Injection molding machine controller, injection molding machine, and injection molding machine control method

Abstract

To provide a technique to reduce the impact caused by the injection member being retracted during the pressure holding process.SOLUTION: A control device of an injection molding machine is equipped with an injection member provided inside a cylinder that heats molding material, and an injection drive source that causes the injection member to move forward to fill the molding material into a mold device. The control device has a limiting portion that limits the retraction speed of the injection member in the pressure holding process that controls the filling pressure acting on the molding material from the injection member. The limiting portion limits the retraction speed of the injection member to a smaller speed when the position of the injection member approaches a stop position during the retraction of the injection member in the pressure holding process.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a control device for an injection molding machine, an injection molding machine, and a control method for an injection molding machine.

Background Art

[0002] An injection molding machine includes a cylinder for heating a molding material, an injection member provided inside the cylinder, an injection drive source for filling the molding material into a mold device by advancing the injection member, and a control device for controlling the injection drive source (see Patent Document 1). The control device performs a filling process and a pressure holding process in this order. The filling process is a process of filling the molding material into the mold device by controlling the injection drive source so that the actual value of the moving speed of the injection member becomes the set value. The pressure holding process is a process of replenishing the molding material lacking due to cooling shrinkage in the mold device by controlling the injection drive source so that the actual value of the filling pressure acting on the molding material from the injection member becomes the set value.

[0003] The switching from the filling process to the pressure holding process is also called V / P switching. After V / P switching, when the actual value of the filling pressure is greater than the set value, the injection member is retracted so that the actual value of the filling pressure becomes smaller. Patent Document 1 describes that by providing a limit value for the retraction speed of the injection member in the pressure holding process, it is possible to eliminate the adverse effect on the quality of the molded product caused by the high-speed retraction of the screw in the pressure holding process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, a nozzle is provided at the tip of the cylinder. The nozzle injects the molding material heated in the cylinder into the inside of the mold device. If at least one of the temperatures of the nozzle and the cylinder is too low, the viscosity of the molding material exceeds the viscosity suitable for the injection pressure, resulting in so-called nozzle clogging. Nozzle clogging is a phenomenon in which the molding material is not injected from the nozzle even when the filling process is started and the injection member is advanced.

[0006] When nozzle clogging occurs, after the V / P switchover, the actual value of the filling pressure is larger than the set value and the deviation is large, so there is a risk that the injection member may be retracted to the retraction limit position within the movable range. If the injection member is retracted to the retraction limit position, an impact will occur on the mechanical elements constituting the injection device, shortening the life of the mechanical elements.

[0007] As an example of the mechanical element, a ball screw can be cited. The ball screw converts the rotational motion of the injection motor into the linear motion of the injection member. The ball screw includes a screw shaft, a screw nut, and balls that roll between the screw shaft and the screw nut. When the screw nut reaches the stroke end of the screw shaft, the injection member reaches the retraction limit position and the retraction of the injection member stops.

[0008] Note that the cause of the injection member being retracted to the retraction limit position is not limited to nozzle clogging. For example, when defective ejection of the molded product occurs, the same problem may occur. When defective ejection of the molded product occurs, the filling process is started with the molded product present inside the mold device. Therefore, after the V / P switchover, the actual value of the filling pressure is larger than the set value and the deviation is large, so there is a risk that the injection member may be retracted to the retraction limit position within the movable range.

[0009] One aspect of the present invention provides a technique for reducing the impact generated when the injection member is retracted in the holding pressure process.

Means for Solving the Problems

[0010] The control device of an injection molding machine according to one aspect of the present invention includes an injection member provided inside a cylinder that heats a molding material, and an injection drive source that fills the molding material into the mold device by advancing the injection member. The control device has a limiting unit that limits the retraction speed of the injection member in a pressure holding process of controlling the filling pressure acting on the molding material from the injection member. In the pressure holding process, when the position of the injection member approaches a stop position during the retraction of the injection member, the limiting unit limits the retraction speed of the injection member to a lower speed.

Effects of the Invention

[0011] According to one aspect of the present invention, when the position of the injection member approaches the stop position during the retraction of the injection member in the pressure holding process, the retraction speed of the injection member is limited to a lower speed. Thereby, even if the injection member is retracted to the retraction limit position, the retraction speed of the injection member at that time is low and the impact is small. Therefore, the impact can be reduced.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted.

[0014] (Injection molding machine) FIG. 1 is a diagram showing the state of an injection molding machine when mold opening is completed according to an embodiment. FIG. 2 is a diagram showing the state of the injection molding machine when the mold is clamped according to an embodiment. In this specification, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction represent the horizontal direction, and the Z-axis direction represents the vertical direction. When the mold clamping device 100 is a horizontal mold, the X-axis direction is the mold opening / closing direction, and the Y-axis direction is the width direction of the injection molding machine 10. The negative side in the Y-axis direction is called the operation side, and the positive side in the Y-axis direction is called the non-operation side.

[0015] As shown in FIGS. 1 to 2, the injection molding machine 10 includes a mold clamping device 100 that opens and closes a mold device 800, an ejector device 200 that ejects a molded product formed by the mold device 800, an injection device 300 that injects a molding material into the mold device 800, a moving device 400 that moves the injection device 300 forward and backward with respect to the mold device 800, a control device 700 that controls each component of the injection molding machine 10, and a frame 900 that supports each component of the injection molding machine 10. The frame 900 includes a mold clamping device frame 910 that supports the mold clamping device 100 and an injection device frame 920 that supports the injection device 300. The mold clamping device frame 910 and the injection device frame 920 are each installed on the floor 2 via a leveling adjuster 930. The control device 700 is disposed in the internal space of the injection device frame 920. Hereinafter, each component of the injection molding machine 10 will be described.

[0016] (Mold clamping device) In the description of the mold clamping device 100, the moving direction of the movable platen 120 when the mold is closed (for example, the positive X-axis direction) is defined as the front, and the moving direction of the movable platen 120 when the mold is opened (for example, the negative X-axis direction) is defined as the rear for explanation.

[0017] The clamping device 100 performs mold closing, pressure boosting, mold clamping, pressure release, and mold opening of the mold device 800. The mold device 800 includes a fixed mold 810 and a movable mold 820.

[0018] The clamping device 100 is, for example, a horizontal type, and the mold opening / closing direction is the horizontal direction. The clamping device 100 has a fixed platen 110 to which the fixed mold 810 is attached, a movable platen 120 to which the movable mold 820 is attached, and a moving mechanism 102 that moves the movable platen 120 in the mold opening / closing direction with respect to the fixed platen 110.

[0019] The fixed platen 110 is fixed to the clamping device frame 910. The fixed mold 810 is attached to the opposing surface of the fixed platen 110 with respect to the movable platen 120.

[0020] The movable platen 120 is disposed movably in the mold opening / closing direction with respect to the clamping device frame 910. A guide 101 for guiding the movable platen 120 is laid on the clamping device frame 910. The movable mold 820 is attached to the opposing surface of the movable platen 120 with respect to the fixed platen 110.

[0021] The moving mechanism 102 performs mold closing, pressure boosting, mold clamping, pressure release, and mold opening of the mold device 800 by advancing and retracting the movable platen 120 with respect to the fixed platen 110. The moving mechanism 102 has a toggle support 130 disposed at an interval from the fixed platen 110, a tie bar 140 connecting the fixed platen 110 and the toggle support 130, a toggle mechanism 150 that moves the movable platen 120 in the mold opening / closing direction with respect to the toggle support 130, a clamping motor 160 that operates the toggle mechanism 150, a motion conversion mechanism 170 that converts the rotational motion of the clamping motor 160 into a linear motion, and a mold thickness adjustment mechanism 180 that adjusts the interval between the fixed platen 110 and the toggle support 130.

[0022] The toggle support 130 is disposed at an interval from the fixed platen 110 and is movably placed on the die clamping device frame 910 in the die opening and closing direction. Incidentally, the toggle support 130 may be movably arranged along a guide laid on the die clamping device frame 910. The guide of the toggle support 130 may be common with the guide 101 of the movable platen 120.

[0023] Incidentally, in the present embodiment, the fixed platen 110 is fixed to the die clamping device frame 910, and the toggle support 130 is movably arranged on the die clamping device frame 910 in the die opening and closing direction. However, the toggle support 130 may be fixed to the die clamping device frame 910, and the fixed platen 110 may be movably arranged on the die clamping device frame 910 in the die opening and closing direction.

[0024] The tie bars 140 connect the fixed platen 110 and the toggle support 130 with an interval L in the die opening and closing direction. A plurality of (for example, four) tie bars 140 may be used. The plurality of tie bars 140 are arranged in parallel in the die opening and closing direction and extend according to the clamping force. At least one of the tie bars 140 may be provided with a tie bar strain detector 141 for detecting the strain of the tie bar 140. The tie bar strain detector 141 sends a signal indicating its detection result to the control device 700. The detection result of the tie bar strain detector 141 is used for detecting the clamping force and the like.

[0025] Incidentally, in the present embodiment, the tie bar strain detector 141 is used as the clamping force detector for detecting the clamping force, but the present invention is not limited thereto. The clamping force detector is not limited to the strain gauge type, and may be a piezoelectric type, a capacitive type, a hydraulic type, an electromagnetic type, etc., and its mounting position is not limited to the tie bar 140.

[0026] The toggle mechanism 150 is disposed between the movable platen 120 and the toggle support 130, and moves the movable platen 120 in the mold opening and closing direction with respect to the toggle support 130. The toggle mechanism 150 has a crosshead 151 that moves in the mold opening and closing direction, and a pair of link groups that flex by the movement of the crosshead 151. Each of the pair of link groups has a first link 152 and a second link 153 that are flexibly connected by a pin or the like. The first link 152 is swingably attached to the movable platen 120 by a pin or the like. The second link 153 is swingably attached to the toggle support 130 by a pin or the like. The second link 153 is attached to the crosshead 151 via a third link 154. When the crosshead 151 is advanced and retracted with respect to the toggle support 130, the first link 152 and the second link 153 flex, and the movable platen 120 advances and retracts with respect to the toggle support 130.

[0027] Note that the configuration of the toggle mechanism 150 is not limited to the configurations shown in FIGS. 1 and 2. For example, in FIGS. 1 and 2, the number of nodes of each link group is five, but it may be four, and one end of the third link 154 may be coupled to the node between the first link 152 and the second link 153.

[0028] The mold clamping motor 160 is attached to the toggle support 130 and operates the toggle mechanism 150. The mold clamping motor 160 advances and retracts the crosshead 151 with respect to the toggle support 130, thereby flexing the first link 152 and the second link 153, and advancing and retracting the movable platen 120 with respect to the toggle support 130. The mold clamping motor 160 is directly connected to the motion conversion mechanism 170, but may be connected to the motion conversion mechanism 170 via a belt, a pulley, or the like.

[0029] The motion conversion mechanism 170 converts the rotational motion of the mold clamping motor 160 into the linear motion of the crosshead 151. The motion conversion mechanism 170 includes a screw shaft and a screw nut that is screwed onto the screw shaft. A ball or a roller may be interposed between the screw shaft and the screw nut.

[0030] The mold clamping device 100 performs a mold closing process, a pressure boosting process, a mold clamping process, a pressure releasing process, a mold opening process, etc. under the control of the control device 700.

[0031] In the mold closing process, the mold clamping motor 160 is driven to move the crosshead 151 forward to the mold closing completion position at the set moving speed, thereby moving the movable platen 120 forward and touching the movable mold 820 against the fixed mold 810. The position and moving speed of the crosshead 151 are detected using, for example, the mold clamping motor encoder 161. The mold clamping motor encoder 161 detects the rotation of the mold clamping motor 160 and sends a signal indicating the detection result to the control device 700.

[0032] Note that the crosshead position detector for detecting the position of the crosshead 151 and the crosshead moving speed detector for detecting the moving speed of the crosshead 151 are not limited to the mold clamping motor encoder 161, and general ones can be used. Also, the movable platen position detector for detecting the position of the movable platen 120 and the movable platen moving speed detector for detecting the moving speed of the movable platen 120 are not limited to the mold clamping motor encoder 161, and general ones can be used.

[0033] In the pressure boosting process, the mold clamping motor 160 is further driven to move the crosshead 151 further forward from the mold closing completion position to the mold clamping position to generate a mold clamping force.

[0034] In the mold clamping process, the mold clamping motor 160 is driven to maintain the position of the crosshead 151 at the mold clamping position. In the mold clamping process, the mold clamping force generated in the pressure boosting process is maintained. In the mold clamping process, a cavity space 801 (see FIG. 2) is formed between the movable mold 820 and the fixed mold 810, and the injection device 300 fills the cavity space 801 with a liquid molding material. By solidifying the filled molding material, a molded product is obtained.

[0035] The number of cavity spaces 801 may be one or more than one. In the latter case, a plurality of molded articles can be obtained simultaneously. An insert material may be disposed in a part of the cavity space 801, and a molding material may be filled in another part of the cavity space 801. A molded article in which the insert material and the molding material are integrated can be obtained.

[0036] In the mold release process, the mold clamping motor 160 is driven to retract the crosshead 151 from the mold clamping position to the mold opening start position, thereby retracting the movable platen 120 and reducing the mold clamping force. The mold opening start position and the mold closing completion position may be the same position.

[0037] In the mold opening process, the mold clamping motor 160 is driven to retract the crosshead 151 from the mold opening start position to the mold opening completion position at a set moving speed, thereby retracting the movable platen 120 and separating the movable mold 820 from the fixed mold 810. Then, the ejector device 200 protrudes the molded article from the movable mold 820.

[0038] The setting conditions in the mold closing process, the pressure boosting process, and the mold clamping process are set together as a series of setting conditions. For example, the moving speed and position of the crosshead 151 (including the mold closing start position, the moving speed switching position, the mold closing completion position, and the mold clamping position) and the mold clamping force in the mold closing process and the pressure boosting process are set together as a series of setting conditions. The mold closing start position, the moving speed switching position, the mold closing completion position, and the mold clamping position are arranged in this order from the rear to the front and represent the start point and the end point of the section where the moving speed is set. The moving speed is set for each section. The number of moving speed switching positions may be one or more than one. The moving speed switching position may not be set. Either the mold clamping position or the mold clamping force may be set alone.

[0039] The setting conditions in the pressure release process and the mold opening process are also set in the same way. For example, the moving speed and position of the crosshead 151 (mold opening start position, moving speed switching position, and mold opening completion position) in the pressure release process and the mold opening process are set together as a series of setting conditions. The mold opening start position, moving speed switching position, and mold opening completion position are arranged in this order from the front to the rear, and represent the start and end points of the section where the moving speed is set. The moving speed is set for each section. The moving speed switching position may be one or more. The moving speed switching position may not be set. The mold opening start position and the mold closing completion position may be the same position. Also, the mold opening completion position and the mold closing start position may be the same position.

[0040] Incidentally, instead of the moving speed and position of the crosshead 151, etc., the moving speed and position of the movable platen 120, etc. may be set. Also, instead of the position of the crosshead 151 (for example, the mold clamping position) and the position of the movable platen 120, the mold clamping force may be set.

[0041] By the way, the toggle mechanism 150 amplifies the driving force of the mold clamping motor 160 and transmits it to the movable platen 120. The amplification factor is also called the toggle ratio. The toggle ratio changes according to the angle θ formed by the first link 152 and the second link 153 (hereinafter also referred to as "link angle θ"). The link angle θ is obtained from the position of the crosshead 151. When the link angle θ is 180°, the toggle ratio becomes the maximum.

[0042] When the thickness of the mold device 800 changes due to the replacement of the mold device 800 or the temperature change of the mold device 800, etc., mold thickness adjustment is performed so that a predetermined mold clamping force can be obtained during mold clamping. In the mold thickness adjustment, for example, the distance L between the fixed platen 110 and the toggle support 130 is adjusted so that the link angle θ of the toggle mechanism 150 becomes a predetermined angle at the time of mold touch when the movable mold 820 touches the fixed mold 810.

[0043] The mold clamping device 100 has a mold thickness adjustment mechanism 180. The mold thickness adjustment mechanism 180 adjusts the mold thickness by adjusting the distance L between the fixed platen 110 and the toggle support 130. Note that the timing of the mold thickness adjustment is performed, for example, between the end of the molding cycle and the start of the next molding cycle. The mold thickness adjustment mechanism 180 includes, for example, a screw shaft 181 formed at the rear end of the tie bar 140, a nut 182 rotatably and non - axially movable and held on the toggle support 130, and a mold thickness adjustment motor 183 that rotates the nut 182 screwed onto the screw shaft 181.

[0044] The screw shaft 181 and the nut 182 are provided for each tie bar 140. The rotational driving force of the mold thickness adjustment motor 183 may be transmitted to a plurality of nuts 182 via a rotational driving force transmission unit 185. The plurality of nuts 182 can be rotated synchronously. In addition, by changing the transmission path of the rotational driving force transmission unit 185, it is also possible to rotate the plurality of nuts 182 individually.

[0045] The rotational driving force transmission unit 185 is composed of, for example, gears. In this case, a driven gear is formed on the outer periphery of each nut 182, a driving gear is attached to the output shaft of the mold thickness adjustment motor 183, and an intermediate gear meshing with the plurality of driven gears and the driving gear is rotatably held at the center of the toggle support 130. Note that the rotational driving force transmission unit 185 may be composed of a belt, a pulley, etc. instead of gears.

[0046] The operation of the mold thickness adjustment mechanism 180 is controlled by a control device 700. The control device 700 drives the mold thickness adjustment motor 183 to rotate the nut 182. As a result, the position of the toggle support 130 relative to the tie bar 140 is adjusted, and the distance L between the fixed platen 110 and the toggle support 130 is adjusted. Note that a plurality of mold thickness adjustment mechanisms may be used in combination.

[0047] The interval L is detected using the mold thickness adjustment motor encoder 184. The mold thickness adjustment motor encoder 184 detects the amount and direction of rotation of the mold thickness adjustment motor 183, and sends a signal indicating the detection result to the control device 700. The detection result of the mold thickness adjustment motor encoder 184 is used for monitoring and controlling the position of the toggle support 130 and the interval L. Note that the toggle support position detector for detecting the position of the toggle support 130 and the interval detector for detecting the interval L are not limited to the mold thickness adjustment motor encoder 184, and general ones can be used.

[0048] The mold clamping device 100 may have a mold temperature controller for adjusting the temperature of the mold device 800. The mold device 800 has a flow path for a temperature control medium inside it. The mold temperature controller adjusts the temperature of the mold device 800 by adjusting the temperature of the temperature control medium supplied to the flow path of the mold device 800.

[0049] Note that the mold clamping device 100 of this embodiment is a horizontal type in which the mold opening and closing direction is the horizontal direction, but it may also be a vertical type in which the mold opening and closing direction is the vertical direction.

[0050] Note that the mold clamping device 100 of this embodiment has a mold clamping motor 160 as a drive unit, but it may have a hydraulic cylinder instead of the mold clamping motor 160. Further, the mold clamping device 100 may have a linear motor for mold opening and closing and an electromagnet for mold clamping.

[0051] (Ejector device) In the description of the ejector device 200, similar to the description of the mold clamping device 100, the moving direction of the movable platen 120 at the time of mold closing (for example, the positive X-axis direction) is defined as the front, and the moving direction of the movable platen 120 at the time of mold opening (for example, the negative X-axis direction) is defined as the rear for explanation.

[0052] The ejector device 200 is attached to the movable platen 120 and moves forward and backward together with the movable platen 120. The ejector device 200 has an ejector rod 210 for protruding the molded product from the mold device 800 and a drive mechanism 220 for moving the ejector rod 210 in the moving direction (X-axis direction) of the movable platen 120.

[0053] The ejector rod 210 is disposed so as to be able to advance and retract in the through-hole of the movable platen 120. The front end of the ejector rod 210 contacts the ejector plate 826 of the movable mold 820. The front end of the ejector rod 210 may or may not be connected to the ejector plate 826.

[0054] The drive mechanism 220 has, for example, an ejector motor and a motion conversion mechanism that converts the rotational motion of the ejector motor into the linear motion of the ejector rod 210. The motion conversion mechanism includes a screw shaft and a screw nut that engages with the screw shaft. Balls or rollers may be interposed between the screw shaft and the screw nut.

[0055] The ejector device 200 performs a protruding process under the control of the control device 700. In the protruding process, the ejector rod 210 is advanced from the standby position to the protruding position at a set moving speed, thereby advancing the ejector plate 826 and protruding the molded product. Thereafter, the ejector motor is driven to retract the ejector rod 210 at the set moving speed, and the ejector plate 826 is retracted to the original standby position.

[0056] The position and moving speed of the ejector rod 210 are detected using, for example, an ejector motor encoder. The ejector motor encoder detects the rotation of the ejector motor and sends a signal indicating the detection result to the control device 700. Note that the ejector rod position detector that detects the position of the ejector rod 210 and the ejector rod moving speed detector that detects the moving speed of the ejector rod 210 are not limited to the ejector motor encoder, and general ones can be used.

[0057] (Injection device) In the description of the injection device 300, unlike the description of the mold clamping device 100 and the ejector device 200, the moving direction of the screw 330 during filling (for example, the negative X-axis direction) is described as the front, and the moving direction of the screw 330 during metering (for example, the positive X-axis direction) is described as the rear.

[0058] The injection device 300 is installed on the slide base 301, and the slide base 301 is arranged to be movable forward and backward relative to the injection device frame 920. The injection device 300 is arranged to be movable forward and backward relative to the mold device 800. The injection device 300 touches the mold device 800 and fills the cavity space 801 in the mold device 800 with the molding material. The injection device 300 includes, for example, a cylinder 310 that heats the molding material, a nozzle 320 provided at the front end of the cylinder 310, a screw 330 arranged to be movable forward and backward and rotatable within the cylinder 310, a metering motor 340 that rotates the screw 330, an injection motor 350 that moves the screw 330 forward and backward, and a load detector 360 that detects the load transmitted between the injection motor 350 and the screw 330.

[0059] The cylinder 310 heats the molding material supplied into it from the supply port 311. The molding material includes, for example, resin and the like. The molding material is formed, for example, in the shape of pellets and is supplied to the supply port 311 in a solid state. The supply port 311 is formed at the rear of the cylinder 310. A cooler 312 such as a water-cooled cylinder is provided on the outer periphery of the rear of the cylinder 310. In front of the cooler 312, a first heater 313 such as a band heater and a first temperature detector 314 are provided on the outer periphery of the cylinder 310.

[0060] The cylinder 310 is divided into a plurality of zones in the axial direction (for example, the X-axis direction) of the cylinder 310. A first heater 313 and a first temperature detector 314 are provided in each of the plurality of zones. A set temperature is set for each of the plurality of zones, and the control device 700 controls the first heater 313 so that the detected temperature of the first temperature detector 314 becomes the set temperature.

[0061] The nozzle 320 is provided at the front end of the cylinder 310 and is pressed against the mold device 800. A second heater 323 and a second temperature detector 324 are provided on the outer periphery of the nozzle 320. The control device 700 controls the second heater 323 so that the detected temperature of the nozzle 320 becomes the set temperature.

[0062] The screw 330 is rotatably and axially movable within the cylinder 310. When the screw 330 is rotated, the molding material is fed forward along the spiral groove of the screw 330. While being fed forward, the molding material is gradually melted by the heat from the cylinder 310. As the liquid molding material is fed forward and accumulates at the front of the cylinder 310, the screw 330 is retracted. Then, when the screw 330 is advanced, the liquid molding material accumulated in front of the screw 330 is injected from the nozzle 320 and fills the mold device 800.

[0063] A backflow prevention ring 331 is axially movably attached to the front of the screw 330 as a backflow prevention valve that prevents the backflow of the molding material from the front to the back of the screw 330 when the screw 330 is pushed forward.

[0064] When the screw 330 is advanced, the backflow prevention ring 331 is pushed backward by the pressure of the molding material in front of the screw 330 and relatively retracts with respect to the screw 330 to a closed position (see FIG. 2) that closes the flow path of the molding material. Thereby, the backflow of the molding material accumulated in front of the screw 330 is prevented.

[0065] On the other hand, when the screw 330 is rotated, the backflow prevention ring 331 is pushed forward by the pressure of the molding material fed forward along the spiral groove of the screw 330 and relatively advances with respect to the screw 330 to an open position (see FIG. 1) that opens the flow path of the molding material. Thereby, the molding material is fed to the front of the screw 330.

[0066] The backflow prevention ring 331 may be either a co-rotating type that rotates with the screw 330 or a non-co-rotating type that does not rotate with the screw 330.

[0067] In addition, the injection device 300 may have a drive source for axially moving the backflow prevention ring 331 with respect to the screw 330 between the open position and the closed position.

[0068] The metering motor 340 rotates the screw 330. The drive source for rotating the screw 330 is not limited to the metering motor 340 and may be, for example, a hydraulic pump or the like.

[0069] The injection motor 350 moves the screw 330 forward and backward. Between the injection motor 350 and the screw 330, a motion conversion mechanism or the like that converts the rotational motion of the injection motor 350 into the linear motion of the screw 330 is provided. The motion conversion mechanism has, for example, a screw shaft and a screw nut that engages with the screw shaft. Between the screw shaft and the screw nut, balls, rollers, or the like may be provided. The drive source for moving the screw 330 forward and backward is not limited to the injection motor 350 and may be, for example, a hydraulic cylinder or the like.

[0070] The load detector 360 detects the load transmitted between the injection motor 350 and the screw 330. The detected load is converted into pressure by the control device 700. The load detector 360 is provided in the load transmission path between the injection motor 350 and the screw 330 and detects the load acting on the load detector 360.

[0071] The load detector 360 sends the signal of the detected load to the control device 700. The load detected by the load detector 360 is converted into the pressure acting between the screw 330 and the molding material, and is used for the control and monitoring of the pressure received by the screw 330 from the molding material, the back pressure on the screw 330, the pressure acting on the molding material from the screw 330, and the like.

[0072] In addition, the pressure detector for detecting the pressure of the molding material is not limited to the load detector 360, and a general one can be used. For example, a nozzle pressure sensor or an in-mold pressure sensor may be used. The nozzle pressure sensor is installed in the nozzle 320. The in-mold pressure sensor is installed inside the mold device 800.

[0073] The injection device 300 performs a metering process, a filling process, a holding pressure process, and the like under the control of the control device 700. The filling process and the holding pressure process may be collectively referred to as an injection process.

[0074] In the metering process, the metering motor 340 is driven to rotate the screw 330 at a set rotational speed, and the molding material is fed forward along the spiral groove of the screw 330. Along with this, the molding material is gradually melted. As the liquid molding material is fed forward of the screw 330 and accumulates at the front part of the cylinder 310, the screw 330 is retracted. The rotational speed of the screw 330 is detected, for example, using the metering motor encoder 341. The metering motor encoder 341 detects the rotation of the metering motor 340 and sends a signal indicating the detection result to the control device 700. Note that the screw rotational speed detector for detecting the rotational speed of the screw 330 is not limited to the metering motor encoder 341, and a general one can be used.

[0075] In the metering process, in order to limit a rapid retraction of the screw 330, the injection motor 350 may be driven to apply a set back pressure to the screw 330. The back pressure on the screw 330 is detected, for example, using the load detector 360. When the screw 330 retracts to the metering completion position and a predetermined amount of molding material accumulates in front of the screw 330, the metering process is completed.

[0076] The position and rotational speed of the screw 330 in the metering process are set together as a series of set conditions. For example, the metering start position, the rotational speed switching position, and the metering completion position are set. These positions are arranged in this order from the front to the rear, and represent the start point and the end point of the section where the rotational speed is set. The rotational speed is set for each section. The rotational speed switching position may be one or a plurality. The rotational speed switching position may not be set. Also, the back pressure is set for each section.

[0077] In the filling process, the injection motor 350 is driven to move the screw 330 forward at a set moving speed, and the liquid molding material accumulated in front of the screw 330 is filled into the cavity space 801 in the mold device 800. The position and moving speed of the screw 330 are detected, for example, using the injection motor encoder 351. The injection motor encoder 351 detects the rotation of the injection motor 350 and sends a signal indicating the detection result to the control device 700. When the position of the screw 330 reaches the set position, the switching from the filling process to the holding pressure process (so-called V / P switching) is performed. The position where the V / P switching is performed is also called the V / P switching position. The set moving speed of the screw 330 may be changed according to the position and time of the screw 330, etc.

[0078] The position and moving speed of the screw 330 in the filling process are set together as a series of set conditions. For example, the filling start position (also called the "injection start position"), the moving speed switching position, and the V / P switching position are set. These positions are arranged in this order from the rear to the front and represent the start and end points of the section where the moving speed is set. The moving speed is set for each section. The moving speed switching position may be one or more. The moving speed switching position may not be set.

[0079] For each section where the moving speed of the screw 330 is set, the upper limit value of the pressure of the screw 330 is set. The pressure of the screw 330 is detected by the load detector 360. When the pressure of the screw 330 is below the set pressure, the screw 330 is advanced at the set moving speed. On the other hand, when the pressure of the screw 330 exceeds the set pressure, for the purpose of mold protection, the screw 330 is advanced at a moving speed slower than the set moving speed so that the pressure of the screw 330 becomes below the set pressure.

[0080] Also, after the position of the screw 330 reaches the V / P switching position in the filling process, the screw 330 may be temporarily stopped at the V / P switching position, and then the V / P switching may be performed. Immediately before the V / P switching, instead of stopping the screw 330, the screw 330 may be advanced or retracted at a very low speed. Also, the screw position detector for detecting the position of the screw 330 and the screw moving speed detector for detecting the moving speed of the screw 330 are not limited to the injection motor encoder 351, and general ones can be used.

[0081] In the holding pressure process, the injection motor 350 is driven to push the screw 330 forward, the pressure of the molding material at the front end of the screw 330 (hereinafter, also referred to as "holding pressure") is maintained at the set pressure, and the molding material remaining in the cylinder 310 is pushed toward the mold device 800. The insufficient molding material due to the cooling shrinkage in the mold device 800 can be replenished. The holding pressure is detected using, for example, the load detector 360. The set value of the holding pressure may be changed according to the elapsed time since the start of the holding pressure process and the like. A plurality of holding pressures and holding times for holding the holding pressure may be set in the holding pressure process, respectively, and may be set together as a series of setting conditions.

[0082] In the holding pressure process, the molding material in the cavity space 801 in the mold device 800 is gradually cooled, and when the holding pressure process is completed, the inlet of the cavity space 801 is blocked by the solidified molding material. This state is called gate sealing, and the backflow of the molding material from the cavity space 801 is prevented. After the holding pressure process, the cooling process is started. In the cooling process, the molding material in the cavity space 801 is solidified. For the purpose of shortening the molding cycle time, the metering process may be performed during the cooling process.

[0083] The injection device 300 of the present embodiment is of the in-line screw type, but it may also be of the pre-plug type or the like. The injection device of the pre-plug type supplies the molding material melted in the plasticizing cylinder to the injection cylinder, and injects the molding material from the injection cylinder into the mold device. In the plasticizing cylinder, a screw is arranged rotatably and non-axially movable, or the screw is arranged rotatably and axially movable. On the other hand, in the injection cylinder, a plunger is arranged axially movable.

[0084] Further, the injection device 300 of the present embodiment is horizontal with the axial direction of the cylinder 310 being the horizontal direction, but it may also be vertical with the axial direction of the cylinder 310 being the vertical direction. The mold clamping device combined with the vertical injection device 300 may be vertical or horizontal. Similarly, the mold clamping device combined with the horizontal injection device 300 may be horizontal or vertical.

[0085] (Moving device) In the description of the moving device 400, similar to the description of the injection device 300, the moving direction of the screw 330 during filling (for example, the negative X-axis direction) is regarded as the front, and the moving direction of the screw 330 during metering (for example, the positive X-axis direction) is regarded as the rear for description.

[0086] The moving device 400 moves the injection device 300 forward and backward with respect to the mold device 800. Further, the moving device 400 presses the nozzle 320 against the mold device 800 to generate a nozzle touch pressure. The moving device 400 includes a hydraulic pump 410, a motor 420 as a drive source, a hydraulic cylinder 430 as a hydraulic actuator, and the like.

[0087] The hydraulic pump 410 has a first port 411 and a second port 412. The hydraulic pump 410 is a pump that can rotate in both directions. By switching the rotation direction of the motor 420, hydraulic fluid (for example, oil) is sucked from one of the first port 411 and the second port 412 and discharged from the other to generate hydraulic pressure. Note that the hydraulic pump 410 can also suck the hydraulic fluid from the tank and discharge the hydraulic fluid from one of the first port 411 and the second port 412.

[0088] The motor 420 actuates the hydraulic pump 410. The motor 420 drives the hydraulic pump 410 with a rotational direction and a rotational torque according to a control signal from the control device 700. The motor 420 may be an electric motor and may be an electric servo motor.

[0089] The hydraulic cylinder 430 has a cylinder body 431, a piston 432, and a piston rod 433. The cylinder body 431 is fixed to the injection device 300. The piston 432 divides the inside of the cylinder body 431 into a front chamber 435 as a first chamber and a rear chamber 436 as a second chamber. The piston rod 433 is fixed to the fixed platen 110.

[0090] The front chamber 435 of the hydraulic cylinder 430 is connected to the first port 411 of the hydraulic pump 410 via a first flow path 401. By supplying the hydraulic fluid discharged from the first port 411 to the front chamber 435 via the first flow path 401, the injection device 300 is pushed forward. The injection device 300 moves forward and the nozzle 320 is pressed against the fixed mold 810. The front chamber 435 functions as a pressure chamber that generates the nozzle touch pressure of the nozzle 320 by the pressure of the hydraulic fluid supplied from the hydraulic pump 410.

[0091] On the other hand, the rear chamber 436 of the hydraulic cylinder 430 is connected to the second port 412 of the hydraulic pump 410 via a second flow path 402. By supplying the hydraulic fluid discharged from the second port 412 to the rear chamber 436 of the hydraulic cylinder 430 via the second flow path 402, the injection device 300 is pushed backward. The injection device 300 moves backward and the nozzle 320 is separated from the fixed mold 810.

[0092] In addition, in this embodiment, the moving device 400 includes the hydraulic cylinder 430, but the present invention is not limited thereto. For example, instead of the hydraulic cylinder 430, an electric motor and a motion conversion mechanism that converts the rotational motion of the electric motor into a linear motion of the injection device 300 may be used.

[0093] (Control device) The control device 700 is composed of, for example, a computer, and has a CPU (Central Processing Unit) 701, a storage medium 702 such as a memory, an input interface 703, and an output interface 704 as shown in FIGS. 1 to 2. The control device 700 performs various controls by causing the CPU 701 to execute a program stored in the storage medium 702. Further, the control device 700 receives a signal from the outside through the input interface 703 and transmits a signal to the outside through the output interface 704.

[0094] The control device 700 repeatedly manufactures molded products by repeatedly performing a metering process, a mold closing process, a pressure boosting process, a mold clamping process, a filling process, a pressure holding process, a cooling process, a pressure releasing process, a mold opening process, a pushing out process, and the like. A series of operations for obtaining a molded product, for example, the operations from the start of the metering process to the start of the next metering process, are also called "shots" or "molding cycles". Also, the time required for one shot is also called "molding cycle time" or "cycle time".

[0095] One molding cycle has, for example, a metering process, a mold closing process, a pressure boosting process, a mold clamping process, a filling process, a pressure holding process, a cooling process, a pressure releasing process, a mold opening process, and a pushing out process in this order. The order here is the order of the start of each process. The filling process, the pressure holding process, and the cooling process are performed during the mold clamping process. The start of the mold clamping process may coincide with the start of the filling process. The completion of the pressure releasing process coincides with the start of the mold opening process.

[0096] Incidentally, for the purpose of shortening the molding cycle time, a plurality of processes may be performed simultaneously. For example, the metering process may be performed during the cooling process of the previous molding cycle or during the mold clamping process. In this case, the mold closing process may be performed first in the molding cycle. Also, the filling process may be started during the mold closing process. Also, the pushing out process may be started during the mold opening process. When an on-off valve for opening and closing the flow path of the nozzle 320 is provided, the mold opening process may be started during the metering process. Even if the mold opening process is started during the metering process, as long as the on-off valve closes the flow path of the nozzle 320, the molding material does not leak from the nozzle 320.

[0097] Furthermore, one molding cycle may have processes other than the metering process, mold closing process, pressure boosting process, mold clamping process, filling process, pressure holding process, cooling process, pressure releasing process, mold opening process, and ejection process.

[0098] For example, after the completion of the pressure holding process and before the start of the metering process, a pre-metering suck-back process of retracting the screw 330 to a preset metering start position may be performed. The pressure of the molding material accumulated in front of the screw 330 can be reduced, and a sudden retraction of the screw 330 at the start of the metering process can be prevented.

[0099] Also, after the completion of the metering process and before the start of the filling process, a post-metering suck-back process of retracting the screw 330 to a preset filling start position (also referred to as the "injection start position") may be performed. The pressure of the molding material accumulated in front of the screw 330 can be reduced, and leakage of the molding material from the nozzle 320 before the start of the filling process can be prevented.

[0100] The control device 700 is connected to an operation device 750 that receives input operations by the user and a display device 760 that displays a screen. The operation device 750 and the display device 760 may be configured by, for example, a touch panel 770 and integrated. The touch panel 770 as the display device 760 displays a screen under the control of the control device 700. On the screen of the touch panel 770, information such as settings of the injection molding machine 10 and the current state of the injection molding machine 10 may be displayed. Further, on the screen of the touch panel 770, operation units such as buttons and input fields for receiving input operations by the user may be displayed. The touch panel 770 as the operation device 750 detects an input operation on the screen by the user and outputs a signal corresponding to the input operation to the control device 700. Thereby, for example, the user can perform settings (including input of set values) of the injection molding machine 10 by operating the operation unit provided on the screen while checking the information displayed on the screen. Further, by the user operating the operation unit provided on the screen, the operation of the injection molding machine 10 corresponding to the operation unit can be performed. Note that the operation of the injection molding machine 10 may be, for example, the operation (including stop) of the mold clamping device 100, the ejector device 200, the injection device 300, the moving device 400, etc. Further, the operation of the injection molding machine 10 may be, for example, the switching of the screen displayed on the touch panel 770 as the display device 760.

[0101] In addition, although the operation device 750 and the display device 760 of the present embodiment have been described as being integrated as the touch panel 770, they may be provided independently. Further, a plurality of operation devices 750 may be provided. The operation device 750 and the display device 760 are arranged on the operation side (Y-axis negative direction) of the mold clamping device 100 (more specifically, the fixed platen 110).

[0102] (Details of the control device) Next, with reference to FIG. 3, an example of the components of the control device 700 will be described. Note that each functional block illustrated in FIG. 3 is conceptual and does not necessarily have to be physically configured as shown. All or part of each functional block can be functionally or physically distributed and integrated in any unit. Each processing function performed in each functional block can be realized by a program executed by a CPU for all or any part of it, or can be realized as hardware by wired logic.

[0103] As shown in FIG. 3, the control device 700 includes, for example, a clamping control unit 711, an ejector control unit 712, an injection control unit 713, and a metering control unit 714. The clamping control unit 711 controls the clamping device 100 and performs the mold closing process, pressure boosting process, clamping process, pressure releasing process, and mold opening process shown in FIG. 4. The ejector control unit 712 controls the ejector device 200 and performs the protruding process. The injection control unit 713 controls the injection drive source of the injection device 300 and performs the injection process. The injection drive source is, for example, an injection motor 350, but may also be a hydraulic cylinder or the like. The injection process includes a filling process and a holding pressure process. The injection process is performed during the clamping process. The metering control unit 714 controls the metering drive source of the injection device 300 and performs the metering process. The metering drive source is, for example, a metering motor 340, but may also be a hydraulic pump or the like. The metering process is performed during the cooling process.

[0104] The filling process is a process of controlling the injection drive source so that the actual value of the moving speed of the injection member provided inside the cylinder 310 becomes the set value. The filling process is a process of moving the injection member forward to fill the liquid molding material accumulated in front of the injection member into the mold device 800. The injection member is, for example, a screw 330 (see FIGS. 1 and 2), but may also be a plunger.

[0105] The moving speed of the injection member is detected using a speed detector. The speed detector is, for example, the injection motor encoder 351. In the filling process, as the injection member moves forward, the pressure acting on the molding material from the injection member (hereinafter also referred to as "filling pressure") increases. The filling process may include a process of temporarily stopping the injection member or a process of retracting the injection member immediately before the holding pressure process.

[0106] The holding pressure process is a process of controlling the injection drive source so that the actual value of the filling pressure becomes the set value. The holding pressure process is a process of replenishing the insufficient molding material due to cooling shrinkage in the mold device 800 by pushing the injection member forward. The filling pressure is detected using a pressure detector such as the load detector 360. As the pressure detector, a nozzle pressure sensor or an in-mold pressure sensor may be used.

[0107] The holding pressure process is controlled by the injection control unit 713. As shown in FIG. 5, the injection control unit 713 has, for example, a speed setting unit 713a and a command creation unit 713b. The speed setting unit 713a creates a set value of the speed of the injection member based on the deviation between the set value and the actual value of the filling pressure. The command creation unit 713b creates a command (for example, a current command) for the injection drive source based on the deviation between the set value and the actual value of the speed of the injection member. The injection drive source is, for example, the injection motor 350. The injection drive source is driven according to the command created by the command creation unit 713b.

[0108] The speed setting unit 713a creates a set value of the speed of the injection member so that the actual value of the filling pressure becomes the set value. The actual value of the filling pressure is obtained using a pressure detector such as the load detector 360. The speed setting unit 713a creates a set value of the speed of the injection member by, for example, PID calculation or PI calculation.

[0109] The command creation unit 713b creates a command for the injection drive source so that the actual value of the speed of the injection member becomes the set value. The actual value of the speed of the injection member is obtained using a speed detector such as the injection motor encoder 351. The command creation unit 713b creates a command for the injection drive source by, for example, PID calculation or PI calculation.

[0110] The injection control unit 713 has a restriction unit 713c. The restriction unit 713c restricts the retreat speed of the injection member to be equal to or less than a preset limit value V1 during the pressure holding process while the injection member is retreating. In the pressure holding process, it is possible to eliminate the adverse effect on the quality of the molded product caused by the injection member retreating at high speed. The limit value V1 is set so as to eliminate the adverse effect on the quality of the molded product caused by the injection member retreating at high speed.

[0111] For example, as shown in FIG. 6, the restriction unit 713c compares the set value (>0) of the retreat speed created by the speed setting unit 713a with the limit value V1 (V1>0). The restriction unit 713c outputs the minimum value (including the case where the set value and the limit value V1 are equal) of the set value (>0) of the retreat speed created by the speed setting unit 713a and the limit value V1 (V1>0) to the command creation unit 713b as the set value of the retreat speed. The command creation unit 713b creates a command for the injection drive source based on the deviation between the set value output by the restriction unit 713c and the actual value.

[0112] Therefore, as shown in FIG. 6, the restriction unit 713c has a correction unit 713d that monitors the position of the injection member during the pressure holding process while the injection member is retreating, corrects the set value of the retreat speed according to the position of the injection member, and outputs the corrected set value to the command creation unit 713b. The correction unit 713d acquires the position of the injection member using a position detector such as the injection motor encoder 351.

[0113] During the pressure holding process, when the position of the injection member reaches a preset deceleration start position A2 (see FIG. 7) while the injection member is retreating, the correction unit 713d corrects the set value of the retreat speed of the injection member to a speed lower than the limit value V1. The deceleration start position A2 is set behind the filling start position A3 and in front of the retreat limit position A0. The filling start position A3 is the position at the start of the filling process.

[0114] As a result, in the pressure holding process, when the position of the injection member reaches the deceleration start position A2 during the retraction of the injection member, the retraction speed of the injection member becomes smaller than the limit value V1. Therefore, even if the position of the injection member is retracted to the retraction limit position A0, the retraction speed at that time is small and the impact is small. Accordingly, the impact can be reduced. Also, until the position of the injection member reaches the deceleration start position A2, the retraction speed can be controlled to the limit value V1, and the filling pressure can be quickly reduced.

[0115] In the pressure holding process, when the position of the injection member reaches a preset stop position A1 during the retraction of the injection member, the correction unit 713d corrects the set value of the retraction speed of the injection member to zero. The stop position A1 is set behind the deceleration start position A2 and in front of the retraction limit position A0. As a result, in the pressure holding process, when the position of the injection member reaches the stop position A1 during the retraction of the injection member, the injection member is stopped. Therefore, it is possible to prevent the position of the injection member from being retracted to the retraction limit position A0, and it is possible to eliminate the impact caused by the position of the injection member being retracted to the retraction limit position A0.

[0116] The correction unit 713d gradually corrects the retraction speed of the injection member to a lower speed as the position of the injection member approaches the stop position A1 from the deceleration start position A2. As a result, as the position of the injection member approaches the stop position A1 from the deceleration start position A2, the retraction speed of the injection member gradually becomes smaller. The retraction speed can be gradually decelerated, and the generation of vibration can be suppressed.

[0117] Next, with reference to FIG. 7, an example of the time change of the screw speed, the filling pressure, and the screw position will be described. In FIG. 7, the screw speed is an example of the speed of the injection member, and the screw position is an example of the position of the injection member. The screw position is represented by the distance from the forward limit position of the movable range of the screw 330. The greater the distance representing the screw position as the screw position retracts from the forward limit position.

[0118] In FIG. 7, t0 represents the start time of the filling process, t1 represents the time of V / P switching, t2 represents the time when the actual value of the screw speed (retreat speed) reaches the limit value V1, t3 represents the time when the screw position reaches the deceleration start position A2, t4 represents the time when the screw position reaches the stop position A1, and t5 represents the end time of the holding pressure process, respectively.

[0119] When the filling process starts at time t0, the screw position advances at the set speed. As a result, the filling pressure rises. When nozzle clogging, or defective ejection of the molded product occurs, even if the screw position advances, since almost no molding material is ejected, the filling pressure rises rapidly.

[0120] Thereafter, when the screw position reaches the V / P switching position at time t1, the holding pressure process starts. In the holding pressure process, the screw position is controlled so that the actual value of the filling pressure becomes the set value P1. When nozzle clogging occurs, the actual value of the filling pressure is greater than the set value P1, and the deviation is large.

[0121] Therefore, when nozzle clogging occurs, after time t1, the screw position is retracted so that the actual value of the filling pressure becomes smaller. Thus, the screw speed (specifically, the retreat speed) gradually increases, and the retreat speed reaches the limit value V1 at time t2.

[0122] The restricting portion 713c restricts the retreat speed to the limit value V1 so that the retreat speed does not exceed the limit value V1. Thereafter, at time t3, when the screw position reaches the deceleration start position A2, the restricting portion 713c controls the retreat speed to a speed smaller than the limit value V1. Thereby, even if the screw position is retracted to the retreat limit position A0, the retreat speed at that time is small and the impact is small. Therefore, the impact can be reduced. Also, until the screw position reaches the deceleration start position A2, the retreat speed can be controlled to the limit value V1, and the filling pressure can be rapidly reduced.

[0123] Thereafter, when the screw position reaches the stop position A1 at time t4, the restricting portion 713c stops the screw 330. The stop position A1 is set forward of the retraction limit position A0. Accordingly, it is possible to prevent the screw position from being retracted to the retraction limit position A0, and it is possible to eliminate the impact caused by the screw position being retracted to the retraction limit position A0.

[0124] As shown in FIG. 7, between time t3 and time t4, as the screw position approaches the stop position A1 from the deceleration start position A2, the restricting portion 713c controls the retraction speed to a gradually lower speed. The retraction speed can be gently decelerated, and the generation of vibration can be suppressed.

[0125] As described above, embodiments of the control device, injection molding machine, and injection molding machine control method according to the present invention have been described, but the present invention is not limited to the above embodiments. Within the scope described in the claims, various changes, modifications, substitutions, additions, deletions, and combinations are possible. Naturally, those also belong to the technical scope of the present invention.

Explanation of Reference Numerals

[0126] 10 Injection molding machine 310 Cylinder 330 Screw (injection member) 350 Injection motor (injection drive source) 700 Control device 713c Restricting portion 800 Mold device

Claims

1. A control device for an injection molding machine including an injection member provided inside a cylinder that heats a molding material, and an injection drive source that fills the molding material into a mold device by moving the injection member forward, a limiting unit that limits a retreat speed of the injection member in a pressure holding step of controlling a filling pressure applied to the molding material from the injection member, A control device for an injection molding machine, wherein the limiting unit limits the retraction speed of the injection member to a slower speed when a position of the injection member approaches a stop position during the holding pressure process while the injection member is retracting.

2. An injection molding machine comprising: the control device according to claim 1 ; the injection member; and the injection drive source.

3. A control method for an injection molding machine including an injection member provided inside a cylinder that heats a molding material, and an injection drive source that fills the molding material into a mold device by moving the injection member forward, comprising: a step of limiting a retraction speed of the injection member in a pressure holding step of controlling a filling pressure acting on the molding material from the injection member; a step of limiting the retraction speed of the injection member to a smaller speed when a position of the injection member approaches a stop position during the retraction of the injection member in the pressure holding step; A method for controlling an injection molding machine comprising the steps of:

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