WO2023170841A1 - Control device and control method - Google Patents

Abstract

A control device (18) for controlling a screw (34) of an injection molding machine (10) comprises: a decompression control unit (80) for reducing the pressure of a resin on the basis of a predetermined decompression condition value (CV) after the resin has been weighed; a first measurement unit (86) for measuring the load applied to the screw (34) due to injection of the resin; a second measurement unit (90) for measuring a time (TM) from the start of an injection operation by the screw (34) until the load reaches a first threshold value (TH1); and a decompression condition correction unit (94) for correcting the predetermined decompression condition value (CV) on the basis of a difference (δ) between the time (TM) and a second threshold value (TH2).

Description

Control device and control method

The present invention relates to a control device and a control method for controlling an injection molding machine.

An injection molding machine is an industrial machine that mass-produces molded products by repeatedly executing a molding cycle that includes multiple steps. The molding cycle includes a metering process, a pressure reduction process, and an injection process (see also JP-A-10-16016). According to Japanese Patent Application Laid-Open No. 10-16016, the pressure reduction step is performed after the metering step. The injection process is performed after the depressurization process.

In the measuring step, a predetermined amount of resin is melted and stored inside the tip (measuring area) of the cylinder of the injection molding machine. In the pressure reduction step, the pressure of the resin stored in the metering area is reduced.

The control device for the injection molding machine controls the injection molding machine based on various set parameters. The parameters include, for example, the rotational speed of the screw that rotates in the metering process, the metering position that indicates the target position of the screw that is retracted, and the like. Here, even if the parameters are not changed at all, the temperature, viscosity, density, amount of resin, etc. of the resin in the measurement area after the pressure reduction process may change for each molding cycle. In this case, the quality of the molded product obtained by performing the injection step after the depressurization step varies from molding cycle to molding cycle.

In order to make the quality of the molded product uniform, it is desirable to appropriately adjust the parameters used in the pressure reduction process, taking into account the possibility that the state of the resin after the pressure reduction process changes with each molding cycle. However, adjusting this parameter is a burden on the operator of the injection molding machine.

The present invention aims to solve the above-mentioned problems.

A first aspect of the present invention is an injection molding machine that includes a cylinder and a screw that injects a predetermined amount of resin measured in the cylinder into a mold. a pressure reduction control unit that controls the screw based on a predetermined pressure reduction condition value to reduce the pressure of the resin after the predetermined amount of the resin is measured in the cylinder; , a first measurement unit that measures a load applied to the screw in response to the resin being injected from the cylinder into the mold after the pressure reduction of the resin is completed; and a first measurement unit configured to inject the resin into the mold. The time from when the screw starts the injection operation until the load reaches the first threshold value, or from the time when the screw starts the injection operation until the load reaches the first threshold value. a second measuring section that measures the amount of movement of the screw; and a reduced pressure condition correction section that corrects the predetermined reduced pressure condition value based on the difference between the time or the amount of movement and a second threshold value. , is a control device.

A second aspect of the present invention is an injection molding machine that includes a cylinder and a screw that injects a predetermined amount of resin measured in the cylinder into a mold. The control method includes a pressure reduction control step of controlling the screw based on a predetermined pressure reduction condition value to reduce the pressure of the resin after the predetermined amount of the resin is measured in the cylinder. , a first measuring step of measuring the load applied to the screw in response to the resin being injected from the cylinder into the mold after the pressure reduction of the resin is completed; and injecting the resin into the mold. time from when the screw starts an injection operation until the load reaches the first threshold value, or from when the screw starts the injection operation until the load reaches the first threshold value. a second measuring step of measuring the amount of movement of the screw until A control method including:

According to the present invention, the operator's work burden related to parameter adjustment for the depressurization process is reduced.

FIG. 1 is a side view of an injection molding machine according to an embodiment. FIG. 2 is a schematic diagram of the injection unit. FIG. 3 is a configuration diagram of the control device. FIG. 4 is a table illustrating the first threshold table. FIG. 5 is a table illustrating the second threshold table. FIG. 6 is a table illustrating a correction amount table. FIG. 7 is a flowchart illustrating the flow of the control method according to the embodiment. FIG. 8 is a time chart illustrating changes in the screw rotational speed and the resin pressure over time when the control method of FIG. 7 is executed. FIG. 9 is a time chart illustrating the time course of the torque of the first motor measured by the first measurement unit. FIG. 10 is a time chart illustrating the respective time changes of the resin pressure and the torque of the first motor in the next molding cycle after the molding cycles shown in FIGS. 8 and 9. FIG. FIG. 11 is a configuration diagram of a control device according to modification 1. FIG. 12 is a flowchart illustrating the flow of the control method according to the first modification.

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

The injection molding machine 10 includes a mold clamping unit 12, an injection unit 14, a machine stand 16, and a control device 18. Note that an arrow D1 in FIG. 1 indicates the front direction of the injection unit 14. An arrow D2 in FIG. 1 indicates the rear direction of the injection unit 14.

The mold clamping unit 12 is a device that opens and closes the mold 20. The mold clamping unit 12 is arranged in front of the injection unit 14. Note that the mold 20 opens and closes in the front and rear directions. The mold 20 in the closed state forms a cavity 20c. The mold 20 in FIG. 1 is in a closed state. The mold clamping unit 12 can apply mold clamping force to the mold 20 so that the mold 20 is maintained in a closed state. However, a more detailed explanation of the mold clamping unit 12 will be omitted.

The machine stand 16 supports the mold clamping unit 12 and the injection unit 14. However, the machine stand 16 may support only the injection unit 14 of the mold clamping unit 12 and the injection unit 14. A guide rail 22 is installed on the machine stand 16. The guide rail 22 extends in the front-rear direction.

The injection unit 14 is supported by the slide base 24. The slide base 24 is guided by the guide rail 22 and slides in the front and rear directions. Therefore, the injection unit 14 slides in the front and back direction together with the slide base 24.

The injection unit 14 includes a cylinder 26. The cylinder 26 is a cylindrical member that extends toward the front of the injection unit 14 .

FIG. 2 is a schematic diagram of the injection unit 14.

The axis L of the cylinder 26 extends parallel to the front-rear direction. The cylinder 26 includes a hopper 28, a heater 30, a nozzle 32, and a screw 34. In addition, the injection unit 14 further includes a first drive device 36, a second drive device 38, and a pressure sensor 40.

The hopper 28 is arranged at the rear end 26r of the cylinder 26. The hopper 28 stores resin solids (pellets). The resin is a raw material for molded products produced by the injection molding machine 10. Further, the hopper 28 has a supply port 28o. The resin in the hopper 28 is supplied into the cylinder 26 via the supply port 28o.

The heater 30 heats the cylinder 26. By heating the cylinder 26, the resin inside the cylinder 26 is heated. The heater 30 includes, for example, a plurality of band heaters. A plurality of band heaters are wrapped around the cylinder 26.

The nozzle 32 is attached to the front end 26f of the cylinder 26. The nozzle 32 has an injection port 32p. The nozzle 32 communicates the inside of the front end portion 26f with the cavity 20c of the mold 20 via the injection port 32p. Note that the injection unit 14 may include a temperature sensor for detecting the temperature of the nozzle 32. Illustration of the temperature sensor is omitted.

The screw 34 is arranged inside the cylinder 26. The axis L of the cylinder 26 is also the axis of the screw 34. The screw 34 has a flight portion 42, a screw head 44, a check sheet 46, and a backflow prevention ring 48.

The flight portion 42 has a single spiral shape and is formed on the surface of the screw 34. However, the flight portion 42 may have a double helical shape. The flight portion 42 forms a flow path 50 inside the cylinder 26 together with the inner wall 26 i of the cylinder 26 . The flow path 50 is formed to guide the resin supplied into the cylinder 26 from the rear end 26r to the front end 26f.

The screw head 44 is the front end of the screw 34. The check sheet 46 is arranged behind the screw head 44. The backflow prevention ring 48 is arranged between the screw head 44 and the check sheet 46.

When forward pressure is applied to the backflow prevention ring 48, the backflow prevention ring 48 moves forward within the range between the screw head 44 and the check sheet 46 according to the pressure. By moving forward, the backflow prevention ring 48 moves away from the check sheet 46. By separating from the check sheet 46, the backflow prevention ring 48 opens a flow path 50 between the screw head 44 and the check sheet 46.

Furthermore, when rearward pressure is applied to the backflow prevention ring 48, the backflow prevention ring 48 moves rearward within the range between the screw head 44 and the check sheet 46 according to the pressure. The backflow prevention ring 48 approaches the check sheet 46 by moving backward. The backflow prevention ring 48 closes the flow path 50 between the screw head 44 and the check sheet 46 by coming into contact with the check sheet 46 .

The first drive device 36 is a device that rotates the screw 34. The first drive device 36 includes a first motor 52a, a first drive pulley 54a, a first belt member 56a, and a first driven pulley 58a.

The first motor 52a is, for example, a servo motor. The first motor 52a includes a first shaft 60a, a first position and speed sensor 62a, and a first current torque sensor 63a. The first shaft 60a rotates according to the drive current supplied to the first motor 52a. The first position and speed sensor 62a outputs a detection signal according to the rotational position of the first shaft 60a to the control device 18. The first current torque sensor 63a outputs a detection signal to the control device 18 according to the drive current supplied to the first motor 52a, the rotational torque of the first shaft 60a, and the like. Note that a more detailed explanation of the control device 18 will be given later.

The first drive pulley 54a is connected to the first shaft 60a. The first drive pulley 54a rotates in accordance with the rotation of the first shaft 60a. The first belt member 56a spans the first driving pulley 54a and the first driven pulley 58a. Thereby, the rotation of the first drive pulley 54a is transmitted to the first driven pulley 58a via the first belt member 56a. As a result, the first driven pulley 58a also rotates in accordance with the rotation of the first drive pulley 54a.

The first driven pulley 58a is provided integrally with the screw 34. Therefore, the screw 34 also rotates in accordance with the rotation of the first driven pulley 58a. The screw 34 rotates around the axis L. By rotating the screw 34, the resin inside the cylinder 26 can be caused to flow along the flow path 50. Note that the rotation direction of the first shaft 60a is switched according to the control of the control device 18. In response to the switching of the rotational direction of the first shaft 60a, the rotational direction of the screw 34 is also switched. By switching the rotational direction of the screw 34, the flow direction of the resin inside the cylinder 26 changes.

In the following description, the direction of rotation of the screw 34 when the resin flows forward is also referred to as the forward rotation direction. Further, the rotational movement of the screw 34 in the forward rotation direction is also referred to as forward rotation.

On the other hand, in the following description, the rotation direction of the screw 34 when the resin flows backward is also described as a reverse rotation direction. Further, the rotational movement of the screw 34 in the reverse rotation direction is also referred to as reverse rotation.

The second drive device 38 is a device that moves the screw 34 forward and backward inside the cylinder 26. The second drive device 38 includes a second motor 52b, a second drive pulley 54b, a second belt member 56b, a second driven pulley 58b, a ball screw 64, and a nut 66.

The second motor 52b is, for example, a servo motor. The second motor 52b includes a second shaft 60b, a second position and speed sensor 62b, and a second current torque sensor 63b. The second shaft 60b rotates according to the drive current supplied to the second motor 52b. The second position and speed sensor 62b outputs a detection signal according to the rotational position of the second shaft 60b to the control device 18. The second current torque sensor 63b outputs a detection signal to the control device 18 according to the drive current supplied to the second motor 52b, the rotational torque of the second shaft 60b, and the like.

The second drive pulley 54b is connected to the second shaft 60b. The second drive pulley 54b rotates in accordance with the rotation of the second shaft 60b. The second belt member 56b spans the second drive pulley 54b and the second driven pulley 58b. Thereby, the rotation of the second drive pulley 54b is transmitted to the second driven pulley 58b via the second belt member 56b. As a result, the second driven pulley 58b also rotates in accordance with the rotation of the second drive pulley 54b.

The second driven pulley 58b is connected to the ball screw 64. The second driven pulley 58b rotates in accordance with the rotation of the second drive pulley 54b transmitted via the second belt member 56b. Therefore, the ball screw 64 also rotates in accordance with the rotation of the second driven pulley 58b.

The nut 66 is screwed onto the ball screw 64. As the ball screw 64 rotates, the relative positional relationship between the nut 66 and the ball screw 64 changes in the axial direction of the ball screw 64. The axis of the ball screw 64 is parallel to the axis L of the cylinder 26 (screw 34). Therefore, the relative positional relationship between the nut 66 and the ball screw 64 changes in parallel to the axis L of the screw 34 in accordance with the rotation of the ball screw 64. That is, the relative positional relationship between the nut 66 and the ball screw 64 changes in the front-back direction according to the rotation of the ball screw 64.

The screw 34 is connected to a nut 66 and moves back and forth inside the cylinder 26 as the relative positional relationship between the nut 66 and the ball screw 64 changes in the front and back direction. Note that the rotation direction of the second shaft 60b is switched according to the control of the control device 18. In response to the switching of the rotational direction of the second shaft 60b, the rotational direction of the ball screw 64 is also switched. By switching the rotational direction of the ball screw 64, the moving direction of the nut 66 and the screw 34 is switched.

According to the injection unit 14 described above, the resin supplied from the hopper 28 into the cylinder 26 flows forward along the flow path 50 as the screw 34 rotates in the forward rotation direction (forward rotation). . While flowing along the flow path 50, the resin melts under the influence of the heat of the heater 30 transmitted via the cylinder 26 and the shear heat generated in the resin by being sheared by the flight portion 42.

The resin located behind the backflow prevention ring 48 flows forward along the flow path 50 and reaches the backflow prevention ring 48 as the screw 34 continues to rotate forward. The resin that has reached the backflow prevention ring 48 presses the backflow prevention ring 48 in the forward direction. As a result, the backflow prevention ring 48 moves forward within the range between the screw head 44 and the check sheet 46 to open the flow path 50. The resin passes through the open channel 50 and reaches a region inside the cylinder 26 in front of the screw head 44 .

In the following description, the area inside the cylinder 26 in front of the screw head 44 is also referred to as a metering area. Further, in the following description, the amount of resin refers to the amount of resin stored in the measurement area unless otherwise specified.

The resin accumulated in the metering area presses the screw head 44 backward, thereby pressing the screw 34 backward. Therefore, backward pressure is applied to the screw 34 from the resin in the metering area.

The pressure sensor 40 is a sensor for detecting the pressure applied to the screw 34 by the resin in the metering area. The pressure sensor 40 outputs a detection signal to the control device 18 in accordance with the pressure applied to the screw 34 by the resin in the measurement area. The pressure sensor 40 is, for example, a load cell.

FIG. 3 is a configuration diagram of the control device 18.

The control device 18 is an electronic device (computer) that controls the injection molding machine 10. The control device 18 is, for example, a numerical control device. The control device 18 includes a display section 68, an operation section 70, a storage section 72, and a calculation section 74.

The display unit 68 is a display device including a display screen 68d. The material of the display screen 68d includes, for example, liquid crystal or OEL (Organic Electro-Luminescence).

The operation unit 70 is an input device that accepts information input to the control device 18. The operation unit 70 includes, for example, an operation panel 70a, a touch panel 70b, and the like. The touch panel 70b is installed on the display screen 68d. Note that the operation unit 70 may include a keyboard, a mouse, and the like.

The storage unit 72 includes a storage circuit. This storage circuit includes one or more memories such as RAM (Random Access Memory) and ROM (Read Only Memory).

The storage unit 72 stores a control program 76. The control program 76 is a program for causing the control device 18 to execute the method for controlling the injection molding machine 10 according to the present embodiment.

Note that the data stored in the storage unit 72 is not limited to the control program 76. The storage unit 72 may store various data as necessary. For example, the storage unit 72 may store the pressure obtained based on the detection signal of the pressure sensor 40. The storage unit 72 also stores, for example, the torque of the first motor 52a (first torque) obtained based on the detection signal of the first current torque sensor 63a, and the torque of the first motor 52a obtained based on the detection signal of the second current torque sensor 63b. The torque of the two motors 52b (second torque), etc. may be stored. Furthermore, the storage unit 72 may store, for example, the drive current and voltage of the first motor 52a or the second motor 52b, the temperature of the nozzle 32, and the like.

The calculation unit 74 includes a processing circuit. This processing circuit includes, for example, one or more processors. However, the processing circuit of the calculation unit 74 may include an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Further, the processing circuit of the calculation unit 74 may include a discrete device.

The calculation section 74 includes a metering control section 78, a pressure reduction control section 80, an injection control section 82, and a display control section 84. The metering control section 78, the pressure reduction control section 80, the injection control section 82, and the display control section 84 are realized by the processor of the calculation section 74 executing the control program 76. However, at least a portion of the metering control section 78, the pressure reduction control section 80, the injection control section 82, and the display control section 84 may be realized by the aforementioned integrated circuit, discrete device, or the like.

The metering control unit 78 performs the control explained below in order to cause the injection molding machine 10 to execute the metering process in the molding cycle. Note that the initial position of the screw 34 (screw head 44) at the start of the metering process is the most forward position within the range of movement in the longitudinal direction inside the cylinder 26. Further, at the start of the metering process, the mold 20 is in a closed state and a mold clamping force is applied from the mold clamping unit 12.

The metering control unit 78 controls the first motor 52a to rotate the screw 34 in the forward direction. Thereby, the resin supplied from the hopper 28 into the cylinder 26 is forced forward along the flow path 50. The resin flowing forward inside the cylinder 26 reaches the metering area while being melted. The amount of resin gradually increases as the metering control section 78 continues to rotate the screw 34 in the forward direction.

The screw 34 retreats as the amount of resin increases. Here, the metering control unit 78 controls the second motor 52b to prevent the screw 34 from retracting excessively. This prevents the pressure of the resin from decreasing excessively as the screw 34 retreats.

Note that the metering control unit 78 controls the second motor 52b so that the pressure of the resin is adjusted to a predetermined pressure (metering pressure) P1 while the screw 34 rotates forward. The metered pressure P1 is stored in the storage section 72 in advance. The pressure of the resin is obtained based on the detection signal of the pressure sensor 40. The metering pressure P1 is, for example, greater than atmospheric pressure. The metering control unit 78 may control the second motor 52b to retract the screw 34 in order to adjust the pressure of the resin to the metering pressure P1.

The screw 34, which retreats as the amount of resin increases, reaches a predetermined position (measuring position) regarding the position of the screw 34. The measuring position is a position behind the initial position of the screw 34 in the measuring process. The metering control unit 78 can accumulate a predetermined amount of resin in the metering area by adjusting the resin pressure to the metering pressure P1 and causing the screw 34 to reach the metering position. When the screw 34 reaches the metering position, the metering control section 78 controls the first motor 52a to stop the forward rotation of the screw 34.

After a predetermined amount of resin is measured in the cylinder 26, the pressure reduction control unit 80 performs the control described below in order to cause the injection molding machine 10 to execute the pressure reduction step of the molding cycle.

The pressure reduction control unit 80 controls the first motor 52a to rotate the screw 34 in the reverse direction. When the screw 34 rotates in the opposite direction, the resin within the metering area flows backward. This reduces the amount of resin. As the amount of resin decreases, the pressure of the resin applied to the screw 34 is reduced.

Furthermore, inertia acts on the screw 34 that rotates in the forward direction. Therefore, the screw 34 continues to rotate even after reaching the metering position. As a result, the amount of resin immediately after measurement strictly exceeds the predetermined amount. The pressure reduction control unit 80 can also adjust the amount of resin to be closer to a predetermined amount by reducing the amount of resin in accordance with the reverse rotation of the screw 34.

Note that the backflow prevention ring 48 is pressed by the resin flowing from the metering area to the rear of the backflow prevention ring 48 in response to the pressure reduction control unit 80 rotating the screw 34 in the reverse direction. This causes the backflow prevention ring 48 to move rearward. When the backflow prevention ring 48 moves rearward, it comes into contact with the check sheet 46 located behind the backflow prevention ring 48 . When the backflow prevention ring 48 comes into contact with the check sheet 46, the flow path 50 is closed. By closing the flow path 50, the resin accumulated in the metering area cannot reach the rear of the backflow prevention ring 48. As a result, the amount of resin is prevented from decreasing more than necessary.

The pressure reduction control unit 80 controls the screw 34 based on a predetermined pressure reduction condition value CV and a target pressure reduction value P0.

The predetermined pressure reduction condition value CV includes three items: reverse rotation time, reverse rotation amount, and reverse rotation speed. The reverse rotation time indicates the duration of reverse rotation. The amount of reverse rotation indicates the amount of rotation that causes the screw 34 to rotate in the reverse direction. The reverse rotation speed indicates the rotation speed of the screw 34 that rotates in reverse. Note that the items of reverse rotation time, amount of reverse rotation, and reverse rotation speed are automatically determined by determining the remaining two items.

The predetermined pressure reduction condition value CV is stored in the storage unit 72. Note that the manufacturer of the injection molding machine 10 may store the recommended default value in the storage unit 72 in advance as the initial value of the predetermined pressure reduction condition value CV. However, the operator may arbitrarily change at least one item among the reverse rotation time, the reverse rotation amount, and the reverse rotation speed via the operation unit 70. In this case, the manufacturer of the injection molding machine 10 may store in the storage unit 72 in advance a predetermined range (upper limit value, lower limit value) in which the predetermined pressure reduction condition value CV can be changed. This limits the range of the predetermined pressure reduction condition value CV that can be changed by the operator.

The target pressure reduction value P0 indicates the target pressure of the resin pressure to be reduced in the pressure reduction step. The pressure reduction control unit 80 (injection control unit 82, which will be described later) determines that the pressure reduction has ended when the resin pressure reaches the target pressure reduction value P0. The target pressure reduction value P0 is, for example, atmospheric pressure.

The target pressure reduction value P0 is stored in the storage unit 72, for example. Note that the manufacturer of the injection molding machine 10 may store the recommended target pressure reduction value P0 in advance in the storage unit 72 as a default value. Further, the operator may specify an arbitrary pressure as the target pressure reduction value P0 via the operation unit 70. In this case, similarly to the predetermined pressure reduction condition value CV, the manufacturer of the injection molding machine 10 may store in the storage unit 72 in advance a changeable range of the target pressure reduction value P0.

In order to cause the injection molding machine 10 to execute the injection step of the molding cycle, the injection control unit 82 controls the second motor 52b to advance the screw 34 after the pressure reduction is completed. Thereby, the resin within the metering area is injected toward the cavity 20c of the mold 20 via the nozzle 32. The injected resin is solidified within the cavity 20c to complete the molded product.

The screw 34 that has advanced in the injection process moves to the most forward position within the range of movement in the longitudinal direction inside the cylinder 26. Here, the screw 34 may be moved to the initial position of the metering process described above. Thereby, the metering control unit 78 can start the metering step of the next molding cycle by sequentially rotating the screw 34 again after the molded product is taken out from the mold 20.

The display control unit 84 controls the display unit 68 to appropriately display various data stored in the storage unit 72 on the display screen 68d. For example, the display control unit 84 may display the resin pressure based on the detection signal of the pressure sensor 40 on the display screen 68d.

By the way, the state of the resin (temperature, viscosity, density, amount of resin, etc.) after the pressure reduction step may differ depending on the molding cycle.

For example, before the injection molding machine 10 starts injection molding, the nozzle 32 and the mold 20 are separated. In this case, the temperature of the nozzle 32 is likely to be different from the temperature of the mold 20. In order to cause the injection molding machine 10 to start injection molding, the injection unit 14 supported by the slide base 24 is slid forward along the guide rail 22, and the nozzle 32 and the mold 20 are brought into contact. As a result, the temperatures of the nozzle 32 and the mold 20 gradually become balanced. However, the temperature of the nozzle 32 is not stable until the temperatures of the nozzle 32 and the mold 20 reach equilibrium. In this case, the temperature of the resin stored in the metering area near the nozzle 32 varies with each molding cycle. When the temperature of the resin varies from molding cycle to molding cycle, the viscosity of the resin also fluctuates from molding cycle to molding cycle.

If the temperature, viscosity, etc. of the resin vary from molding cycle to molding cycle, the way the resin flows in each of the pressure reduction process and the injection process will vary from molding cycle to molding cycle. Therefore, for example, when the screw 34 is reversely rotated in the pressure reduction step, the amount of decrease in the amount of resin varies from molding cycle to molding cycle. In this case, since the amount of resin filled into the cavity 20c during the injection process varies from molding cycle to molding cycle, the quality of the molded product varies from molding cycle to molding cycle. Furthermore, if the way the resin flows into the cavity 20c during the injection process varies from molding cycle to molding cycle, there is a greater possibility that the quality of the molded product will vary from molding cycle to molding cycle.

Note that the cause of variations in the state of the resin from molding cycle to molding cycle is not limited to variations in the temperature of the nozzle 32. For example, even if the temperatures of the nozzle 32 and the mold 20 are balanced, the resin supplied into the cylinder 26 may change due to changes in room temperature, humidity, etc. due to seasonal changes. Drying conditions may vary from molding cycle to molding cycle. In this case, even if the same type of resin continues to be supplied into the cylinder 26, the state of the resin after being melted in the metering process varies from cycle to cycle depending on changes in room temperature, humidity, etc.

Furthermore, for example, the lot of resin supplied to the inside of the cylinder 26 may be changed during a plurality of molding cycles. In this case, there may be a difference in the physical properties of the resin between the resin lots before and after the change. As a result, a difference occurs in the state of the resin before and after changing the resin lot.

Further, for example, molded products may be produced using recycled resin, fiber-reinforced resin, etc. Recycled resin is resin containing recycled material. Fiber-reinforced resin is a resin containing reinforcing fibers as a material. The reinforcing fiber is, for example, glass fiber. The physical properties of the recycled resin and the fiber-reinforced resin are not stable compared to the physical properties of virgin material made from new materials. Therefore, when the injection molding machine 10 produces a molded product using recycled resin, fiber-reinforced resin, etc., the state of the resin accumulated in the metering area during the metering process tends to vary from molding cycle to molding cycle.

For the above reasons, it is desirable that the predetermined pressure reduction condition value CV used by the pressure reduction control section 80 in the pressure reduction step is appropriately adjusted depending on the state of the resin. Based on this, the control device 18 (calculating section 74) includes a first measuring section 86, a first threshold determining section 88, a second measuring section 90, a second threshold determining section 92, and a decompression condition correcting section 94. Furthermore, it is equipped with. The first measuring section 86, the first threshold determining section 88, the second measuring section 90, the second threshold determining section 92, and the depressurization condition correcting section 94 are, for example, a calculation section, similar to the metering control section 78, etc. 74 is realized by executing the control program 76.

The first measurement unit 86 measures the load applied to the screw 34 in response to resin being injected from the cylinder 26 into the mold 20 after the resin has been depressurized. That is, the first measurement unit 86 measures the load applied to the screw 34 as the screw 34 moves forward during the injection process.

The load applied to the screw 34 as the screw 34 moves forward in the injection process is, for example, the torque of the first motor 52a. That is, the resin adheres to the screw 34 along the spiral flow path 50. The resin attached to the screw 34 provides viscous resistance in the rotational direction of the screw 34 to the advancing screw 34. This viscous resistance affects the torque of the first motor 52a. Therefore, the torque of the first motor 52a reflects the load on the screw 34. The first measurement unit 86 can calculate the torque of the first motor 52a based on the detection signal of the first current torque sensor 63a.

The first threshold value determination unit 88 determines the first threshold value TH1 based on the first threshold value table TB1. The first threshold table TB1 is a data table that stores a plurality of first threshold values TH1 according to at least one of a plurality of types of screws 34 and a plurality of types of resin. The first threshold value determination unit 88 sets a first threshold value TH1 corresponding to the type of screw 34 provided in the injection molding machine 10 and the type of resin supplied into the inside of the cylinder 26 in the first threshold value table TB1. Search from.

FIG. 4 is a table illustrating the first threshold table TB1.

A plurality of types of screws 34 are stored in the first column (screw types) of the first threshold table TB1 illustrated in FIG. 4. For illustrative purposes, FIG. 4 shows multiple types of screws 34, including a full-flight screw, a barrier-flight screw, and a highly plasticized screw.

A plurality of types of resin are stored in the second column (types of resin) of the first threshold table TB1 illustrated in FIG. 4. For illustrative purposes, FIG. 4 shows PA (polyamide), PBT (polybutylene terephthalate), and PE (polyethylene) as a plurality of types of resin.

The third column (first threshold) of the first threshold table TB1 illustrated in FIG. 4 stores a plurality of first thresholds TH1 (V1 to V7) corresponding to each data in the first column and the second column. be done. The specific value of each of the plurality of first threshold values TH1 is determined in advance based on experiments. Note that, as shown in the bottom row of FIG. 4, the first threshold value TH1 depending on the type of screw 34 may be stored in the first threshold value table TB1 regardless of the type of resin. Furthermore, regardless of the type of screw 34, the first threshold value TH1 depending on the type of resin may be stored in the first threshold value table TB1.

The first threshold table TB1 is stored in advance in the storage unit 72 (see also FIG. 3). The type of screw 34 provided in the injection molding machine 10 and the type of resin supplied to the inside of the cylinder 26 are instructed by the operator to the first threshold value determination unit 88 via the operation unit 70, for example.

The second measurement unit 90 measures the required time TM from when the screw 34 starts an injection operation for injecting resin into the mold 20 until the load applied to the screw 34 reaches the first threshold value TH1. That is, the second measurement unit 90 measures the time TM required from when the screw 34 starts moving forward in the injection process until the torque of the first motor 52a reaches the first threshold value TH1.

The measured required time TM is stored in the storage unit 72.

The second threshold determination unit 92 determines the second threshold TH2 based on the second threshold table TB2. The second threshold table TB2 is a data table that stores a plurality of second threshold values TH2 according to at least one of the plurality of types of screws 34 and the plurality of types of resin. The second threshold determination unit 92 sets a second threshold TH2 corresponding to the type of screw 34 provided in the injection molding machine 10 and the type of resin supplied into the cylinder 26 in the second threshold table TB2. Search from.

FIG. 5 is a table illustrating the second threshold table TB2.

A plurality of types of screws 34 are stored in the first column (types of screws 34) of the second threshold table TB2 illustrated in FIG. A plurality of types of resin are stored in the second column (types of resin) of the second threshold table TB2 illustrated in FIG. 5 . The third column (second threshold) of the second threshold table TB2 illustrated in FIG. 5 stores a plurality of second thresholds TH2 (U1 to U7) corresponding to each data in the first column and the second column. be done.

The specific value of each of the plurality of second threshold values TH2 is determined in advance based on experiments. Note that the second threshold value TH2 according to the type of screw 34 may be stored in the second threshold value table TB2 regardless of the type of resin. Furthermore, regardless of the type of screw 34, the second threshold value TH2 depending on the type of resin may be stored in the second threshold value table TB2.

The second threshold table TB2 is stored in advance in the storage unit 72 (see also FIG. 3). The type of screw 34 provided in the injection molding machine 10 and the type of resin to be supplied into the cylinder 26 are specified by an operator to the second threshold value determination unit 92 via the operation unit 70, for example.

However, in order to have the first threshold value determination unit 88 determine the first threshold value TH1, the operator may have already input the type of screw 34 and the type of resin into the control device 18. In this case, the second threshold determination unit 92 may use the type of screw 34 and the type of resin that have already been input to the control device 18.

The decompression condition correction unit 94 corrects the predetermined decompression condition value CV based on the difference δ between the required time TM and the second threshold TH2. Here, the decompression condition correction unit 94 corrects at least one of the reverse rotation time, the reverse rotation amount, and the reverse rotation speed out of the predetermined pressure reduction condition value CV.

The difference δ between the required time TM and the second threshold TH2 may be the value obtained by subtracting the second threshold TH2 from the required time TM (δ = TM - TH2), or the value obtained by subtracting the required time TM from the second threshold TH2 ( δ=TH2-TM).

The decompression condition correction unit 94 determines the amount of correction for the predetermined decompression condition value CV based on the correction amount table TBC. The correction amount table TBC is a data table in which a plurality of correction amounts are stored according to the difference δ between the required time TM and the second threshold TH2.

FIG. 6 is a table illustrating the correction amount table TBC.

The first column (difference range) of the correction amount table TBC illustrated in FIG. 6 stores a plurality of ranges regarding the difference δ between the required time TM and the second threshold TH2. The second column (correction amount) of the correction amount table TBC illustrated in FIG. 6 stores a plurality of correction amounts (C1 to C6,...) corresponding to each of the plurality of ranges stored in the first column. Ru. Specific values of the plurality of correction amounts are determined in advance based on experiments. Note that the correction amount table TBC separately stores a correction amount for correcting the reverse rotation time, a correction amount for correcting the reverse rotation amount, and a correction amount for correcting the reverse rotation speed. Good too.

The correction amount table TBC is stored in advance in the storage unit 72 (see also FIG. 3). The decompression condition correction unit 94 determines the correction amount by referring to the correction amount table TBC based on the difference δ between the required time TM and the second threshold TH2. Further, the depressurization condition correction unit 94 corrects the predetermined depressurization condition value CV based on the determined correction amount.

For example, when the difference δ between the required time TM and the second threshold TH2 is D1, the correction amount is C1 according to FIG. Therefore, when the difference δ between the required time TM and the second threshold TH2 is D1, the decompression condition correction section 94 corrects the predetermined decompression condition value CV based on the correction amount C1.

However, if a predetermined range in which the predetermined decompression condition value CV can be changed is stored in advance in the storage unit 72, the decompression condition correction unit 94 adjusts the predetermined decompression condition value CV so that it falls within the predetermined range. It is preferable to correct it.

For example, if the predetermined pressure reduction condition value CV exceeds the upper limit value due to correction based on the correction amount, the pressure reduction condition correction unit 94 sets the upper limit value as the correction result of the predetermined pressure reduction condition value CV.

Further, when the predetermined pressure reduction condition value CV is lower than the lower limit value by correcting based on the correction amount, the pressure reduction condition correction unit 94 sets the lower limit value as the correction result of the predetermined pressure reduction condition value CV.

By correcting the predetermined pressure reduction condition value CV so that it falls within a predetermined range, the injection molding machine 10 is prevented from performing an operation that is not recommended by the manufacturer.

Note that the correction amount table TBC stores correction amounts that decrease the predetermined pressure reduction condition value CV as the required time TM is larger than the second threshold TH2. Therefore, when the required time TM exceeds the second threshold TH2, the decompression condition correction unit 94 decreases the predetermined depressurization condition value CV as the difference δ between the required time TM and the second threshold TH2 increases.

By correcting the predetermined pressure reduction condition value CV to a smaller value, the density of the resin stored in the measurement area is increased in the pressure reduction step performed after the correction. By increasing the density of the resin stored in the metering area, the backward pressure applied to the resin is increased. As a result, the resin in the metering area becomes more likely to flow forward in a short time. That is, by correcting the predetermined pressure reduction condition value CV to a smaller value, the pressure of the resin during the injection process is likely to increase quickly. As a result, the required time TM approaches the second threshold value TH2 in the injection process after the pressure reduction process performed based on the corrected predetermined pressure reduction condition value CV.

Further, the correction amount table TBC stores a correction amount that increases the predetermined pressure reduction condition value CV as the required time TM is smaller than the second threshold TH2. Therefore, when the required time TM is less than the second threshold TH2, the depressurization condition correction unit 94 increases the predetermined depressurization condition value CV as the difference δ between the required time TM and the second threshold TH2 increases.

By correcting the predetermined pressure reduction condition value CV to a larger value, the density of the resin accumulated in the measurement area is reduced in the pressure reduction step performed after the correction. By lowering the density of the resin stored in the metering area, the backward pressure applied to the resin is weakened. As a result, the resin within the metering area becomes more difficult to flow forward. That is, by correcting the predetermined pressure reduction condition value CV to a larger value, the pressure of the resin during the injection process becomes difficult to increase. As a result, the required time TM approaches the second threshold value TH2 in the injection process after the pressure reduction process performed based on the corrected predetermined pressure reduction condition value CV.

The predetermined pressure reduction condition value CV corrected by the pressure reduction condition correction section 94 is stored in the storage section 72. The display control unit 84 may display the corrected predetermined pressure reduction condition value CV on the display screen 68d. The corrected predetermined pressure reduction condition value CV is used by the pressure reduction control unit 80 in a pressure reduction process executed after the correction.

According to the reduced pressure condition correction unit 94, the quality of the molded product can be stabilized, as described below.

As mentioned above, the way the resin flows changes depending on the state of the resin. Further, as the resin flows, it applies a load to the screw. Therefore, there is a correlation between the state of the resin and the way the resin flows, and a correlation between the way the resin flows and the load applied to the screw. For the above reasons, there is a correlation between the state of the resin and the load applied to the screw.

The change in the load applied to the screw according to the flow of the resin is reflected in the required time TM. Therefore, by correcting the predetermined pressure reduction condition value CV so that the required time TM approaches the second threshold value TH2, it is possible to uniformly adjust the state of the resin over a plurality of molding cycles. Thereby, the quality of the molded product can be made uniform while reducing the burden on the operator in adjusting the predetermined pressure reduction condition value CV.

FIG. 7 is a flowchart illustrating the flow of the control method according to the embodiment.

The control device 18 executes the control method illustrated in FIG. 7, for example. The control method of FIG. 7 includes a first threshold value determination step S1, a second threshold value determination step S2, a pressure reduction control step S3, a first measurement step S4, a second measurement step S5, and a pressure reduction condition correction step S6. include.

In the first threshold value determination step S1, the first threshold value determination unit 88 refers to the first threshold value table TB1 based on the type of screw 34 provided in the injection molding machine 10 and the type of resin used for injection molding. Then, the first threshold TH1 is determined. Note that the first threshold value determination step S1 may be executed at any time between START and the second measurement step S5 in the flowchart of FIG.

Similarly, in the second threshold value determination step S2, the second threshold value determination unit 92 generates a second threshold value table TB2 based on the type of screw 34 provided in the injection molding machine 10 and the type of resin used for injection molding. The second threshold value TH2 is determined with reference to. Note that the second threshold value determination step S2 may be executed at any time between START and the depressurization condition correction step S6 in the flowchart of FIG.

In the pressure reduction control step S3, the pressure reduction control section 80 controls the screw 34 to reduce the pressure of the resin. The pressure reduction control step S3 is included in the pressure reduction step of the molding cycle. Note that the measuring process ends before the pressure reduction process starts. Therefore, the start point of the pressure reduction control step S3 is after the screw 34 has reached the metering position and a predetermined amount of resin has been metered within the cylinder 26.

FIG. 8 is a time chart illustrating the respective time changes of the rotational speed of the screw 34 and the pressure of the resin when the control method of FIG. 7 is executed. When the rotational speed of the screw 34 is less than 0, the screw 34 is rotating in the opposite direction.

At time t0, the screw 34 reaches the metering position. That is, time t0 indicates the end time of the weighing process. Time t0 is also the start time of the pressure reduction process (pressure reduction control step S3). At time t0, the pressure of the resin is metering pressure P1. Further, since the forward rotation of the screw 34 does not stop immediately, the screw 34 is rotating forward at time t0. In FIG. 8, when the rotational speed is greater than 0, the screw 34 is rotating forward.

In the pressure reduction control step S3, the screw 34 rotates in reverse based on a predetermined pressure reduction condition value CV. For example, the predetermined pressure reduction condition value CV includes the reverse rotation speed Vrb. In this case, after time t0, the rotational speed of the screw 34 is adjusted to the reverse rotational speed Vrb. As the screw 34 rotates in the opposite direction, the pressure of the resin is reduced. At time t1 when the pressure of the resin is reduced to the target pressure reduction value P0, the pressure reduction process (pressure reduction control step S3) ends.

In the first measurement step S4, the first measurement unit 86 measures the load applied to the screw 34 in response to resin being injected from the cylinder 26 to the mold 20. The first measurement step S4 can be included in the injection step of the molding cycle. The load applied to the screw 34 in response to the resin being injected from the cylinder 26 to the mold 20 is, for example, the torque (first torque) of the first motor 52a. The torque of the first motor 52a is calculated based on the current that drives the first motor 52a.

For example, the injection control unit 82 outputs a control command to the second drive device 38 to move the screw 34 forward in order to start the injection process. This command is output from the injection control section 82 at time t2 in FIG. 8, for example. Time t2 is the start time of the injection process and also the start time of the first measurement step S4. The second motor 52b is controlled based on a control command from the injection control section 82 to move the screw 34 forward.

As a result, after time t2, the resin in the measurement area is injected into the cavity 20c of the mold 20. Furthermore, after time t2, the pressure of the resin increases. However, the cavity 20c is hollow before being filled with resin. Therefore, for a while after the resin starts being injected, the flow resistance applied to the injected resin is small. While the flow resistance applied to the resin is small, the pressure applied from the resin to the screw increases slowly.

FIG. 9 is a time chart illustrating the time course of the torque of the first motor 52a measured by the first measurement unit 86. In FIG. 9, time t2 corresponds to FIG. 8.

When the flow resistance applied to the injected resin is small, the load applied to the screw 34 is also small. Therefore, the load applied to the screw 34 gradually increases for a while after the resin starts being injected.

Note that as the filling of the resin into the cavity 20c progresses to a certain extent, the pressure of the resin increases sharply. Correspondingly, after the resin filling into the cavity 20c has progressed to a certain extent, the load applied to the screw 34 also increases sharply.

In the second measurement step S5, the required time TM from when the screw 34 starts the injection operation for injecting the resin into the mold 20 until the load applied to the screw 34 reaches the first threshold value TH1 is calculated. The second measuring section 90 measures. For example, according to FIG. 9, the torque of the first motor 52a, which is measured as a load, reaches the first threshold value TH1 at time t3. The second measurement step S5 measures the required time TM from time t2 to time t3. The second measurement step S5 can also be included in the injection process.

In the pressure reduction condition correction step S6, the pressure reduction condition correction section 94 corrects the predetermined pressure reduction condition value CV. The depressurization condition correction unit 94 can determine the correction amount for the predetermined depressurization condition value CV by referring to the correction amount table TBC based on the difference δ between the required time TM and the second threshold value TH2. Note that in the example of FIG. 9, the required time TM exceeds the second threshold TH2. In this case, the predetermined pressure reduction condition value CV is corrected to a smaller value based on the difference δ between the required time TM and the second threshold TH2 (δ=TM−TH2). For example, when the difference δ between the required time TM and the second threshold TH2 is within the range of 0<δ≦D1, the correction amount is determined to be C1 based on the correction amount table TBC. In this case, the corrected pressure reduction condition value CV is a value obtained by subtracting the correction amount C1 from the predetermined pressure reduction condition value CV. The pressure reduction control unit 80 may reduce the pressure of the resin in the pressure reduction step of the next molding cycle by controlling the screw 34 using the corrected pressure reduction condition value CV.

FIG. 10 is a time chart illustrating the time course of the resin pressure and the torque of the first motor 52a in the next molding cycle after the molding cycles shown in FIGS. 8 and 9. For comparison, the time course of the resin pressure shown in FIG. 8 and the time course of the torque of the first motor 52a shown in FIG. 9 are shown by broken lines in FIG.

The injection molding machine 10 repeatedly executes the molding cycle even after the control method shown in FIG. 7 ends (RETURN). That is, after the control method of FIG. 7 is completed (RETURN), the metering process, the pressure reduction process, and the injection process are performed again. According to this embodiment, the required time TM approaches the second threshold value TH2 in the injection process that is performed again after the reduced pressure condition correction step S6 (see FIG. 10). In this way, by continuing to automatically adjust the required time TM in each molding cycle to a time length close to the second threshold value TH2, it is possible to reduce the burden on the operator and make the quality of molded products uniform. .

[Modified example]
Modifications of the above embodiment will be described below. However, descriptions that overlap with the above embodiments will be omitted as much as possible in the following description. Elements already described in the above embodiments are given the same reference numerals as in the above embodiments, unless otherwise specified.

(Modification 1)
FIG. 11 is a configuration diagram of a control device 181 (18) according to Modification 1.

The control device 181 is a modification of the control device 18. The control device 181 includes the components of the control device 18 (see the embodiment). In addition, the control device 181 further includes a measurement frequency determination section 96 and a statistics calculation section 98. The measurement count determination unit 96 and the statistic calculation unit 98 are realized, for example, by the calculation unit 74 executing the control program 76, similarly to the measurement control unit 78 and the like.

In this modification, the second measurement unit 90 measures the required time TM for each molding cycle (depressurization process) repeatedly executed by the injection molding machine 10. The storage unit 72 stores a plurality of required times TM measured by the second measurement unit 90 during a plurality of molding cycles.

The measurement number determination unit 96 determines whether the required time TM for a predetermined number of times, which is measured by repeating the molding cycle a predetermined number of times, has been stored in the storage unit 72. The predetermined number of times is specified in advance by the manufacturer of the injection molding machine 10 based on experiments. However, the operator may instruct a predetermined number of times to the measurement number determination section 96 via the operation section 70.

When the required time TM for a predetermined number of times is stored in the storage unit 72, the statistics calculation unit 98 calculates the statistics of the required time TM for a predetermined number of times. The statistic calculation unit 98 calculates, for example, a weighted average value of the required time TM for a predetermined number of times as a statistic.

The weighting coefficients used to calculate the weighted average value are determined in advance, for example, based on experiments, and are stored in the storage unit 72. For example, the weighting coefficient is smaller as the weighting coefficient is applied to the required time TM obtained in a molding cycle in the past. The calculated statistics are stored in the storage unit 72.

The decompression condition correction unit 94 corrects the predetermined decompression condition value CV based on the difference δ between the required time TM and the second threshold TH2. However, in this modification, the decompression condition correction section 94 uses the statistics calculated by the statistics calculation section 98 as the required time TM. This reduces the possibility that the predetermined pressure reduction condition value CV will be corrected based on an outlier value of the required time TM.

FIG. 12 is a flowchart illustrating the flow of the control method according to Modification 1.

The control device 181 can execute the control method shown in FIG. 12, for example. The control method of FIG. 12 includes the components of the control method of FIG. 7 (see embodiment). Moreover, the control method of FIG. 12 further includes a measurement number determination step S7 and a calculation step S8.

The measurement count determination step S7 is performed after the second measurement step S5. In the measurement number determination step S7, the measurement number determination unit 96 determines whether it is possible to calculate the statistics. That is, in the measurement number determination step S7, the measurement number determination unit 96 determines whether the storage unit 72 stores the required time TM for a predetermined number of times necessary to calculate the statistics.

If the required time TM for the predetermined number of times is not stored in the storage unit 72 (S7: NO), the required time TM is measured again in the injection process of the next molding cycle. If the required time TM for the predetermined number of times is stored in the storage unit 72 (S7: YES), calculation step S8 is executed.

In calculation step S8, the statistics calculation unit 98 calculates statistics based on the required time TM for a predetermined number of times.

In this modification, the reduced pressure condition correction step S6 is performed after the calculation step S8. In the pressure reduction condition correction step S6, the pressure reduction condition correction section 94 corrects the predetermined pressure reduction condition value CV based on the difference δ between the required time TM and the second threshold value TH2. However, in the decompression condition correction step S6, the statistic calculated in the calculation step S8 is used as the required time TM.

This prevents the predetermined pressure reduction condition value CV from being corrected based on an outlier value of the required time TM.

Note that the statistics calculation unit 98 may calculate an arithmetic mean value, a weighted harmonic mean value, a pruned mean value, a two-section sum mean square root, a mode, or a weighted median value of a plurality of required times TM as a statistic. good.

(Modification 2)
The operator may indicate at least one of the first threshold TH1 and the second threshold TH2. The operator inputs the first threshold value TH1 into the control device 18, for example, via the operation unit 70. The second measurement unit 90 measures the required time TM using the input first threshold TH1.

The operator may change the first threshold value TH1 determined by the first threshold value determination unit 88 or the second threshold value TH2 determined by the second threshold value determination unit 92 via the operation unit 70.

(Modification 3)
The amount of correction of the predetermined pressure reduction condition value CV may be determined in advance depending on whether the required time TM exceeds the second threshold TH2 or when the required time TM is less than the second threshold TH2. In other words, the correction amount of the predetermined pressure reduction condition value CV is determined based only on the magnitude relationship between the required time TM and the second threshold TH2, regardless of the magnitude of the difference δ between the required time TM and the second threshold TH2. It's okay.

The depressurization condition correction unit 94 corrects the predetermined depressurization condition value CV based on the correction amount according to the magnitude relationship between the required time TM and the second threshold value TH2. Note that the absolute value of the correction amount when the required time TM exceeds the second threshold TH2 may be the same as the absolute value of the correction amount when the required time TM is less than the second threshold TH2.

(Modification 4)
The first measurement unit 86 may measure the pressure of the resin as a load applied to the screw 34. The rearward pressure is a load on the advancing screw 34.

(Modification 5)
The first measurement unit 86 may measure the torque of the second motor 52b calculated based on the detection signal of the second current torque sensor 63b as the load applied to the screw 34. The backward pressure applied by the resin to the screw 34 affects the torque of the second motor 52b that moves the screw 34 forward. Therefore, the torque of the second motor 52b shows a value according to the load on the screw 34.

(Modification 6)
The first measurement unit 86 may measure both the torque of the first motor 52a and the torque of the second motor 52b as the load applied to the screw 34. The first threshold value TH1 with which the torque of the first motor 52a is compared and the first threshold value TH1 with which the torque of the second motor 52b is compared may be different.

The second measurement unit 90 determines which of the time TM required for the torque of the first motor 52a to reach the first threshold TH1 and the time TM required for the torque of the second motor 52b to reach the first threshold TH1. , the shorter one is stored in the storage unit 72.

However, the second measurement unit 90 determines the time TM required for the torque of the first motor 52a to reach the first threshold TH1, and the time TM required for the torque of the second motor 52b to reach the first threshold TH1. Of these, the longer one may be stored in the storage unit 72.

The depressurization condition correction unit 94 corrects the predetermined decompression condition value CV based on the difference δ between the required time TM stored in the storage unit 72 and the second threshold value TH2.

(Modification 7)
The second measurement unit 90 measures, in place of the required time TM, the amount of movement of the screw 34 from when the screw 34 starts the injection operation until the load on the screw 34 reaches the first threshold value TH1. It's okay. The amount of movement is measured as the distance that the screw 34 has moved in the front-back direction based on the detection signal of the second position and speed sensor 62b included in the second motor 52b. The load applied to the screw 34 after the start of the injection operation is measured as, for example, the torque of the first motor 52a (see also the embodiment).

(Modification 8)
The pressure reduction control unit 80 may control the second motor 52b to suck back the screw 34 in order to reduce the pressure of the resin. Suckback is a backward movement of the screw 34. By sucking back, the screw 34 moves further rearward from the measuring position. In this case, the predetermined pressure reduction condition value CV includes three items: the suckback time of the screw 34, the suckback distance, and the suckback speed.

The suckback time indicates the duration of suckback of the screw 34. The suckback distance indicates the distance that the screw 34 sucks back. The suckback speed indicates the backward speed of the screw 34 that sucks back. The suckback time, suckback distance, and suckback speed are automatically determined by determining the remaining two items.

When the screw 34 sucks back without reverse rotation during the pressure reduction process, the decompression condition correction unit 94 corrects at least one of the suckback time, the suckback distance, and the suckback speed.

However, the pressure reduction control unit 80 may cause the screw 34 to perform both reverse rotation and suckback during the pressure reduction process. In this case, the decompression condition correction unit 94 corrects at least one item of the reverse rotation time, the reverse rotation amount, the reverse rotation speed, the suckback time, the suckback distance, and the suckback speed.

(Modification 9)
The first threshold value table TB1 may store a plurality of first threshold values TH1 according to not only the type of screw 34 and the type of resin but also the type of nozzle 32.

Similarly, the second threshold value table TB2 may store a plurality of second threshold values TH2 according to not only the type of screw 34 and the type of resin but also the type of nozzle 32.

(Modification 10)
The control device 18 may further control the mold clamping unit 12.

(Modification 11)
The method in which the axis L of the cylinder 26 and the axis of the screw 34 overlap is also referred to as an in-line (in-line screw) method. An injection molding machine to which an in-line method is applied is also referred to as an in-line injection molding machine. The injection unit (14) of the in-line injection molding machine (10) is easier to maintain than injection units of other types.

However, the control device 18 may be included in an injection molding machine that is not an in-line type. A method other than the inline method is, for example, a pre-pura method.

(Combination of multiple variations)
The plurality of modifications described above may be combined as appropriate within the scope of consistency.

For example, the required time TM according to each of Modifications 1 to 7 described above may be transformed to the movement amount according to Modification 8.

[Invention obtained from embodiment]
The inventions that can be understood from the above embodiments and modifications are described below.

<First invention>
A first invention provides an injection molding machine (10) that includes a cylinder (26) and a screw (34) that injects a predetermined amount of resin measured within the cylinder into a mold (20). A control device (18) that controls rotation and forward/backward movement within the cylinder, the control device (18) controlling the screw based on a predetermined pressure reduction condition value (CV) after the predetermined amount of the resin has been measured in the cylinder. a pressure reduction control unit (80) that controls to reduce the pressure of the resin; and a load applied to the screw in response to the resin being injected from the cylinder to the mold after the resin pressure reduction is completed. a first measurement unit (86) that measures the time from when the screw starts an injection operation for injecting the resin into the mold until the load reaches a first threshold value (TH1); TM), or a second measurement unit (90) that measures the amount of movement of the screw from when the screw starts the injection operation until the load reaches the first threshold; The control device includes a depressurization condition correction unit (94) that corrects the predetermined decompression condition value based on the difference (δ) between the amount and the second threshold value (TH2).

As a result, the operator's work burden related to parameter adjustment for the depressurization process is reduced.

The first measurement unit measures at least one of a first torque of a first motor (52a) that rotates the screw and a second torque of a second motor (52b) that advances the screw as the load. You may. Thereby, the load on the screw can be detected based on the current torque sensor originally provided in the motor, so an increase in equipment cost for load detection can be suppressed.

The first measurement unit may measure the pressure of the resin in the cylinder as the load. Thereby, the load on the screw can be detected based on the pressure sensor originally provided in the injection molding machine, so an increase in equipment cost for load detection can be suppressed.

The predetermined pressure reduction condition value may include at least one of a suckback time, a suckback distance, and a suckback speed of the screw. Thereby, the first invention can be applied to a control device for an injection molding machine equipped with a screw that performs suckback during the depressurization process.

The predetermined pressure reduction condition value may include at least one of a reverse rotation time, a reverse rotation amount, and a reverse rotation speed of the screw. Thereby, the first invention can be applied to a control device for an injection molding machine equipped with a screw that rotates in reverse during the decompression process.

The decompression condition correction unit reduces the predetermined depressurization condition value when the time or the movement amount exceeds the second threshold, and decreases the predetermined decompression condition value when the time or the movement amount is less than the second threshold. The reduced pressure condition value may be increased. Thereby, the predetermined pressure reduction condition value is corrected so as to approach an appropriate pressure reduction condition value depending on the state of the resin.

The decompression condition correction unit adjusts the predetermined decompression condition value based on a correction amount table (TBC) in which a plurality of correction amounts are stored according to the difference between the time or the movement amount and the second threshold value. may be corrected. Thereby, the predetermined pressure reduction condition value is corrected to a more appropriate pressure reduction condition value depending on the state of the resin.

The amount of correction of the predetermined pressure reduction condition value is predetermined for a case where the time or the amount of movement exceeds the second threshold and a case where the time or the amount of movement is less than the second threshold. The decompression condition correction unit may correct the predetermined depressurization condition value based on the difference between the time or the movement amount and the second threshold value, and the correction amount. Thereby, the predetermined pressure reduction condition value is corrected so as to approach an appropriate pressure reduction condition value depending on the state of the resin.

A first invention provides the first threshold value table (TB1) in which a plurality of first threshold values are stored according to at least one of the plurality of types of the screws and the plurality of types of the resins. The device further includes a first threshold determining unit (88) that determines a threshold, and the second measuring unit measures the time or the amount of movement using the first threshold determined by the first threshold determining unit. Good too. Thereby, the time or the amount of movement is measured based on an appropriate first threshold value depending on the screw, resin, etc. used in injection molding.

A first invention provides the second threshold value table (TB2) in which a plurality of second threshold values are stored according to at least one of the plurality of types of the screws and the plurality of types of the resins. The system further includes a second threshold value determination section (92) that determines a threshold value, and the decompression condition correction section corrects the predetermined decompression condition value using the second threshold value determined by the second threshold value determination section. Good too. Thereby, the predetermined pressure reduction condition value is corrected based on an appropriate second threshold value depending on the screw, resin, etc. used in injection molding.

The first invention may further include an operation unit (70) for an operator to specify the first threshold value or the second threshold value. Thereby, the operator can arbitrarily set the first threshold value or the second threshold value.

A first invention includes a storage unit (72) that stores a plurality of the times or a plurality of movement amounts measured by the second measuring unit during a plurality of molding cycles; The depressurization condition correction unit further includes a statistics calculation unit (98) that calculates statistics based on the movement amount, and the depressurization condition correction unit uses the statistics as the time or the movement amount to determine the predetermined value. The reduced pressure condition value may be corrected. This prevents the predetermined pressure reduction condition value from being corrected based on outliers in time or movement amount.

The decompression condition correction unit may correct the predetermined decompression condition value so that the predetermined decompression condition value does not deviate from a predetermined range. This prevents the injection molding machine from performing operations that are not recommended.

When the predetermined pressure reduction condition value is corrected, the pressure reduction control unit may reduce the pressure of the resin based on the corrected predetermined pressure reduction condition value. Thereby, after the predetermined reduced pressure condition value is corrected, molded products of uniform quality can be produced over a plurality of molding cycles.

The first invention may further include a display control section (84) that causes the display section (68) to display the corrected predetermined decompression condition value. Thereby, the corrected predetermined pressure reduction condition value is notified to the operator.

<Second invention>
A second invention provides an injection molding machine (10) that includes a cylinder (26) and a screw (34) that injects a predetermined amount of resin measured within the cylinder into a mold (20). A control method for controlling rotation and forward and backward movement within the cylinder, the method comprising: controlling the screw based on a predetermined pressure reduction condition value (CV) after the predetermined amount of the resin has been measured within the cylinder; , a pressure reduction control step (S3) for reducing the pressure of the resin, and after the pressure reduction of the resin is completed, measuring the load applied to the screw in response to the resin being injected from the cylinder to the mold. a first measuring step (S4); a time (TM) from when the screw starts an injection operation for injecting the resin into the mold until the load reaches a first threshold value (TH1); Alternatively, a second measuring step (S5) of measuring the amount of movement of the screw after the screw starts the injection operation until the load reaches the first threshold; , a depressurization condition correction step (S6) of correcting the predetermined depressurization condition value based on the difference (δ) from the second threshold value (TH2).

This reduces the operator's work burden related to parameter adjustment for the depressurization process.

DESCRIPTION OF SYMBOLS 10... Injection molding machine 18... Control device 20... Mold 26... Cylinder 34... Screw 40... Pressure sensor 52a... First motor 52b... Second motor 68... Display part 70... Operation part 72... Memory part 80... Decompression control part 84...Display control unit 86...First measurement unit 88...First threshold value determination unit 90...Second measurement unit 92...Second threshold value determination unit 94...Decompression condition correction unit 98...Statistics calculation unit CV...Predetermined decompression condition value TB1...First threshold table TB2...Second threshold table TBC...Correction amount table TH1...First threshold TH2...Second threshold TM...Time (required time)
δ...Difference between time (required time) or amount of movement and second threshold

Claims (16)

rotation of the screw in the cylinder of an injection molding machine (10) comprising a cylinder (26) and a screw (34) for injecting a predetermined amount of resin measured in the cylinder into the mold (20); A control device (18) for controlling advancement and retreat,
After the predetermined amount of the resin is measured in the cylinder, a pressure reduction control unit (80) controls the screw based on a predetermined pressure reduction condition value (CV) to reduce the pressure of the resin;
a first measurement unit (86) that measures the load applied to the screw in response to the resin being injected from the cylinder into the mold after the pressure reduction of the resin is completed;
The time (TM) from when the screw starts an injection operation for injecting the resin into the mold until the load reaches a first threshold (TH1), or when the screw starts the injection operation a second measurement unit (90) that measures the amount of movement of the screw until the load reaches the first threshold;
a decompression condition correction unit (94) that corrects the predetermined decompression condition value based on a difference (δ) between the time or the movement amount and a second threshold (TH2);
A control device comprising: The control device according to claim 1,
The first measurement unit measures at least one of a first torque of a first motor (52a) that rotates the screw and a second torque of a second motor (52b) that advances the screw as the load. control device. The control device according to claim 1,
The first measurement unit is a control device that measures the pressure of the resin in the cylinder as the load. The control device according to any one of claims 1 to 3,
The predetermined pressure reduction condition value includes at least one of a suckback time, a suckback distance, and a suckback speed of the screw. The control device according to any one of claims 1 to 4,
The predetermined pressure reduction condition value includes at least one of a reverse rotation time, a reverse rotation amount, and a reverse rotation speed of the screw. The control device according to claim 4 or 5,
The decompression condition correction unit reduces the predetermined depressurization condition value when the time or the movement amount exceeds the second threshold, and decreases the predetermined decompression condition value when the time or the movement amount is less than the second threshold. A control device that increases the reduced pressure condition value. The control device according to claim 6,
The decompression condition correction unit adjusts the predetermined decompression condition value based on a correction amount table (TBC) in which a plurality of correction amounts are stored according to the difference between the time or the movement amount and the second threshold value. A control device that corrects. The control device according to claim 6,
The amount of correction of the predetermined pressure reduction condition value is predetermined for a case where the time or the amount of movement exceeds the second threshold and a case where the time or the amount of movement is less than the second threshold. ,
The decompression condition correction unit is a control device that corrects the predetermined depressurization condition value based on the difference between the time or the movement amount and the second threshold value, and the correction amount. The control device according to any one of claims 1 to 8,
a first threshold value that determines the first threshold value based on a first threshold table (TB1) in which a plurality of first threshold values are stored according to at least one of the plurality of types of the screws and the plurality of types of the resin; further comprising a threshold value determination unit (88),
The second measurement unit is a control device that measures the time or the amount of movement using the first threshold determined by the first threshold determination unit. The control device according to any one of claims 1 to 9,
a second threshold value that determines the second threshold value based on a second threshold table (TB2) in which a plurality of second threshold values are stored according to at least one of the plurality of types of the screws and the plurality of types of the resin; further comprising a threshold determination unit (92),
The pressure reduction condition correction section is a control device that corrects the predetermined pressure reduction condition value using the second threshold determined by the second threshold value determination section. The control device according to any one of claims 1 to 10,
The control device further includes an operation unit (70) for an operator to specify the first threshold value or the second threshold value. The control device according to any one of claims 1 to 11,
a storage unit (72) that stores the plurality of times or the plurality of movement amounts measured by the second measurement unit during the plurality of molding cycles;
a statistics calculation unit (98) that calculates statistics based on the plurality of times or the plurality of movement amounts;
Furthermore,
The depressurization condition correction unit is a control device that corrects the predetermined depressurization condition value by using the statistical amount as the time or the movement amount. The control device according to any one of claims 1 to 12,
The pressure reduction condition correction unit is a control device that corrects the predetermined pressure reduction condition value so that the predetermined pressure reduction condition value does not deviate from a predetermined range. The control device according to any one of claims 1 to 13,
The pressure reduction control unit is a control device that, when the predetermined pressure reduction condition value is corrected, reduces the pressure of the resin based on the corrected predetermined pressure reduction condition value. The control device according to any one of claims 1 to 14,
The control device further includes a display control section (84) that causes a display section (68) to display the corrected predetermined pressure reduction condition value. rotation of the screw in the cylinder of an injection molding machine (10) comprising a cylinder (26) and a screw (34) for injecting a predetermined amount of resin measured in the cylinder into the mold (20); A control method for controlling advancement and retreat,
After the predetermined amount of the resin is measured in the cylinder, a pressure reduction control step (S3) in which the screw is controlled based on a predetermined pressure reduction condition value (CV) to reduce the pressure of the resin;
a first measuring step (S4) of measuring the load applied to the screw in response to the resin being injected from the cylinder into the mold after the pressure reduction of the resin is completed;
The time (TM) from when the screw starts the injection operation for injecting the resin into the mold until the load reaches the first threshold value (TH1), or when the screw starts the injection operation. a second measuring step (S5) of measuring the amount of movement of the screw from when the load reaches the first threshold;
a decompression condition correction step (S6) of correcting the predetermined decompression condition value based on a difference (δ) between the time or the movement amount and a second threshold (TH2);
including control methods.

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