Injection molding machine

Abstract

To provide an injection molding machine capable of discharging an inert gas in a cavity at an appropriate timing without being affected by other injection conditions.SOLUTION: There is provided an injection molding machine that executes: an injection process in which a screw is advanced from an injection start position to an injection completion position in a heating cylinder to inject molten resin into a cavity; and during execution of the injection process, a gas supply / exhaust process is performed in which a gas supply / exhaust device exhausts the inert gas from the cavity when the screw reaches a pressure reduction start position by supplying inert gas to the cavity until the screw reaches the pressure reduction start position. The pressure reduction start position is a position that is advanced from the injection start position by a distance obtained by multiplying an injection stroke, which is a distance from the injection start position to the injection completion position, by a predetermined compression / decompression rate.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an injection molding machine that injects molten resin into a mold to produce an injection-molded product. [Background technology]

[0002] 2. Description of the Related Art There have been known injection molding machines capable of so-called "gas counter pressure (GCP) molding," in which molten resin is injected into a mold cavity filled with an inert gas (see, for example, Patent Documents 1 and 2).

[0003] In GCP molding, the timing of discharging the inert gas from the cavity during the injection of the molten resin is important. The timing of discharging the inert gas can be determined, for example, by the absolute position of the screw or the elapsed time from the start of injection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 61-239917 [Patent Document 2] JP 2010-247414 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a method of specifying the discharge timing based on the absolute position of the screw, the discharge timing also shifts when the injection start position shifts. Also, in a method of specifying the discharge timing based on the elapsed time from the injection start position, it becomes necessary to change the set value of the discharge timing every time other injection conditions (e.g., injection speed) are adjusted.

[0006] The present invention has been made to solve such problems of the conventional technology, and its purpose is to provide a technology that can discharge the inert gas in the cavity at an appropriate timing in an injection molding machine capable of GCP molding, without being affected by other injection conditions. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an injection molding machine including a clamping device for opening / closing and clamping a mold, an injection device for injecting molten resin into a cavity of the clamped mold, a gas supply / exhaust device for supplying and discharging an inert gas to the cavity, and a control device for controlling the clamping device, the injection device, and the gas supply / exhaust device, wherein the injection device includes a heating cylinder whose tip is in communication with the clamped mold, and a screw which advances and retreats inside the heating cylinder, and the control device controls the screw to move forward and backward in an injection manner from an injection start position to an injection completion position within the heating cylinder. the gas supply / discharge device supplies the inert gas to the cavity until the screw reaches a decompression start position during the injection process, and discharges the inert gas from the cavity at the timing when the screw reaches the decompression start position, and the decompression start position is a position advanced from the injection start position by a distance obtained by multiplying an injection stroke, which is the distance from the injection start position to the injection completion position, by a predetermined pressurization / decompression rate. Effect of the Invention

[0008] According to the present invention, in an injection molding machine capable of GCP molding, the inert gas in the cavity can be discharged at an appropriate timing without being affected by other injection conditions. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an injection molding machine according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a diagram showing the configuration of a foaming agent supply device and a gas supply / discharge device. [Diagram 3] FIG. 2 is a hardware block diagram of the injection molding machine. [Figure 4] 13 is an example of an injection condition setting screen. [Diagram 5] 4 is a flowchart of an injection control process. [Figure 6] FIG. 11 is a diagram showing the tip position of the screw in the injection control process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An injection molding machine 10 according to the present invention will be described below with reference to the drawings. The injection molding machine 10 is a device that injects a measured amount of molten resin (molding material) into a mold to mold an injection-molded product (hereinafter referred to as "injection molding"). The injection molding machine 10 is also a device capable of so-called "gas counter pressure (GCP) molding", in which molten resin is injected into a mold cavity filled with an inert gas.

[0011] [Configuration of injection molding machine 10] Fig. 1 is a side view of an injection molding machine 10 according to this embodiment. Fig. 2 is a diagram showing the configurations of a foaming agent supplying device 40 and a gas supplying and discharging device 50. Fig. 3 is a hardware block diagram of the injection molding machine 10. As shown in Figs. 1 to 3, the injection molding machine 10 mainly includes a mold clamping device 20, an injection device 30, a foaming agent supplying device 40, a gas supplying and discharging device 50, and a control device 60.

[0012] The clamping device 20 opens, closes, and clamps the mold 21. Specifically, the clamping device 20 mainly includes a fixed die plate 23 that supports a fixed-side mold 22, and a movable die plate 25 that supports a movable-side mold 24. The fixed-side mold 22 and the movable-side mold 24 are supported so as to face each other in the left-right direction (horizontal direction) of the injection molding machine 10.

[0013] The movable die plate 25 moves left and right along the tie bars 27 by transmitting the driving force of the die opening / closing motor 28 through the toggle link mechanism 26. When the movable die plate 25 moves leftward, the fixed die 22 and the movable die 24 move away from each other. On the other hand, when the movable die plate 25 moves rightward, the fixed die 22 and the movable die 24 come into contact with each other, forming a cavity C (internal space) inside the die 21. Then, when pressure is further applied in a direction that moves the movable die plate 25 rightward, the fixed die 22 and the movable die 24 are clamped.

[0014] The injection device 30 plasticizes, measures, and injects the molding material. The injection device 30 according to this embodiment is disposed apart from the mold clamping device 20 in the horizontal direction (to the right of the mold clamping device 20). The injection device 30 mainly includes a heating cylinder 31, a screw 32, a hopper 33, and a hopper block 34.

[0015] The heating cylinder 31 is a cylindrical member extending in the left-right direction of the injection molding machine 10. The heating cylinder 31 mainly includes a resin passage 35 and a nozzle 36. In addition, a band heater for heating the heating cylinder 31 is attached to the outer circumferential surface of the heating cylinder 31.

[0016] The resin passage 35 is a cylindrical space extending in the axial direction (longitudinal direction) inside the heating cylinder 31. The resin passage 35 communicates with the outside of the heating cylinder 31 (cavity C of the mold 21) through a nozzle 36 provided at the tip (front end) of the heating cylinder 31. In other words, the resin passage 35 is a space extending from the nozzle 36 along the axial direction.

[0017] The screw 32 is a cylindrical member. A spiral groove is formed on the outer circumferential surface of the screw 32. The screw 32 is accommodated in the internal space of the heating cylinder 31 in a state in which the screw 32 can move in the left-right direction of the injection molding machine 10 (hereinafter, referred to as "advance and retreat") and can rotate. The screw 32 advances and retreats when a driving force of an injection motor 37 is transmitted thereto, and rotates when a driving force of a metering motor 38 is transmitted thereto.

[0018] More specifically, when the injection motor 37 is rotated in the forward direction, the screw 32 moves (forward) toward the tip of the heating cylinder 31 (i.e., the nozzle 36). On the other hand, when the injection motor 37 is rotated in the reverse direction, the screw 32 moves (rearward) toward the base end of the heating cylinder 31 (i.e., the side opposite the nozzle 36). Hereinafter, within the range that the tip position of the screw 32 can reach within the heating cylinder 31, the position closest to the nozzle 36 is referred to as the "forward limit," and the position farthest from the nozzle 36 is referred to as the "rear limit." In addition, the terms "forward rotation" and "reverse rotation" of the injection motor 37 do not specify an absolute direction of rotation, but merely specify a relative relationship (i.e., forward rotation and reverse rotation are rotations in opposite directions).

[0019] The hopper 33 is a funnel-shaped member that stores the raw molding material. The hopper block 34 is a member that supports the heating cylinder 31 and the hopper 33. The hopper 33 communicates with a resin passage 35 through the hopper block 34 at a portion of the heating cylinder 31 closer to the base end than the tip end. The molding material stored in the hopper 33 is supplied to the resin passage 35 of the heating cylinder 31 through an opening provided at the lower end. The molding material used in this injection molding machine 10 is, for example, so-called "pellets" that are formed into a cylindrical shape.

[0020] In the injection device 30, the screw 32 moves backward while rotating by rotating the injection motor 37 in the reverse direction and rotating the metering motor 38. As a result, the pellets supplied through the hopper 33 are filled (metered) into the resin passage 35 ahead of the screw 32 while being plasticized. In addition, in the injection device 30, the injection motor 37 rotates forward to move the screw 32 forward. As a result, the plasticized resin ahead of the screw 32 is injected into the cavity of the mold 21 through the nozzle 36.

[0021] Furthermore, the nozzle 36 is a so-called "shut-off valve" that includes a shut-off valve (on-off valve) 39. The shut-off valve 39 is disposed in the passage of the molten resin in the nozzle 36. The shut-off valve 39 is an electromagnetic valve that can be switched between an open position that opens the passage and a closed position that closes the passage under the control of the control device 60. That is, when the shut-off valve 39 is in the open position, the molten resin in the resin passage 35 can be injected into the cavity C through the nozzle 36. On the other hand, when the shut-off valve 39 is in the closed position, the molten resin in the resin passage 35 cannot enter the cavity C, and the inert gas in the cavity C does not leak out into the resin passage 35.

[0022] The foaming agent supplying device 40 is a device that supplies a raw material gas (e.g., carbon dioxide gas, nitrogen gas) serving as a physical foaming agent to the resin passage 35 of the heating cylinder 31. More specifically, the foaming agent supplying device 40 supplies the raw material gas to the molten resin that has been metered and plasticized by the screw 32. The foaming agent supplying device 40 according to this embodiment includes a gas cylinder 41 that stores the raw material gas, and an injection device 42 that brings the raw material gas stored in the gas cylinder 41 into a supercritical state and injects it into the resin passage 35.

[0023] The gas supply and exhaust device 50 is a device that supplies and exhausts an inert gas (e.g., nitrogen gas) to and from the cavity C of the clamped mold 21. The gas supply and exhaust device 50 is connected to the cavity C, for example, through a gas passage provided in the movable mold 24. The gas supply and exhaust device 50 according to this embodiment includes a gas cylinder 51 that stores the inert gas, and a directional control valve 52 that switches the supply and exhaust of the inert gas to the cavity C.

[0024] The directional control valve 52 is an electromagnetic valve that can be switched between a discharge position A and a supply position B under the control of the control device 60. The discharge position A is a position of the directional control valve 52 that does not supply the inert gas stored in the gas cylinder 51 to the cavity C and connects the cavity C to the outside of the injection molding machine 10 (i.e., discharges the inert gas in the cavity C to the outside). On the other hand, the supply position B is a position of the directional control valve 52 that supplies the inert gas stored in the gas cylinder 51 to the cavity C and does not discharge the inert gas in the cavity C to the outside.

[0025] [Configuration of control device 60] 3, the control device 60 includes a central processing unit (CPU) 61, which is a calculation means, a read only memory (ROM) 62 that stores various programs, and a random access memory (RAM) 63, which is a working area for the calculation means. The ROM 62 and the RAM 63 are examples of memory. The CPU 61 may read and execute the programs stored in the ROM 62 to realize each process described below.

[0026] However, the specific configuration of the control device 60 is not limited to this, and may be realized by hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0027] The control device 60 controls the overall operation of the injection molding machine 10. More specifically, the control device 60 controls the mold opening / closing motor 28, the injection motor 37, the metering motor 38, the shutoff valve 39, the injector 42, and the directional control valve 52 based on various signals output from a rotary encoder 64, a load cell 65 (pressure sensor), and a display / input device 67.

[0028] The mold opening / closing motor 28, the injection motor 37, and the metering motor 38 are servo motors that generate driving forces to open and close the mold 21, driving forces to move the screw 32 back and forth, and driving forces to rotate the screw 32, for example, under the control of a servo amplifier (not shown).

[0029] The rotary encoder 64 is a sensor that detects the speed and tip position of the screw 32. More specifically, the rotary encoder 64 outputs a pulse signal corresponding to the rotation of the injection motor 37 to the control device 60. Then, the control device 60 specifies the speed of the screw 32 based on the number of pulse signals output per unit time. The control device 60 also specifies the tip position of the screw 32 based on the accumulated value of the pulse signals.

[0030] The load cell 65 is a sensor that detects the pressure applied to the screw 32. More specifically, the load cell 65 outputs a pressure signal (voltage value) corresponding to the pressure applied to the screw 32 to the control device 60. Then, the control device 60 identifies the pressure applied to the screw 32 based on the pressure signal output from the load cell 65.

[0031] Furthermore, a display input device 67 is connected to the control device 60. The display input device 67 is a user interface that includes a display (display device) that displays various information to be notified to the operator, and buttons, switches, dials, and the like (input devices) that accept input operations by the operator. The display input device 67 may also include a touch panel superimposed on the display. The display input device 67 accepts input operations by the operator, and outputs an input signal corresponding to the accepted input operation to the control device 60.

[0032] 4 is an example of an injection condition setting screen. The injection condition setting screen is a screen that allows an operator to set execution conditions for injection molding. As shown in FIG. 4, the injection condition setting screen includes text boxes that accept input of a metering completion position, an injection completion position, and a pressurization / depressurization ratio, and a [Settings] icon. When the [Settings] icon is tapped, the control device 60 stores the metering completion position, the injection completion position, and the pressurization / depressurization ratio inputted in each text box in the RAM 63.

[0033] The metering completion position is a position that the tip of the screw 32 reaches when the metering of the molten resin is completed. The injection completion position is a position that the tip of the screw 32 reaches when the injection of the molten resin into the cavity C is completed. In other words, the metering completion position is a position rearward of the injection completion position (farther from the nozzle 36). The metering completion position, injection completion position, injection start position and decompression start position described below are the tip positions of the screw 32 within the heating cylinder 31. The tip position of the screw 32 can be expressed as the distance from the forward limit (0 mm) toward the base end of the heating cylinder 31.

[0034] The pressurization / depressurization ratio indicates the ratio between the distance over which the inert gas is filled into the cavity C (i.e., pressurized) and the distance over which the inert gas is discharged from the cavity C (i.e., depressurized) during the injection stroke of the screw 32 in the injection process. In other words, the pressurization / depressurization ratio indicates the timing of discharging the inert gas (i.e., the depressurization start position) during the injection process (while the screw 32 is moving forward in injection). More specifically, the injection stroke is the distance from the injection start position to the injection completion position. And the depressurization start position is a position that is advanced from the injection start position by the distance obtained by multiplying the injection stroke by the pressurization / depressurization ratio.

[0035] The injection conditions set through the injection condition setting screen are not limited to the above-mentioned examples. Other examples include the injection speed, injection pressure, the amount of raw material gas supplied from the foaming agent supply device 40 to the heating cylinder 31, and the pressure of the inert gas supplied from the gas supply / exhaust device 50 to the cavity C.

[0036] [Injection control processing] Fig. 5 is a flowchart of the injection control process. Fig. 6 is a diagram showing the tip position of the screw 32 in the injection control process. The injection control process is a process for injecting molten resin into the cavity C of the clamped mold 21 to form an injection molded product. The control device 60 repeatedly executes the injection control process at predetermined time intervals. As a result, a plurality of injection molded products are successively molded.

[0037] Note that, prior to the execution of the current injection control process, steps S19 to S24 of the previous injection control process are executed. That is, at the start of the current injection control process, the mold 21 is opened, the screw 32 is located at the current injection start position P3, the resin passage 35 is filled with the molten resin and the raw material gas, the shutoff valve 39 is in the closed position, and the directional control valve 52 is in the discharge position A.

[0038] First, the control device 60 rotates the mold opening / closing motor 28 to close and clamp the mold 21 (S11). As a result, a cavity C is formed in the mold 21. Next, the control device 60 switches the directional control valve 52 to the supply position B (S12). As a result, the inert gas stored in the gas cylinder 51 is filled into the cavity C through the directional control valve 52, and the inert gas in the cavity C is maintained at a predetermined pressure.

[0039] Next, the control device 60 switches the shutoff valve 39 to the open position (S13). The control device 60 also rotates the injection motor 37 in the forward direction to cause the screw 32 to move forward for injection from the injection start position P3 to the injection completion position P5 (S14). The injection forward movement refers to moving the screw 32 forward at a higher speed than the pushing forward movement described below in order to inject the molten resin and raw material gas filled in the resin passage 35 ahead of the screw 32 into the cavity C.

[0040] The control device 60 continues the forward injection movement of the screw 32 until the tip of the screw 32 reaches the injection completion position P5 (S17: No). Then, the control device 60 stops the injection motor 37 (i.e., the screw 32) (S18) at the timing when the tip of the screw 32 reaches the injection completion position P5 (S17: Yes). The processes of steps S14, S17 to S18 are an example of the injection process.

[0041] During the injection process, the control device 60 continues the state of step S12 until the tip of the screw 32 moving forward for injection reaches the pressure reduction start position P4 (S15: No). When the tip of the screw 32 moving forward for injection reaches the pressure reduction start position P4 (S15: Yes), the control device 60 switches the directional control valve 52 to the discharge position A (S16). That is, during the injection process, the control device 60 causes the gas supply and discharge device 50 to supply the inert gas to the cavity C until the screw 32 reaches the pressure reduction start position P4 (S15: No), and discharges the inert gas from the cavity when the screw 32 reaches the pressure reduction start position P4 (S15: Yes→S16). The processes of steps S15 to S16 are an example of a supply and discharge process.

[0042] In other words, in the first half of the injection process until the screw 32 reaches the decompression start position P4, the control device 60 injects the molten resin containing the raw material gas into the cavity C filled with the inert gas. Also, in the second half of the injection process after the screw 32 reaches the decompression start position P4, the control device 60 injects the molten resin containing the raw material gas into the cavity C from which the inert gas has been discharged. This makes it possible to appropriately control the foaming of the molten resin containing the raw material gas in the cavity C.

[0043] Note that the injection start position P3, the pressure reduction start position P4, and the injection completion position P5 may differ for each injection process. More specifically, the injection start position P3, the pressure reduction start position P4, and the injection completion position P5 in the current injection control process vary depending on the position reached by the tip of the screw 32 in the previous push-in process (S21 to S23). Specific methods for calculating the injection start position P3, the pressure reduction start position P4, and the injection completion position P5 will be described later.

[0044] Next, the control device 60 switches the shutoff valve 39 to the closed position after the tip of the screw 32 stops at the injection completion position P5 (S19). Next, the control device 60 rotates the injection motor 37 in the reverse direction and rotates the metering motor 38 to move the screw 32 backward to the metering completion position P2 (=30 mm) while rotating (S20). As a result, the pellets supplied through the hopper 33 are filled (metered) into the resin passage 35 ahead of the screw 32 while being plasticized. In addition, the control device 60 drives the injector 42 to supply the raw material gas stored in the gas cylinder 41 to the resin passage 35. The process of step S20 is an example of a metering process.

[0045] Incidentally, by setting the shutoff valve 39 to the closed position, the inert gas filled in the cavity C does not leak into the resin passage 35, and the molten resin and raw material gas supplied to the resin passage 35 do not enter the cavity C.

[0046] Next, after the tip position of the screw 32 reaches the metering completion position P2, the control device 60 rotates the injection motor 37 in the forward direction to push the screw 32 forward from the metering completion position P2 (S21). Pushing forward refers to advancing the screw 32 at a slower speed than the injection forward speed in order to compress the molten resin filled ahead of the screw 32 at a predetermined pressure. Then, the control device 60 continues pushing forward the screw 32 until the pressure detected by the load cell 65 reaches the predetermined pressure (S22: No). Then, the control device 60 stops the injection motor 37 (i.e., the screw 32) at the timing when the pressure detected by the load cell 65 reaches the predetermined pressure (S22: Yes) (S23). The processes of steps S21 to S23 are an example of a pushing process.

[0047] The control device 60 then sets the position reached by the screw 32 in the pushing process as a new injection start position P3 (=25 mm). The control device 60 also sets the position advanced from the injection completion position P1 previously set via the injection condition setting screen by the distance (=5 mm) between the metering completion position P2 and the new injection start position P3 as a new injection completion position P5 (=5 mm). In other words, the injection start position P3 and the injection completion position P5 may differ for each injection process. On the other hand, the injection stroke (=20 mm) is common to all injection processes.

[0048] Furthermore, the control device 60 calculates a depressurization start position P4 at which the gas supply / exhaust device 50 exhausts the inert gas from the cavity C. The depressurization start position P4 is a position between the injection start position P3 and the injection completion position P5. More specifically, the depressurization start position P4 (=15 mm) is a position advanced from the injection start position P3 (=25 mm) by a distance (=10 mm) obtained by multiplying the injection stroke (=20 mm) by the pressurization / depressurization rate (=50%).

[0049] That is, when the injection start position P3 and the injection completion position P5 change, the absolute position of the pressure reduction start position P4 also changes. However, the relative positions of the injection start position P3, the pressure reduction start position P4, and the injection completion position P5 (in this example, the midpoint between the injection start position P3 and the injection completion position P5 is the pressure reduction start position P4) are common to all injection processes. The injection start position P3, the pressure reduction start position P4, and the injection completion position P5 calculated here are used in the next injection process and the supply and discharge process (S14 to S18).

[0050] Next, the control device 60 rotates the mold opening / closing motor 28 to open the mold 21. Furthermore, the control device 60 causes a robot arm (not shown) to remove the injection molded product from the opened mold 21 (S24), and ends the injection control process.

[0051] [Effects of the embodiment] According to the above embodiment, by specifying the decompression start position P4 using the compression / decompression ratio, even if the injection start position P3 shifts each time the injection process is performed, the timing of discharging the inert gas can be kept constant during the injection stroke. Also, even if other injection conditions such as the injection speed are changed, there is no need to change the compression / decompression ratio. As a result, the inert gas in the cavity C can be discharged at an appropriate timing without being affected by other injection conditions.

[0052] Furthermore, according to the above embodiment, by performing the previous metering process (S20) and pushing process (S21-S23) prior to the current injection process (S14, S17-S18), it is possible to inject molten resin with an appropriate mixture of raw material gas into the cavity C. By performing the pushing process (S21-S23), the injection start position P3 and the injection completion position P5 are shifted for each injection process, so that specifying the discharge timing of the inert gas using the pressurization / depressurization rate becomes particularly effective.

[0053] Furthermore, according to the above embodiment, the metering completion position, the injection completion position, and the pressurization / depressurization ratio are set by the operator, so that the pressure reduction start position P4 can be appropriately set according to the type of molten resin and the injection molded product. However, the parameters set for identifying the pressure reduction start position P4 are not limited to the example in Fig. 4. As another example, the metering completion position, the stroke amount, and the pressurization / depressurization ratio may be set by the operator.

[0054] The above-described embodiments are illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention. [Explanation of symbols]

[0055] 10... injection molding machine, 20... mold clamping device, 21... mold, 22... fixed side mold, 23... fixed die plate, 24... movable side mold, 25... movable die plate, 26... toggle link mechanism, 27... tie bar, 28... mold opening and closing motor, 30... injection device, 31... heating cylinder, 32... screw, 33... hopper, 34... hopper block, 35... resin passage, 36... nozzle, 37... injection motor, 38... metering motor, 39... shutoff valve, 40... foaming agent supply device, 41, 51... gas cylinder, 42... injection device, 50... gas supply and exhaust device, 52... directional control valve, 60... control device, 61... CPU, 62... ROM, 63... RAM, 64... rotary encoder, 65... load cell, 67... display input device

Claims

1. A mold clamping device that opens, closes, and clamps the mold; an injection device that injects molten resin into a cavity of the clamped mold; a gas supply / exhaust device for supplying and discharging an inert gas to the cavity; In an injection molding machine including a control device that controls the mold clamping device, the injection device, and the gas supply and exhaust device, The injection device is A heating cylinder whose tip is in communication with the clamped mold; A screw that advances and retreats inside the heating cylinder, The control device includes: an injection process in which the screw is advanced from an injection start position to an injection completion position in the heating cylinder to inject the molten resin into the cavity; During the injection process, the gas supply / exhaust device is caused to supply the inert gas to the cavity until the screw reaches a pressure reduction start position, and a supply / exhaust process is performed to exhaust the inert gas from the cavity at the timing when the screw reaches the pressure reduction start position. an injection molding machine, characterized in that the decompression start position is a position that is advanced from the injection start position by a distance obtained by multiplying an injection stroke, which is a distance from the injection start position to the injection completion position, by a predetermined compression / decompression rate.

2. The control device includes: a measuring process in which the screw is rotated and retracted from the injection completion position in the previous injection process to a measuring completion position, thereby measuring the molten resin into a space in front of the screw of the heating cylinder; a push-in process for pushing the screw forward from the metering completion position to a position where the screw receives a predetermined pressure from the molten resin is performed prior to the current injection process; The control device, in the current injection process, The position reached by the screw in the pushing process is set as a new injection start position, 2. The injection molding machine according to claim 1, wherein a position advanced from the preset injection completion position by a distance between the metering completion position and the new injection start position is set as the new injection completion position.

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