JP7108157B1 - Control device and control method - Google Patents

Abstract

The control device (18) for controlling the screw (34) of the injection molding machine (10) includes a decompression control section (80) for decompressing the resin based on a predetermined decompression condition value (CV) after the resin is weighed. ), a first measuring unit (86) that measures the load applied to the screw (34) according to the injection of the resin, and the load reaches the first threshold value (TH1) after the screw (34) starts the injection operation. A second measurement unit (90) that measures the time (TM) until the pressure is reduced, and corrects the predetermined pressure reduction condition value (CV) based on the difference (δ) between the time (TM) and the second threshold (TH2). and a depressurization condition correction unit (94).

Description

The present invention relates to a control device and 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 processes. The molding cycle includes a weighing process, a decompression process, and an injection process (see also Japanese Patent Application Laid-Open No. 10-16016). According to Japanese Patent Application Laid-Open No. 10-16016, the decompression step is performed after the weighing step. The injection process is performed after the decompression process.

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

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

In order to uniform the quality of the molded product, it is desirable to appropriately adjust the parameters used in the depressurization process, taking into consideration the possibility that the state of the resin after the depressurization process may change for each molding cycle. However, this parameter adjustment work is a burden on the operator of the injection molding machine.

An object of the present invention is to solve the problems described above.

A first aspect of the present invention is an injection molding machine comprising a cylinder and a screw for injecting a predetermined amount of resin weighed in the cylinder into a mold. a decompression control unit for controlling the screw based on a predetermined decompression condition value to reduce the pressure of the resin after the predetermined amount of the resin is weighed in the cylinder; a first measuring unit for measuring the load applied to the screw according to the injection of the resin from the cylinder into the mold after the resin is decompressed; and the resin being injected into the mold. The time from when the screw starts the injection operation until the load reaches the first threshold, or until the load reaches the first threshold after the screw starts the injection operation and a decompression condition correction unit that corrects the predetermined decompression condition value based on the difference between the time or the movement amount and a second threshold value. , the controller.

A second aspect of the present invention is an injection molding machine comprising a cylinder and a screw for injecting a predetermined amount of resin weighed in the cylinder into a mold. 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 weighed in the cylinder; a first measuring step of measuring the load applied to the screw according to the injection of the resin from the cylinder into the mold after the resin is depressurized; and injecting the resin into the mold. The time from when the screw starts the injection operation until the load reaches the first threshold, or when the load reaches the first threshold after the screw starts the injection operation and a pressure reduction condition correction step of correcting the predetermined pressure reduction condition value based on the difference between the time or the movement amount and a second threshold value. control method, including

According to the present invention, the operator's work load 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 configuration diagram of an injection unit. FIG. 3 is a configuration diagram of the control device. FIG. 4 is a table illustrating a first threshold table. FIG. 5 is a table illustrating a second threshold table. FIG. 6 is a table exemplifying a correction amount table. FIG. 7 is a flow chart illustrating the flow of the control method according to the embodiment. FIG. 8 is a time chart illustrating temporal transitions of the screw rotation speed and the resin pressure when the control method of FIG. 7 is executed. FIG. 9 is a time chart exemplifying temporal transition of the torque of the first motor measured by the first measuring unit. FIG. 10 is a time chart illustrating temporal transitions of the pressure of the resin and the torque of the first motor in the molding cycle subsequent to the molding cycle shown in FIGS. FIG. 11 is a configuration diagram of a control device according to Modification 1. As shown in FIG. FIG. 12 is a flowchart illustrating the flow of the control method according to Modification 1. FIG.

[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 base 16 and a control device 18 . An arrow D1 in FIG. 1 indicates the forward direction of the injection unit 14. As shown in FIG. An arrow D2 in FIG. 1 indicates the rearward direction of the injection unit 14. As shown in FIG.

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 . The mold 20 opens and closes in the front-rear direction. The closed mold 20 forms a cavity 20c. The mold 20 in FIG. 1 is in a closed state. The mold clamping unit 12 can apply a mold clamping force to the mold 20 so that the mold 20 is maintained in a closed state. However, a more detailed description of the mold clamping unit 12 is omitted.

The machine base 16 supports the mold clamping unit 12 and the injection unit 14 . However, the machine base 16 may support only the injection unit 14 out of the mold clamping unit 12 and the injection unit 14 . A guide rail 22 is installed on the machine base 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 rails 22 and slides in the front-rear direction. Therefore, the injection unit 14 slides in the front-rear direction together with the slide base 24 .

The injection unit 14 has a cylinder 26 . The cylinder 26 is a tubular member extending forward of the injection unit 14 .

FIG. 2 is a schematic configuration diagram of the injection unit 14. As shown in FIG.

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

A hopper 28 is arranged at a rear end portion 26 r of the cylinder 26 . The hopper 28 stores resin solids (pellets). Resin is a raw material for molded products produced by the injection molding machine 10 . The hopper 28 also has a supply port 28o. Resin in the hopper 28 is supplied to the inside of the cylinder 26 through the supply port 28o.

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

Nozzle 32 is attached to front end 26 f of cylinder 26 . The nozzle 32 has an injection port 32p. The nozzle 32 allows the inside of the front end portion 26f and the cavity 20c of the mold 20 to communicate with each other through the injection port 32p. In addition, 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 helix shape. The flight portion 42 forms a flow path 50 inside the cylinder 26 together with the inner wall 26i of the cylinder 26 . The flow path 50 is formed to guide the resin supplied inside the cylinder 26 from the rear end portion 26r to the front end portion 26f.

The screw head 44 is the front end of the screw 34 . The check sheet 46 is arranged behind the screw head 44 . A 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 in response to the pressure within the range between the screw head 44 and the check seat 46 . The anti-backflow ring 48 moves away from the check sheet 46 by moving forward. By separating from the check sheet 46 , the anti-backflow ring 48 opens the flow path 50 between the screw head 44 and the check sheet 46 .

Further, when a backward pressure is applied to the backflow prevention ring 48 , the backflow prevention ring 48 moves rearward in accordance with the pressure within the range between the screw head 44 and the check seat 46 . The anti-backflow ring 48 approaches the check sheet 46 by moving backward. The anti-backflow 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 driving 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 servomotor. The first motor 52a includes a first shaft 60a, a first position/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/speed sensor 62a outputs to the control device 18 a detection signal corresponding to the rotational position of the first shaft 60a. 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. A more detailed description of the control device 18 will be given later.

A first drive pulley 54a is connected to a first shaft 60a. The first drive pulley 54a rotates as the first shaft 60a rotates. The first belt member 56a is stretched over the first drive 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 according to the rotation of the first driving pulley 54a.

The first driven pulley 58 a is provided integrally with the screw 34 . Therefore, the screw 34 also rotates according to the rotation of the first driven pulley 58a. The screw 34 rotates about the axis L. The screw 34 can cause the resin inside the cylinder 26 to flow along the flow path 50 by rotating. The direction of rotation of the first shaft 60a is switched under the control of the control device 18. FIG. As the rotation direction of the first shaft 60a switches, the rotation direction of the screw 34 also switches. By switching the rotation direction of the screw 34, the flow direction of the resin inside the cylinder 26 changes.

In the following description, the rotation direction of the screw 34 when the resin flows forward is also referred to as forward rotation direction. In addition, the rotation operation of the screw 34 in the forward rotation direction is also described 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 the reverse rotation direction. Further, the rotating operation of the screw 34 in the reverse rotation direction is also described as reverse rotation.

The second driving device 38 is a device that advances and retracts the screw 34 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 servomotor. The second motor 52b includes a second shaft 60b, a second position/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/speed sensor 62b outputs to the control device 18 a detection signal corresponding to the rotational position of the second shaft 60b. The second current torque sensor 63b outputs to the control device 18 a detection signal corresponding to the drive current supplied to the second motor 52b, the rotational torque of the second shaft 60b, and the like.

A second drive pulley 54b is connected to a second shaft 60b. The second drive pulley 54b rotates as the second shaft 60b rotates. The second belt member 56b is stretched over 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 according to the rotation of the second driving pulley 54b.

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

A 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 parallel to the axis L of the screw 34 as the ball screw 64 rotates. That is, the relative positional relationship between the nut 66 and the ball screw 64 changes in the longitudinal direction as the ball screw 64 rotates.

The screw 34 is connected to the nut 66 and advances and retreats in the longitudinal direction inside the cylinder 26 according to the relative positional relationship between the nut 66 and the ball screw 64 changing in the longitudinal direction. Note that the rotation direction of the second shaft 60b is switched under the control of the control device 18. FIG. As the rotation direction of the second shaft 60b switches, the rotation direction of the ball screw 64 also switches. By switching the rotation 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 to the inside of 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 is melted under the influence of the heat of the heater 30 transmitted through the cylinder 26 and the shear heat generated in the resin by being sheared by the flight portion 42 .

As the screw 34 continues forward rotation, the resin behind the backflow prevention ring 48 flows forward along the flow path 50 and reaches the backflow prevention ring 48 . The resin reaching the backflow prevention ring 48 pushes the backflow prevention ring 48 forward. As a result, the anti-backflow 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 opened flow path 50 and reaches a region inside the cylinder 26 ahead 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. Also, in the following description, the amount of resin refers to the amount of resin accumulated in the metering area unless otherwise specified.

The resin accumulated in the metering area pushes the screw 34 rearward by pushing the screw head 44 rearward. Therefore, the screw 34 is subjected to rearward pressure 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 within the metering area. The pressure sensor 40 outputs to the control device 18 a detection signal corresponding to the pressure applied to the screw 34 by the resin within the measurement area. The pressure sensor 40 is, for example, a load cell.

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

The control device 18 is an electronic device (computer) that controls the injection molding machine 10 . The controller 18 is, for example, a numerical controller. 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 having 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 receives 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), for example.

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 control method of the injection molding machine 10 according to this embodiment.

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 pressure obtained based on the detection signal of the pressure sensor 40 . Further, the storage unit 72 stores, for example, the torque (first torque) of the first motor 52a obtained based on the detection signal of the first current torque sensor 63a and the first torque obtained based on the detection signal of the second current torque sensor 63b. The torque (second torque) of the second motor 52b and the like 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. The processing circuitry includes, for example, one or more processors. However, the processing circuit of the calculation unit 74 may include integrated circuits such as ASIC (Application Specific Integrated Circuit) and FPGA (Field-Programmable Gate Array). Moreover, the processing circuit of the arithmetic unit 74 may include a discrete device.

The calculation unit 74 includes a metering control unit 78 , a pressure reduction control unit 80 , an injection control unit 82 and a display control unit 84 . The metering control section 78 , the decompression control section 80 , the injection control section 82 , and the display control section 84 are implemented by the processor of the calculation section 74 executing the control program 76 . However, at least a part of the metering control section 78, the depressurization 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 weighing control section 78 performs control described below in order to cause the injection molding machine 10 to execute the weighing process of the molding cycle. Note that the initial position of the screw 34 (screw head 44 ) at the start of the weighing process is the most forward position within the range of movement in the longitudinal direction inside the cylinder 26 . Moreover, at the start of the weighing process, the mold 20 is in a closed state and a mold clamping force is applied from the mold clamping unit 12 .

The metering controller 78 controls the first motor 52a to rotate the screw 34 forward. Thereby, the resin supplied from the hopper 28 to the inside of the cylinder 26 is pumped 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 unit 78 continues the forward rotation of the screw 34 .

The screw 34 retreats as the amount of resin increases. Here, the weighing controller 78 controls the second motor 52b to prevent the screw 34 from retreating excessively. As a result, an excessive decrease in the pressure of the resin accompanying the retreat of the screw 34 is suppressed.

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 measured pressure P1 is pre-stored in the storage unit 72 . The resin pressure is acquired based on the detection signal of the pressure sensor 40 . Metering pressure P1 is, for example, greater than atmospheric pressure. The metering controller 78 may control the second motor 52b to retract the screw 34 in order to adjust the resin pressure to the metering pressure P1.

The screw 34 retreating as the amount of resin increases reaches a predetermined position (metering position) relative to the position of the screw 34 . The weighing position is a position behind the initial position of the screw 34 in the weighing process. The metering control unit 78 adjusts the pressure of the resin to the metering pressure P1 and causes the screw 34 to reach the metering position, thereby collecting a predetermined amount of resin in the metering area. When the screw 34 reaches the metering position, the metering controller 78 controls the first motor 52a to stop forward rotation of the screw 34 .

After a predetermined amount of resin has been weighed in the cylinder 26, the decompression control section 80 performs control described below in order to cause the injection molding machine 10 to perform the decompression 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. Reverse rotation of the screw 34 causes the resin in the metering area to flow 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.

Inertia acts on the screw 34 that rotates forward. Therefore, the screw 34 continues forward rotation even after reaching the metering position. As a result, the amount of resin immediately after weighing strictly exceeds the predetermined amount. The depressurization control unit 80 can also adjust the resin amount closer to the predetermined amount by reducing the resin amount according to the reverse rotation of the screw 34 .

The backflow prevention ring 48 is pressed by the resin flowing behind the backflow prevention ring 48 from the metering area in response to the reverse rotation of the screw 34 by the decompression control unit 80 . As a result, the anti-backflow ring 48 moves backward. The backflow prevention ring 48 contacts the check sheet 46 behind the backflow prevention ring 48 by moving backward. The flow path 50 is closed by the backflow prevention ring 48 coming into contact with the check sheet 46 . By closing the flow path 50 , the resin accumulated in the metering area cannot reach behind the anti-backflow 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 by which the screw 34 is rotated in reverse. The reverse rotation speed indicates the rotation speed of the screw 34 rotating in reverse. The items of reverse rotation time, reverse rotation amount, and reverse rotation speed are naturally determined by determining the remaining two items.

A predetermined pressure reduction condition value CV is stored in the storage unit 72 . Note that the manufacturer of the injection molding machine 10 may pre-store a recommended default value in the storage unit 72 as the initial value of the predetermined depressurization condition value CV. However, the operator may arbitrarily change at least one of 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) within which the predetermined pressure reduction condition value CV can be changed. This restricts the range of predetermined pressure reduction condition values CV that can be changed by the operator.

The target depressurization value P0 indicates the target pressure of the resin to be depressurized in the depressurization step. The decompression control unit 80 (injection control unit 82 described later) determines that decompression has ended when the pressure of the resin reaches the target decompression value P0. The target pressure reduction value P0 is, for example, the 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 pre-store the recommended target pressure reduction value P0 in the storage unit 72 as a default value. Also, the operator may specify an arbitrary pressure as the target pressure reduction value P0 via the operation unit 70 . In this case, the manufacturer of the injection molding machine 10 may pre-store the changeable range of the target pressure reduction value P0 in the storage unit 72 in the same manner as the predetermined pressure reduction condition value CV.

The injection control unit 82 controls the second motor 52b to advance the screw 34 after the decompression is completed, in order to cause the injection molding machine 10 to perform the injection step of the molding cycle. As a result, the resin in the metering area is injected toward the cavity 20c of the mold 20 through the nozzle 32. As shown in FIG. The injected resin is solidified in the cavity 20c to complete the molded product.

The screw 34 advanced in the injection process moves to the most forward position within the movement range in the front-rear direction inside the cylinder 26 . Here, the screw 34 may be moved to the initial position of the weighing process described above. As a result, the weighing control unit 78 can start the weighing process of the next molding cycle by rotating the screw 34 forward 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 depressurization process may differ for each molding cycle.

For example, the nozzle 32 and the mold 20 are separated before the injection molding machine 10 starts injection molding. In this case, the temperature of the nozzle 32 tends to differ 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 rails 22, and the nozzle 32 and the mold 20 are brought into contact. This gradually balances the temperatures of the nozzle 32 and the mold 20 . However, the temperature of the nozzle 32 is not stable during the period until the temperatures of the nozzle 32 and the mold 20 are balanced. In this case, the temperature of the resin accumulated in the metering area near the nozzle 32 varies from molding cycle to molding cycle. If the resin temperature varies from molding cycle to molding cycle, the resin viscosity also varies from molding cycle to molding cycle.

When the temperature, viscosity, etc. of the resin varies in each molding cycle, the flow of the resin in each of the decompression process and the injection process varies in each molding cycle. Therefore, for example, when the screw 34 is reversely rotated in the depressurization process, the amount of decrease in the amount of resin varies for each molding cycle. In this case, since the amount of resin filled into the cavity 20c in the injection process varies for each molding cycle, the quality of the molded product varies for each molding cycle. In addition, if the flow of the resin that flows into the cavity 20c in the injection process varies from molding cycle to molding cycle, the quality of the molded product may vary from molding cycle to molding cycle.

The cause of variations in the state of the resin in each 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 to the inside of the cylinder 26 may be Dryness may vary from molding cycle to molding cycle. In this case, even if the same type of resin continues to be supplied to the inside of the cylinder 26, the state of the resin after being melted in the weighing process varies from cycle to cycle according to changes in room temperature, humidity, and the like.

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

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

For the above reasons, it is desirable that the predetermined decompression condition value CV used by the decompression control unit 80 in the decompression step is appropriately adjusted according to 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. further provide. The first measurement unit 86, the first threshold determination unit 88, the second measurement unit 90, the second threshold determination unit 92, and the decompression condition correction unit 94 are similar to the weighing control unit 78, for example, the calculation unit 74 is realized by executing the control program 76 .

The first measuring unit 86 measures the load applied to the screw 34 in accordance with the resin being injected from the cylinder 26 into the mold 20 after the resin is decompressed. That is, the first measurement unit 86 measures the load applied to the screw 34 as the screw 34 advances in the injection process.

The load applied to the screw 34 as the screw 34 advances 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 adhering to the screw 34 imparts 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. FIG. The first measuring section 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 determination unit 88 determines the first threshold TH1 based on the first threshold table TB1. The first threshold value 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 determination unit 88 stores a first threshold TH1 corresponding to the type of the screw 34 provided in the injection molding machine 10 and the type of resin supplied to the inside of the cylinder 26 in the first threshold table TB1. Search from

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

A plurality of types of the screw 34 are stored in the first column (screw type) of the first threshold value table TB1 illustrated in FIG. For purposes of illustration, multiple types of screws 34 are shown in FIG. 4, including full-flighted screws, barrier-flighted screws, and highly plasticized screws.

A plurality of resin types are stored in the second column (resin type) of the first threshold value table TB1 illustrated in FIG. FIG. 4 shows PA (polyamide), PBT (polybutylene terephthalate), and PE (polyethylene) as several types of resins for illustration purposes.

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 the data in the first and second columns. be done. A specific value for each of the plurality of first thresholds TH1 is determined in advance based on experiments. Note that, as shown in the bottom row of FIG. 4, the first threshold value TH1 corresponding to the type of the screw 34 may be stored in the first threshold value table TB1 regardless of the type of resin. Also, the first threshold value TH1 corresponding to the type of resin may be stored in the first threshold value table TB1 regardless of the type of the screw 34 .

The first threshold value table TB1 is stored in advance in the storage unit 72 (see also FIG. 3). The type of the 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 section 88 via the operation section 70, for example.

The second measuring unit 90 measures 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 TH1. That is, the second measuring unit 90 measures the required time TM from when the screw 34 starts moving forward until the torque of the first motor 52a reaches the first threshold TH1 in the injection process.

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

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

A plurality of types of screws 34 are stored in the first column (types of screws 34) of the second threshold value table TB2 illustrated in FIG. A plurality of resin types are stored in the second column (resin type) of the second threshold value table TB2 illustrated in FIG. 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 the data in the first and second columns. be done.

A specific value for each of the plurality of second thresholds TH2 is determined in advance based on experiments. Note that the second threshold TH2 corresponding to the type of the screw 34 may be stored in the second threshold table TB2 regardless of the type of resin. Further, the second threshold value TH2 corresponding to the type of resin may be stored in the second threshold value table TB2 regardless of the type of the screw 34 .

The second threshold value table TB2 is stored in advance in the storage unit 72 (see also FIG. 3). The type of the 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 second threshold determination section 92 via the operation section 70, for example.

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

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

The difference .delta. δ=TH2-TM).

The pressure reduction condition correction unit 94 determines the correction amount of the predetermined pressure reduction condition value CV based on the correction amount table TBC. The correction amount table TBC is a data table that stores a plurality of correction amounts according to the difference δ between the required time TM and the second threshold TH2.

FIG. 6 is a table exemplifying 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. be. Specific values of the plurality of correction amounts are determined in advance based on experiments. 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 pressure reduction condition correction unit 94 corrects the predetermined pressure reduction 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 pressure reduction condition correction unit 94 corrects the predetermined pressure reduction condition value CV based on the correction amount C1.

However, if a predetermined range in which the predetermined pressure reduction condition value CV can be changed is stored in advance in the storage unit 72, the pressure reduction condition correction unit 94 adjusts the predetermined pressure reduction condition value CV so that it falls within the predetermined range. Correction is preferred.

For example, when the predetermined pressure reduction condition value CV exceeds the upper limit value by 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 below the lower limit value by correction 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 depressurization condition value CV so that it falls within the predetermined range, the injection molding machine 10 is prevented from performing operations not recommended by the manufacturer.

The correction amount table TBC stores a correction amount that reduces the predetermined pressure reduction condition value CV as the required time TM is greater than the second threshold TH2. Therefore, when the required time TM exceeds the second threshold TH2, the pressure reducing condition correction unit 94 reduces the predetermined pressure reducing 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 accumulated in the metering area is increased in the pressure reduction process performed after the correction. By increasing the density of the resin pooled in the metering area, the rearward pressure applied to the resin is increased. As a result, the resin in the metering area is in a state where it is easier to flow forward in a short period of time. In other words, by correcting the predetermined depressurization condition value CV to a smaller value, the pressure of the resin tends to rise early during the injection process. As a result, the required time TM approaches the second threshold 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 pressure reducing condition correction unit 94 increases the predetermined pressure reducing condition value CV as the difference δ between the required time TM and the second threshold TH2 increases.

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

The predetermined pressure reduction condition value CV corrected by the pressure reduction condition correction unit 94 is stored in the storage unit 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 section 80 in the pressure reduction process executed after the correction.

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

As described above, the flow of the resin changes depending on the state of the resin. In addition, the resin applies a load to the screw as it flows. Therefore, there is a correlation between the state of the resin and the way the resin flows, and there is 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.

A 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 depressurization condition value CV so that the required time TM approaches the second threshold TH2, it is possible to uniformly adjust the state of the resin over a plurality of molding cycles. As a result, the quality of the molded product can be made uniform while reducing the burden on the operator involved in the work of adjusting the predetermined depressurization condition value CV.

FIG. 7 is a flow chart 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 determination step S1, a second threshold 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 determination step S1, the first threshold determination unit 88 refers to the first threshold table TB1 based on the type of the screw 34 provided in the injection molding machine 10 and the type of resin used for injection molding. to determine the first threshold TH1. Note that the first threshold 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 uses the second threshold value table TB2 based on the type of the screw 34 provided in the injection molding machine 10 and the type of resin used for injection molding. to determine the second threshold TH2. Note that the second threshold determination step S2 may be executed at any time between START and the pressure reduction 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 weighing process ends before the decompression process starts. Therefore, the depressurization control step S3 is started after the screw 34 reaches the metering position and a predetermined amount of resin is metered in the cylinder 26 .

FIG. 8 is a time chart illustrating temporal transitions of the rotational speed of the screw 34 and the pressure of the resin when the control method of FIG. 7 is executed. If the rotational speed of the screw 34 is less than 0, the screw 34 is rotating in reverse.

At time t0, the screw 34 reaches the metering position. That is, time t0 indicates the end 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 resin pressure is the metering pressure P1. Further, since forward rotation of the screw 34 does not stop immediately, the screw 34 is rotating forward at time t0. When the rotation speed is greater than 0 in FIG. 8, the screw 34 rotates forward.

In the pressure reduction control step S3, the screw 34 rotates in the reverse direction based on the predetermined pressure reduction condition value CV. For example, the predetermined pressure reduction condition value CV includes the reverse rotation speed Vrb. In this case, the rotation speed of the screw 34 is adjusted to the reverse rotation speed Vrb after time t0. As the screw 34 rotates in the reverse 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 step (pressure reduction control step S3) ends.

In the first measurement step S<b>4 , the first measurement unit 86 measures the load applied to the screw 34 as the resin is injected from the cylinder 26 to the mold 20 . The first measurement step S4 can be included in the injection process of the molding cycle. The load applied to the screw 34 in response to injection of resin 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 driving the first motor 52a.

For example, the injection control unit 82 outputs a control command to advance the screw 34 to the second driving device 38 in order to start the injection process. This command is output from the injection control unit 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, the resin in the measurement area is injected into the cavity 20c of the mold 20 after time t2. Also, after time t2, the pressure of the resin rises. However, the cavity 20c before being filled with resin is hollow. Therefore, the flow resistance given to the injected resin is small for a while after the injection of the resin starts. While the flow resistance applied to the resin is small, the pressure applied to the screw from the resin gently increases.

FIG. 9 is a time chart exemplifying temporal transition of the torque of the first motor 52a measured by the first measuring unit 86. As shown in FIG. Time t2 in FIG. 9 conforms to FIG.

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

It should be noted that the pressure of the resin sharply rises as the filling of the resin into the cavity 20c progresses to some extent. Accordingly, the load applied to the screw 34 also rises steeply after the filling of the resin into the cavity 20c progresses to some extent.

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 The second measurement unit 90 measures. For example, according to FIG. 9, the torque of the first motor 52a measured as the load reaches the first threshold TH1 at time t3. The second measuring step S5 measures the required time TM from time t2 to time t3. A 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 unit 94 corrects the predetermined pressure reduction condition value CV. The pressure reduction condition correction unit 94 can refer to the correction amount table TBC based on the difference δ between the required time TM and the second threshold TH2 to determine the correction amount for the predetermined pressure reduction condition value CV. In addition, in the illustration 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 (δ=TM−TH2) between the required time TM and the second threshold 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 as C1 based on the correction amount table TBC. In this case, the corrected pressure reduction condition value CV becomes 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 by controlling the screw 34 using the corrected pressure reduction condition value CV in the pressure reduction step of the next molding cycle.

FIG. 10 is a time chart illustrating temporal transitions of the resin pressure and the torque of the first motor 52a in the molding cycle subsequent to the molding cycle shown in FIGS. For comparison, the temporal transition of the resin pressure shown in FIG. 8 and the temporal transition of the torque of the first motor 52a shown in FIG. 9 are indicated by dashed lines in FIG.

The injection molding machine 10 repeats the molding cycle even after the control method of FIG. 7 ends (RETURN). That is, after the control method of FIG. 7 is terminated (RETURN), the metering process, depressurization process, and injection process are performed again. Here, according to the present embodiment, the required time TM approaches the second threshold TH2 in the injection process that is performed again after the depressurization condition correcting step S6 (see FIG. 10). In this way, by automatically adjusting the required time TM in each molding cycle to a length of time close to the second threshold TH2, the operator's burden can be reduced and the quality of the molded product can be made uniform. .

[Modification]
Modifications of the above embodiment will be described below. However, explanations overlapping with the above embodiment will be omitted as much as possible in the following explanation. Elements already described in the above embodiment are given the same reference numerals as in the above embodiment unless otherwise specified.

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

A control device 181 is a modification of the control device 18 . The control device 181 comprises the components of the control device 18 (see embodiments). The control device 181 further includes a measurement count determination unit 96 and a statistic calculation unit 98 . The number-of-measurements determination unit 96 and the statistic calculation unit 98 are implemented by, for example, the calculation unit 74 executing the control program 76 in the same manner as the weighing control unit 78 and the like.

In this modified example, the second measuring 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 measuring unit 90 in a plurality of molding cycles.

The measurement number determination unit 96 determines whether or not the required time TM for the predetermined number of times measured by repeating the predetermined number of molding cycles is 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 the measurement number determination unit 96 to set the predetermined number of times via the operation unit 70 .

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

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

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

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

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

The measurement number 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 or not the statistic can be calculated. That is, in the measurement number determination step S7, the measurement number determination unit 96 determines whether or not the required time TM for the predetermined number of times necessary for calculating the statistic is stored in the storage unit 72 or not.

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 times TM for the predetermined number of times are stored in the storage unit 72 (S7: YES), the calculation step S8 is executed.

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

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

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

In addition, the statistic calculation unit 98 may calculate the arithmetic mean value, weighted harmonic mean value, trimmed mean value, two-row mean square, mode value or weighted median value of the 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 to the control device 18 via the operation unit 70, for example. The second measurement unit 90 measures the required time TM using the input first threshold TH1.

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

(Modification 3)
The correction amount for the predetermined pressure reduction condition value CV may be determined in advance depending on whether the required time TM exceeds the second threshold TH2 and when the required time TM is less than the second threshold TH2. That is, 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. may

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 TH2. 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 measuring section 86 may measure the pressure of the resin as the load applied to the screw 34 . The rearward pressure is a load on the advancing screw 34 .

(Modification 5)
The first measuring section 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 rearward pressure exerted by the resin on the screw 34 affects the torque of the second motor 52b that advances the screw 34 . Therefore, the torque of the second motor 52b indicates a value corresponding to the load on the screw 34. FIG.

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

The second measuring unit 90 measures the required time TM until the torque of the first motor 52a reaches the first threshold TH1 and the required time TM until the torque of the second motor 52b reaches the first threshold TH1. , the shorter one is stored in the storage unit 72 .

However, the second measuring unit 90 measures the required time TM until the torque of the first motor 52a reaches the first threshold TH1 and the required time TM until the torque of the second motor 52b reaches the first threshold TH1. Of these, the longer one may be stored in the storage unit 72 .

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

(Modification 7)
The second measuring unit 90 measures the movement amount of the screw 34 from when the screw 34 starts the injection operation until the load applied to the screw 34 reaches the first threshold value TH1 instead of the required time TM. may The amount of movement is measured as the distance that the screw 34 moves in the front-rear direction based on the detection signal of the second position/speed sensor 62b provided in the second motor 52b. The load applied to the screw 34 after the start of the injection operation is measured, for example, as 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. Suck-back is the backward motion of the screw 34 . The screw 34 moves further rearward from the weighing position by sucking back. In this case, the predetermined pressure reduction condition value CV includes three items: the suck-back time of the screw 34, the suck-back distance, and the suck-back speed.

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

The decompression condition correction unit 94 corrects at least one of the suckback time, the suckback distance, and the suckback speed when the screw 34 sucks back without reverse rotation in the decompression process.

However, the pressure reduction control section 80 may cause the screw 34 to perform both reverse rotation and suck back in the pressure reduction process. In this case, the decompression condition corrector 94 corrects at least one 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)
Controller 18 may further control mold clamping unit 12 .

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

However, the control device 18 may be provided in a non-inline injection molding machine. A method other than the in-line method is, for example, the pre-plastic method.

(combination of multiple modifications)
A plurality of modifications described above may be appropriately combined within a consistent range.

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

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

<First Invention>
A first aspect of the invention is directed to an injection molding machine (10) comprising a cylinder (26) and a screw (34) for injecting a predetermined amount of resin weighed in the cylinder into a mold (20). A control device (18) for controlling rotation and advance/retreat in the cylinder, wherein after the predetermined amount of the resin is weighed in the cylinder, the screw is moved based on a predetermined decompression condition value (CV). a decompression control unit (80) for controlling the pressure of the resin to be decompressed; and the time ( 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, and the time or the movement and a pressure reduction condition correction section (94) for correcting the predetermined pressure reduction condition value based on a difference (δ) between the amount and a second threshold value (TH2).

This reduces the work burden on the operator involved in parameter adjustment for the decompression process.

The first measuring unit measures, as the load, 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. You may As a result, the load of 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 measuring unit may measure the pressure of the resin inside the cylinder as the load. As a result, the load of the screw can be detected based on the pressure sensor originally provided in the injection molding machine, so an increase in facility cost for load detection can be suppressed.

The predetermined depressurization condition value may include at least one of a suck-back time of the screw, a suck-back distance, and a suck-back speed. As a result, the first invention can be applied to a control device for an injection molding machine having a screw that sucks back during the decompression 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. As a result, the first invention can be applied to a control device for an injection molding machine having a screw that reversely rotates during the decompression process.

The decompression condition correction unit reduces the predetermined decompression condition value when the time or the movement amount exceeds the second threshold, and reduces the predetermined decompression condition value when the time or the movement amount is less than the second threshold. may be increased. As a result, the predetermined depressurization condition value is corrected so as to approach an appropriate depressurization condition value according to the state of the resin.

The decompression condition correction unit determines 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. As a result, the predetermined decompression condition value is corrected to a more appropriate decompression condition value according to the state of the resin.

The amount of correction for the predetermined decompression condition value is determined in advance depending on whether the time or the movement amount exceeds the second threshold and when the time or the movement amount is less than the second threshold. The decompression condition correction unit may correct the predetermined decompression condition value based on the difference between the time or the movement amount and the second threshold value and the correction amount. As a result, the predetermined depressurization condition value is corrected so as to approach an appropriate depressurization condition value according to the state of the resin.

The first invention is based on a first threshold table (TB1) storing a plurality of first thresholds according to at least one of a plurality of types of screws and a plurality of types of resins. A first threshold determination unit (88) that determines a threshold is further provided, and the second measurement unit measures the time or the movement amount using the first threshold determined by the first threshold determination unit. good too. As a result, the time or movement amount is measured based on the appropriate first threshold value according to the screw, resin, etc. used for injection molding.

The first invention is based on a second threshold table (TB2) storing a plurality of second thresholds corresponding to at least one of a plurality of types of screws and a plurality of types of resins. A second threshold determination unit (92) for determining a threshold value is further provided, and the pressure reduction condition correction unit corrects the predetermined pressure reduction condition value using the second threshold value determined by the second threshold value determination unit. good too. As a result, the predetermined pressure reduction condition value is corrected based on the appropriate second threshold value corresponding to the screw, resin, etc. used for 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. This allows the operator to arbitrarily set the first threshold or the second threshold.

A first invention comprises a storage unit (72) for storing a plurality of times or a plurality of movement amounts measured by the second measuring unit in a plurality of molding cycles; A statistic calculation unit (98) that calculates a statistic based on the movement amount, and the decompression condition correction unit uses the statistic as the time or the movement amount to obtain the predetermined The decompression condition value may be corrected. This prevents the predetermined pressure reduction condition value from being corrected based on an outlier in time or movement amount.

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

When the predetermined pressure reduction condition value is corrected, the pressure reduction control section may reduce the pressure of the resin based on the corrected predetermined pressure reduction condition value. Thereby, after the predetermined depressurization condition value is corrected, it is possible to produce molded products of uniform quality over a plurality of molding cycles.

The first invention may further include a display control section (84) for displaying the corrected predetermined pressure reduction condition value on the display section (68). As a result, the operator is notified of the corrected predetermined pressure reduction condition value.

<Second Invention>
A second aspect of the invention is directed to an injection molding machine (10) comprising a cylinder (26) and a screw (34) for injecting a predetermined amount of resin weighed in the cylinder into a mold (20). A control method for controlling the rotation and advance/retreat in the cylinder, wherein the screw is controlled based on a predetermined pressure reduction condition value (CV) after the predetermined amount of the resin is weighed in the cylinder. a pressure reduction control step (S3) for reducing the pressure of the resin; and measuring the load applied to the screw in response to injection of the resin from the cylinder into the mold after the pressure reduction of the resin is completed. a first measuring step (S4), and 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 measurement step (S5) of measuring a movement amount of the screw from when the screw starts the injection operation until the load reaches the first threshold value; and a pressure reduction condition correction step (S6) for correcting the predetermined pressure reduction condition value based on the difference (δ) from the second threshold value (TH2).

This reduces the work load on the operator involved in adjusting the parameters for the decompression 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... Storage part 80... Decompression control part 84 Display control unit 86 First measurement unit 88 First threshold determination unit 90 Second measurement unit 92 Second threshold determination unit 94 Decompression condition correction unit 98 Statistic 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 ... Time (required time) or difference between movement amount 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 weighed in the cylinder into the mold (20); A control device (18) for controlling advance and retreat,
a pressure reduction control unit (80) for controlling the screw based on a predetermined pressure reduction condition value (CV) after the predetermined amount of the resin is weighed in the cylinder to reduce the pressure of the resin;
a first measuring unit (86) for measuring the load applied to the screw according to the injection of the resin from the cylinder into the mold after the pressure reduction of the resin is completed;
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), or when the screw starts the injection operation a second measuring unit (90) for measuring the amount of movement of the screw until the load reaches the first threshold value after
a decompression condition correction unit (94) that corrects the predetermined decompression condition value based on the difference (δ) between the time or the movement amount and a second threshold value (TH2);
A controller. The control device according to claim 1,
The first measuring unit measures, as the load, 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. control device. The control device according to claim 1,
The control device, wherein the first measuring unit 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 control device, wherein the predetermined decompression condition value includes at least one of a suck-back time of the screw, a suck-back distance, and a suck-back speed. The control device according to any one of claims 1 to 4,
The control device, wherein the predetermined decompression 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 decompression condition value when the time or the movement amount exceeds the second threshold, and reduces the predetermined decompression condition value when the time or the movement amount is less than the second threshold. A control device that increases the decompression condition value of A control device according to claim 6,
The decompression condition correcting unit determines 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 compensates for A control device according to claim 6,
The amount of correction for the predetermined decompression condition value is determined in advance for a case where the time or the movement amount exceeds the second threshold and a case where the time or the movement amount is less than the second threshold. ,
The control device, wherein the pressure reduction condition correction unit corrects the predetermined pressure reduction 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 for determining the first threshold based on a first threshold table (TB1) storing a plurality of the first thresholds according to at least one of a plurality of types of the screws and a plurality of types of the resin. Further comprising a threshold determination unit (88),
The control device, wherein the second measurement unit measures the time or the movement amount 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 for determining the second threshold based on a second threshold table (TB2) storing a plurality of the second thresholds corresponding 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 control device, wherein the pressure reduction condition correction section corrects the predetermined pressure reduction condition value using the second threshold determined by the second threshold determination section. The control device according to any one of claims 1 to 10,
A control device further comprising an operation unit (70) for an operator to indicate 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 a plurality of times or a plurality of movement amounts measured by the second measurement unit in a plurality of molding cycles;
a statistic calculation unit (98) that calculates a statistic based on the plurality of times or the plurality of movement amounts;
further comprising
The control device, wherein the pressure reduction condition correction unit corrects the predetermined pressure reduction condition value by using the statistic as the time or the movement amount. The control device according to any one of claims 1 to 12,
The control device, wherein the pressure reduction condition correction unit 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 reduces the pressure of the resin based on the corrected predetermined pressure reduction condition value when the predetermined pressure reduction condition value is corrected. The control device according to any one of claims 1 to 14,
A control device, further comprising a display control section (84) for displaying the corrected predetermined decompression condition value on a display section (68). 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 weighed in the cylinder into the mold (20); A control method for controlling advance and retreat,
a decompression control step (S3) of controlling the screw based on a predetermined decompression condition value (CV) to reduce the pressure of the resin after the predetermined amount of the resin is weighed in the cylinder;
a first measuring step (S4) of measuring the load applied to the screw according to the injection of the resin from the cylinder into the mold after the pressure reduction of the resin is completed;
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), or when the screw performs the injection operation a second measurement step (S5) of measuring the amount of movement of the screw from the start until the load reaches the first threshold;
a pressure reduction condition correction step (S6) for correcting the predetermined pressure reduction condition value based on a difference (δ) between the time or the movement amount and a second threshold value (TH2);
control methods, including;

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