Injection molding machine and control method thereof

Abstract

The injection molding machine according to the present embodiment is provided with: an injection device that injects a material into a metal mold; and a control section that is a control section that controls the injection device, controls an injection speed of an injection process in which the injection device injects the material into the metal mold, based on a past speed setting of an injection speed set in advance in a molding cycle performed in advance and a past speed detection result detected in advance by a speed sensor that detects the injection speed.

Description

Technical Field

[0001] According to embodiments of the present invention, there is an injection molding machine and a control method thereof. Background Technology

[0002] In injection molding, low-pressure injection molding is sometimes performed, where less pressure is applied to the molten resin or other materials. As one type of low-pressure injection molding, a method is known to switch from speed control to pressure control midway through the injection process. For example, at the start of injection, speed control is applied so that the actual injection speed reaches the speed setpoint. Subsequently, when the actual injection pressure reaches near a set low pressure setpoint, pressure control is applied to ensure that the actual injection pressure does not exceed the pressure setpoint.

[0003] However, in the molding method described above, the injection speed under pressure control sometimes deviates in each injection. Furthermore, due to this deviation in injection speed, the quality of the resulting molded article sometimes differs from injectioners.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2001-191383. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The aim is to provide an injection molding machine and its control method that can improve the reproducibility of product quality.

[0009] Solution for solving the problem

[0010] The injection molding machine according to this embodiment includes: an injection device that injects material into a metal mold; and a control unit that controls the injection device, which controls the injection speed of the material injection process of the injection device into the metal mold based on a previously set injection speed of a pre-performed molding cycle and the detection result of a speed sensor that detects the previously detected injection speed. Attached Figure Description

[0011] Figure 1 This is a block diagram illustrating an example of the configuration of an injection molding machine according to the first embodiment.

[0012] Figure 2 This is a block diagram illustrating an example of the configuration of a control device according to the first embodiment.

[0013] Figure 3 This is a chart showing an example of the speed and pressure waveforms in low-pressure injection molding.

[0014] Figure 4 It is shown that Figure 3 A chart illustrating an example of the speed and pressure waveforms in injection molding, based on the molding cycle.

[0015] Figure 5 This is a flowchart illustrating an example of the operation of an injection molding machine according to the first embodiment.

[0016] Figure 6A This is a graph illustrating an example of speed waveforms for multiple control methods.

[0017] Figure 6B This is a graph illustrating an example of pressure waveforms for multiple control methods.

[0018] Figure 7 This is a graph showing an example of the velocity and pressure waveforms for laminar flow control.

[0019] Figure 8 This is a block diagram showing the configuration of the control device according to the second embodiment.

[0020] Figure 9 This is a graph illustrating an example of how speed commands change based on feedforward control.

[0021] Figure 10 This is a diagram illustrating an example of the changes in the speed command based on feedforward control for the second process. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. These embodiments do not limit the present invention. The drawings are schematic or conceptual, and the proportions of the parts are not necessarily identical to actual proportions. In the specification and drawings, the same reference numerals are used for the same elements as those described in the foregoing drawings, and detailed descriptions are omitted where appropriate.

[0023] (First Embodiment)

[0024] Figure 1 This is a block diagram illustrating an example of the configuration of the injection molding machine 1 according to the first embodiment. The injection molding machine 1 is a machine capable of repeatedly performing a series of injection molding operations, for example, repeatedly performing the operation of molding an article once as a cycle operation. The time for performing a series of cycle operations is called the cycle time.

[0025] The injection molding machine 1 includes a frame 2, a fixed plate 3, a movable plate 4, a tie rod 5, a mold closing drive mechanism 6, an injection device 7, a control device 8, an ejection mechanism 9, a human-machine interface 60, a storage device 110, an injection pressure sensor S1, and a screw position sensor S2.

[0026] Frame 2 is the base of injection molding machine 1. Fixed platen 3 is fixed to frame 2. Fixed metal mold 11, which serves as the first metal mold, is installed on fixed platen 3. One end of tie rod 5 is fixed to fixed platen 3, and the other end is connected to support platen 10. Tie rod 5 extends from fixed platen 3 through movable platen 4 to support platen 10.

[0027] The movable disk 4 is mounted on a linear guide, slide plate, or roller (not shown) provided on the frame 2. Guided by the tie rod 5 or the linear guide, the movable disk 4 can move towards or away from the fixed disk 3. A movable metal mold 12, serving as a second metal mold, is mounted on the movable disk 4. The movable metal mold 12 faces the fixed metal mold 11 and approaches the fixed metal mold 11 together with the movable disk 4, merging with the fixed metal mold 11. The movable metal mold 12 and the fixed metal mold 11 come into contact, thereby forming a space between the movable metal mold 12 and the fixed metal mold 11 that corresponds to the shape of the product.

[0028] The mold clamping drive mechanism 6 includes a toggle mechanism 13 and a toggle mechanism drive unit 14. The toggle mechanism drive unit 14 includes a mold clamping servo motor 21, a ball screw 22, and a transmission mechanism 23 for driving the toggle mechanism 13. A crosshead 15 is mounted at the top end of the ball screw 22. The ball screw 22 rotates, causing the crosshead 15 to move towards or away from the moving disk 4. The transmission mechanism 23 transmits the rotation of the mold clamping servo motor 21 to the ball screw 22, causing the crosshead 15 to move.

[0029] If the toggle mechanism drive unit 14 moves the crosshead 15, the toggle mechanism 13 operates. For example, if the crosshead 15 moves toward the moving platen 4, the moving platen 4 moves toward the fixed platen 3, and the metal molds 11 and 12 are closed. Conversely, if the crosshead 15 moves away from the moving platen 4, the moving platen 4 moves away from the fixed platen 3, and the metal molds 11 and 12 are opened.

[0030] To unload the molded product from the movable metal mold 12, the ejection mechanism 9 includes an ejection servo motor 71, a ball screw 72, a transmission mechanism 73, and an ejection pin 74. The tip of the ejection pin 74 penetrates the inner surface of the movable metal mold 12. The ball screw 72 rotates, thereby ejecting the product attached to the inner surface of the movable metal mold 12 from the ejection pin 74. The transmission mechanism 73 transmits the rotation of the ejection servo motor 71 to the ball screw 72, and the rotation of the ball screw 72 causes the ejection pin 74 to move along... Figure 1 It moves in the left and right directions.

[0031] The injection unit 7 includes a heating cylinder (belt heater) 41, a screw 42, a metering drive unit 43, and an injection drive unit 44. The heating cylinder 41 has a nozzle 41a that injects molten resin into the cavity of a closed metal mold. The heating cylinder 41 heats and melts resin from a hopper 45 and stores it simultaneously, then injects the molten resin from the nozzle. The screw 42 is arranged inside the heating cylinder 41 in a manner that allows it to move while rotating or without rotating. In the metering process, the screw 42 rotates, pushing the molten resin towards the top of the heating cylinder 41, and then the screw 42 is pushed backward by the pushed-out molten resin. The amount of molten resin injected from the cylinder 41 is metered and determined based on the backward movement distance of the screw 42. In the injection process, the screw 42 moves without rotating, injecting molten resin from the nozzle.

[0032] The metering drive unit 43 includes a metering servo motor 46 and a transmission mechanism 47 that transmits the rotation of the metering servo motor 46 to the screw 42. When the metering servo motor 46 is driven, the screw 42 rotates inside the heating cylinder 41, and resin is introduced from the hopper 45 into the heating cylinder 41. The introduced resin is heated and mixed, and simultaneously conveyed to the top side of the heating cylinder 41. The resin is melted and stored in the top portion of the heating cylinder 41. By moving the screw 42 in the opposite direction to that during metering, molten resin is ejected from the cylinder 41. At this time, the screw 42 moves without rotating, pushing the molten resin out of the nozzle. Furthermore, in this embodiment, molten resin is used as a molding material, but the molding material is not limited to molten resin; it can also be metal, glass, rubber, carbonized compounds including carbon fibers, etc.

[0033] The injection drive unit 44 includes an injection servo motor 51, a ball screw 52, ​​and a transmission mechanism 53. The ball screw 52 rotates, causing the screw 42 to move within the heating cylinder 41 along... Figure 1 The screw 42 moves in the left and right directions. The transmission mechanism 53 transmits the rotation of the injection servo motor 51 to the ball screw 52. Thus, if the injection servo motor 51 rotates, the screw 42 moves. The screw 42 pushes the molten resin stored in the top part of the heating cylinder 41 out of the nozzle 41a, thereby injecting molten resin from the nozzle 41a.

[0034] Injection pressure sensor S1 detects the filling pressure when molten resin is poured from barrel 41 into the metal mold, or the holding pressure during the holding process. During the injection process, injection pressure sensor S1 detects the injection pressure of the molten resin material from barrel 41 into the metal mold. During the holding process, injection pressure sensor S1 detects the holding pressure of the molten resin after the switch from speed control to pressure control.

[0035] The screw position sensor S2 detects the position of the screw 42. Since the screw 42 moves in tandem with the rotation of the injection servo motor 51, the screw position sensor S2 can also detect the position of the screw 42 based on the rotational speed or angular position of the injection servo motor 51. By detecting the position of the screw 42 in each predetermined control cycle, the speed or acceleration of the screw 42 can be determined.

[0036] The Human-Machine Interface (HMI / F) 60 displays various information related to the injection molding machine 1. The HMI / F 60 may also include, for example, a display unit 100 and a keyboard, or it may be a touch panel display. Users can input settings such as commands related to the operation of the injection molding machine 1 through the HMI / F 60. For example, the injection molding machine 1 molds the product in each molding cycle through an injection process that injects molten resin into a closed metal mold, a holding process that controls the holding pressure of the molten resin in the metal mold, and a cooling process that cools the molten resin in the metal mold.

[0037] The control device 8 monitors sensor information received from various sensors (not shown) and controls the injection device 7 based on this sensor information. Furthermore, the control device 8 controls the screw 42 according to the aforementioned set values ​​set via the HMI / F60. Finally, the control device 8 causes the display unit 100 to display the required data.

[0038] The storage device 110 stores multiple action information of the injection molding machine 1. The action information shows the actions of the metal molds 11 and 12, the mold closing drive mechanism 6, or the injection device 7. In addition, the storage device 110 may be located inside the control device 8 or outside the injection molding machine 1.

[0039] Figure 2 This is a block diagram illustrating an example of the configuration of the control device 8 according to the first embodiment.

[0040] The control device 8 includes an interface 81, a position / speed conversion unit 82, a storage control unit 83, an injection speed setting unit 84, an injection control unit 85, an injection control servo amplifier 86, an interface 87, an injection pressure control unit 88, and an alarm 89. Furthermore, Figure 2 In the example shown, the storage device 110 is located within the control device 8.

[0041] The position / speed conversion unit 82 is connected to the screw position sensor S2 via interface 81. The screw position sensor S2 is, for example, an encoder. In this case, the position / speed conversion unit 82 converts the encoder position into the injection speed. The position / speed conversion unit 82 calculates the fill time (injection time) based, for example, on a signal from a sequencer (not shown). The position / speed conversion unit 82 outputs the waveform (time variation) of the injection speed to the storage device 110, for example, in a sampling mode corresponding to the injection time.

[0042] The storage device 110 has a data memory 111 and a reference waveform memory 112.

[0043] The data storage 111 records the injection speed waveform transmitted from the position / speed conversion unit 82 in each molding cycle.

[0044] The reference waveform memory 112, serving as the storage unit, stores the previous speed settings and previous speed detection results of the previously performed molding cycle. "Previous speed setting" refers to the previously set injection speed for the previously performed molding cycle. This speed setting is, for example, the speed setting of the screw 42. "Previous speed detection results" refers to the detection results previously detected by the speed sensor that detects the injection speed in the previously performed molding cycle. The injection speed detection results are, for example, the injection speed waveform for each molding cycle. The speed sensor is, for example, the screw position sensor S2. The position of the screw 42 detected by the screw position sensor S2 is converted into the injection speed by the position / speed conversion unit 82, as described above.

[0045] The storage control unit 83 stores the previous speed settings and previous speed detection results of the previously performed molding cycle in the storage device 110 (reference waveform memory 112). More specifically, the storage control unit 83 stores the previous speed settings and previous speed detection results in the reference waveform memory 112 based on user operations. For example, the storage control unit 83 stores the injection speed waveform stored in the data memory 111 in the reference waveform memory 112 via the HMI / F60. In addition, the storage control unit 83 stores the previous speed settings input in previous molding cycles in the reference waveform memory 112 via the HMI / F60. Furthermore, the storage control unit 83 can also store the previous speed settings and previous speed detection results in the reference waveform memory 112 from a storage unit located outside the injection molding machine 1. The HMI / F60 has, for example, a key input device to accept various operations from the user.

[0046] The firing speed setting unit 84, which is a speed information acquisition unit, acquires previous speed settings and previous speed detection results stored in the reference waveform memory 112. For example, the firing speed setting unit 84 automatically acquires previous speed settings and previous speed detection results and transmits them to the firing control unit 85. In addition, the firing speed setting unit 84 can also acquire previous speed settings and previous speed detection results stored in the storage device 110 (data memory 111) based on user operation.

[0047] The injection control unit 85, acting as a control unit, controls the injection device 7. The injection control unit 85 controls the injection of the injection device 7 through speed control and pressure control. For example, the injection control unit 85 converts the previous speed setting and previous speed detection results transmitted from the injection speed setting unit 84 into speed commands and transmits them to the injection control servo amplifier 86. Thus, the injection control unit 85 can control the movement of the screw 42 via the injection servo motor 51, thereby controlling the injection performed by the injection device 7. Furthermore, in the following text, refer to... Figure 3 and Figure 4 The details of the injection control performed by the injection control unit 85 will be explained.

[0048] The injection pressure control unit 88 is connected to the injection pressure sensor S1 via interface 87. The injection pressure control unit 88 includes a pressure setting unit 881 and a comparison unit 882.

[0049] The pressure setting unit 881 sets the injection pressure setting Lps and the upper limit change value of the set pressure based on the user's operation from the HMI / F60 (see reference). Figure 3 Furthermore, the sum of the injection pressure setting Lps and the upper limit change value is called the upper limit injection pressure setting Lps2 (see [reference]). Figure 4 The pressure setting unit 881 transmits the injection pressure setting Lps and the upper limit change value to the injection control unit 85. Thus, the injection control unit 85 can control the injection through pressure control. For example, the injection control unit 85 performs pressure control to ensure that the injection pressure does not exceed the injection pressure setting Lps.

[0050] The comparison unit 882 compares the detected value (actual pressure) of the injection pressure sensor S1 with the upper limit injection pressure setting Lps2. If the actual pressure exceeds the upper limit injection pressure setting Lps2, the comparison unit 882 transmits a signal to the alarm 89.

[0051] Alarm 89 notifies, for example, that the actual pressure exceeds the upper limit injection pressure setting Lps2.

[0052] Next, the injection control performed by the injection control unit 85 will be explained. Furthermore, the injection control of the injection process will be explained below.

[0053] Figure 3 This is a graph showing an example of the speed and pressure waveforms in low-pressure injection molding. The vertical axis represents the injection speed and injection pressure. The horizontal axis represents time. Furthermore, the origin O is the start of the injection process. Therefore, at the origin O, the speed and pressure are approximately zero.

[0054] Lvs indicates the injection speed setting, such as the setting value input to the injection speed setting unit 84. Lv indicates the actual speed, such as the injection speed converted by the position / speed conversion unit 82. Lps indicates the injection pressure setting, such as the setting value input to the pressure setting unit 881. Lp indicates the actual pressure, such as the injection pressure detected by the injection pressure sensor S1.

[0055] Low-pressure injection molding is a low-pressure injection molding method as follows: In the initial stage of the injection process, the injection speed (actual speed Lv) is controlled by setting the injection speed Lvs. From the middle of the injection process, pressure control is implemented to ensure that the actual pressure Lp does not exceed the upper limit of the set injection pressure Lps. Therefore, as... Figure 3 As shown, the injection process in low-pressure injection molding is divided into a speed control process and a pressure control process. The switching timing t between the speed control process and the pressure control process is, for example, the timing when the actual pressure Lp rises to reach the injection pressure setting Lps. Alternatively, the switching timing t can also be the timing when the actual pressure Lp reaches a predetermined pressure range including the injection pressure setting Lps.

[0056] In low-pressure injection molding, molding is performed without applying excessive pressure to the molten resin. Therefore, damage to the metal mold caused by overfilling can be suppressed. Furthermore, injection molding machines capable of high-pressure filling are not required, resulting in lower equipment costs. Additionally, low-pressure filling reduces the operating costs of the injection molding machine. Moreover, low-pressure injection allows for miniaturization of the metal mold and peripheral equipment, further reducing equipment and operating costs. Additionally, residual stress in the molded product is reduced.

[0057] However, in low-pressure injection molding, the injection speed in the pressure control process sometimes deviates in each injection. This is believed to be because, since resin injection depends on pressure control, there are variations in the resin behavior within the metal molds 11 and 12. Due to this deviation in injection speed, the filling time for each injection varies, potentially leading to inconsistent appearance quality. In other words, due to the deviation in injection speed, the quality of the molded part obtained in each injection may differ. Therefore, it is not always possible to obtain a qualified product.

[0058] Therefore, the injection control unit 85 controls the injection speed of the material injection process of the injection device 7 into the metal molds 11 and 12 based on the previously set injection speed of the pre-performed molding cycle and the previously detected speed by the speed sensor. First, as Figure 3 As shown, the speed pattern, which serves as a baseline, is sampled through a pre-executed low-pressure injection molding process. Subsequently, as... Figure 4 As shown, the molding process utilizes previous speed settings and previous speed detection results, which serve as a reference speed mode. The injection control unit 85 controls the speed throughout the injection process, thereby suppressing deviations in the injection speed for each injection. As a result, the reproducibility of the quality of low-pressure injection molded products can be improved.

[0059] Furthermore, more specifically, the injection control unit 85 controls the injection speed of the injection process based on the previous speed settings and previous speed detection results of the molding cycle in which the molded product is a qualified product. That is, the reference molding cycle is a molding cycle in which a qualified product can be obtained through low-pressure injection molding.

[0060] (Based on sampling of the speed pattern of low-pressure injection molding)

[0061] like Figure 3 As shown, in the first step of the pre-performed molding cycle, the injection control unit 85 controls the injection speed based on the previous speed setting from the start of the injection step until the pressure detection result of the pressure sensor detecting the injection pressure reaches a predetermined upper limit value. "The first step" includes the period from the start of the injection step until it is completed. In low-pressure injection molding, the first step is a speed control step. The pressure sensor is, for example, the injection pressure sensor S1. The "predetermined upper limit value" is the injection pressure setting Lps. The previous speed setting is the injection speed setting Lvs. Furthermore, Figure 3 The ejection velocity setting Lvs shown is, for example, a command value such as 100 mm / sec, and the waveform is shown as a stepped (rectangular) shape. Figure 3 The injection speed setting Lvs shown does not take into account the rise and fall of the actual speed command to the motor.

[0062] In the speed control process, the actual speed Lv increases from the start of the injection process. The injection control unit 85 controls the injection servo motor 51 in a manner that follows the injection speed setting Lvs. Feedback control, such as PID control, is used to control the injection servo motor 51. Therefore, the actual speed Lv is delayed relative to the injection speed setting Lvs, which is the actual speed command. Figure 3In the example shown, at the end of the speed control process, the actual speed Lv reaches the injection speed setting Lvs. Meanwhile, the actual pressure Lp increases along with the actual speed Lv from the start of the injection process. The timing at which the actual pressure Lp reaches the injection pressure setting Lps is called the switching timing t. After this, the pressure control process is performed.

[0063] Furthermore, the timing for the actual speed Lv to reach the set ejection speed Lvs is not limited to... Figure 3 The examples shown sometimes vary depending on the rate of increase of the actual pressure Lp. For instance, if the rate of increase of the actual pressure Lp is slow, it is possible that the actual speed Lv reaches the injection speed setting Lvs, and after a predetermined period roughly consistent with the injection speed setting Lvs, the actual pressure Lp reaches the injection pressure setting Lps. The rate of increase of the actual pressure Lp varies, for example, depending on factors such as the cavity volume of the metal mold and the size of the injection speed setting Lvs.

[0064] Furthermore, in the second step of the pre-performed molding cycle, the injection control unit 85 controls the injection pressure to ensure that the pressure detection result is below a predetermined upper limit. The "second step" refers to the step following the first step, including the injection process from its midpoint until its end. In low-pressure injection molding, the second step is a pressure control step. The pressure control step begins in conjunction with the switching timing t. For example, if the actual pressure Lp exceeds the injection pressure setting Lps, the injection control unit 85 reduces the injection speed. While maintaining the injection speed immediately following the speed control step, the actual pressure Lp continues to rise. Therefore, the injection control unit 85 significantly reduces the injection speed through pressure control. Figure 3 As shown, when switching to the pressure control step, the actual speed Lv immediately decreases sharply. Even after the sudden deceleration, the injection pressure rises due to continued injection. Therefore, the actual speed Lv continues to decrease slowly so that the actual pressure Lp does not exceed the injection pressure setting Lps. Furthermore, in the pressure control step, the injection speed setting Lvs is ignored (see reference). Figure 3 (The dotted line indicates the end of the pressure control process (end of the injection process), for example, set according to the position of screw 42. After the pressure control process ends, a pressure holding process is performed.

[0065] For example, the user will Figure 3 The molding cycle shown is used as a reference low-pressure injection molding cycle. In this case, the storage control unit 83 stores the injection speed setting Lvs of the speed control process and the actual speed Lv of the pressure control process in the reference waveform memory 112.

[0066] (Molding operation using speed mode)

[0067] Figure 4 It is shown that Figure 3A chart illustrating an example of the speed and pressure waveforms in injection molding, based on the molding cycle.

[0068] Lps2 indicates the upper limit injection pressure setting. As described above, the upper limit injection pressure setting Lps2 is the value obtained by adding the upper limit change value to the injection pressure setting Lps. By increasing the injection pressure setting value associated with switching to the pressure control process, pressure control that causes the injection speed to become unstable can be avoided. That is, after the molding cycle that has been determined as the baseline, speed control can be performed throughout the entire injection process. The upper limit injection pressure setting Lps2 is set in a way that is sufficiently higher than the injection pressure setting Lps.

[0069] In the first step of the injection process, the injection control unit 85 controls the injection speed based on a previously set speed. More specifically, the first step includes the step at the beginning of the injection process. In the first step, the injection control unit 85 uses... Figure 3 The injection speed setting Lvs shown is the same as the baseline injection speed setting Lvs for low-pressure injection molding. Therefore, Figure 4 The actual speed Lv shown in the figure is... Figure 3 The actual speed Lv shown is approximately consistent. Therefore, the injection speed of the speed control process during low-pressure injection molding, which serves as a benchmark, can be reproduced almost completely.

[0070] Furthermore, in the second step after the first step in the injection process, the injection control unit 85 controls the injection speed based on previous speed detection results. Therefore, in the second step, Figure 3 The actual speed Lv shown in the figure becomes the benchmark for low-pressure injection molding. Figure 4 The injection speed setting Lvs is shown in the diagram. During low-pressure injection molding, which serves as a reference, the injection speed setting Lvs is ignored in the pressure control process. Therefore, previous speed detection results, which represent the actual speed Lv during low-pressure injection molding, are used for speed control. As a result, injection molding can be performed through speed control to reproduce the pressure control process used in low-pressure injection molding, which serves as a reference. Consequently, deviations in the injection speed for each injection can be suppressed, and the reproducibility of the molded product's quality can be improved.

[0071] Furthermore, more specifically, the injection control unit 85 controls the injection speed of the injection process by using a previous speed setting and previous speed detection results as the injection speed setting. This "speed setting" differs from a previous speed setting; it is the setting of the injection speed for the current or subsequent molding cycle. As described above, the previous speed setting from the speed control process during low-pressure injection molding is used for the speed setting of the first process. Similarly, the previous speed detection results from the pressure control process during low-pressure injection molding are used for the speed setting of the second process. The injection control unit 85 controls the injection speed of the injection process in a manner that follows the previous speed setting and previous speed detection results. The injection control unit 85 performs feedback control, such as PID control.

[0072] Next, the control method of injection molding machine 1 will be explained.

[0073] Figure 5 This is a flowchart illustrating an example of the operation of the injection molding machine 1 according to the first embodiment.

[0074] First, the injection molding machine 1 performs low-pressure injection molding, and the data memory 111 stores the injection speed waveform based on the low-pressure injection molding (S10).

[0075] Next, the user determines whether the molded product is a qualified product (S20). If the molded product is not a qualified product (No in S20), step S10 is executed again. Therefore, steps S10 and S20 are repeated until a qualified product is obtained. In addition, for example, steps S10 and S20 are executed in each molding cycle.

[0076] On the other hand, if the molded product is a qualified product (S20), the storage control unit 83 stores the previous speed setting and previous speed detection results in the reference waveform memory 112 (S30). The user, for example, operates the storage control unit 83 through the operation of the HMI / F60, so that the previous speed setting set by the injection speed setting unit 84 and the previous speed detection results stored in the data memory 111 are stored in the reference waveform memory 112.

[0077] Next, the injection speed setting unit 84 automatically sets the injection speed (S40). The injection speed setting unit 84 obtains the previous speed settings and previous speed detection results stored in the reference waveform memory 112, and uses them as the speed settings for subsequent molding operations.

[0078] Next, the injection molding machine 1 starts molding operation based on the settings made by the injection speed setting unit 84 (S50).

[0079] Next, the user determines whether the molded product is a qualified product (S60). If the molded product is not a qualified product (No in S60), the user adjusts the injection speed (S70). That is, the user adjusts the speed setting of the injection speed setting unit 84. After that, step S50 is executed again. Therefore, steps S50 to S70 are repeated until a qualified product is obtained. In addition, for example, steps S50 to S70 are executed in each molding cycle.

[0080] On the other hand, if the molded product is a qualified product (as in S60), the user continues to operate as before. Therefore, mass production of the product is carried out.

[0081] also, Figure 5 The low-pressure injection molding (step S10) and molding operation (step S50) shown are not limited to being performed using a series of operations. For example, low-pressure injection molding can be performed separately before the molding operation, and then, in the independently performed molding operation, the previous speed settings and previous speed detection results obtained using low-pressure injection molding can be used. Therefore, in various small-batch production processes, even if the metal mold is frequently changed due to variations in the molded product, the previous speed settings and previous speed detection results of the same metal mold can be reused. As a result, sampling of the speed waveform during low-pressure injection molding can be omitted, improving manufacturing efficiency.

[0082] Figure 6A This is a graph illustrating an example of speed waveforms for multiple control methods. Figure 6B This is a graph illustrating an example of pressure waveforms for multiple control methods. Figure 6A and Figure 6B The velocity and pressure waveforms shown are measured values.

[0083] V1 shows the actual speed during low-pressure injection molding, which serves as a benchmark. V2 shows the actual speed of the molding operation in this embodiment. V3 shows the actual speed of laminar flow control, which serves as a comparative example. Figure 6A The actual velocities V1 to V3 shown in the image Figure 3 and Figure 4 The actual speed Lv shown in the figure peaks as it does, and then decreases.

[0084] P1 shows the actual pressure during low-pressure injection molding, which serves as a benchmark. P2 shows the actual pressure during the molding operation of this embodiment. P3 shows the actual pressure for laminar flow control, which is used as a comparative example. Figure 6B The actual pressure images P1 to P3 shown in the figure Figure 3 and Figure 4 The actual pressure Lp, as shown in the figure, rises and then becomes approximately constant. Furthermore, as... Figure 6BAs shown in the diagram, the actual pressures P1 through P3 do not always become roughly constant, but rather rise gradually.

[0085] Laminar flow control is a method of controlling the injection speed throughout the injection process based on pre-executed speed detection results from low-pressure injection molding. Therefore, in laminar flow control, previous speed settings are not used. Furthermore, in the following text, refer to... Figure 7 The details of laminar flow control will be explained.

[0086] like Figure 6A As shown, the time until the actual speed V1 reaches its maximum speed is approximately 65 ms. Furthermore, the time until the actual speed V2 reaches its maximum speed is approximately 64 ms. These arrival times are close values. Therefore, the actual speed V2 of the molding operation in this embodiment shows a time variation similar to that of the actual speed V1 used as a reference in low-pressure injection molding.

[0087] From 0 ms to approximately 40 ms, the actual speed V2 is approximately the same as the actual speed V1. However, from approximately 40 ms to approximately 65 ms, the actual speed V2 is lower than the actual speed V1. This is because a control method that begins deceleration before the end of the first stage is used to suppress the actual speed exceeding the maximum value set for the injection speed relative to the set delay (overshoot). Furthermore, for example, if the first stage ends after the actual speed Lv has been approximately the same as the injection speed set Lvs for a predetermined period (stable), the actual speed V2 of the first stage is approximately the same as the actual speed V1. Alternatively, a control method that does not decelerate in the first stage can also be used. In this case, the actual speed V2 of the first stage is also approximately the same as the actual speed V1.

[0088] From approximately 65 ms to approximately 150 ms, the actual velocity V2 follows the actual velocity V1 with a delay. Furthermore, after approximately 150 ms, the actual velocity V2 is roughly the same as the actual velocity V1.

[0089] like Figure 6B As shown, the actual pressure P1 during the baseline low-pressure injection molding peaks at approximately 77 ms. The time until the actual pressure P2 reaches the peak pressure of the actual pressure P1 is approximately 90 ms. Therefore, the actual pressure P2 during the molding operation of this embodiment exhibits a similar time variation to the actual pressure P1 during the baseline low-pressure injection molding.

[0090] Therefore, in the molding operation of this embodiment, injection molding can be performed using injection speed and injection pressure that are close to those used in low-pressure injection molding as a reference.

[0091] As described above, according to the first embodiment, the injection control unit 85 controls the injection speed of the injection process based on the previous speed setting and previous speed detection results of the pre-performed molding cycle. Therefore, the injection process can be performed by speed control to reproduce the injection speed and injection pressure of low-pressure injection molding, which serves as a reference for previous molding cycles. As a result, metal mold protection, low-pressure molding, and low residual stress molding are possible, and the reproducibility of the quality of low-pressure injection molded articles can be improved by speed control.

[0092] Figure 7 This is a graph showing an example of the velocity and pressure waveforms for laminar flow control.

[0093] like Figure 7 As shown in the diagram, in laminar flow control, the actual speed Lv of the entire injection process during low-pressure injection molding, which will serve as the benchmark, is used as the injection speed setting Lvs. That is, laminar flow control and... Figure 4 The molding operation shown in this embodiment is different: at the beginning of the injection process, the conventional speed detection results are also used for speed setting, while the conventional speed setting is not used for speed setting.

[0094] Figure 7 The actual velocity Lv shown is equal to the velocity Lv immediately after the injection process begins. Figure 3 and Figure 4 The actual speed Lv shown is lower. This is because, in laminar flow control, the actual speed Lv during low-pressure injection molding, which will become the benchmark, is used as the injection speed setting Lvs. That is, Figure 7 The actual velocity Lv shown in the figure is relative to Figure 3 The injection speed setting Lvs shown as the baseline for low-pressure injection molding is affected by a dual control delay. In laminar flow control, speed control is performed throughout the entire injection process, thus achieving reproducibility of the quality of each injection, similar to the molding operation of this embodiment. However, the time variations in injection speed and injection pressure in laminar flow control sometimes differ significantly from the baseline molding cycle. In this case, there is a possibility of molding defects that do not occur in the baseline molding cycle.

[0095] like Figure 6A As shown, the time until the actual speed V3 reaches its maximum speed is approximately 95 ms. This approximately 95 ms is longer than the approximately 65 ms and approximately 64 ms that are the arrival times of the actual speeds V1 and V2, respectively. That is, the actual speed V3 of laminar flow control is significantly delayed from 0 ms to approximately 150 ms relative to the actual speeds V1 and V2.

[0096] like Figure 6BAs shown, the time until the actual pressure P3 reaches the peak pressure of the actual pressure P1 is approximately 117 ms. This approximately 117 ms is longer than the approximately 77 ms and approximately 90 ms that are the arrival times of the actual pressures P1 and P2, respectively. That is, the actual pressure P3 in laminar flow control is significantly delayed from 0 ms to approximately 150 ms relative to the actual pressures P1 and P2.

[0097] In contrast, in this embodiment, in the first step, the previous speed setting is used for speed control instead of the previous speed detection result. This allows the actual speed Lv and actual pressure Lp of the first step to be approximately the same as those used in low-pressure injection molding. As a result, the actual speed Lv and actual pressure Lp of the second step following the first step can be made close to those used in low-pressure injection molding. Therefore, the quality of the molded product, such as appearance quality, can be improved compared to laminar flow control.

[0098] (Second Implementation)

[0099] Figure 8 This is a block diagram showing the configuration of the control device 8 according to the second embodiment. The second embodiment differs from the first embodiment in that, in the second step, feedforward control (also known as FF (Feed Forward) control) is used for controlling the injection speed.

[0100] In the molding operation of the first embodiment, such as Figure 4 As shown, the actual speed Lv in the second step follows the injection speed setting Lvs with a delay due to control latency. Therefore, in cases where the injection speed setting Lvs changes drastically, such as at the beginning of the second step, there is a possibility that the actual speed Lv and the injection speed setting Lvs may not be consistent. Therefore, by using feedforward control to suppress the control latency, the actual speed Lv in the second step can be made closer to the injection speed setting Lvs. Furthermore, no feedforward control is performed in the first step. Therefore, the first step of the second embodiment is the same as that of the first embodiment.

[0101] The control unit 8 also includes an integrator IN and an instruction correction unit C.

[0102] The injection control unit 85 generates a speed command for the screw 42 based on previous speed detection results set by the injection speed setting unit 84.

[0103] The integrator IN, which functions as a command conversion unit, integrates the speed command from the injection control unit 85 and converts it into a position command. The integrator IN then transmits the converted position command to the injection control servo amplifier 86.

[0104] The command correction unit C corrects the position command of the screw 42 based on the speed command. More specifically, the command correction unit C corrects the position command so that the speed detection result detected by the speed sensor is close to the previous speed detection result. The "speed detection result" is different from the previous speed detection result; it is the detection result of the injection speed of the current or subsequent molding cycle.

[0105] In addition, the instruction correction unit C includes a feedforward control unit FC and an adder A.

[0106] The feedforward control unit (FC) calculates the product of the speed command for screw 42 based on previous speed detection results and a predetermined value. The predetermined value is, for example,... Figure 8 The feedforward control quantity (also known as the FF quantity) F is shown in the figure. The feedforward control quantity F is, for example, a constant.

[0107] Adder A corrects the position command by adding the product of the screw 42 speed command (based on previous speed detection results) and the feedforward control quantity F to the position command based on previous speed detection results. Adder A then transmits the position command as the result of the addition operation to the injection control servo amplifier 86. Therefore, the sum of the original position command and the feedforward control quantity F is transmitted as a command to the injection control servo amplifier 86. This improves the speed responsiveness of the second process and suppresses the speed feedback delay caused by control latency.

[0108] Figure 9 This is a graph illustrating an example of the variation in speed command based on feedforward control. Furthermore, the speed command is obtained by time differentiation of the position command.

[0109] L1 (dashed line) shows the time variation of the speed command without feedforward control (when the feedforward control quantity F is zero). L1 rises over time, becomes constant, and then falls. L2 (solid line) shows the time variation of the speed command with feedforward control.

[0110] like Figure 9 As shown in the figure, when feedforward control is performed, the speed command is expressed as a speed waveform that is different from the original command speed by adding the feedforward control quantity F.

[0111] Figure 10 This is a diagram illustrating an example of the changes in the speed command based on feedforward control for the second process. Figure 10 The speed shown is an overview of the time variation of the speed command.

[0112] L1a (dashed line) shows the time variation of the speed command without feedforward control. Therefore, L1a shows... Figure 4The diagram shows an overview of the injection speed setting Lvs. Furthermore, L1a considers the speed increase at the start of the injection process. L2a (solid line) shows the time variation of the speed command when feedforward control is in effect. Additionally, Figure 10 The time intervals of 150ms to 300ms shown in the figure are... Figure 6A The time correspondence is shown in the figure.

[0113] exist Figure 10 In the example shown, the feedforward control variable F for the first step is set to zero. Since no feedforward control is performed, L2a for the first step is approximately the same as L1a.

[0114] At the switching time ta between the first and second processes, the setting of the feedforward control quantity F is input, and feedforward control is executed. Therefore, L2a is smaller than L1a. Thus, the speed reduction immediately following the switching time ta can be made more abrupt. This suppresses the control delay of speed feedback relative to the speed command, for example, enabling... Figure 4 The actual speed Lv of the second process is close to the injection speed setting Lvs.

[0115] At 150ms, the difference between L1a and L2a decreases. This is because the value of the feedforward control quantity F decreases. In the second step, the setting of the feedforward control quantity F can also be changed accordingly to the magnitude of the feedback control delay (i.e., the magnitude of the change in the speed command).

[0116] Furthermore, the feedforward control quantity F is set in a manner that is approximately equal to the deviation from the position command and the position feedback of the screw 42. The position feedback is, for example, the detection result of the screw position sensor S2. This allows the control delay of the feedback to be offset (suppressed). The feedforward control quantity F is, for example, preset by the user to a desired value, so that the feedback delay can be appropriately eliminated. The user, for example, confirms the actual speed and simultaneously determines the value of the feedforward control quantity F during performance verification of the injection molding machine 1. The feedforward control quantity F can be stored, for example, in a storage unit such as a reference waveform memory 112.

[0117] In addition, Figure 10 In this process, the movement of screw 42 is obtained by integrating the velocity. Figure 10 In the example shown, it can be seen that the amount of movement differs between L1a and L2a. However, strictly speaking, if feedforward control is initiated, a speed command is generated in the direction that cancels out the difference in movement between L1a and L2a, corresponding to the first control scan immediately following the start. As a result, the amounts of movement of L1a and L2a are approximately equal. Furthermore, since it is only a single control scan, the resulting speed command has almost no effect on changes in speed feedback.

[0118] In this way, by using feedforward control, the delay in injection speed during the second process can be suppressed. Furthermore, not only the delay in injection speed but also the delay in injection pressure can be suppressed. As a result, the time variations of the actual speed Lv and the actual pressure Lp can be made closer to the values ​​of the molding cycle reference (when a qualified product is molded). Therefore, the quality of the molded product is further improved, and it can approach the quality of the molding process that serves as the reference.

[0119] The other configurations of the injection molding machine 1 according to the second embodiment are the same as the corresponding configurations of the injection molding machine 1 according to the first embodiment, and therefore their detailed descriptions are omitted.

[0120] The injection molding machine 1 according to the second embodiment can achieve the same effect as the first embodiment.

[0121] At least a portion of the injection molding machine 1 and its control method according to this embodiment can be constructed in hardware or software. In the case of software construction, a program implementing at least a portion of the functions of the injection molding machine 1 and its control method can be stored on a recording medium such as a floppy disk or CD-ROM, and then read and executed by a computer. The recording medium is not limited to removable objects such as disks or optical discs, but can also be a fixed recording medium such as a hard disk drive or memory. Furthermore, the program implementing at least a portion of the functions of the injection molding machine 1 and its control method can be distributed via communication lines (including wireless communication) such as the Internet. Moreover, the program can be distributed via wired or wireless lines such as the Internet or stored on a recording medium while being encrypted or compressed by modulation.

[0122] Several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments or variations thereof are included in the scope or spirit of the invention, and likewise, are included in the scope of the invention as set forth in the claims and their equivalents.

Claims

1. An injection molding machine comprising: an injection device that injects a material into a metal mold that is clamped; and a control section that is a control section that controls the injection device, controls an injection speed of an injection process in which the injection device injects the material into the metal mold based on a past speed setting of an injection speed of a molding cycle that is performed in advance and a past speed detection result that is detected by a speed sensor that detects the injection speed in the past, the control section: controls the injection speed based on the past speed setting in a first process in the injection process, starts deceleration before the first process ends compared to the past speed detection result, controls the injection speed based on the past speed detection result in a second process after the first process in the injection process, the injection device injects the material into the metal mold that is clamped by moving a screw in a cylinder, the control section generates a speed command of the screw based on the past speed detection result, further comprises a command correction section that corrects a position command of the screw based on the speed command, the command correction section corrects the position command by adding a product of the speed command of the screw based on the past speed detection result and a predetermined value to the position command based on the past speed detection result.

2. The injection molding machine according to claim 1, wherein the control section: controls the injection speed based on the past speed setting in the first process of the molding cycle that is performed in advance from the start of the injection process until a pressure detection result of a pressure sensor that detects an injection pressure reaches a predetermined upper limit value, controls the injection pressure so that the pressure detection result becomes below the predetermined upper limit value in the second process of the molding cycle that is performed in advance.

3. The injection molding machine according to claim 2, wherein the command correction section corrects the position command so that a speed detection result detected by the speed sensor approaches the past speed detection result.

4. The injection molding machine according to claim 3, wherein the predetermined value is set in a manner that a deviation from a position feedback of the screw and the position command is substantially equal.

5. The injection molding machine according to any one of claims 1 to 4, wherein the control section controls the injection speed of the injection process by using the past speed setting and the past speed detection result as a speed setting of the injection speed.

6. The injection molding machine according to any one of claims 1 to 4, wherein the control section controls the injection speed of the injection process in a manner that follows the past speed setting and the past speed detection result.

7. The injection molding machine according to any one of claims 1 to 4, wherein the control section controls the injection speed of the injection process based on the past speed setting and the past speed detection result of a molding cycle in which a molded product is a good product in the molding cycle that is performed in advance.

8. The injection molding machine according to any one of claims 1 to 4, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The storage control section stores the past speed setting of the previously performed molding cycle and the past speed detection result in a storage section.

9. A control method of an injection molding machine, which is a control method of an injection molding machine provided with an injection device that injects a material into a metal mold that is clamped, and a control section that controls the injection device, wherein the injection device injects the material into the metal mold by moving a screw in a cylinder, the control section controls an injection speed of the injection device in an injection process based on a past speed setting of a past injection speed that is set in advance for a previously performed molding cycle and a past speed detection result that is detected by a speed sensor that detects the injection speed, the control section: in a first process in the injection process, controls the injection speed based on the past speed setting, and starts deceleration before the first process ends compared to the past speed detection result, in a second process after the first process in the injection process, controls the injection speed based on the past speed detection result, the injection device injects the material into the metal mold by moving the screw in the cylinder, the control section generates a speed command of the screw based on the past speed detection result, the injection molding machine is further provided with a command correction section that corrects a position command of the screw that is based on the speed command, the command correction section corrects the position command by adding a product of the speed command of the screw based on the past speed detection result and a predetermined value to the position command based on the past speed detection result.

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