine provided with an injection molding control device according to an embodiment of the present disclosure. It is a graph showing an example of a change in the target pressure in the injection molding control device of FIG. 1. It is a graph showing an example different from FIG. 2 of the change in the target pressure in the injection molding control device of FIG. 1. It is a graph showing an example different from FIGS. 2 and 3 of the change in the target pressure in the injection molding control device of FIG. 1. It is a graph showing an example different from FIGS. 2 to 4 of the change in the target pressure in the injection molding control device of FIG. 1.

[0007] Embodiments of the present disclosure will be described below with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of an injection molding machine 1 equipped with an injection molding control device 30 according to one embodiment of the present disclosure. The injection molding machine 1 comprises an injection device 10, a mold clamping device 20, and an injection molding control device 30. The injection molding machine 1 is a device that injects molten resin R into a cavity C formed between a fixed mold M1 and a movable mold M2, and obtains a molded product in which the molten resin R has hardened in the cavity C.

[0008] The injection device 10 comprises a barrel 11, a screw 12 housed within the barrel 11, a screw rotation mechanism 13 for rotating the screw 12, and a screw movement mechanism 14 for moving the screw 12 in the axial direction. The screw 12 can also be used as a pressurizing member to pressurize the molten resin R in the cavity C during the so-called holding pressure process, and the screw movement mechanism 14 can also be used as a pressurizing drive mechanism to move the pressurizing member during the holding pressure process. Since such injection devices 10 are well known, a detailed explanation will be omitted.

[0009] The clamping device 20 includes a fixed platen 21 for holding the fixed mold M1, a movable platen 22 for holding the movable mold M2, a mold moving mechanism 23 for moving the movable platen 22, and a pressure detector 24 for detecting the pressure of the molten resin R in the cavity C (actually, the pressure in the flow path which can be considered equivalent to the pressure in the cavity C). Since such a clamping device 20 and molds M1 and M2 are well known, a detailed explanation will be omitted.

[0010] The injection molding control device 30 controls the injection device 10 and the clamping device 20. The injection molding control device 30 may be composed of one or more computer devices that have, for example, memory, a processor, an input / output interface, etc., and execute an appropriate control program. The injection molding control device 30 includes a pressure setting unit 31, a pressure control unit 32, and a movement adjustment unit 33. These components of the injection molding control device 30 are classifications of the functions of the injection molding control device 30 and do not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration.

[0011] The pressure setting unit 31 sets the pressure value of the molten resin R. The pressure setting unit 31 may determine the pressure value based on information described in the processing program, determine the pressure value according to user input, or determine the pressure value by referring to a database.

[0012] The pressure control unit 32 performs holding pressure control, which controls the operation of the pressurizing drive mechanism 14 so that the value detected by the pressure detector 24 approaches the set value of the pressure setting unit 31. The pressure control unit 32 may be configured to perform well-known feedback control. Specifically, the pressure control unit 32 moves the pressurizing member 12 toward the cavity C in order to compensate for the pressure drop due to the shrinkage of the molten resin R in the cavity C as it cools.

[0013] The movement adjustment unit 33 performs movement adjustment control to adjust the operation of the pressurizing drive mechanism 14 so that the frictional force generated by the movement of the pressurizing member 12 (frictional force acting on the pressurizing member 12) acts in a direction that increases the pressure of the molten resin R in the cavity C. As a result, the frictional force can be used as part of the force pressing the molten resin R for holding pressure, and the load (power consumption) of the pressurizing drive mechanism 14 can be reduced by the amount of the frictional force. The movement adjustment unit 33 may be configured to perform movement adjustment control after a predetermined adjustment waiting time has elapsed, after the start of holding pressure control by the pressure control unit 32, which is considered to be the time when the pressure of the molten resin R is expected to stabilize at the target pressure. This ensures that the direction of the frictional force acts in a direction that increases the pressure of the molten resin R.

[0014] The movement adjustment control by the movement adjustment unit 33 may be a control that reduces the target pressure of the pressure control unit 32 by a predetermined friction equivalent pressure. The friction equivalent pressure can be set to a value calculated in advance by experimental operation, for example. In this case, as shown in Figure 2, the target pressure of the molten resin R is first set to the injection pressure when injecting the molten resin R into the empty cavity C, then, when the system moves to holding pressure control, it is set to the set pressure set in the pressure setting unit 31, and further, after the adjustment waiting time has elapsed since the transition to holding pressure control, the pressure can be changed by the movement adjustment control to a pressure reduced by the friction equivalent pressure from the set pressure. The amount of movement adjustment (the amount of drive of the pressurizing drive mechanism 14) in response to this pressure change varies depending on the resin and molding conditions. It is preferable to reduce the target value by the friction equivalent pressure gradually, for example, by changing it in a ramp shape as shown in the figure, so that hunting does not occur due to the movement adjustment control. If the movement adjustment control only provides an offset to the target pressure, the holding pressure control by the pressure control unit 32 is not stopped, so that the quality of injection molding is not adversely affected.

[0015] Furthermore, the movement adjustment control by the movement adjustment unit 33 may be a control that subtracts a predetermined amount of frictional force equivalent speed from the speed command value output by the pressure control unit 32 to the pressurizing drive mechanism 14. The frictional force equivalent speed may also be set to a value calculated in advance by experimental operation, for example. The subtraction of the frictional force equivalent speed from the speed command value may also be performed so as to provide an offset after the adjustment waiting time has elapsed.

[0016] Even if the frictional force is applied to pressurize the molten resin R by the movement adjustment control, as time passes, the pressure control unit 32 controls the contraction of the molten resin R, causing the frictional force to act in the opposite direction to the force applied by the pressurizing member 12 to the molten resin R. For this reason, the movement adjustment unit 33 may repeatedly perform the movement adjustment control at predetermined intervals, as illustrated in Figure 3, so that the frictional force acts again in the direction of pressurizing the molten resin R. Furthermore, as illustrated in Figure 4, the movement adjustment unit 33 may perform compensation control to compensate for the movement of the pressurizing member 12 caused by the previous movement adjustment control before performing the movement adjustment control. Specifically, if the target pressure is reduced in the previous movement adjustment control, the target pressure can be temporarily set to the value before the movement adjustment control, and then the target pressure can be reduced again after the pressure has increased, thereby preventing the pressure of the molten resin R from deviating from the set value of the pressure setting unit 31.

[0017] Furthermore, as shown in Figure 5, the movement adjustment unit 33 may perform movement adjustment control when the torque of the pressurizing drive mechanism 14 increases. After some time has passed since the movement adjustment control, a frictional force will act in the opposite direction to the force with which the pressurizing member 12 pressurizes the molten resin R, so the torque of the drive mechanism required to maintain the pressure of the molten resin R will increase. Therefore, it is possible to detect that the direction of the frictional force due to the torque of the pressurizing drive mechanism 14 has become such that it acts as a load on the drive mechanism. Accordingly, by performing movement adjustment control to reapply a frictional force in the direction of pressurizing the molten resin R when the torque of the pressurizing drive mechanism 14 increases above a predetermined standard, the time during which the effect of reducing energy consumption due to frictional force can be obtained can be maximized.

[0018] In the injection molding machine 1 controlled by the injection molding control device 30 having the above configuration, during the holding pressure process, the pressurizing member 12 that pressurizes the molten resin R in the cavity C is temporarily retracted, thereby causing the frictional force acting on the pressurizing member 12 to act in the direction of pressurizing the molten resin R. As a result, the energy consumption for holding pressure by the pressurizing drive mechanism 14 in the injection molding machine 1 is reduced.

[0019] The following additional information is disclosed regarding the above embodiments and modifications. (Addendum 1) The injection molding control device (30) controls an injection molding machine (1) having a pressurizing member (12) for pressurizing molten resin (R) in a cavity (C) formed between a plurality of molds (M1, M2), a pressurizing drive mechanism (14) for moving the pressurizing member (12), and a pressure detector (24) for detecting the pressure of the molten resin (R). The control device (30) includes a pressure setting unit (31) for setting a set value for the pressure of the molten resin (R), a pressure control unit (32) for controlling the operation of the pressurizing drive mechanism (14) so ​​as to bring the detected value of the pressure detector (24) closer to the set value of the pressure setting unit (31), and a movement adjustment unit (33) for performing movement adjustment control to adjust the operation of the pressurizing drive mechanism (14) so ​​as to adjust the frictional force generated by the movement of the pressurizing member (12) in a direction that increases the pressure of the molten resin (R).

[0020] (Note 2) In the injection molding control device (30) of Note 1, the movement adjustment control may be a control that reduces the target pressure of the pressure control unit (32) by a predetermined friction equivalent pressure.

[0021] (Note 3) In the injection molding control device (30) of Note 1, the movement adjustment control may be a control that subtracts a predetermined friction force equivalent speed from the speed command value output by the pressure control unit (32) to the pressurizing drive mechanism (14).

[0022] (Note 4) In the injection molding control device (30) of Notes 1 to 3, the movement adjustment unit (33) may repeatedly perform movement adjustment control at predetermined intervals.

[0023] (Note 5) In the injection molding control device (30) of Note 4, the movement adjustment unit (33) may perform compensation control to compensate for the movement of the pressurizing member (12) caused by the preceding movement adjustment control before performing movement adjustment control.

[0024] (Note 6) In the injection molding control device (30) of Notes 1 to 3, the movement adjustment unit (33) may perform movement adjustment control when the torque of the pressurizing drive mechanism (14) increases.

[0025] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the spirit of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0026] For example, the position of the pressure detector is arbitrary and may be provided on the injection device. Furthermore, the movable member is not limited to a screw; based on well-known technology, a movable mold, ejector plate, etc., can be used, and in this case, the moving mechanism may be a clamping mechanism, an ejector moving mechanism, etc.

[0027] 1 Injection molding machine 10 Injection device 11 Barrel 12 Screw (pressure member) 13 Screw rotation mechanism 14 Screw movement mechanism (pressure drive mechanism) 20 Clamping device 21 Fixed platen 22 Movable platen 23 Mold movement mechanism 24 Pressure detector 30 Injection molding control device 31 Pressure setting unit 32 Pressure control unit 33 Movement adjustment unit C Cavity M1 Fixed mold M2 Movable mold R Molten resin

Claims

1. An injection molding control device for controlling an injection molding machine having a pressurizing member for pressurizing molten resin in a cavity formed between a plurality of molds, a pressurizing drive mechanism for moving the pressurizing member, and a pressure detector for detecting the pressure of the molten resin, comprising: a pressure setting unit for setting a set value for the pressure of the molten resin; a pressure control unit for controlling the operation of the pressurizing drive mechanism so that the value detected by the pressure detector approaches the set value of the pressure setting unit; and a movement adjustment unit for performing movement adjustment control to adjust the operation of the pressurizing drive mechanism so that the frictional force generated by the movement of the pressurizing member acts in a direction that increases the pressure of the molten resin.

2. The injection molding control device according to claim 1, wherein the movement adjustment control is a control that reduces the target pressure of the pressure control unit by a predetermined friction equivalent pressure.

3. The injection molding control device according to claim 1, wherein the movement adjustment control is a control that subtracts a predetermined frictional force equivalent speed from the speed command value output by the pressure control unit to the pressurizing drive mechanism.

4. The injection molding control device according to any one of claims 1 to 3, wherein the movement adjustment unit repeatedly performs the movement adjustment control at predetermined intervals.

5. The injection molding control device according to claim 4, wherein the movement adjustment unit performs compensation control to compensate for the movement of the pressurizing member caused by the preceding movement adjustment control before performing the movement adjustment control.

6. The injection molding control device according to any one of claims 1 to 3, wherein the movement adjustment unit performs the movement adjustment control when the torque of the pressurizing drive mechanism increases.

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