Control device and control method

Abstract

Provided is a control device (20) which is for an injection molding machine (10) and which comprises: a suck-back control unit (76) that causes a screw (28) which has reached a prescribed measurement position to be sucked back at a prescribed suck-back velocity; a reverse rotation control unit (78) that causes the screw to be reversely rotated on the basis of a prescribed reverse rotation condition value (CVrb) at and after the initiation of the suck-back; a measurement unit (80) that measures a reverse rotation state value (SVrb) of the screw; and a suck-back completion control unit (82) that causes the suck-back to be completed when the reverse rotation state value (SVrb) has reached a threshold value (Th).

Description

[Technical field]

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

[0002] The molding cycle of an injection molding machine includes a process (decompression process) of reducing the pressure of the measured molten resin to a predetermined target pressure. Japanese Patent Laid-Open Publication No. 1-148526 discloses that, regarding the decompression process, the resin pressure is monitored and the suck-back is terminated when the resin pressure has decreased to a certain value. Summary of the Invention

[0003] The injection molding machine includes a cylinder and a screw. The screw is capable of sucking back (retreating) within the cylinder. The pressure of the resin within the cylinder is quickly reduced as the screw sucks back. However, the pressure of the resin varies due to the influence of the viscous resistance of the resin or the load applied to the screw. Therefore, in JP-A-1-148526, there was a problem that the timing of the end of sucking back varied for each molding cycle.

[0004] Therefore, an object of the present invention is to reduce the variation in the timing at which the suck back ends.

[0005] A first aspect of the present invention is a control device for an injection molding machine having a cylinder and a screw that rotates and advances and retreats within the cylinder, which measures the resin in the cylinder by rotating the screw forward while retracting it to a predetermined metering position, and which comprises a suck-back control unit that sucks back the screw at a predetermined suck-back speed after the screw reaches the predetermined metering position, a reverse rotation control unit that rotates the screw in reverse based on a predetermined reverse rotation condition value after suck-back of the screw begins, a measurement unit that measures a reverse rotation state value that indicates the reverse rotation state of the screw after the reverse rotation begins, and a suck-back end control unit that ends the suck-back of the screw by the suck-back control unit when the reverse rotation state value reaches a threshold value.

[0006] A second aspect of the present invention is a control method for measuring the resin in an injection molding machine having a cylinder and a screw that rotates and moves back and forth within the cylinder by rotating the screw forward while retracting it to a predetermined metering position, the control method including: a suck-back control step for sucking back the screw at a predetermined suck-back speed after the screw reaches the predetermined metering position; a reverse rotation control step for rotating the screw in reverse based on a predetermined reverse rotation condition value after the start of suck-back of the screw; a measurement step for measuring a reverse rotation state value that indicates the reverse rotation state of the screw after the reverse rotation has started; and a suck-back termination step for terminating the suck-back of the screw by the suck-back control step when the reverse rotation state value reaches a threshold value.

[0007] According to an aspect of the present invention, the variation in the timing at which the suck back ends is reduced. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of an injection molding machine according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the injection unit. [Diagram 3]FIG. 3 is a schematic configuration diagram of the control device. [Figure 4] FIG. 4 is a first flowchart illustrating the flow of a control method according to the embodiment. [Diagram 5] FIG. 5 is a first time chart illustrating the transition over time of the screw retraction speed, the screw rotation speed, and the resin pressure when the control method of FIG. 4 is executed. [Figure 6] FIG. 6 is a second flowchart illustrating the flow of the control method according to the embodiment. [Figure 7] FIG. 7 is a second time chart illustrating the transition over time of the screw retraction speed, the screw rotation speed, and the resin pressure when the control method of FIG. 6 is executed. [Figure 8] FIG. 8 is a schematic configuration diagram of a control device according to the second modification. [Figure 9] FIG. 9 shows an example of the structure of a table stored in the storage unit of the second modification. [Figure 10] FIG. 10 is a schematic configuration diagram of a control device according to the third modification. [Figure 11] FIG. 11 is a schematic configuration diagram of a control device according to the fifth modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device and a control method according to preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0010] [Embodiment Mode] FIG. 1 is a side view of an injection molding machine 10 according to an embodiment.

[0011] The injection molding machine 10 includes a mold clamping unit 14, an injection unit 16, a machine base 18, and a control device 20. The mold clamping unit 14 has an openable and closable mold 12. The injection unit 16 is installed behind the mold clamping unit 14 (see FIG. 1). The machine base 18 supports the mold clamping unit 14 and the injection unit 16. The mold clamping unit 14 and the machine base 18 may be configured based on known technology.

[0012] First, the injection unit 16 will be described below. The injection unit 16 is controlled by a control device 20.

[0013] The injection unit 16 is supported by a base 22. The base 22 is supported by a guide rail 24 so as to be movable forward and backward. The guide rail 24 is installed on the machine base 18. This allows the injection unit 16 to move forward and backward on the machine base 18.

[0014] FIG. 2 is a schematic diagram of the injection unit 16. As shown in FIG.

[0015] The injection unit 16 includes a cylinder (heated barrel) 26, a screw 28, a pressure sensor 30, a first driving device 32, and a second driving device 34. The cylinder 26 is a cylindrical member. The screw 28 is disposed within the cylinder 26. The pressure sensor 30 is disposed on the screw 28. The first driving device 32 and the second driving device 34 are connected to the screw 28.

[0016] The imaginary line L in Fig. 2 is the axis of the cylinder 26. The imaginary line L extends parallel to the front-rear direction. The imaginary line L is also the axis of the screw 28. A system in which the axis of the cylinder 26 and the axis of the screw 28 overlap (become the same imaginary line L) is also called the "inline (inline screw) system." An injection molding machine to which the inline system is applied is also called an "inline type injection molding machine."

[0017] The structure of the injection unit 16 of the in-line injection molding machine is simpler than that of other types of injection units. Therefore, the injection unit 16 is easier to maintain than other types of injection units. The other types are, for example, the pre-plastication type.

[0018] The cylinder 26 includes a hopper 36, a heater 38, and a nozzle 40 (see FIG. 2). The hopper 36 is installed toward the rear end of the cylinder 26. The hopper 36 is provided with a supply port for supplying resin as a molding material to the cylinder 26. The resin supplied to this supply port has, for example, a pellet-like shape. The heater 38 heats the cylinder 26. The nozzle 40 is installed at the front end of the cylinder 26. The nozzle 40 has an injection port 41. The injection port 41 communicates between the inside and outside of the cylinder 26.

[0019] The screw 28 has a flight portion 42. The flight portion 42 is provided in a single spiral shape over the front-rear direction. The flight portion 42 and the inner wall of the cylinder 26 form a flow path 44. The flow path 44 is in a single spiral shape. The resin in the cylinder 26 is guided forward along the flow path 44 in response to the forward rotation of the screw 28.

[0020] The screw 28 having a single-helix flight portion 42 is classified as a type also called a "single-flight type." However, the type of the screw 28 is not limited to the single-flight type. For example, the screw 28 may be a "double-flight type." When the screw 28 is a double-flight type, the flight portion 42 is provided in a double-helix shape.

[0021] The screw 28 has a screw head 46, a check seat 48, and a backflow prevention ring 50. The screw head 46 is the front end of the screw 28. The check seat 48 is disposed at a distance in the rear direction from the screw head 46. The backflow prevention ring 50 is movable relative to the check seat 48 in the front-rear direction between the screw head 46 and the check seat 48.

[0022] The backflow prevention ring 50 opens or closes the flow path 44 by moving relative to the check sheet 48. For example, during metering, which will be described later, the backflow prevention ring 50 receives forward pressure from the resin behind the backflow prevention ring 50. When the backflow prevention ring 50 receives forward pressure, it moves forward relative to the check sheet 48. In this case, the backflow prevention ring 50 gradually opens the flow path 44. As a result, the resin behind the backflow prevention ring 50 is able to flow along the flow path 44 in the forward direction of the check sheet 48.

[0023] Furthermore, the backflow prevention ring 50 receives rearward pressure from resin located forward of the backflow prevention ring 50, for example, during injection, which will be described later. When the backflow prevention ring 50 receives rearward pressure, it moves rearward relative to the check sheet 48. In this case, the backflow prevention ring 50 gradually closes the flow path 44. As a result, the resin located forward of the backflow prevention ring 50 is prevented from flowing (backflowing) along the flow path 44 in a direction rearward of the check sheet 48. In particular, when the backflow prevention ring 50 and the check sheet 48 come into contact, the backflow of the resin is most effectively prevented.

[0024] The pressure sensor 30 is, for example, a load cell. The pressure sensor 30 is attached, for example, to the rear end of the screw 28. The screw 28 receives pressure (resin pressure) P from the resin flowing along the flow path 44. The pressure sensor 30 outputs a detection signal corresponding to the resin pressure P. This detection signal is input to the control device 20.

[0025] The first driving device 32 is a device that rotates the screw 28 in the cylinder 26. The first driving device 32 includes a servo motor 52a, a driving pulley 54a, a driven pulley 56a, and a belt member 58a. The servo motor 52a includes a rotating shaft. The driving pulley 54a rotates integrally with the shaft of the servo motor 52a. The driven pulley 56a is provided integrally with the screw 28. The belt member 58a transmits the rotational force of the shaft of the servo motor 52a from the driving pulley 54a to the driven pulley 56a.

[0026] The shaft of the servo motor 52a transmits a rotational force to the screw 28 via the drive pulley 54a, the belt member 58a, and the driven pulley 56a. The screw 28 rotates in response to the transmitted rotational force. The rotation direction of the screw 28 can be switched between forward and reverse rotation in response to a change in the rotation direction of the shaft of the servo motor 52a.

[0027] The servo motor 52a is provided with a position and speed sensor 60a. The position and speed sensor 60a outputs a detection signal corresponding to the rotational position of the shaft of the servo motor 52a. The detection signal is input to the control device 20. This allows the control device 20 to obtain the amount of rotation and the rotational speed of the screw 28 based on the detection signal of the position and speed sensor 60a. The control device 20 may further obtain the rotational acceleration of the screw 28 based on the detection signal of the position and speed sensor 60a.

[0028] The second driving device 34 is a device for advancing and retreating the screw 28 in the cylinder 26. In this embodiment, unless otherwise specified, the advancement and retreat of the screw 28 refers to the relative movement of the screw 28 with respect to the cylinder 26 in the front-rear direction.

[0029] The second driving device 34 includes a servo motor 52b, a driving pulley 54b, a driven pulley 56b, a belt member 58b, a ball screw 62, and a nut 64. The servo motor 52b includes a rotating shaft. The driving pulley 54b rotates integrally with the shaft of the servo motor 52b. The belt member 58b transmits the rotational force of the shaft of the servo motor 52b from the driving pulley 54b to the driven pulley 56b. The driven pulley 56b is connected to a ball screw 62. The ball screw 62 is screwed into the nut 64. The ball screw 62 is installed parallel to the forward and backward direction (front-rear direction) of the screw 28. The axis of the ball screw 62 overlaps with the imaginary line L. The ball screw 62 is connected to the screw 28.

[0030] The shaft of the servo motor 52b transmits a rotational force to the ball screw 62 via the drive pulley 54b, the belt member 58b, and the driven pulley 56b. The ball screw 62 rotates in response to the transmitted rotational force. The nut 64 moves back and forth in response to the rotation of the ball screw 62. As a result, the screw 28 moves linearly in the front-rear direction. The forward and backward movement of the screw 28 can be changed in response to a change in the rotation direction of the shaft of the servo motor 52b.

[0031] The servo motor 52b is provided with a position and speed sensor 60b. The position and speed sensor 60b outputs a detection signal corresponding to the rotational position of the shaft of the servo motor 52b. The position and speed sensor 60b is, for example, a sensor similar to the position and speed sensor 60a. The detection signal of the position and speed sensor 60b is input to the control device 20. This allows the control device 20 to calculate the retraction distance and retraction speed of the screw 28 based on the detection signal of the position and speed sensor 60b.

[0032] In consideration of the above-mentioned injection unit 16, the following describes a number of steps that the injection molding machine 10 executes to obtain a molded product. Note that, within the cylinder 26, the area in front of the check sheet 48 is also referred to as the "metering area" in the following description.

[0033] The screw 28 of the injection unit 16 rotates at a predetermined rotation speed (metering speed) V rf The hopper 36 rotates forward based on the rotational force of the screw 28. As a result, the resin supplied to the cylinder 26 from the supply port of the hopper 36 is pumped forward along the flow path 44. During this pumping, the resin is melted (plasticized) by the heating by the heater 38 and the rotational force of the screw 28. The molten resin is pumped forward by the forward rotation of the screw 28 and reaches the metering area. The metering area collects the molten resin.

[0034] The pumping of resin to the metering area starts when the screw 28 has fully advanced inside the cylinder 26. That is, the pumping of resin to the metering area starts when the volume of the metering area is at its minimum. When the amount of resin in the metering area increases, the resin pressure P increases. Here, the screw 28 retreats in order to reduce the resin pressure P. That is, when the screw 28 retreats, the metering area is expanded. This reduces the resin pressure P. Note that the screw 28 continues to rotate forward (pumping the resin) even after starting to retreat. Also, the control device 20 controls the retreat speed of the screw 28. As a result, the resin pressure P is maintained at a predetermined value (metering pressure) P1 while the screw 28 is retreating.

[0035] The resin is pumped until the retreating screw 28 reaches a predetermined position (metering position).

[0036] The process of pumping the resin until the screw 28 reaches the metering position is called a "metering process" or "metering." The injection unit 16 can store a certain amount of resin in the metering area by performing metering.

[0037] The injection unit 16 has a metering speed V rf The operator performs metering based on the metering speed V rf and the metering pressure P1 may be appropriately set, provided that the metering pressure P1 is higher than the atmospheric pressure.

[0038] After the screw 28 reaches the metering position, the injection unit 16 reduces the resin pressure P from the metering pressure P1 to the target pressure P0. The process of reducing the resin pressure P from the metering pressure P1 to the target pressure P0 is called the "pressure reduction process" or "pressure reduction." When the resin pressure P decreases, the momentum of the resin attempting to flow forward weakens. By reducing the pressure after metering, the injection unit 16 suppresses the resin in the metering region from flowing to the injection port 41. This suppresses drowning or cold slugs.

[0039] In this embodiment, the target pressure P0 is atmospheric pressure (the detection value of the pressure sensor 30=zero). However, the target pressure P0 may be set to a pressure other than atmospheric pressure as long as it is within a range less than the metering pressure P1.

[0040] In order to reduce the resin pressure P in the depressurization process, the injection unit 16 in this embodiment sucks back or reverses the rotation of the screw 28. By sucking back in the depressurization process, the screw 28 retreats further from the metering position. Here, the volume of the metering region expands according to the retreat distance of the screw 28. This causes the volume of the resin in the metering region to expand. Also, the density of the resin in the metering region decreases. As a result, the resin pressure P decreases.

[0041] During the suck-back, the screw 28 retreats at a predetermined speed. This predetermined speed is referred to below as the suck-back speed V sb Also called the suck-back velocity V sb is set in the control device 20. The operator selects the suck-back speed V sb However, the operator may set the suck-back speed V sb A default value of may be set in the control device 20.

[0042] The direction of reverse rotation of the screw 28 is opposite to the direction of rotation (forward rotation) during metering. When the screw 28 rotates in reverse, the resin flows backward in the cylinder 26. This causes the resin to be scraped out rearward from the cylinder 26, and the overall density of the resin in the cylinder 26 decreases. As a result, the pressure P of the resin decreases.

[0043] The screw 28 in this embodiment has a reverse rotation condition value CV rb The reverse rotation condition value CV rb is the target reverse rotation speed V rb and duration T rb and the target reverse rotation amount R rb The information includes at least two of the following: rbis the target value of the rotation speed of the screw 28 during reverse rotation. The rotation speed of the screw 28 during reverse rotation is the target reverse rotation speed V rb The control is aimed at the duration T rb is the target value for the time length for which reverse rotation is to continue. rb is a target value for the rotation amount (rotation angle) of the screw 28 in the reverse rotation direction.

[0044] The operator sets the target reverse rotation speed V rb and duration T rb and the target reverse rotation amount R rb Which of the following is the reverse rotation condition value CV rb The operator may select whether to include the reverse rotation condition value CV rb The operator may examine and set at least one of the multiple values ​​included in the reverse rotation condition value CV rb At least one of the multiple values ​​included in the reverse rotation condition value CV may be a default value preset by the manufacturer of the injection molding machine 10. rb is the target reverse rotation speed V determined by the operator. rb and the default duration T rb and

[0045] Target reverse rotation speed V rb and duration T rb and the target reverse rotation amount R rb When two of these values ​​are determined, the remaining value is automatically determined. For example, the target reverse rotation speed V rb and duration T rb Once this is determined, the target reverse rotation amount R rb is the target reverse rotation speed V rb and duration T rb This is automatically determined as a result of multiplication with

[0046] After the decompression step, the injection unit 16 advances the screw 28. As a result, the resin in the metering area is pushed out of the cylinder 26 (to the mold 12) through the injection port 41. This step is called the "injection step" or "injection." The injection unit 16 fills the mold 12 with resin by performing injection. Note that the mold 12 is in a closed state while injection is being performed. The mold clamping unit 14 applies a clamping force to the mold 12 in the closed state.

[0047] The resin filled in the mold 12 is solidified by cooling. This process is called the "cooling process" or "cooling". When the resin in the mold 12 has solidified, the mold clamping unit 14 opens the mold 12. The process of opening the mold 12 is called the "mold opening process" or "mold opening". The solidified resin (molded product) can be removed from the open mold 12. The process of removing the molded product from the mold 12 is called the "removal process" or "removal". The mold clamping unit 14 closes the mold 12 again after the molded product has been removed. The process of closing the mold 12 is called the "mold closing process" or "mold closing".

[0048] The multiple steps described above (measurement, decompression, injection, cooling, mold opening, removal, and mold closing) are routinely performed as a "molding cycle." The injection molding machine 10 can mass-produce molded products by repeatedly performing the molding cycle. The time required to complete one molding cycle is also called the "cycle time."

[0049] The depressurization step will be further described below. In the depressurization step, the screw 28 performs suck back or reverse rotation. Here, when the screw 28 sucks back, the volume of the metering area expands quickly. In this case, the resin pressure P decreases quickly. On the other hand, when the screw 28 rotates in the reverse direction, the resin flows back slowly. In this case, the resin pressure P decreases slowly. In other words, sucking back the screw 28 can reduce the resin pressure P more quickly than rotating the screw 28 in the reverse direction.

[0050] However, if the end condition of the suck-back is that the resin pressure P reaches the target pressure P0, the problem of the end timing of the suck-back varying for each molding cycle occurs. In other words, the resin pressure P varies depending on the viscous resistance of the molten resin in the cylinder 26 and the bite load of the screw 28. It is practically impossible to make this variation constant over multiple molding cycles. This is because the resin has acquired fluidity. For the above reasons, if the suck-back is performed with the end condition that the resin pressure P reaches the target pressure P0, the end timing of the suck-back is not fixed. If the end timing of the suck-back is not fixed, the cycle time during mass production of molded products will vary.

[0051] In addition, compared to reverse rotation, suckback has a problem that the amount of resin excessively measured in the metering process cannot be adjusted. That is, the screw 28 is affected by the inertia related to the rotational drive of the screw 28 and the viscous resistance of the resin during forward rotation. This causes a time difference between the time when the screw 28 reaches the metering position and the time when the screw 28 stops rotating forward. That is, the screw 28 continues rotating forward for a short time even after reaching the metering position. As a result, after the screw 28 reaches the metering position, excess resin is pumped into the metering area. This phenomenon is also called overrun because the forward rotation of the screw 28 does not stop when the screw 28 reaches the metering position, but continues to rotate forward. From the operator's point of view, it is preferable to prevent overrun so that the amount of resin in the metering area is appropriate. However, it is a physical phenomenon that cannot be avoided in reality that the screw 28 is affected by inertia and the viscous resistance of the resin. Therefore, it is practically difficult to completely prevent overrun. Therefore, instead of preventing overrun, it has been considered to make the amount of resin closer to the appropriate amount by making the excess resin flow back from inside the metering area to outside the metering area. In this respect, the suck back is an operation that expands the volume of the metering area, and is not an operation that encourages the resin to flow back from inside the metering area to outside the metering area. Therefore, it is difficult for the screw 28 to reduce the excess resin in the metering area by performing suck back.

[0052] On the other hand, the reverse rotation of the screw 28 causes the resin to flow back from inside the metering area to outside the metering area, thereby making it possible to bring the amount of resin in the metering area closer to the appropriate amount.

[0053] However, the reverse rotation of the screw 28 needs to be performed more slowly than the forward rotation in the metering process so that the screw 28 is not damaged by the effect of the rotation load. Therefore, the force of the decrease in the resin pressure P during the reverse rotation is gentler than when the screw 28 is sucked back. For this reason, in terms of quickly decreasing the resin pressure P, it is preferable to suck back the screw 28 rather than rotating it in the reverse direction.

[0054] The control device 20 of this embodiment will be described based on the above description.

[0055] FIG. 3 is a schematic configuration diagram of the control device 20. As shown in FIG.

[0056] The control device 20 is an electronic device (computer) that controls at least the injection unit 16 of the injection molding machine 10. In this embodiment, the control device 20 controls the injection unit 16 based on a CNC (Computerized Numerical Control) method. The control device 20 includes a display unit 66, an operation unit 68, a storage unit 70, and a calculation unit 72.

[0057] The display unit 66 displays information. The display unit 66 is, for example, a display device. The display unit 66 has a display screen. The display screen contains liquid crystal or OEL (Organic Electro-Luminescence) as a material. The display screen of the display unit 66 displays, for example, a reverse rotation condition value CV rb , or the reverse rotation state value SV of the screw 28 rb Display (see below).

[0058] The operation unit 68 accepts information input (instructions) to the control device 20. For example, the operator may input the suck-back speed V sb and reverse rotation condition value CV rb and input the above to the control device 20 via the operation unit 68. The operation unit 68 includes, for example, a keyboard, a mouse, and a touch panel. The touch panel is provided on the display unit 66, for example.

[0059] The storage unit 70 stores information. The storage unit 70 includes a memory. For example, the storage unit 70 includes a RAM (Random Access Memory) and a ROM (Read Only Memory). The storage unit 70 stores a control program 74. The control program 74 is a program for causing the control device 20 to execute the control method of the present embodiment (the control method of the injection molding machine 10). The storage unit 70 also stores a threshold value Th and a suck-back speed Vsb and the reverse rotation condition value CV rb The storage unit 70 stores the control program 74, the threshold value Th, and the suck-back velocity V sb and the reverse rotation condition value CV rb Information other than the above may be stored.

[0060] The calculation unit 72 processes information by calculation. The calculation unit 72 includes a processor. For example, the calculation unit 72 includes a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The calculation unit 72 includes a measurement control unit 75, a suck-back control unit 76, a reverse rotation control unit 78, a measurement unit 80, a suck-back end control unit 82, a pressure acquisition unit 84, a threshold setting unit 86, and a display control unit 88 (see FIG. 3). The measurement control unit 75, the suck-back control unit 76, the reverse rotation control unit 78, the measurement unit 80, the suck-back end control unit 82, the pressure acquisition unit 84, the threshold setting unit 86, and the display control unit 88 are virtually realized by the calculation unit 72 executing the control program 74.

[0061] The metering control unit 75 controls the injection unit 16 during the metering process. More specifically, the metering control unit 75 drives the servo motor 52a during the metering process. As a result, the metering control unit 75 rotates the screw 28 at a predetermined rotation speed (metering speed) V rf The measurement control unit 75 drives the servo motor 52b in the measurement process to control the retreat speed of the screw 28. This adjusts the resin pressure P to a predetermined measurement pressure P1. Here, the measurement speed V rf and the metering pressure P1 are stored in the memory unit 70. However, the metering speed V rf The pressure P of the resin can be acquired from a pressure acquisition unit 84, which will be described later.

[0062] After the metering, the suck-back control unit 76 drives the servo motor 52b to suck back the screw 28. This allows the suck-back control unit 76 to reduce the resin pressure P. Here, the suck-back control unit 76 controls the suck-back speed V sb That is, after the screw 28 reaches a predetermined metering position, the suck-back control unit 76 sucks back the screw 28 at the suck-back speed stored in the storage unit 70.

[0063] The reverse rotation control unit 78 controls the screw 28 to rotate in a predetermined reverse rotation condition value CV rb , and rotates the screw 28 in the reverse direction based on the predetermined reverse rotation condition value CV. In this manner, the reverse rotation control unit 78 can reduce the pressure P of the resin. In the case of this embodiment, the reverse rotation control unit 78 can rotate the screw 28 in the reverse direction by driving the servo motor 52a. The reverse rotation control unit 78 may start the reverse rotation of the screw 28 simultaneously with the start of the suck back. The reverse rotation control unit 78 rotates the screw 28 in the reverse direction based on the predetermined reverse rotation condition value CV. rb In order to achieve this, the reverse rotation control unit 78 may control the screw 28 while monitoring the rotation speed and rotation time of the screw 28. The rotation speed and rotation time of the screw 28 are measured by a measurement unit 80 (described later).

[0064] Predetermined reverse rotation condition value CV rb is preferably a condition for rotating the screw 28 in the reverse direction more slowly than the forward rotation of the screw 28 in the metering step. This reduces the influence of inertia and viscous resistance of the resin on the screw 28 during reverse rotation. As a result, excessive reverse rotation of the screw 28 is suppressed.

[0065] The suck back of the screw 28 and the reverse rotation of the screw 28 may be executed in a overlapping manner. This causes the expansion of the volume of the metering area due to the suck back of the screw 28 and the reverse flow of the resin due to the reverse rotation of the screw 28 to occur in a overlapping manner. As a result, the pressure P of the resin is quickly reduced. Also, by executing the suck back and the reverse rotation in a overlapping manner, the cycle time can be shortened. Note that when the suck back and the reverse rotation are executed in a overlapping manner, not only the resin but also the screw 28 moves backward. In this case, the resin stored in the metering area is prevented from flowing out from the injection port 41.

[0066] The measurement unit 80 measures the reverse rotation state value SV rb Measure the reverse rotation status value SV rb indicates the reverse rotation state of the screw 28. rb is the rotation speed of the reverse-rotating screw 28, the amount of rotation of the screw 28, or the elapsed time. In the present embodiment, the rotation speed and amount of rotation of the reverse-rotating screw 28 are measured based on the detection signal of the position and speed sensor 60a. The elapsed time is measured, for example, by implementing a timer function in the calculation unit 72.

[0067] The measuring unit 80 may measure at least two of the following: the rotation speed of the screw 28 during the reverse rotation, the rotation amount of the screw 28 during the reverse rotation, and the elapsed time from the start of the reverse rotation of the screw 28. Here, the reverse rotation state value SV rb Among these, the type of value measured by the measurement unit 80 and the reverse rotation condition value CV rb The type of value measured by the measurement unit 80 may be different from that of the reverse rotation condition value CV rb Target reverse rotation amount R rb If the reverse rotation state value SV rb The amount of rotation may be measured as follows.

[0068] After the start of reverse rotation, the suck-back end control unit 82 determines the reverse rotation state value SV rbWhen the reverse rotation state value SV rb Whether or not to end the suck back is determined based on a comparison between the pressure P of the resin and the threshold value Th. In this case, it is not necessary for the suck back end control unit 82 to monitor the pressure P of the resin.

[0069] The timing of the end of the suckback is set by the reverse rotation state value SV rb The reason is as follows. When the reverse rotation of the screw 28 is determined based on the reverse rotation condition value CV rb Therefore, the reverse rotation state value SV rb The timing at which the reverse rotation state value SV reaches the threshold value Th has good repeatability over a plurality of molding cycles. rb reaches the threshold value Th. This allows the end timing of the suck-back of the screw 28 to have good repeatability over a plurality of molding cycles.

[0070] In addition, the timing of the end of the suck back is set to the reverse rotation state value SV rb By making a judgment based on this, the linkage between the suck back and the reverse rotation can be improved.

[0071] The threshold value Th is the reverse rotation state value SV rb For example, the measurement unit 80 stores (sets) the reverse rotation state value SV rb When the rotation speed (reverse rotation speed) of the screw 28 is measured as the reverse rotation speed, a threshold value Th is set for the reverse rotation speed of the screw 28. rb When the rotation amount of the screw 28 during reverse rotation is measured as the reverse rotation amount, a threshold value Th for the reverse rotation amount is set. rbWhen measuring the elapsed time from the start of reverse rotation of the screw 28 as the time elapsed, a threshold value Th for the elapsed time is set.

[0072] It is preferable that the threshold value Th is set so that the suck-back ends before the resin pressure P reaches the target pressure P0. As a result, after the suck-back ends, the resin pressure P reaches the target pressure P0 by only performing the reverse rotation out of the suck-back and reverse rotation. Here, the screw 28 reverses without retreating, so that the resin flows out of the metering area. As a result, the amount of resin in the metering area approaches the appropriate amount. The operator can set a predetermined reverse rotation condition value CV taking into account the threshold value Th. rb By setting the above, the resin pressure P can be accurately adjusted to the target pressure P0.

[0073] The pressure acquisition unit 84 acquires the pressure P of the resin. The pressure acquisition unit 84 acquires the pressure P of the resin based on a detection signal of the pressure sensor 30. The threshold setting unit 86 sets a threshold Th. Setting the threshold Th includes changing an already-set threshold Th.

[0074] When the resin pressure P reaches a predetermined suck-back end pressure P2, the threshold setting unit 86 sets the reverse rotation state value SV rb is stored in the storage unit 70 as the threshold value Th. Thus, the threshold value Th is set in the control device 20. In relation to this, the suck-back end control unit 82 may exceptionally set the suck-back end condition to be that the resin pressure P reaches a predetermined suck-back end pressure P2 in order to have the threshold value setting unit 86 set the threshold value Th.

[0075] The predetermined suck-back end pressure P2 is determined in advance within a range of less than the metering pressure P1 and equal to or greater than the target pressure P0 (P1>P2≧P0). The predetermined suck-back end pressure P2 is stored in advance in the storage unit 70 and is referred to by the threshold setting unit 86.

[0076] When only reverse rotation is performed after the suck back and reverse rotation are performed simultaneously, the predetermined suck back end pressure P2 is preferably set within the range of P1>P2>P0. This allows the threshold setting unit 86 to set a threshold Th that ends the suck back before the resin pressure P reaches the target pressure P0. It is also more preferable that the predetermined suck back end pressure P2 is as close to the target pressure P0 as possible. This allows the resin pressure P to quickly drop to the target pressure P0.

[0077] In addition, when the threshold value Th is set for the reverse rotation speed of the screw 28, the predetermined suck-back end pressure P2 is set when the reverse rotation speed of the screw 28 is the target reverse rotation speed V rb The resin pressure P can reach the range before it reaches the suck-back speed V sb By adjusting the pressure P2, it is possible to keep the predetermined suck-back end pressure P2 within the range.

[0078] The display control unit 88 controls the display unit 66. For example, the display control unit 88 causes the display unit 66 to display the threshold value Th. It is preferable that the display control unit 88 causes the display unit 66 to display the threshold value Th set by the threshold value setting unit 86. This allows the operator to know that the threshold value Th has been automatically set and the specific value of the threshold value Th.

[0079] The display control unit 88 may display information other than the threshold value Th on the display unit 66. For example, the display control unit 88 may display the reverse rotation condition value CV rb and reverse rotation status value SV rb and the suck-back speed V sb and the pressure P of the resin may be displayed on the display unit 66.

[0080] The configuration of the control device 20 is not limited to the above. For example, the control device 20 may further include an element that controls the injection unit 16 in the injection process. The control device 20 may further include an element that controls the mold clamping unit 14. The element that controls the injection unit 16 and the element that controls the mold clamping unit 14 may be realized based on known technology. This completes the description of the control device 20.

[0081] Fig. 4 is a first flow chart illustrating the flow of the control method of the embodiment. Fig. 5 is a first time chart illustrating the retreat speed of the screw 28, the rotation speed of the screw 28, and the time transition of the resin pressure P when the control method of Fig. 4 is executed.

[0082] The control method of this embodiment will be described below. This control method is executed by the control device 20. The control method of this embodiment includes a metering step S1, a suck-back control step S2, a reverse rotation control step S3, a measurement step S4, and a suck-back end step S5 (see FIG. 4). In the example described below, the storage unit 70 pre-stores a threshold value Th related to the duration of reverse rotation of the screw 28. The suck-back control step S2 to the suck-back end step S5 are included in the depressurization process.

[0083] The metering step S1 is a step for carrying out a metering process. In the metering step S1, the metering control unit 75 meters the resin by rotating the screw 28 forward and retracting it. As a result, the resin is accumulated in the metering area, and the pressure P of the resin is adjusted to a predetermined metering pressure P1.

[0084] In the suck-back control step S2, after the screw 28 reaches a predetermined metering position, the suck-back control unit 76 controls the suck-back speed V sb Then, the screw 28 is sucked back.

[0085] Point t0 in FIG. 5 indicates the start point of the suck-back control step S2. Point t0 is also the end point of the metering process. Point t0 is also the start point of the depressurization process. The resin pressure P reaches a predetermined metering pressure P1 at point t0. At point t0, the suck-back control unit 76 sucks back the screw 28. After point t0, the suck-back control unit 76 controls the backward speed of the screw 28 to a predetermined suck-back speed V sb (See Figure 5.) Furthermore, when the suck back starts, the resin pressure P starts to decrease from the metering pressure P1.

[0086] In the reverse rotation control step S3, the reverse rotation control unit 78 controls the screw 28 to rotate in a direction perpendicular to the direction of the screw 28 after the start of the suck-back. rb Based on this, the screw 28 is reversed.

[0087] Point t1 in FIG. 5 indicates the start time of the reverse rotation control step S3. That is, point t1 indicates the start time of the reverse rotation of the screw 28. In the time chart relating to the rotation speed of the screw 28 in FIG. 5, "+" indicates the forward rotation direction of the screw 28. In the time chart relating to the rotation speed of the screw 28 in FIG. 5, "-" indicates the reverse rotation direction of the screw 28. In the time period from point t0 to point t1, the rotation direction of the screw 28 is the forward rotation direction. In the time period from point t0 to point t1, the rotation speed of the screw 28 gradually decreases. Note that in the time period from point t0 to point t1, the screw 28 may overrun. If the screw 28 overruns, an excess amount of resin is pumped into the metering area. After point t1, the screw 28 rotates in a direction equal to or greater than the reverse rotation condition value CV rb The rotation speed of the screw 28 is accelerated in the reverse rotation direction at a predetermined acceleration based on the target reverse rotation speed V rb After point t1, the screw 28 simultaneously executes suck back and reverse rotation, causing the resin pressure P to decrease more quickly after point t1 than in the period from point t0 to point t1.

[0088] In the measurement step S4, the measurement unit 80 measures a reverse rotation state value SV rb Measure.

[0089] The measurement step S4 starts at point t1. That is, the measurement step S4 starts simultaneously with the reverse rotation control step S3. The threshold value Th indicates the duration of the reverse rotation. Therefore, the measurement unit 80 measures the duration of the reverse rotation by the reverse rotation state value SV rb Measured as.

[0090] In the suck-back end step S5, the reverse rotation state value SV rb When the suck-back time reaches the threshold value Th, the suck-back end control unit 82 ends the suck-back of the screw 28.

[0091] Point t2 in Figure 5 indicates the reverse rotation state value SV rb The screw 28 ends the suck-back at point t2. However, the screw 28 stops sucking back when the reverse rotation condition value CV rb The reverse rotation continues after point t2 until the target pressure P0 is satisfied. Therefore, after point t2, the resin pressure P decreases in response to the reverse rotation of the screw 28. As a result, the resin pressure P reaches the target pressure P0. In addition, the screw 28 rotates in the reverse direction without sucking back, causing the resin in the metering region to flow backward. As a result, after point t2, the amount of resin in the metering region, which has become excessive due to overrun during the metering process, is brought closer to the appropriate amount.

[0092] The above is an example of the flow of the control method of the injection molding machine 10 by the control device 20. Note that, although the example in FIG. 5 shows an example in which reverse rotation is started after the start of suck back, suck back and reverse rotation may be started simultaneously. In that case, the screw 28 is made to wait to start suck back until the time when the rotation speed of the screw 28 turns to reverse rotation (point t1 in FIG. 5). This causes the backward speed of the screw 28 to become zero once after the end of the metering process (point t0 in FIG. 5). As a result, the screw 28 can start suck back and reverse rotation simultaneously.

[0093] Next, a flow of a control method in which the threshold setting unit 86 sets the threshold value Th will be described.

[0094] Fig. 6 is a second flow chart illustrating the flow of the control method of the embodiment. Fig. 7 is a second time chart illustrating the retreat speed of the screw 28, the rotation speed of the screw 28, and the time transition of the resin pressure P when the control method of Fig. 6 is executed.

[0095] The control method in Fig. 6 includes a weighing step S1, a suck-back control step S2, a reverse rotation control step S3, a measurement step S4, a pressure acquisition step S6, a suck-back end step S7, and a threshold setting step S8. The explanations of the weighing step S1, the suck-back control step S2, the reverse rotation control step S3, and the measurement step S4 overlap with the explanations of the steps with the same names and reference numerals shown in Fig. 4, and therefore will be omitted below as appropriate.

[0096] In the pressure acquisition step S6, the pressure acquisition unit 84 acquires the pressure P of the resin in the cylinder 26. Acquisition of the resin pressure P is started together with the suck-back control step S2, and is continued until the suck-back end step S7, which will be described later.

[0097] The start point of the pressure acquisition step S6 is point t0 in the example of Fig. 7. Point t0 is the start point of the depressurization step (suck-back control step S2). Point t0 is also the end point of the metering step. After point t0, the resin pressure P starts to decrease from the predetermined metering pressure P1 due to the start of suck-back. The pressure acquisition unit 84 continues to acquire the decreasing resin pressure P.

[0098] After point t0, the reverse rotation control step S3 and the measurement step S4 are executed in the same manner as in the example of Fig. 5. Fig. 7 shows point t1 similar to that in Fig. 5. Point t1 indicates the start time of the reverse rotation control step S3 and the measurement step S4.

[0099] In the suck-back end step S7, when the resin pressure P reaches a predetermined suck-back end pressure P2, the suck-back end control unit 82 ends the suck-back. That is, the suck-back end control unit 82 determines the end timing of the suck-back based on a comparison between the resin pressure P and the predetermined suck-back end pressure P2.

[0100] Point t3 in FIG. 7 indicates the time when the resin pressure P reaches a predetermined suck-back end pressure P2. The suck-back ends at point t3. The reverse rotation of the screw 28 continues even after point t3 if the reverse rotation condition value CV rb Therefore, after point t3, in response to the reverse rotation of the screw 28, the pressure P of the resin reaches the target pressure P0.

[0101] In the threshold setting step S8, the threshold setting unit 86 sets the reverse rotation state value SV rb 7. The threshold value setting unit 86 sets the duration of reverse rotation measured in the measurement step S4, for example, as the threshold value Th in the control device 20. This sets the threshold value Th relating to the duration of reverse rotation. In the next and subsequent molding cycles, the control device 20 executes the control method of FIG. 4 based on the threshold value Th set in the threshold value setting step S8. In this case, point t3 shown in FIG. 7 indicates point t2 in FIG. 5 (point t3 in FIG. 7=point t2 in FIG. 5).

[0102] The above is an explanation of the control method of the injection molding machine 10 in the case where the threshold setting unit 86 sets the threshold Th. The control method illustrated in FIG. 4 is executed when the threshold Th has already been set in the control device 20. The control device 20 executes the control method of FIG. 4 to suitably reduce the variation in the timing of the end of the suck-back. On the other hand, the control device 20 executes the control method of FIG. 6 when the threshold Th has not yet been set. Specifically, the control device 20 executes the control method of FIG. 6, for example, at the stage of a test run of the injection molding machine 10. However, even if the threshold Th has been set, the control device 20 may execute the control method of FIG. 6 when, for example, an operator desires to reset the threshold Th. The control device 20 may receive an instruction to execute either the control method of FIG. 4 or the control method of FIG. 6, for example, via the operation unit 68. In addition, the display control unit 88 may appropriately display information on the display unit 66 in parallel with each step illustrated in each of FIG. 4 and FIG. 6 (display step).

[0103] As described above, according to the control device 20 and the control method of the present embodiment, the variation in the timing of the end of suck-back with respect to the control of the injection molding machine 10 is reduced. This reduces the variation in the operation for each molding cycle, and the cycle time for manufacturing a molded product is stabilized. Furthermore, the screw 28 of the present embodiment executes suck-back and reverse rotation in an overlapping manner. This allows the resin pressure P to drop quickly. As a result, the time required for the decompression process is shortened, and production efficiency is improved. Furthermore, the screw 28 of the present embodiment continues reverse rotation even after the end of suck-back. This brings the amount of resin excessively stored in the metering area closer to the appropriate amount. As a result, the risk of variation in the mass (shape) of the molded product is reduced.

[0104] [Variations] The embodiment of the present invention has been described above as an example. Various modifications and improvements can be made to the above embodiment. Furthermore, it is clear from the claims that such modifications and improvements are included within the technical scope of the present invention.

[0105] Modifications of the embodiment will be described below. However, descriptions that overlap with the embodiment will be omitted as much as possible. The reference numerals of the components already described in the embodiment will be used from the embodiment unless otherwise specified.

[0106] (Variation 1) The threshold value setting unit 86 sets the reverse rotation state value SV rb The minimum, maximum, average, median, or mode of the reverse rotation state value SV may be set as the threshold value Th. For example, by performing a molding cycle multiple times, multiple reverse rotation state values ​​SV rb The threshold value setting unit 86 acquires the multiple reverse rotation state values ​​SV rb The average value of the multiple reverse rotation state values ​​SV rb , multiple reverse rotation status values ​​SV rb In some cases, the reverse rotation state value SV may include values ​​(outliers) that are significantly different from the average value of the reverse rotation state value SV. The outliers are determined based on, for example, whether they deviate from a predetermined range based on the average value. In this case, the threshold value setting unit 86 rb The median or mode of the reverse rotation state value SV may be set as the threshold value Th. The median and mode are less susceptible to outliers than the average value. rb This allows the operator to display the reverse rotation status value SV rb The operator can visually check the spraying status of the reverse rotation status value SV rb The type of threshold value Th can be selected taking into consideration the distribution state of the particles.

[0107] According to this modification, the threshold value Th is, for example, a reverse rotation state value SV measured in a certain molding cycle. rb Therefore, according to this modification, it is possible to set a more reliable threshold value Th.

[0108] (Variation 2) The method of setting the threshold value Th is not limited to the method described in the embodiment or the first modification.

[0109] FIG. 8 is a schematic configuration diagram of the control device 20 of the second modification.

[0110] The control device 20 of this modification differs from the control device 20 of the embodiment (see FIG. 3) in the following points (see also FIG. 8). The memory unit 70 of this modification stores a table 90. The calculation unit 72 of this modification includes an acquisition unit 92. The calculation unit 72 of this modification does not include a pressure acquisition unit 84.

[0111] FIG. 9 shows an example of the configuration of a table 90 stored in the storage unit 70 of the second modification.

[0112] Table 90 shows the correspondence between at least one of the type of screw 28 and the type of resin, and the coefficient A. For example, table 90 in Fig. 9 shows a coefficient A of "0.71" corresponding to the combination of the type of screw 28 "single flight screw" and the type of resin "PA (polyamide resin)." Table 90 in Fig. 9 also shows a coefficient A of "0.51" corresponding to the type of screw 28 "highly plasticized screw."

[0113] Although not illustrated in Fig. 9, the table 90 may include a coefficient A corresponding to a "single-flight screw" or a "double-flight screw" without corresponding to a type of resin. The table 90 may also include a coefficient A corresponding to a type of resin without corresponding to a type of screw 28. Furthermore, the table 90 may include a type of screw 28 or a type of resin not illustrated in Fig. 9.

[0114] The acquisition unit 92 acquires the type of the screw 28 and the type of resin used in the injection molding. The acquisition unit 92 acquires the type of the screw 28 and the type of resin input by the operator via the operation unit 68, for example.

[0115] The threshold setting unit 86 of this modified example acquires the coefficient A by referring to the table 90 based on the type of the screw 28 and the type of resin acquired by the acquisition unit 92. The threshold setting unit 86 of this modified example acquires the coefficient A and a predetermined reverse rotation condition value CVrb Set the product with as the threshold Th. For example, the type of the obtained screw 28 is "double flight screw". Also, the type of the obtained resin is "PBT (polybutylene terephthalate resin)". The coefficient A in this case is "0.62" (see Fig. 9). Therefore, the threshold setting unit 86 sets the reverse rotation condition value CV rb (e.g., the duration T rb ) multiplied by "0.62" as the threshold Th. The value of the calculated threshold Th becomes larger as the coefficient A becomes larger. Therefore, the execution time of the suck-back becomes longer as the coefficient A becomes larger, and the execution time of the suck-back becomes shorter as the coefficient A becomes smaller.

[0116] The range of the coefficient A is 0 < A ≤ 1, more preferably 0 < A < 1. When the threshold Th is calculated based on the coefficient A within the range of 0 < A < 1, the suck-back end control unit 82 can end the suck-back before the end of the reverse rotation. That is, the suck-back end control unit 82 can secure a time zone for adjusting the resin amount in the metering area by performing the reverse rotation after the overlapping execution of the suck-back and the reverse rotation.

[0117] The reason for preferably determining the coefficient A for each type of screw 28 is that the ability to cause the backflow of the resin varies depending on the type of screw 28. For example, the ability of a single flight screw to cause the backflow of the resin is relatively lower compared to a double flight screw or a highly plasticized screw. In this case, it is preferable that the coefficient A associated with the single flight screw is larger than the coefficient A associated with the double flight screw or the highly plasticized screw. Thereby, when the type of the screw 28 is a single flight screw, the execution time of the suck-back becomes longer. That is, the pressure P of the resin can be reduced as quickly as possible.

[0118] The reason why it is preferable to determine the coefficient A for each type of resin is that the likelihood of backflow occurring during reverse rotation differs depending on the type of resin. For example, a resin with high viscosity is less likely to backflow. In other words, the pressure P of a highly viscous resin is less likely to decrease with the reverse rotation of the screw 28. Therefore, it is preferable to assign a larger coefficient A to a resin with high viscosity. This increases the time required to perform suck-back. As a result, even when a highly viscous resin is used in injection molding, the pressure P of the resin can be quickly reduced.

[0119] According to this modification, if the operator specifies the type of the screw 28 and the type of the resin of the injection molding machine 10 that he / she uses via the operation unit 68, the threshold setting unit 86 can set the threshold value Th. However, in this modification, the reverse rotation condition value CV rb The coefficient A, which is multiplied by the coefficient A to derive the threshold value Th, must be determined in advance according to the type of the screw 28 and the type of the resin. In this regard, it is preferable that the manufacturer of the injection molding machine 10 provides the operator with a table 90 that has been constructed based on experiments, for example. This reduces the burden on the operator in constructing the table 90.

[0120] The storage unit 70 may store a plurality of tables 90. For example, the storage unit 70 may store the target reverse rotation speed V rb Table 90 showing the coefficient A for the duration T rb Table 90 showing the coefficient A for the target reverse rotation amount R rb In addition, when the coefficient A can be specified based on only one of the type of the screw 28 and the type of the resin, the acquisition unit 92 does not need to acquire the remaining other.

[0121] (Variation 3) FIG. 10 is a schematic configuration diagram of the control device 20 of the third modified example.

[0122] The control device 20 may further include a change receiving unit 94 and a correction unit 96 (see FIG. 10). The change receiving unit 94 receives an operator's instruction (change instruction) to change the threshold value Th set by the threshold setting unit 86. The change instruction is input to the change receiving unit 94 via the operation unit 68, for example.

[0123] The threshold setting unit 86 automatically sets the threshold Th (see the embodiment). However, from the viewpoint of an operator, there may be cases where the operator wants to adjust the threshold Th set by the threshold setting unit 86 to a value of his / her own choosing. The change acceptance unit 94 can provide convenience to such an operator.

[0124] When the threshold value Th deviates from a predetermined range, the correction unit 96 corrects the threshold value Th so that it falls within the range. The range of the threshold value Th is determined in advance, for example, based on an experiment performed by the manufacturer of the injection molding machine 10. The range of the threshold value Th is stored in the storage unit 70. The correction unit 96 prevents, for example, a threshold value Th that is not assumed by the manufacturer from being set. The correction unit 96 may correct not only the threshold value Th changed by the operator, but also the threshold value Th automatically set by the threshold value setting unit 86.

[0125] (Variation 4) The suck-back end control unit 82 may forcefully end the suck-back of the screw 28 when the reverse rotation of the screw 28 ends before the suck-back of the screw 28 ends. For example, when a threshold value Th is set that is large enough that the suck-back continues even after the reverse rotation of the screw 28 ends, the suck-back end control unit 82 may forcefully end the suck-back at the timing when the reverse rotation of the screw 28 ends. In this way, the suck-back end control unit 82 can minimize the suck-back operation that is not intended by the manufacturer of the injection molding machine 10.

[0126] (Variation 5) FIG. 11 is a schematic configuration diagram of the control device 20 of the fifth modified example.

[0127] The control device 20 may further include a notification unit 98 (see FIG. 11). When the reverse rotation ends before the suck back of the screw 28 ends, the notification unit 98 notifies the operator that the reverse rotation has ended before the suck back of the screw 28 ends. This allows the operator to recognize that the suck back did not end normally.

[0128] The notification unit 98 notifies the operator, for example, by displaying a message indicating that reverse rotation has ended before the end of suck back on the display unit 66. However, this modified example is not limited to this. For example, the notification unit 98 may turn on a notification light (lamp) provided in the injection molding machine 10. The notification unit 98 may also emit a sound from a speaker provided in the injection molding machine 10.

[0129] (Variation 6) The injection molding machine 10 to which the control device 20 is applied is not limited to an in-line type injection molding machine. The injection molding machine 10 may be, for example, a pre-plasticization type injection molding machine.

[0130] (Variation 7) The above-described modified examples may be combined as appropriate within a range that does not cause contradictions.

[0131] [Invention Obtained from the Embodiments] The invention that can be understood from the above-described embodiment and modifications will be described below.

[0132] <First invention> A control device (20) for an injection molding machine (10) including a cylinder (26) and a screw (28) that rotates and advances and retreats within the cylinder, the control device (20) measures resin in the cylinder by retracting the screw to a predetermined measurement position while rotating in a forward direction, and after the screw reaches the predetermined measurement position, the control device (20) measures resin in the cylinder by retracting the screw to a predetermined suck-back speed (V sb A suck-back control unit (76) that sucks back the screw at a predetermined reverse rotation condition value (CV rb) to rotate the screw in the reverse direction, and a reverse rotation state value (SV rb and a suck-back end control unit (82) that ends the suck-back of the screw by the suck-back control unit when the reverse rotation state value reaches a threshold value (Th).

[0133] This provides a control device that reduces the variation in the timing at which the suck back ends.

[0134] The first invention further comprises a threshold setting unit (86) for setting the threshold, a table (90) storing a coefficient (A) corresponding to at least one of the type of the screw and the type of the resin, and an acquisition unit (92) for acquiring the type of at least one of the screw and the resin used in injection molding, and the threshold setting unit may set the threshold value as a value obtained by multiplying the coefficient corresponding to at least one of the type of the screw and the resin acquired by the acquisition unit by the predetermined reverse rotation condition value. This makes it possible to easily set the threshold value, for example.

[0135] The first invention further comprises a threshold setting unit (86) for setting the threshold, and a pressure acquisition unit (84) for acquiring the pressure (P) of the resin in the cylinder, and when the threshold setting unit sets the threshold, the suck-back end control unit does not end the suck-back of the screw by the suck-back control unit (76) until the resin pressure (P) reaches a predetermined suck-back end pressure (P2), and the threshold setting unit may set the threshold based on the reverse rotation state value when the resin pressure (P) during suck-back reaches the predetermined suck-back end pressure (P2). This makes it possible to set the threshold, for example, in an appropriate manner.

[0136] The threshold setting unit may calculate, as the threshold, a minimum value, a maximum value, an average value, a median value, or a mode value of the reverse rotation state value measured a predetermined number of times while the injection molding machine executes a molding cycle a predetermined number of times. This makes it possible to more appropriately set the threshold.

[0137] The first invention may further include a change receiving unit (94) that receives an instruction from an operator to change the threshold set by the threshold setting unit, thereby making it possible to provide convenience to an operator who wishes to change the threshold set by the threshold setting unit to a value of his / her own choosing.

[0138] The first invention may further include a correction unit (96) that corrects the threshold value so that it falls within a predetermined range when the threshold value deviates from the predetermined range. This makes it possible to prevent a situation in which injection molding is performed based on an abnormal value even if an abnormal value is set as the threshold value.

[0139] The first invention may further include a display control unit (88) that displays the threshold value on the display unit (66). This makes it possible to notify an operator that a threshold value has been set and a specific value of the threshold value.

[0140] The suck-back end control unit may forcefully end the suck-back of the screw when the reverse rotation ends before the suck-back of the screw ends. This makes it possible to minimize the suck-back operation even if the injection molding machine performs a suck-back operation unintended by an operator.

[0141] The first invention may further include a notification unit (98) that notifies an operator that the reverse rotation has ended before the suck back of the screw has ended, when the reverse rotation has ended before the suck back of the screw has ended. This allows the operator to recognize that the suck back has not ended normally.

[0142] The predetermined reverse rotation condition value is the duration of the reverse rotation (Trb ), target reverse rotation speed (V rb ), and the target reverse rotation amount (R rb ) may include at least two of

[0143] The reverse rotation state value may be the rotation speed of the screw rotating in reverse, or the amount of rotation or elapsed time since the screw starts to rotate in reverse.

[0144] <Second Invention> A control method for an injection molding machine (10) including a cylinder (26) and a screw (28) that rotates and advances and retreats within the cylinder, in which the screw is rotated forward while being retreated to a predetermined metering position to measure a resin in the cylinder, the control method being performed after the screw reaches the predetermined metering position by controlling a predetermined suck-back speed (V sb A suck-back control step (S2) for sucking back the screw at a predetermined reverse rotation condition value (CV rb ) to reversely rotate the screw based on the reverse rotation control step (S3), and a reverse rotation state value (SV rb and a suck-back termination step (S5) of terminating the suck-back of the screw by the suck-back control step when the reverse rotation state value reaches a threshold value (Th).

[0145] This provides a control method that reduces the variation in the timing at which the suck back ends.

[0146] The second invention further includes a threshold setting step (S8) for setting the threshold, and an acquisition step for acquiring the type of at least one of the screw and the resin used in the injection molding, and in the threshold setting step, a value obtained by multiplying the coefficient corresponding to at least one of the screw and the resin acquired in the acquisition step by the predetermined reverse rotation condition value may be set as the threshold based on a table (90) storing a coefficient (A) corresponding to at least one of the screw type and the resin type. This makes it possible to easily set the threshold, for example.

[0147] The method further includes a threshold setting step (S8) for setting the threshold, and a pressure acquisition step (S6) for acquiring the pressure (P) of the resin in the cylinder, and in the suck-back end step, when the threshold setting step (S8) is performed, the suck-back of the screw by the suck-back control step is not ended until the resin pressure (P) reaches a predetermined suck-back end pressure (P2), and in the threshold setting step, the threshold may be set based on the reverse rotation state value when the resin pressure (P) during suck-back reaches the predetermined suck-back end pressure (P2). This allows, for example, the threshold to be set appropriately.

Claims

1. A control device for an injection molding machine including a cylinder and a screw that rotates and advances and retreats within the cylinder, the control device measuring a resin in the cylinder by retracting the screw to a predetermined measuring position while rotating in a forward direction, A suck-back control unit that sucks back the screw at a predetermined suck-back speed after the screw reaches the predetermined metering position; A reverse rotation control unit that reversely rotates the screw based on a predetermined reverse rotation condition value after the start of the suck back of the screw; A measurement unit that measures a reverse rotation state value indicating a reverse rotation state of the screw after the reverse rotation is started; A suck-back end control unit that ends the suck-back of the screw by the suck-back control unit when the reverse rotation state value reaches a threshold value; Equipped with A control device, wherein the reverse rotation state value is a rotation speed of the screw rotating in reverse, or an amount of rotation or elapsed time since the screw starts to rotate in reverse.

2. The control device according to claim 1 , A threshold setting unit that sets the threshold; A table storing coefficients corresponding to at least one of the type of the screw and the type of the resin; An acquisition unit that acquires the type of at least one of the screw and the resin used in injection molding; Further equipped with The threshold setting unit sets, as the threshold, a value obtained by multiplying the coefficient corresponding to the type of at least one of the screw and the resin acquired by the acquisition unit by the predetermined reverse rotation condition value.

3. The control device according to claim 1 , A threshold setting unit that sets the threshold; a pressure acquisition unit that acquires a pressure of the resin in the cylinder; Further equipped with When the threshold setting unit sets the threshold, the suck-back end control unit does not end the suck-back of the screw by the suck-back control unit until the pressure of the resin reaches a predetermined suck-back end pressure, The threshold setting unit sets the threshold based on the reverse rotation state value when the pressure of the resin during suck back reaches the predetermined suck back end pressure.

4. The control device according to claim 3, The threshold setting unit calculates, as the threshold, a minimum value, a maximum value, an average value, a median value or a mode value of the reverse rotation state value measured a predetermined number of times while the injection molding machine executes a molding cycle a predetermined number of times.

5. The control device according to any one of claims 2 to 4, The control device further comprises a change receiving unit that receives an instruction from an operator to change the threshold value set by the threshold setting unit.

6. The control device according to any one of claims 1 to 5, The control device further comprises a correction unit that, when the threshold value deviates from a predetermined range, corrects the threshold value so that the threshold value falls within the range.

7. The control device according to any one of claims 1 to 6, The control device further includes a display control unit that causes the threshold value to be displayed on a display unit.

8. The control device according to any one of claims 1 to 7, The suck-back end control unit is a control device that, when the reverse rotation ends before the suck-back of the screw ends, forcibly ends the suck-back of the screw.

9. The control device according to any one of claims 1 to 8, The control device further includes an alarm unit that, when the reverse rotation ends before the suck back of the screw ends, notifies that the reverse rotation has ended before the suck back of the screw ends.

10. The control device according to any one of claims 1 to 9, A control device, wherein the predetermined reverse rotation condition values ​​include at least two of a duration of the reverse rotation, a target reverse rotation speed, and a target reverse rotation amount at which the reverse rotation is terminated.

11. A control method for an injection molding machine including a cylinder and a screw that rotates and advances and retreats within the cylinder, the method comprising: rotating the screw in a forward direction while retracting the screw to a predetermined measurement position to measure a resin in the cylinder, the method comprising the steps of: A suck-back control step of sucking back the screw at a predetermined suck-back speed after the screw reaches the predetermined metering position; A reverse rotation control step of rotating the screw in reverse based on a predetermined reverse rotation condition value after the start of the suck back of the screw; A measurement step of measuring a reverse rotation state value indicating a reverse rotation state of the screw after the reverse rotation is started; A suck-back end step for ending the suck-back of the screw by the suck-back control step when the reverse rotation state value reaches a threshold value; Including, A control method, wherein the reverse rotation state value is a rotation speed of the screw rotating in reverse, or an amount of rotation or elapsed time since the screw starts to rotate in reverse.

12. 12. The control method according to claim 11, a threshold setting step of setting the threshold; An acquisition step of acquiring the type of at least one of the screw and the resin used in injection molding; Further comprising: In the threshold setting step, a value obtained by multiplying the coefficient corresponding to at least one of the types of the screw and the resin acquired in the acquisition step by the specified reverse rotation condition value is set as the threshold value based on a table storing coefficients corresponding to at least one of the types of the screw and the type of the resin.

13. 12. The control method according to claim 11, a threshold setting step of setting the threshold; a pressure acquiring step of acquiring a pressure of the resin in the cylinder; Further comprising: In the suck-back end step, when the threshold setting step is performed, the suck-back of the screw by the suck-back control step is not ended until the pressure of the resin reaches a predetermined suck-back end pressure, In the threshold setting step, the threshold is set based on the reverse rotation state value when the pressure of the resin during suck back reaches the predetermined suck back end pressure.

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