Injection molding machine, control method and computer program

Abstract

To provide an injection molding machine capable of extending a life of a ball screw by preventing deterioration of lubricity and deviation of heat generating parts even under molding conditions of a short injection stroke.SOLUTION: An injection molding machine includes: a screw that is provided so as to be drivable in a rotational direction and an axial direction in a cylinder having a nozzle at a tip; a drive device that drives the screw; and a control device that controls an operation of the drive device. The drive device includes: a ball screw shaft provided rotatably; a nut that is screwed onto the ball screw shaft and moves back and forth as the ball screw shaft rotates; and a ball screw that drives the screw in the axial direction by moving the nut back and forth. The control device sequentially moves a screw position before and after injection in a molding process cycle so that a range of the nut's advance and retreat movement in the molding process cycle is distributed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an injection molding machine, a control method, and a computer program. [Background technology]

[0002] An injection molding machine includes an injection device that melts and injects molding material, and a mold clamping device. The injection device includes a heating cylinder with a nozzle at its tip, and a screw that is arranged within the heating cylinder so as to be rotatable in the circumferential and axial directions. The screw is driven in the rotational and axial directions by a drive mechanism. The drive mechanism includes a ball screw that converts the rotational drive force of an injection servo motor into axial drive force for the screw and transmits it (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-166702 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the molding conditions, only a part of the total stroke range in which the nut can move on the ball screw shaft may be used. If the nut's movement range is concentrated in a specific range, the lubrication of the grease decreases, and the amount of heat that accumulates in the ball screw shaft becomes uneven. Such molding conditions with a short injection stroke are disadvantageous compared to molding conditions using the entire stroke range. In the long term, only a part of the ball screw shaft is likely to wear out or break, which tends to shorten the life of the ball screw.

[0005] An object of the present disclosure is to provide an injection molding machine, a control method, and a computer program that can prevent a decrease in lubrication and uneven distribution of heat generation areas, even under molding conditions with a short injection stroke, and extend the life of the ball screw. [Means for solving the problem]

[0006] An injection molding machine according to one embodiment of the present invention comprises a drive unit for driving a screw and a control unit, the drive unit having a rotatably arranged ball screw shaft and a nut, and a ball screw for driving the screw in the axial direction by the forward and backward movement of the nut, and the control unit sequentially moves the screw position before injection and the screw position after injection in a molding process cycle so that the range of forward and backward movement of the nut in the molding process cycle is dispersed.

[0007] A control method according to one embodiment of the present invention is a control method for controlling the operation of a drive unit that has a ball screw shaft and a nut and drives the screw of an injection molding machine by moving the nut back and forth, and sequentially moves the screw position before injection and the screw position after injection in a molding process cycle so that the range of forward and backward movement of the nut in a molding process cycle is dispersed.

[0008] A computer program according to one embodiment of the present invention is a computer program for causing a computer to control the operation of a drive device that has a ball screw shaft and a nut and drives the screw of an injection molding machine by moving the nut back and forth, and causes the computer to execute a process of sequentially moving the screw position before injection and the screw position after injection in a molding process cycle so that the range of forward and backward movement of the nut in a molding process cycle is dispersed. Effect of the Invention

[0009] According to the present invention, even under molding conditions of a short injection stroke, it is possible to prevent a decrease in lubrication and uneven distribution of heat generation, thereby extending the life of the ball screw. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration example of an injection molding machine according to a first embodiment. FIG. [Diagram 2]1 is a cross-sectional view showing an example of the configuration of a drive device of an injection molding machine according to a first embodiment. [Diagram 3] 4 is a flowchart showing a processing procedure of a processor according to the first embodiment. [Figure 4A] 4 is an explanatory diagram showing a state before the advance / retreat movement range is changed in the control method according to the first embodiment. FIG. [Figure 4B] 4 is an explanatory diagram showing a state before the advance / retreat movement range is changed in the control method according to the first embodiment. FIG. [Figure 5A] 10 is an explanatory diagram showing a state after the advance / retreat movement range is changed in the control method according to the first embodiment. FIG. [Figure 5B] 10 is an explanatory diagram showing a state after the advance / retreat movement range is changed in the control method according to the first embodiment. FIG. [Figure 6] 10 is a flowchart showing a processing procedure of a processor according to the second embodiment. [Figure 7] FIG. 11 is a schematic diagram showing a configuration example of an injection molding machine according to a third embodiment. [Figure 8] 11 is a flowchart showing a processing procedure of a processor according to the third embodiment. [Figure 9] 13 is a flowchart showing details of a process for changing the advance / retreat movement range. [Figure 10] 13 is a flowchart showing details of a process for changing the advance / retreat movement range. [Figure 11] FIG. 11 is a schematic diagram showing an example of a status display screen according to the third embodiment. [Figure 12] FIG. 13 is a block diagram showing an example of the configuration of a control device according to a fourth embodiment. [Figure 13] 13 is a flowchart showing a processing procedure of a processor according to the fourth embodiment. [Figure 14] FIG. 13 is a block diagram showing an adjustment learning model according to the fifth embodiment. [Figure 15] 13 is a flowchart showing a processing procedure of a processor according to the fifth embodiment. [Figure 16] 13 is a flowchart showing a processing procedure of a processor according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Specific examples of an injection molding machine, a control method, and a computer program according to embodiments of the present invention will be described below with reference to the drawings. At least some of the embodiments described below may be combined in any manner. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0012] 1 is a schematic diagram showing a configuration example of an injection molding machine 1 according to embodiment 1. The injection molding machine 1 according to embodiment 1 includes a clamping device 2 that clamps a mold 21, an injection device 3 that melts and injects a molding material, and a control device 4.

[0013] The mold clamping device 2 includes a fixed platen 22 fixed on a bed 20, a mold clamping housing 23 slidably provided on the bed 20, and a movable platen 24 that similarly slides on the bed 20. The fixed platen 22 and the mold clamping housing 23 are connected by a plurality of, for example, four tie bars 25, 25, .... The movable platen 24 is configured to be slidable between the fixed platen 22 and the mold clamping housing 23. A mold clamping mechanism 26 is provided between the mold clamping housing 23 and the movable platen 24. The mold clamping mechanism 26 is configured, for example, by a toggle mechanism. The mold clamping mechanism 26 may be configured as a direct pressure type mold clamping mechanism, that is, by a mold clamping cylinder. The fixed platen 22 and the movable platen 24 are provided with a fixed mold 27 and a movable mold 28, respectively, and the mold 21 is opened and closed when the mold clamping mechanism 26 is driven.

[0014] The injection device 3 is provided on a base 30. The injection device 3 includes a heating cylinder 31 having a nozzle 31a at its tip, and a screw 32 arranged within the heating cylinder 31 so as to be rotatable in the circumferential and axial directions. A heater for melting the molding material is provided inside or on the outer periphery of the heating cylinder 31. The screw 32 is driven by a drive device 5 in the rotational and axial directions.

[0015] A hopper 33 into which molding material is poured is provided near the rear end of the heating cylinder 31. The injection molding machine 1 also includes a nozzle touch device 34 that moves the injection unit 3 in the front-rear direction (the left-right direction in FIG. 1). When the nozzle touch device 34 is driven, the injection unit 3 moves forward and the nozzle 31a of the heating cylinder 31 touches the mold 21.

[0016] The control device 4 is a computer that controls the operations of the mold clamping device 2 and the injection device 3, and includes a processor 41, a storage unit 42, an operation unit 43, and the like as a hardware configuration. The control device 4 may be a server device connected to a network. The control device 4 may also be configured to perform distributed processing by using multiple computers, may be realized by multiple virtual machines provided in one server, or may be realized by using a cloud server.

[0017] The processor 41 includes arithmetic circuits such as a CPU (Central Processing Unit), a multi-core CPU, a GPU (Graphics Processing Unit), a GPGPU (General-purpose computing on graphics processing units), a TPU (Tensor Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and an NPU (Neural Processing Unit), internal storage devices such as a ROM (Read Only Memory) and a RAM (Random Access Memory), an I / O terminal, etc. The processor 41 implements the control method according to the first embodiment by executing a computer program (program product) 42a stored in a storage unit 42 described later.

[0018] The storage unit 42 is a non-volatile memory such as a hard disk, an EEPROM (Electrically Erasable Programmable ROM), a flash memory, etc. The storage unit 42 stores a computer program 42a for causing a computer to execute a process for sequentially moving the forward and backward movement ranges of the screw 32 and the nut 51b. The storage unit 42 also stores information indicating the movable range of the nut 51b.

[0019] The computer program 42a according to the first embodiment may be recorded in a computer-readable manner on the recording medium 6. The storage unit 42 stores the computer program 42a read from the recording medium 6 by a reading device. The recording medium 6 is a semiconductor memory such as a flash memory. The recording medium 6 may also be an optical disk such as a CD (Compact Disc)-ROM, a DVD (Digital Versatile Disc)-ROM, or a BD (Blu-ray (registered trademark) Disc). The recording medium 6 may also be a magnetic disk such as a flexible disk or a hard disk, a magnetic optical disk, or the like. The computer program 42a according to the first embodiment may also be downloaded from an external server connected to a communication network and stored in the storage unit 42.

[0020] The operation unit 43 is an input device such as a touch panel, soft keys, hard keys, a keyboard, and a mouse.

[0021] In the injection molding machine 1, set values ​​are set to determine molding conditions such as injection start time, resin temperature in the mold, nozzle temperature, cylinder temperature, hopper temperature, mold clamping force, injection speed, injection acceleration, injection peak pressure, injection stroke, etc. In addition, set values ​​are set to determine molding conditions such as cylinder tip resin pressure, back pressure switching pressure, holding pressure switching speed, holding pressure switching position, holding pressure completion position, cushion position, metering back pressure, metering torque, etc. In addition, set values ​​are set to determine molding conditions such as metering completion position, screw 32 retreat speed, cycle time, mold closing time, injection time, holding pressure time, holding pressure pressure, holding pressure speed, metering time, mold opening time, etc. In addition, the injection molding machine 1, in which these set values ​​are set, operates according to the set values.

[0022] 2 is a cross-sectional view showing an example of the configuration of the drive unit 5 of the injection molding machine 1 according to the first embodiment. The drive unit 5 includes an injection servomotor 50 and a ball screw 51 for driving the screw 32 in the axial direction. The injection servomotor 50 is provided with an encoder that detects a rotation angle and outputs a signal indicating the rotation angle to the control device 4. The control device 4 controls the rotation of the injection servomotor 50 based on the signal output from the encoder. A small pulley 50a is provided on the output shaft of the injection servomotor 50.

[0023] The ball screw 51 includes a ball screw shaft 51a and a nut 51b screwed onto the ball screw shaft 51a. A base end of the ball screw shaft 51a is rotatably supported via a bearing 52a on a first plate 52 having a hole and a bearing seat. A large pulley 50c is provided on the base end of the ball screw shaft 51a. The small pulley 50a and the large pulley 50c are connected by a timing belt 50b, and the rotational force of the small pulley 50a is reduced and transmitted to the large pulley 50c, causing the ball screw shaft 51a to rotate. Hereinafter, the direction toward the base end of the ball screw shaft 51a (right side in FIG. 1) will be referred to as the backward direction, and the opposite direction (left side in FIG. 1) will be referred to as the forward direction. The forward and backward directions will be collectively referred to as the forward and backward directions. When the injection servo motor 50 is driven to rotate the large pulley 50c and the ball screw shaft 51a, the nut 51b moves in the forward or backward direction depending on the direction of rotation.

[0024] A load cell 53 is provided on the surface of the nut 51b facing the forward direction, and the surface of the load cell 53 facing the forward direction is fixed to a second plate 54. A plurality of through holes are formed in the second plate 54, and a guide shaft 55 is inserted into the through holes. The second plate 54 moves in the forward and backward directions while being guided by the guide shaft 55. A third plate 56 is provided on the forward direction side of the first plate 52, and one end and the other end of the guide shaft 55 are supported by the first plate 52 and the third plate 56, respectively. When the ball screw shaft 51a rotates, the nut 51b, the load cell 53, and the second plate 54 move integrally in the forward and backward directions along the guide shaft 55.

[0025] The second plate 54 is provided with a hole and a bearing seat, and the output shaft 58 is supported in the hole via a bearing 54a. The output shaft 58 is provided with a plasticizing pulley 57. The plasticizing pulley 57 is connected to a pulley attached to a screw rotation motor (not shown) via a timing belt (not shown). The center of rotation of the output shaft 58 coincides with the center of rotation of the ball screw shaft 51a. The output shaft 58 is formed with a recess into which the tip of the ball screw shaft 51a enters when the nut 51b moves forward and backward. In addition, one end of the screw 32 is fixed to the output shaft 58 so that the central axes coincide. The third plate 56 is formed with a through hole through which the screw 32 is inserted. One end of the heating cylinder 31 is fixed to the third plate 56 so that the screw 32 inserted through the through hole of the third plate 56 can move axially inside the heating cylinder 31.

[0026] The molding process cycle is outlined below, and the control device 4 performs a process of sequentially moving the forward and backward movement range of the nut 51b in the repeated molding process cycle. During injection molding, the well-known mold closing process, mold clamping process, injection unit advancement process, injection process, measurement process, injection unit retreat process, mold opening process, and ejection process are performed in this order.

[0027] Particularly in the metering process, molding material made of resin or low-melting point metal is supplied from a hopper 33 to the rear of the heating cylinder 31. The molding material supplied to the rear of the heating cylinder 31 is melted and kneaded by heating with a heater and by a shearing action caused by rotating the screw 32, and is sent to the tip region of the heating cylinder 31. As the plasticized molding material accumulates in the tip region of the screw 32, the screw 32 gradually moves backward. The screw 32 moves to a set metering completion position, and a fixed amount of molding material is metered.

[0028] In the injection process, the injection servo motor 50 is driven, and its rotational force is transmitted to the ball screw shaft 51a via the small pulley 50a, timing belt 50b, and large pulley 50c, and the nut 51b, load cell 53, second plate 54, and screw 32 move forward. As the screw 32 moves forward, the molding material stored in the tip region of the heating cylinder 31 is injected and filled into the mold 21 from the nozzle 31a. The screw 32 moves to a set holding pressure switching position, whereby a fixed amount of molding material is injected into the mold 21.

[0029] 3 is a flowchart showing a processing procedure of the processor 41 according to the first embodiment. The processor 41 accepts the selection of the transition mode or the normal mode via the operation unit 43 (step S111). The operator can select the transition mode or the normal mode by manually operating the operation unit 43. The transition mode is a mode in which the control method according to the first embodiment is used, and the advance / retract movement range of the nut 51b is moved sequentially. The normal mode is a mode in which the control method according to the first embodiment is not used, and the nut 51b is moved advance / retract according to the set molding conditions. In other words, the normal mode is a mode in which the advance / retract movement range of the nut 51b is not changed.

[0030] Next, the processor 41 sets the molding conditions (step S112). The molding conditions include the screw position before injection and the screw position after injection as set values ​​particularly related to the present embodiment 1. The screw position before injection is the screw position when injection starts, or the screw position when metering of the molding material is completed. The screw position after injection is the screw position when injection is completed, or the pressure holding switch position. The processor 41 executes processing related to injection molding control based on the molding conditions (step S113). The processor 41 executes a mold closing process, a mold clamping process, an injection unit forward movement process, an injection process, a metering process, an injection unit backward movement process, a mold opening process, and an ejection process by controlling the operation of the mold clamping device 2, the injection device 3, the nozzle touch device 34, the drive device 5, etc.

[0031] Next, the processor 41 determines whether or not the transition mode is selected (step S114). When it is determined that the transition mode is not selected (step S114: NO), the processor 41 returns the process to step S113 and repeatedly executes the molding process cycle without changing the metering completion position and the holding pressure switching position of the screw 32. In other words, the molding process cycle is repeated without changing the forward and backward movement range of the screw 32.

[0032] When it is determined that the transition mode is selected (step S114: YES), the processor 41 moves the forward / backward movement range of the nut 51b by a predetermined amount within the movable range (step S115), and returns the process to step S113. The forward / backward movement range is, for example, a range from the position of the nut 51b corresponding to the metering completion position to the position of the nut 51b corresponding to the holding pressure switching position. In other words, the processor 41 moves the screw position before injection and the screw position after injection by a predetermined amount within the movable range based on the information indicating the movable range of the nut 51b stored in the storage unit 42. Specifically, the processor 41 increases or decreases the metering completion position and the holding pressure switching position by a predetermined amount.

[0033] 4A and 4B are explanatory diagrams showing a state before changing the advance / retract movement range in the control method according to the first embodiment. FIG. 4A shows the driving device 5 at the pressure holding switching position, and FIG. 4B shows the driving device 5 at the metering completion position. The molding resin is metered and melt-kneaded while the nut 51b and the screw 32 move from the position shown in FIG. 4A to the position shown in FIG. 4B. Then, the plasticized molding resin is injected into the mold 21 by the movement of the nut 51b and the screw 32 from the position shown in FIG. 4B to the position shown in FIG. 4A. The nut 51b moves a part of the ball screw shaft 51a forward and backward, and depending on the molding conditions, an unused area exists as shown in FIG. 4B.

[0034] 5A and 5B are explanatory diagrams showing a state after changing the advance / retract movement range in the control method according to the first embodiment. FIG. 5A shows the drive unit 5 at the holding pressure switching position, and FIG. 5B shows the drive unit 5 at the metering completion position. As in FIG. 4A and FIG. 4B, the molding material is metered and injected by moving the nut 51b and the screw 32. In the example shown in FIG. 5A and FIG. 5B, the advance / retract movement range of the nut 51b moves in the backward direction, and metering and injection are performed using the unused area in FIG. 4A and FIG. 4B. Both the metering completion position and the holding pressure switching position move in the same direction by a predetermined amount, and there is no change in the moving distance from the metering completion position to the holding pressure switching position, so the weight of the molding material injected into the mold 21 is basically the same.

[0035] In a molding process cycle in which the transition mode is selected, the processes of steps S113 to S115 are repeatedly executed, and the advance / retract movement ranges of the nut 51b and the screw 32 move by a predetermined amount. Note that the processor 41 may move the advance / retract movement range by reciprocating within the movable range of the nut 51b.

[0036] That is, the processor 41 moves the metering completion position and the holding pressure switching position in the backward direction by a predetermined amount, and when the metering completion position reaches the limit of the movable range of the nut 51b (the backward direction end), the processor 41 changes the moving direction of the metering completion position and the holding pressure switching position and moves them in the forward direction by a predetermined amount. Also, the processor 41 moves the metering completion position and the holding pressure switching position in the forward direction by a predetermined amount, and when the metering completion position reaches the limit of the movable range of the nut 51b (the forward direction end), the processor 41 changes the moving direction of the metering completion position and the holding pressure switching position and moves them in the backward direction by a predetermined amount. By moving the metering completion position and the holding pressure switching position by a predetermined amount in the above-mentioned method, the forward and backward movement range can be reciprocated.

[0037] According to the injection molding machine 1 of this embodiment 1 configured as described above, even under molding conditions of a short injection stroke, the nut 51b moves back and forth within the movable range of the ball screw shaft 51a, thereby preventing a decrease in lubrication and uneven distribution of heat generation, and extending the life of the ball screw 51.

[0038] In this embodiment 1, an example has been described in which the metering completion position and the holding pressure switching position are moved by the same amount, but the metering completion position and the holding pressure switching position may be configured to be moved by different amounts depending on the type of molding material, the position of the forward / backward movement range, etc., so that the injection amount does not change.

[0039] (Embodiment 2) The injection molding machine 1 according to the second embodiment differs from the first embodiment in that the forward and backward movement range of the nut 51b is moved randomly. Since the other configurations of the injection molding machine 1 are the same as those of the injection molding machine 1 according to the first embodiment, the same reference numerals are used for the same parts and detailed description is omitted.

[0040] 6 is a flowchart showing the processing procedure of the processor 41 according to the embodiment 2. As in the embodiment 1, the processor 41 accepts the selection of a mode (step S211), sets molding conditions (step S212), and executes processing related to injection molding control (step S213).

[0041] When it is determined that the transition mode is not selected (step S214: NO), the processor 41 returns the process to step S213. When the transition mode is selected (step S214: YES), the processor 41 randomly determines and changes the forward / backward movement range of the nut 51b within the movable range (step S215), and returns the process to step S213. In other words, based on the information indicating the movable range of the nut 51b stored in the storage unit 42, the processor 41 randomly changes the position of the screw position before and after injection within the movable range while maintaining the relative distance between the screw positions before and after injection. It can also be said that the processor 41 randomly changes the positions of the metering completion position and the holding pressure switching position while maintaining the relative distance between the metering completion position and the holding pressure switching position. Since the relative distance between the metering completion position and the holding pressure switching position is constant, the weight of the molding material injected into the mold 21 is basically the same.

[0042] According to the injection molding machine 1 of this embodiment 1, as in the first embodiment, even under molding conditions of a short injection stroke, it is possible to prevent a decrease in lubrication and uneven distribution of heat generation, and to extend the life of the ball screw 51.

[0043] (Embodiment 3) The injection molding machine 1 according to the third embodiment differs from the first embodiment in that the nut 51b moves within a forward and backward movement range while avoiding wear areas of the ball screw shaft 51a. Since the other configurations of the injection molding machine 1 are the same as those of the injection molding machine 1 according to the first embodiment, the same reference numerals are used for the same parts and detailed description will be omitted.

[0044] FIG. 7 is a schematic diagram showing a configuration example of the injection molding machine 1 according to the third embodiment. The injection molding machine 1 according to the third embodiment includes a measuring unit 7. The measuring unit 7 is, for example, a vibration sensor or an acceleration sensor provided on the nut 51b, and outputs a detected acceleration signal to the control device 4. The processor 41 of the control device 4 acquires the acceleration signal output from the measuring unit 7 by AD conversion into acceleration data. The control device 4 can detect wear of the ball screw shaft 51a based on the acceleration data. For example, when the average value of the acceleration is equal to or greater than a predetermined value, the processor 41 determines that the ball screw shaft 51a is worn. In addition, the control device 4 acquires the signal output from the encoder of the injection servo motor 50 by AD conversion into rotation angle data. The control device 4 can identify the position of the nut 51b on the ball screw shaft 51a based on the rotation angle data. The processor 41 can identify the worn part based on the detection result related to the wear of the ball screw shaft 51a and the position of the nut 51b. The processor 41 may store in the memory unit 42 the acceleration data detected at each portion of the ball screw shaft 51a or the degree of wear based on the acceleration data in association with each other.

[0045] The control device 4 also includes a display unit 40. The display unit 40 is a liquid crystal panel, an organic EL display, electronic paper, a plasma display, etc. The display unit 40 displays various information according to image data provided from the processor 41.

[0046] 8 is a flowchart showing a processing procedure of the processor 41 according to the third embodiment. As in the first embodiment, the processor 41 accepts a mode selection (step S311), sets molding conditions (step S312), and executes a process related to injection molding control (step S313). Then, the processor 41 measures the vibration and the position of the nut 51b (step S314). Next, the processor 41 calculates the position and wear degree of the nut 51b on the ball screw shaft 51a (step S315).

[0047] Next, the processor 41 determines whether or not the transition mode is selected (step S316). When it is determined that the transition mode is not selected (step S316: NO), the processor 41 returns the process to step S313. When it is determined that the transition mode is selected (step S316: YES), the processor 41 determines and changes the advance / retract movement range while avoiding the worn parts of the ball screw shaft 51a (step S317). The processor 41 may move the advance / retract movement range of the nut 51b by a predetermined amount in the same manner as in the first embodiment while avoiding the worn parts of the ball screw shaft 51a, or may randomly change the advance / retract movement range of the nut 51b in the same manner as in the second embodiment.

[0048] FIG. 9 is a flowchart showing a first example of the change process of the advance / retract movement range. The processor 41 identifies the wear part of the ball screw shaft based on the calculation result of the position and wear degree of the nut 51b on the ball screw shaft 51a calculated in step S315 (step S731). Next, the processor 41 identifies the movable range of the nut 51b excluding the wear part based on the information indicating the movable range of the nut 51b stored in the storage unit 42 and the information indicating the identified wear part (step S732). Then, the processor 41 moves the advance / retract movement range by a predetermined amount in the movable range identified in step S732 (step S733). In other words, the processor 41 moves the positions of the screw positions before and after injection by a predetermined amount in the movable range while maintaining the relative distance between the screw positions before and after injection. It can also be said that the processor 41 increases or decreases the metering completion position and the pressure holding switching position by a predetermined amount in the movable range.

[0049] FIG. 10 is a flowchart showing a second example of the change process of the advance / retract movement range. The processor 41 identifies the wear part of the ball screw shaft based on the calculation result of the position and wear degree of the nut 51b on the ball screw shaft 51a calculated in step S315 (step S751). Next, the processor 41 identifies the movable range of the nut 51b excluding the wear part based on the information indicating the movable range of the nut 51b stored in the storage unit 42 and the information indicating the identified wear part (step S752). Then, the processor 41 randomly determines and changes the advance / retract movement range of the nut 51b in the movable range identified in step S752 (step S753). In other words, the processor 41 randomly changes the position of the screw position before and after injection in the movable range of the nut 51b excluding the wear part while maintaining the relative distance between the screw positions before and after injection. It can also be said that the processor 41 randomly changes the positions of the metering completion position and the holding pressure switching position within the movable range of the nut 51b excluding the worn portion, while maintaining the relative distance between the metering completion position and the holding pressure switching position.

[0050] Then, the processor 41 displays the worn parts of the ball screw shaft 51a and the state of the advance / retract movement of the nut 51b on the display unit 40 (step S318), and returns the process to step S313.

[0051] FIG. 11 is a schematic diagram showing an example of a state display screen according to the third embodiment. In step S318, the processor 41 displays the state display image 8 on the display unit 40. The state display image 8 includes a movable range image 81 showing a movable range of the nut 51b. The movable range image 81 is, for example, a horizontally long rectangular image. The movable range image 81 may be configured to display a wear state of the ball screw shaft 51a. For example, the movable range image 81 displays a worn portion of the ball screw shaft 51a in red and a non-worn portion in green. The color coding is an example, and the worn portion may be displayed according to the brightness of the image or the type of the pattern image. The degree of wear may be detected by the magnitude of the vibration acceleration, or may be determined by the accumulated amount of use by which the nut 51b has moved. The processor 41 displays an image showing the current forward and backward movement range (stroke) of the nut 51b, for example, an arrow image 82, superimposed on the movable range image 81. The arrow image 82 is displayed superimposed at a position where the range of advance / retract movement of the nut 51b relative to the ball screw shaft 51a corresponds to the range of the arrow image 82 relative to the movable range image 81. The processor 41 also superimposes a transition direction image 83 indicating the direction in which the advance / retract movement range is being moved, on the movable range image 81. The transition direction image 83 is, for example, an image like an arrow, and is displayed superimposed on the movable range image 81 so that the movement direction of the advance / retract movement range of the nut 51b matches the direction of the arrow.

[0052] According to the injection molding machine 1 of embodiment 3, the forward / backward movement range of the nut 51b is gradually moved while avoiding the worn parts of the ball screw shaft 51a, so that it is possible to more effectively prevent a decrease in lubrication and uneven distribution of heat generating parts, and to extend the life of the ball screw 51.

[0053] Furthermore, the status display image 8 allows the user to visually recognize the current status of the ball screw shaft 51a, the current advance / retract movement range of the nut 51b, and the movement direction of the advance / retract movement range.

[0054] In this embodiment 3, an example has been described in which a vibration sensor or an acceleration sensor is used to detect worn locations on the ball screw shaft 51a. However, the wear on the ball screw shaft 51a may also be detected based on the current value or torque of the injection servo motor 50.

[0055] The display technique for the movable range image 81 according to the third embodiment can also be applied to the other embodiments. In the case of a configuration in which worn parts are not detected, the movable range image 81 is configured not to display the worn state of the ball screw shaft 51a, and the arrow image 82 and the transition direction image 83 are displayed in the same manner as described above.

[0056] (Embodiment 4) The injection molding machine 1 according to the fourth embodiment differs from the first embodiment in that the molding conditions are corrected according to the degree of defect of the molded product when the forward and backward movement range of the nut 51b is moved. Since the other configurations of the injection molding machine 1 are the same as those of the injection molding machine 1 according to the first embodiment, the same reference numerals are used for the same parts and detailed description will be omitted.

[0057] FIG. 12 is a block diagram showing a configuration example of the control device 4 according to the fourth embodiment. The injection molding machine 1 according to the fourth embodiment includes a measurement unit 7. The measurement unit 7 includes a thermometer, a pressure gauge, a speed measuring device, an acceleration measuring device, a position sensor, a timer, a weight meter, and the like. The information measured by the measurement unit 7 includes, for example, molded product information obtained from the molded product. The molded product information includes, for example, a camera image obtained by imaging the molded product, the deformation amount of the molded product obtained by a laser displacement sensor, optical measurement values ​​such as the chromaticity and brightness of the molded product obtained by an optical measuring device, the weight of the molded product measured by a weight meter, and the strength of the molded product measured by a strength measuring device. The measurement unit 7 may obtain information such as the temperature, vibration, and pressure of each part from the injection unit 3, the drive unit 5, and other peripheral devices.

[0058] The storage unit 42 according to the fourth embodiment stores a defect degree determination learning model 44 and an adjustment learning model 45. The processor 41 reads out the defect degree determination learning model 44 and the adjustment learning model 45, as well as the computer program 42a, from the storage unit 42 and executes them.

[0059] The defect degree determination learning model 44 is a neural network that outputs the degree of defect of a molded product when physical quantity data, for example a measurement value, is input. The defect degree determination learning model 44 includes an input layer, a hidden layer, and an output layer. The input layer has a plurality of nodes to which the physical quantity data is input. The hidden layer includes a plurality of intermediate layers each having a plurality of nodes, and the nodes of the intermediate layer on the input side are connected to the nodes of the input layer. The output layer has nodes that output the degree of defect of a molded product. Each node of the output layer is connected to a node of the intermediate layer on the output side.

[0060] The defect degree determination learning model 44 can be generated by machine learning using training data including, for example, physical quantity data measured by the measuring unit 7 during injection molding and the defect degree of the molded product obtained at this time. For example, the processor 41 optimizes the weighting coefficient of the defect degree determination learning model 44 by an error backpropagation method, an error gradient descent method, or the like using the training data, thereby performing machine learning on the defect degree determination learning model 44.

[0061] The adjustment learning model 45 is a neural network that outputs a correction amount of a set value when, for example, a set value of a molding condition and a defectiveness of a molded product are input. The adjustment learning model 45 has an input layer, a hidden layer, and an output layer. The input layer has a plurality of nodes to which the set value and the defectiveness are input. The hidden layer has a plurality of intermediate layers each having a plurality of nodes, and the nodes of the intermediate layer on the input side are connected to the nodes of the input layer. The output layer has a node that outputs a correction amount of the set value. Each node of the output layer is connected to a node of the intermediate layer on the output side. The set value to be corrected is, for example, a VP switching position, a metering completion position, an injection speed, a dwell time, a dwell pressure, a dwell speed, a dwell switching position, etc.

[0062] The adjustment learning model 45 can be generated by machine learning using training data including, for example, the set values ​​of the molding conditions and the defect degree of the molded product obtained at that time. For example, the processor 41 optimizes the weight coefficients of the adjustment learning model 45 by an error backpropagation method, an error gradient descent method, or the like using the training data, thereby causing the adjustment learning model 45 to undergo machine learning.

[0063] 13 is a flowchart showing the processing procedure of the processor 41 according to the fourth embodiment. As in the first embodiment, the processor 41 accepts the selection of a mode (step S411), sets molding conditions (step S412), and executes processing related to injection molding control (step S413). Then, the processor 41 measures the physical quantities and the like of the molded product using the measuring unit 7, and acquires physical quantity data indicating the state of the molded product (step S414). The processor 41 inputs the acquired physical quantity data into the defect degree judgment learning model 44 to calculate the defect degree of the molded product (step S415).

[0064] Next, the processor 41 determines whether or not the transition mode is selected (step S416). If it is determined that the transition mode is not selected (step S416: NO), the processor 41 returns the process to step S413. If it is determined that the transition mode is selected (step S416: YES), the processor 41 moves the forward / backward movement range of the nut 51b by a predetermined amount within the movable range (step S417).

[0065] Next, the processor 41 judges whether the degree of defect is equal to or greater than a predetermined value (step S418). If the degree of defect is less than the predetermined value (step S418: NO), the processor 41 returns the process to step S413. If the degree of defect is equal to or greater than the predetermined value (step S418: YES), the processor 41 corrects the set value of the molding condition (step S419) and returns the process to step S413. Specifically, the processor 41 inputs the set value and the degree of defect into the adjustment learning model 45 to calculate the correction amount of the set value, and corrects the set value of the molding condition using the calculated correction amount. The set value to be corrected is, for example, the VP switching position, the metering completion position, the injection speed, the dwell time, the dwell pressure, the dwell speed, the dwell switching position, etc.

[0066] According to the injection molding machine 1 of the fourth embodiment, it is possible to correct the molding conditions so as not to deteriorate the quality of the molded product by changing the forward and backward movement ranges of the nut 51b and the screw 32. Therefore, it is possible to prevent a decrease in lubrication and uneven distribution of heat generation without adversely affecting the quality of the molded product, and to extend the life of the ball screw 51.

[0067] In the fourth embodiment, an example of calculating the defectiveness of the molded product and the correction amount of the set value using a learning model of a neural network has been described, but the defectiveness of the molded product and the correction amount of the set value may be calculated using other known machine learning models such as SVM (Support Vector Machine) and Bayesian network. The defectiveness of the molded product may be calculated on a rule basis, and the molding conditions may be corrected. For example, the defectiveness of the molded product may be calculated by a pattern matching process for an image obtained by photographing the molded product, a process of calculating the difference between the weight of the molded product and the weight of a normal product, or the like. In addition, when the defectiveness of the molded product increases, the movement of the metering completion position and the holding pressure switching position may be stopped, or the metering completion position and the holding pressure switching position may be returned to the previous state.

[0068] Furthermore, although an example in which the molding conditions are corrected by supervised learning has been described, the molding conditions may be corrected by reinforcement learning.

[0069] Furthermore, in the present embodiment, the nut 51b is moved by a predetermined amount, but the predetermined amount of movement may be increased or decreased depending on the degree of defect of the molded product. For example, it is preferable to control the predetermined amount to be smaller as the degree of defect increases.

[0070] Furthermore, the fourth embodiment can also be applied to the second and third embodiments.

[0071] (Embodiment 5) The injection molding machine 1 according to the fifth embodiment differs from the first embodiment in that the molding conditions are corrected according to the movement of the forward and backward movement range of the nut 51b. Since the other configurations of the injection molding machine 1 are the same as those of the injection molding machine 1 according to the first embodiment, the same reference numerals are used for the same parts and detailed description will be omitted.

[0072] The storage unit 42 according to the fifth embodiment stores an adjustment learning model 545. The processor 41 reads out the adjustment learning model 545 and the computer program 42a from the storage unit 42 and executes them.

[0073] FIG. 14 is a block diagram showing an adjustment learning model 545 according to the fifth embodiment. The adjustment learning model 545 is a neural network that outputs a correction amount of a set value when, for example, a set value of a molding condition and a movement amount of an advance / retreat movement range are input. The adjustment learning model 545 includes an input layer, a hidden layer, and an output layer. The input layer has a plurality of nodes to which the set value and the movement amount of the advance / retreat movement range are input. The hidden layer includes a plurality of intermediate layers each having a plurality of nodes, and the nodes of the intermediate layer on the input side are connected to the nodes of the input layer. The output layer has a node that outputs a correction amount of the set value. Each node of the output layer is connected to a node of the intermediate layer on the output side.

[0074] The adjustment learning model 545 can be generated by machine learning using training data including, for example, the set values ​​of the molding conditions, the movement amount of the advance / retract movement range of the nut 51b, and the correction amount of the set values ​​suitable for changing the advance / retract movement range. For example, the processor 41 optimizes the weight coefficients of the adjustment learning model 545 by the error backpropagation method, the error gradient descent method, or the like using the training data, thereby machine learning the adjustment learning model 545.

[0075] FIG. 15 is a flowchart showing the processing procedure of the processor 41 according to the fifth embodiment. As in the first embodiment, the processor 41 accepts the selection of the mode (step S511), sets the molding conditions (step S512), and executes the process related to the injection molding control (step S513). When it is determined that the transition mode is not selected (step S514: NO), the processor 41 returns the process to step S513. When the transition mode is selected (step S514: YES), the processor 41 moves the advance / retract movement range of the nut 51b by a predetermined amount within the movable range (step S515). Then, the processor 41 calculates the correction amount of the molding condition according to the movement of the advance / retract movement range, corrects the molding condition (step S516), and returns the process to step S513. Specifically, the processor 41 inputs the set value of the molding condition and the movement amount of the advance / retract movement range to the adjustment learning model 545, thereby calculating the correction amount of the set value of the molding condition. Then, the set value of the molding condition is corrected using the calculated correction amount. The set values ​​to be corrected include the metering completion position and the pressure holding switch position of the screw 32.

[0076] According to the injection molding machine 1 of the fifth embodiment, it is possible to correct the molding conditions so as not to deteriorate the quality of the molded product by changing the forward and backward movement ranges of the nut 51b and the screw 32. Therefore, it is possible to prevent a decrease in lubrication and uneven distribution of heat generation without adversely affecting the quality of the molded product, and to extend the life of the ball screw 51.

[0077] (Embodiment 6) The injection molding machine 1 according to the sixth embodiment differs from the first embodiment in that the forward and backward movement range of the nut 51b is changed depending on the degree of difficulty of molding. Since the other configurations of the injection molding machine 1 are the same as those of the injection molding machine 1 according to the first embodiment, the same reference numerals are used for the same parts and detailed description is omitted.

[0078] FIG. 16 is a flowchart showing a processing procedure of the processor 41 according to the sixth embodiment. The processor 41 according to the sixth embodiment acquires data related to the molding difficulty (step S611). The data related to the molding difficulty is stored in the storage unit 42 in association with, for example, the molding conditions. The processor 41 may also acquire data related to the molding difficulty via the operation unit 43. Furthermore, the processor 41 may be configured to calculate data related to the molding difficulty based on the molding conditions. The processor 41 selects a mode based on the acquired data related to the molding difficulty (step S612). For example, when the molding difficulty is equal to or greater than a threshold, the processor 41 selects the normal mode, and when the molding difficulty is less than the threshold, the processor 41 selects the transition mode. Thereafter, the same processing as steps S112 to S115 of the first embodiment is executed (steps S613 to S616).

[0079] According to the injection molding machine 1 of embodiment 6, the forward / backward movement range of the nut 51b and the screw 32 is moved when the possibility of the quality of the molded product deteriorating is low, taking into consideration the degree of difficulty of molding, thereby preventing a decrease in lubrication and uneven distribution of heat generation areas, and extending the life of the ball screw 51. [Explanation of symbols]

[0080] 1 injection molding machine 2 Mold clamping device 3 Injection device 4. Control device 5. Drive unit 6 Recording media 7. Measurement section 31 Heating Cylinder 32 Screw 50 Injection servo motor 51 Ball screw 41 Processors 51 Ball screw 51a Ball screw shaft 51b Nut 44 Defectiveness Judgment Learning Model 45,545 Tuning learning model

Claims

1. a screw provided in a cylinder having a nozzle at a tip end thereof so as to be drivable in a rotational direction and an axial direction; A drive device that drives the screw; A control device for controlling the operation of the driving device; Equipped with The drive device is a ball screw including a rotatably provided ball screw shaft and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, the ball screw driving the screw in the axial direction by the forward and backward movement of the nut; The control device includes: Under molding conditions in which only a part of the stroke range of the entire stroke range in which the nut can move on the ball screw shaft is used, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Injection molding machine.

2. A screw that is provided in a cylinder having a nozzle at its tip and that can be driven in a rotational direction and an axial direction; A drive device that drives the screw; A control device for controlling the operation of the driving device; Equipped with The drive device is a ball screw including a rotatably provided ball screw shaft and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, the ball screw driving the screw in the axial direction by the forward and backward movement of the nut; The control device includes: A worn portion of the ball screw shaft is monitored, and a screw position before and after injection is determined so that the forward and backward movement range of the nut does not overlap with the worn portion; The screw position before injection and the screw position after injection are sequentially moved in the molding process cycle so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Injection molding machine.

3. A screw that is drivable in a rotational direction and an axial direction within a cylinder having a nozzle at a tip thereof; A drive device that drives the screw; A control device for controlling the operation of the driving device; Equipped with The drive device is a ball screw including a rotatably provided ball screw shaft and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, the ball screw driving the screw in the axial direction by the forward and backward movement of the nut; The control device includes: Obtain data related to molding difficulty, When the molding difficulty level is less than a predetermined value, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Injection molding machine.

4. The control device includes: The screw position is moved by a predetermined amount before and after injection, so that the nut moves back and forth within the movable range of the nut. The injection molding machine according to any one of claims 1 to 3.

5. The control device includes: Randomly determine pre- and post-injection screw positions The injection molding machine according to any one of claims 1 to 3.

6. Obtaining physical quantity data that indicates the condition of the molded product, Calculating the degree of defects of the molded product based on the acquired physical quantity data; If the degree of defects in the molded product is equal to or greater than a threshold, the molding conditions set in the molding machine are changed. The injection molding machine according to any one of claims 1 to 5.

7. A control method for controlling an operation of a drive device that drives a screw of an injection molding machine by the forward and backward movement of a nut that is screwed onto a rotatable ball screw shaft and that moves forward and backward in accordance with the rotation of the ball screw shaft, comprising: Under molding conditions in which only a part of the stroke range of the entire stroke range in which the nut can move on the ball screw shaft is used, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Control methods.

8. A control method for controlling the operation of a drive device that drives a screw of an injection molding machine by the forward and backward movement of a ball screw shaft that is rotatably provided and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, comprising: By monitoring the wear location of the ball screw shaft, a screw position before and after injection is determined so that the forward and backward movement range of the nut does not overlap with the wear location; The screw position before injection and the screw position after injection are sequentially moved in the molding process cycle so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Control methods.

9. A control method for controlling the operation of a drive device that drives a screw of an injection molding machine by the forward and backward movement of a ball screw shaft that is rotatably provided and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, comprising: Obtain data related to molding difficulty, When the molding difficulty level is less than a predetermined value, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. Control methods.

10. A computer program for causing a computer to control an operation of a drive device that includes a rotatably provided ball screw shaft and a nut that is screwed onto the ball screw shaft and moves forward and backward in accordance with the rotation of the ball screw shaft, the drive device driving a screw of an injection molding machine by the forward and backward movement of the nut, Under molding conditions in which only a part of the stroke range of the entire stroke range in which the nut can move on the ball screw shaft is used, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. A computer program for causing the computer to execute a process.

11. A computer program for causing a computer to control the operation of a drive device that drives a screw of an injection molding machine by the forward and backward movement of a ball screw shaft that is rotatably provided and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, the computer program comprising: By monitoring the wear location of the ball screw shaft, a screw position before and after injection is determined so that the forward and backward movement range of the nut does not overlap with the wear location; The screw position before injection and the screw position after injection are sequentially moved in the molding process cycle so that the forward and backward movement range of the nut in the molding process cycle is dispersed. A computer program for causing the computer to execute a process.

12. A computer program for causing a computer to control the operation of a drive device that drives a screw of an injection molding machine by the forward and backward movement of a ball screw shaft that is rotatably provided and a nut that is screwed onto the ball screw shaft and moves back and forth with the rotation of the ball screw shaft, the computer program comprising: Obtain data related to molding difficulty, When the molding difficulty level is less than a predetermined value, the screw position before injection and the screw position after injection in the molding process cycle are sequentially moved so that the forward and backward movement range of the nut in the molding process cycle is dispersed. A computer program for causing the computer to execute a process.

Images