Determination device and determination method

Abstract

A determination device (70) is provided with: a load acquisition unit (82) that acquires a load (LO) applied to a screw (34) of an injection molding machine (10) as a resin is injected in a plurality of molding cycles; an operation information acquisition unit (86) that acquires operation information (INF) on the screw (34) before the load (LO) exceeds a first threshold (TH1); a statistical amount calculation unit (88) that calculates a statistical amount (ST) on the basis of a plurality of pieces of the operation information (INF); and a determination unit (92) that determines the quality of a state of the resin measured by the injection molding machine (10) on the basis of the statistical amount (ST).

Description

Determination device and determination method

[0001] The present invention relates to a determination device and a determination method for determining whether or not the state of resin measured by an injection molding machine is good.

[0002] 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 metering process and an injection process (see also JP 10-16016 A). The metering process is a process for metering the resin to be injected into the mold. The injection process is a process for injecting the metered resin into the mold. The resin injected into the mold solidifies to complete the molded product.

[0003] The state of the measured resin may vary between multiple molding cycles, i.e., the temperature, viscosity, density, amount of the measured resin, etc. may vary between multiple molding cycles.

[0004] Variations in the state of the weighed resin cause variations in the quality (weight, shape, etc.) of molded products. However, it is difficult for an operator to determine whether the state of the resin weighed in one molding cycle varies compared to the state of the resin weighed in another molding cycle. In other words, it is difficult for an operator to determine whether the state of the weighed resin is good or bad.

[0005] The present invention aims to solve the above-mentioned problems.

[0006] A first aspect of the present invention is a judgment device that judges whether the state of resin metered in an injection molding machine having a cylinder and a screw that injects the resin metered in the cylinder into a mold is good or bad, and includes: a load acquisition unit that acquires the load on the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles; an operation information acquisition unit that acquires operation information including at least one of the movement amount, rotation amount, and required time of the screw from when the screw starts an injection operation to inject the resin into the mold to when the load exceeds a first threshold value in a plurality of the molding cycles; a statistical quantity calculation unit that calculates at least one statistical quantity of the movement amount, the rotation amount, and the required time based on the plurality of pieces of operation information acquired in the plurality of the molding cycles; and a judgment unit that judges whether the state of the metered resin is good or bad based on the statistical quantity.

[0007] A second aspect of the present invention is a method for determining whether the state of resin metered in an injection molding machine having a cylinder and a screw that injects resin metered in the cylinder into a mold is good or bad, the method including: a load acquisition step for acquiring, in a plurality of molding cycles, the load applied to the screw in response to the resin being injected from the cylinder into the mold; an operation information acquisition step for acquiring, in a plurality of molding cycles, operation information including at least one of the movement amount, rotation amount, and required time of the screw from when the screw starts an injection operation to inject the resin into the mold until the load exceeds a threshold; a statistical quantity calculation step for calculating at least one statistical quantity of the movement amount, the rotation amount, and the required time based on the plurality of pieces of operation information acquired in the plurality of molding cycles; and a determination step for determining whether the state of the metered resin is good or bad based on the statistical quantity.

[0008] According to the present invention, it is possible to determine whether the state of the weighed resin is good or bad.

[0009] FIG. 1 is a configuration diagram of an injection molding system according to an embodiment. FIG. 2 is a schematic configuration diagram of an injection device. FIG. 3 is a configuration diagram of a determination device according to an embodiment. FIG. 4 is a table illustrating an example of a threshold value table. FIG. 5 is a time chart illustrating the time progression of the screw load (resin pressure) in the injection process of each molding cycle, for a molding cycle repeated three times. FIG. 6 is a flowchart illustrating the flow of a determination method according to an embodiment. FIG. 7 is a configuration diagram of a determination device according to Modification 6. FIG. 8 is a configuration diagram of a determination device according to Modification 7. FIG. 9 is a flowchart illustrating the flow of a determination method according to Modification 7. FIG. 10 is a configuration diagram of an injection molding system according to Modification 13. FIG. 11 is a configuration diagram of another injection molding system according to Modification 13.

[0010] [Embodiment] FIG. 1 is a configuration diagram of an injection molding system SYS according to an embodiment.

[0011] The injection molding system SYS includes an injection molding machine 10 and a determination device 70 .

[0012] The injection molding machine 10 includes a mold clamping unit 12, an injection unit 14, a machine base 16, and a control unit 18. Note that an arrow D1 in Fig. 1 indicates a forward direction in this embodiment. An arrow D2 in Fig. 1 indicates a rearward direction in this embodiment. The rearward direction is the opposite direction to the forward direction.

[0013] The mold clamping unit 12 is a unit that opens and closes the mold 20. The mold clamping unit 12 is disposed in front of the injection unit 14. The mold 20 opens and closes in the front-to-rear direction. The mold 20 in the closed state forms a cavity 20c. The mold 20 in FIG. 1 is in the closed state. The mold clamping unit 12 can apply a clamping force to the mold 20 so that the mold 20 is maintained in the closed state. However, a more detailed description of the mold clamping unit 12 will be omitted.

[0014] 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 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.

[0015] The injection device 14 is supported by a slide base 24. The slide base 24 slides in the front-rear direction while being guided by the guide rails 22. Therefore, the injection device 14 slides in the front-rear direction together with the slide base 24.

[0016] The injection device 14 includes a cylinder 26. The cylinder 26 is a cylindrical member that extends toward the front of the injection device 14.

[0017] FIG. 2 is a schematic diagram of the injection device 14.

[0018] The axis LA of the cylinder 26 extends parallel to the front-rear direction. The cylinder 26 includes a hopper 28, a heater 30, a temperature sensor 31, a nozzle 32, and a screw 34. The injection device 14 further includes a first drive device 36, a second drive device 38, and a pressure sensor 40.

[0019] The hopper 28 is disposed at a rear end 26r of the cylinder 26. The hopper 28 stores solid resin (pellets). The resin is the raw material for the molded products produced by the injection molding machine 10. The hopper 28 also has a supply port 28o. The resin in the hopper 28 is supplied into the cylinder 26 through the supply port 28o.

[0020] The heater 30 heats the cylinder 26. By heating the cylinder 26, the resin inside the cylinder 26 is heated. The heater 30 is made up of, for example, a plurality of band heaters. The plurality of band heaters are wrapped around the cylinder 26.

[0021] The temperature sensor 31 is a sensor that outputs a detection signal corresponding to the temperature of the cylinder 26. The detection signal from the temperature sensor 31 is input to the control device 18. The temperature sensor 31 is, for example, a thermocouple. The temperature sensor 31 is disposed on the surface of the cylinder 26 or in a hole formed in the surface of the cylinder 26. The cylinder 26 may be provided with multiple temperature sensors 31 (see also FIG. 2). The control device 18 will be described in detail later.

[0022] The nozzle 32 is attached to the front end 26f of the cylinder 26. The nozzle 32 is also connected to the mold 20. The nozzle 32 has an injection port 32p for injecting the resin. When the nozzle 32 and the mold 20 are connected, the resin inside the cylinder 26 is injected from the injection port 32p into the cavity 20c.

[0023] The screw 34 is disposed inside the cylinder 26. The axis LA 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 seat 46, and a backflow prevention ring 48.

[0024] The flight portions 42 have a single helix shape and are formed on the surface of the screw 34. However, the flight portions 42 may have a double helix shape. The flight portions 42, together with the inner wall 26i of the cylinder 26, form a flow path 50 inside 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.

[0025] The screw head 44 is the front end of the screw 34. The check seat 46 is disposed rearward of the screw head 44. The backflow prevention ring 48 is disposed between the screw head 44 and the check seat 46.

[0026] When forward pressure is applied to the backflow prevention ring 48, it moves forward in response to the pressure within the range between the screw head 44 and the check seat 46. By moving forward, the backflow prevention ring 48 moves away from the check seat 46. This causes the backflow prevention ring 48 to open the flow path 50. When the backflow prevention ring 48 contacts the rear end of the screw head 44, the flow path 50 is most open.

[0027] Furthermore, when a rearward pressure is applied to the backflow prevention ring 48, the backflow prevention ring 48 moves rearward in response to the pressure within the range between the screw head 44 and the check seat 46. By moving rearward, the backflow prevention ring 48 approaches the check seat 46. As a result, the backflow prevention ring 48 closes the flow path 50. When the backflow prevention ring 48 contacts the front end of the check seat 46, the flow path 50 is narrowest.

[0028] The first driving device 36 is a device that rotates the screw 34. The first driving device 36 includes a first motor 52a, a first driving pulley 54a, a first belt member 56a, and a first driven pulley 58a.

[0029] 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 and torque sensor 63a. The first shaft 60a rotates in response to a drive current supplied to the first motor 52a. The first position and speed sensor 62a outputs a detection signal corresponding to the rotational position of the first shaft 60a to the control device 18. The first current and torque sensor 63a outputs a detection signal corresponding to the drive current supplied to the first motor 52a, the torque of the rotation of the first shaft 60a, and the like to the control device 18.

[0030] The first drive pulley 54a is connected to the first shaft 60a. The first drive pulley 54a rotates in response to the rotation of the first shaft 60a. The first belt member 56a is stretched across the first drive pulley 54a and the first driven pulley 58a. This transmits the rotation of the first drive pulley 54a to the first driven pulley 58a via the first belt member 56a. As a result, the first driven pulley 58a also rotates in response to the rotation of the first drive pulley 54a.

[0031] The first driven pulley 58a is provided integrally with the screw 34. Therefore, the screw 34 also rotates in response to the rotation of the first driven pulley 58a. The screw 34 rotates about the axis LA. By rotating, the screw 34 can cause the resin inside the cylinder 26 to flow along the flow path 50. The rotation direction of the first shaft 60a is switched in response to the control of the control device 18. In response to the switching of the rotation direction of the first shaft 60a, the rotation direction of the screw 34 also switches. Switching the rotation direction of the screw 34 changes the flow direction of the resin inside the cylinder 26.

[0032] In the following description, the rotation direction of the screw 34 when the resin flows forward is also referred to as the forward rotation direction. Furthermore, the rotational movement of the screw 34 in the forward rotation direction is also referred to as forward rotation.

[0033] Meanwhile, in the following description, the rotation direction of the screw 34 when the resin flows backward is also referred to as the reverse rotation direction. Also, the rotational operation of the screw 34 in the reverse rotation direction is also referred to as reverse rotation.

[0034] The second drive device 38 is a device that moves the screw 34 back and forth 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.

[0035] The second motor 52b is, for example, a servo motor. 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 in response to a drive current supplied to the second motor 52b. The second position / speed sensor 62b outputs a detection signal corresponding to the rotational position of the second shaft 60b to the control device 18. The second current / torque sensor 63b outputs a detection signal corresponding to the drive current supplied to the second motor 52b, the torque of the rotation of the second shaft 60b, and the like to the control device 18.

[0036] The second drive pulley 54b is connected to the second shaft 60b. The second drive pulley 54b rotates in response to the rotation of the second shaft 60b. The second belt member 56b is stretched between the second drive pulley 54b and the second driven pulley 58b. This transmits the rotation of the second drive pulley 54b to the second driven pulley 58b via the second belt member 56b. As a result, the second driven pulley 58b also rotates in response to the rotation of the second drive pulley 54b.

[0037] The second driven pulley 58b is connected to the ball screw 64. The second driven pulley 58b rotates in response to the rotation of the second drive pulley 54b transmitted via the second belt member 56b. Therefore, the ball screw 64 also rotates in response to the rotation of the second driven pulley 58b.

[0038] The nut 66 is threadedly engaged with 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 LA 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 LA of the screw 34 in response to the rotation of the ball screw 64. In other words, the relative positional relationship between the nut 66 and the ball screw 64 changes in the front-to-rear direction in response to the rotation of the ball screw 64.

[0039] The screw 34 and the ball screw 64 are connected so that the rotational force of the ball screw 64 (second shaft 60b) is not transmitted to the screw 34. Note that this connection method is known in the art, and therefore a detailed description of this connection method will be omitted.

[0040] The screw 34 is connected to the ball screw 64, and therefore moves forward and backward inside the cylinder 26 in response to changes in the relative positional relationship between the nut 66 and the ball screw 64 in the forward and backward direction. That is, the screw 34 moves forward and backward in response to the rotation of the ball screw 64. However, since the rotational force of the ball screw 64 is not transmitted to the screw 34, the screw 34 does not rotate in response to the rotation of the ball screw 64.

[0041] The rotation direction of the second shaft 60b is switched in accordance with the control of the control device 18. In response to the switching of the rotation direction of the second shaft 60b, the rotation direction of the ball screw 64 is also switched. By switching the rotation direction of the ball screw 64, the movement directions of the nut 66 and the screw 34 are switched.

[0042] According to the injection device 14, 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 melts due to the influence of the heat from the heater 30 transmitted via the cylinder 26 and the shear heat generated in the resin as a result of being sheared by the flight portion 42.

[0043] As the screw 34 continues to rotate forward, the resin behind the backflow prevention ring 48 flows forward along the flow path 50 and reaches the backflow prevention ring 48. The resin that reaches the backflow prevention ring 48 presses the backflow prevention ring 48 forward. This causes the backflow prevention ring 48 to move forward within the range between the screw head 44 and the check sheet 46, opening the flow path 50. The resin passes through the opened flow path 50 and reaches the area inside the cylinder 26 that is forward of the screw head 44.

[0044] In the following description, the area inside the cylinder 26 that is forward of the screw head 44 is also referred to as a metering area. In addition, in the following description, unless otherwise specified, the resin amount refers to the amount of resin stored in the metering area.

[0045] The resin accumulated in the metering region applies a backward pressure to the screw head 44. In the following description, unless otherwise specified, the resin pressure refers to the backward pressure applied to the screw 34 by the resin in the metering region.

[0046] The pressure sensor 40 is a sensor for detecting the pressure of the resin. The pressure sensor 40 is, for example, a load cell. The pressure sensor 40 outputs a detection signal corresponding to the pressure of the resin to the control device 18.

[0047] The control device 18 is, for example, a numerical control device. The control device 18 includes one or more processors and one or more memories. A predetermined control program 68 is stored in the memory of the control device 18. The processor of the control device 18 executes the control program 68 to control the mold clamping device 12 and the injection device 14. For example, the control device 18 executes the control program 68 to perform a metering process, a decompression process, and an injection process, which will be described below.

[0048] The initial position of the screw 34 (screw head 44 ) at the start of the metering process is the forwardmost position within the range of movement of the screw 34 in the front-rear direction inside the cylinder 26 .

[0049] (Metering Process) The control device 18 controls the first motor 52a to rotate the screw 34 in the forward direction. As a result, the resin supplied from the hopper 28 to the inside of the cylinder 26 is pressure-fed forward along the flow path 50. The resin flowing forward inside the cylinder 26 reaches the metering area while melting. The amount of resin gradually increases as the control device 18 continues to rotate the screw 34 in the forward direction.

[0050] Here, the control device 18 controls the first motor 52a so that the screw 34 rotates forward at a predetermined rotational speed. For example, a predetermined measurement condition value CV is stored in advance in the memory of the control device 18. The measurement condition value CV includes a target rotational speed of the screw 34 during the measurement process. The target rotational speed may be any rotational speed instructed by an operator or may be a rotational speed specified by the manufacturer of the injection molding machine 10. The control device 18 rotates the screw 34 forward based on the target rotational speed.

[0051] The rotation speed of the screw 34 is the amount of rotation per unit time of the screw 34. The control device 18 rotates the screw 34 forward while appropriately calculating the amount of rotation, rotation speed, etc. of the screw 34 based on the detection signal of the second position and speed sensor 62b.

[0052] As the amount of resin increases, the screw 34 retreats. Here, the control device 18 controls the second motor 52b to prevent the screw 34 from retreating excessively. That is, the control device 18 controls the second motor 52b to adjust the retreat speed (rearward movement speed) of the screw 34. This prevents the pressure of the resin from decreasing excessively as the screw 34 retreats.

[0053] Here, the control device 18 controls the second motor 52b so that the pressure of the resin is adjusted to a predetermined pressure while the screw 34 is rotating forward. For example, the metering condition value CV includes a target pressure during the metering process. Like the target rotation speed, the target pressure may be any pressure specified by the operator or may be a pressure specified by the manufacturer of the injection molding machine 10. The control device 18 adjusts the retraction speed of the screw 34 during the metering process based on the target pressure.

[0054] The retraction speed of the screw 34 is the amount of retraction per unit time of the screw 34. The control device 18 retracts the screw 34 while appropriately calculating the amount of retraction (movement amount), retraction speed, etc. of the screw 34 based on the detection signal of the first position and speed sensor 62a.

[0055] The screw 34, which moves backward as the amount of resin increases, reaches a predetermined position (metering position) relative to the position of the screw 34. The metering position is a position behind the initial position of the screw 34 in the metering process. The control device 18 adjusts the resin pressure to the metering pressure while causing the screw 34 to reach the metering position, thereby allowing a predetermined amount of resin to accumulate in the metering area. When the screw 34 reaches the metering position, the control device 18 controls the first motor 52a to stop the forward rotation of the screw 34. This ends the metering process.

[0056] The measurement condition value CV may include a target temperature of the cylinder 26. In this case, the control device 18 may control the heater 30 based on the target temperature. As a result, the temperature of the cylinder 26 during the measurement process is adjusted based on the target temperature. By adjusting the temperature of the cylinder 26, the temperature of the resin inside the cylinder 26 is adjusted. Here, the control device 18 controls the heater 30 while appropriately calculating the temperature of the cylinder 26 based on, for example, a detection signal from the temperature sensor 31.

[0057] As described above, shear heat is generated as the flight portion 42 shears the resin. This shear heat affects the temperature of the cylinder 26. Here, the higher the rotation speed of the screw 34, the greater the shear heat. On the other hand, the lower the rotation speed of the screw 34, the more suppressed the increase in shear heat. In light of this, the control device 18 may adjust the rotation speed of the screw 34 to adjust the temperature of the cylinder 26.

[0058] (Depressurization Process) After a predetermined amount of resin has been metered into the cylinder 26, the control device 18 starts the depressurization process. In the depressurization process, the control device 18 controls the first motor 52a to rotate the screw 34 in the reverse direction. When the screw 34 rotates in the reverse direction, the resin in the metering area flows backward. This reduces the amount of resin. As the amount of resin decreases, the resin pressure applied to the screw 34 is reduced.

[0059] Furthermore, inertia acts on the screw 34 as it rotates forward during the metering process. Therefore, the screw 34 continues to rotate forward even after reaching the metering position during the metering process. As a result, the amount of resin immediately after metering exceeds the predetermined amount, strictly speaking. The control device 18 can also adjust the amount of resin to be closer to the predetermined amount by reducing the amount of resin in accordance with the reverse rotation of the screw 34 during the decompression process.

[0060] The backflow prevention ring 48 is pressed by the resin flowing from the metering region to the rear of the backflow prevention ring 48 as the control device 18 reverses the rotation of the screw 34. This causes the backflow prevention ring 48 to move rearward. As the backflow prevention ring 48 moves rearward, it comes into contact with the check sheet 46, which is located rearward of 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. With the flow path 50 closed, the resin accumulated in the metering region cannot reach the area behind the backflow prevention ring 48. As a result, the amount of resin is prevented from decreasing more than necessary.

[0061] The control device 18 controls the screw 34 based on the target reduced pressure value. The target reduced pressure value indicates the target pressure of the resin to be reduced in the depressurization process. The target reduced pressure value is, for example, atmospheric pressure. However, the operator or the manufacturer of the injection molding machine 10 may set the target reduced pressure value in the control device 18. The control device 18 ends the depressurization process when the resin pressure reaches the target reduced pressure value.

[0062] (Injection Process) After the decompression process is completed, the control device 18 starts the injection process. The injection process is performed with the mold 20 in a closed state. Therefore, the control device 18 controls the mold clamping device 12 to close the mold 20 before the injection process is started.

[0063] In the injection process, the control device 18 controls the second motor 52b to advance the screw 34. As a result, the resin in the metering region is injected through the nozzle 32 toward the cavity 20c of the mold 20. The injected resin solidifies in the cavity 20c and is completed as a molded product.

[0064] The molding cycle of the injection molding machine 10 includes the above-mentioned metering step, decompression step, and injection step. The injection molding machine 10 can mass-produce molded products by repeatedly executing the molding cycle.

[0065] FIG. 3 is a configuration diagram of a determination device 70 according to the embodiment.

[0066] The determination device 70 is an electronic device (computer) that determines whether the state of the resin measured by the injection molding machine 10 is good or bad.

[0067] The determination device 70 is communicably connected to the control device 18. For example, the determination device 70 communicates with the control device 18 via a predetermined network. This allows the determination device 70 and the control device 18 to mutually obtain data they possess. The predetermined network may be a wireless network or a wired network. The predetermined network may be realized using, for example, serial communication, optical communication, a wireless LAN, or the like.

[0068] The determination device 70 includes a display unit 72 , an operation unit 74 , a storage unit 76 , and a calculation unit 78 .

[0069] The display unit 72 is a display device including a display screen 72d. The material of the display screen 72d includes, for example, liquid crystal or OEL (Organic Electro-Luminescence).

[0070] The operation unit 74 is an input device that accepts information input to the determination device 70. The operation unit 74 includes, for example, an operation panel 74a, a touch panel 74b, etc. However, the operation unit 74 may also include a keyboard, a mouse, etc. The touch panel 74b is installed on the display screen 72d.

[0071] The storage unit 76 includes a storage circuit, which includes one or more memories such as a random access memory (RAM) or a read only memory (ROM).

[0072] The storage unit 76 stores a determination program 80. The determination program 80 is a program for causing the determination device 70 to execute the determination method according to this embodiment.

[0073] The data stored in the memory unit 76 is not limited to the determination program 80. As described above, the memory unit 76 may store various data as needed. For example, the memory unit 76 may store the resin pressure obtained based on the detection signal of the pressure sensor 40. The memory unit 76 may also store, for example, the torque (first torque) of the first motor 52a obtained based on the detection signal of the first current torque sensor 63a, the torque (second torque) of the second motor 52b obtained based on the detection signal of the second current torque sensor 63b, etc. Furthermore, the memory unit 76 may also store, for example, the drive current, voltage, and temperature of the cylinder 26 of the first motor 52a or the second motor 52b. The pressure, first torque, second torque, drive current, voltage, temperature, etc. may all be acquired from the control device 18.

[0074] The arithmetic unit 78 includes a processing circuit. This processing circuit includes, for example, one or more processors. However, the processing circuit of the arithmetic unit 78 may include an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Alternatively, the processing circuit of the arithmetic unit 78 may include a discrete device.

[0075] The calculation unit 78 includes a load acquisition unit 82, a threshold determination unit 84, a motion information acquisition unit 86, a statistics calculation unit 88, a range determination unit 90, a determination unit 92, a correction command unit 94, and a display control unit 96. The load acquisition unit 82, the threshold determination unit 84, the motion information acquisition unit 86, the statistics calculation unit 88, the range determination unit 90, the determination unit 92, the correction command unit 94, and the display control unit 96 are realized by the processor of the calculation unit 78 executing the determination program 80. However, at least a portion of the load acquisition unit 82, the threshold determination unit 84, the motion information acquisition unit 86, the statistics calculation unit 88, the range determination unit 90, the determination unit 92, the correction command unit 94, and the display control unit 96 may be realized by the aforementioned integrated circuit, discrete device, etc.

[0076] The load acquisition unit 82 acquires the load LO applied to the screw 34 in response to the resin being injected from the cylinder 26 into the mold 20. The load LO is, for example, the pressure of the resin. Therefore, the load acquisition unit 82 acquires the resin pressure from the control device 18, for example, via a predetermined network.

[0077] The load acquisition unit 82 acquires the load LO in each of the plurality of molding cycles. The storage unit 76 may store the plurality of loads LO acquired in the plurality of molding cycles.

[0078] The threshold value determining unit 84 determines the first threshold value TH1 based on the threshold value table TB. The first threshold value TH1 is a value used by the operation information acquiring unit 86 for processing. The processing details of the operation information acquiring unit 86 will be described later. The threshold value table TB is a data table that stores multiple first threshold values ​​TH1 corresponding to at least one of multiple types of screws 34 and multiple types of resin. The threshold value table TB is stored in advance in the storage unit 76.

[0079] The threshold value determination unit 84 searches the threshold value table TB for a first threshold value TH1 that corresponds to the type of screw 34 provided in the injection molding machine 10 and the type of resin supplied inside the cylinder 26. The type of screw 34 provided in the injection molding machine 10 and the type of resin supplied inside the cylinder 26 are specified to the threshold value determination unit 84 by an operator via the operation unit 74, for example.

[0080] FIG. 4 is a table illustrating the threshold table TB.

[0081] The first column (type of screw 34) of the threshold table TB illustrated in FIG. 4 stores multiple types of screws 34. For illustrative purposes, FIG. 4 shows a full-flight screw, a barrier-flight screw, and a high-plasticization screw as multiple types of screws 34. For example, as described above, the screw 34 rotates forward in the metering process to pressure-feed the resin supplied to the interior of the cylinder 26 forward along the flow path 50. Here, the performance of pressure-feeding the resin supplied to the interior of the cylinder 26 forward along the flow path 50 differs depending on the type of screw 34. Therefore, the metering condition value CV for obtaining a good molded product differs depending on the type of screw 34.

[0082] The second column (type of resin) of the threshold table TB illustrated in Fig. 4 stores multiple types of resin. For the sake of illustration, Fig. 4 shows PA (polyamide), PBT (polybutylene terephthalate), and PE (polyethylene) as the multiple types of resin. For example, the temperature at which the resin melts, the viscosity of the resin melted in the metering process, and the density of the resin melted in the metering process vary depending on the type of resin.

[0083] The third column (first threshold value) of the threshold value table TB illustrated in FIG. 4 stores multiple first threshold values ​​TH1 (th1 to th7) corresponding to the data in the first and second columns. The specific values ​​of each of the multiple first threshold values ​​TH1 are determined in advance based on experiments. As shown in the bottom row of FIG. 4 , a first threshold value TH1 corresponding to the type of screw 34 may be stored in the threshold value table TB, regardless of the type of resin. Also, a first threshold value TH1 corresponding to the type of resin may be stored in the threshold value table TB, regardless of the type of screw 34. Furthermore, the injection molding machine 10 may produce molded products using a mixed resin containing multiple types of resin as raw material. In this case, multiple first threshold values ​​TH1 corresponding to the proportions of each type of resin contained in the mixed resin may be stored in the threshold value table TB.

[0084] The operation information acquisition unit 86 acquires operation information INF related to the screw 34. The operation information INF includes, for example, the time required from when the screw 34 starts the injection operation (forward movement) for injecting resin into the mold 20 until the load LO exceeds the first threshold value TH1.

[0085] The motion information acquisition unit 86 acquires the motion information INF in a plurality of molding cycles. The storage unit 76 may store a plurality of pieces of motion information INF acquired by the motion information acquisition unit 86 in a plurality of molding cycles.

[0086] In the following description, unless otherwise specified, the required time refers to the time required from when the screw 34 starts the injection operation to inject resin into the mold 20 until the load LO exceeds the first threshold value TH1.

[0087] The statistical quantity calculation unit 88 calculates the statistical quantity ST based on a plurality of pieces of motion information INF acquired during a plurality of molding cycles. For example, the statistical quantity calculation unit 88 calculates the statistical quantity ST based on a predetermined number of pieces of motion information INF acquired from a molding cycle that is a predetermined number of times before the last molding cycle to the last molding cycle.

[0088] The predetermined number may be instructed by an operator to the statistics calculation unit 88 via the operation unit 74, or may be set in advance by the manufacturer of the injection molding machine 10. Furthermore, the storage unit 76 may store the statistics ST calculated by the statistics calculation unit 88.

[0089] The statistic ST is, for example, a representative value of a plurality of required times. That is, the statistic calculation unit 88 may calculate the average, minimum, maximum, mode, or weighted median of a plurality of required times acquired in a plurality of molding cycles as the statistic ST. The average value may be any of the arithmetic mean value, weighted mean value, weighted harmonic mean value, harmonic mean value, trimmed mean value, and sum-of-squares mean value.

[0090] The operator may instruct the type of value to be calculated as the statistic ST from among the average value, minimum value, maximum value, mode value, and weighted median value to the statistic calculation unit 88 via the operation unit 74. Furthermore, the manufacturer of the injection molding machine 10 may set in advance the type of value to be calculated as the statistic ST from among the average value, minimum value, maximum value, mode value, and weighted median value of the required time.

[0091] FIG. 5 is a time chart illustrating the change over time in the load LO (resin pressure) on the screw 34 in the injection step of each molding cycle, which is repeated three times.

[0092] In Fig. 5, the vertical axis represents load LO (resin pressure). Also, in Fig. 5, the horizontal axis represents time. Fig. 5 shows a first transition CYC1, a second transition CYC2, and a third transition CYC3. The first transition CYC1 represents the transition of resin pressure in the injection process of the first molding cycle of the three repeated molding cycles. The second transition CYC2 represents the transition of resin pressure in the injection process of the second molding cycle of the three repeated molding cycles. The third transition CYC3 represents the transition of resin pressure in the injection process of the third molding cycle of the three repeated molding cycles.

[0093] In Figure 5, the first transition CYC1, the second transition CYC2, and the third transition CYC3 are plotted overlapping each other with respect to the start time t0 of the injection process as the reference point. Time t1 indicates the time when the resin pressure reaches the first threshold value TH1 in the first molding cycle. The required time τ1 for the first molding cycle is the elapsed time from time t0 to time t1. Time t2 indicates the time when the resin pressure reaches the first threshold value TH1 in the second molding cycle. The required time τ2 for the second molding cycle is the elapsed time from time t0 to time t2. Time t3 indicates the time when the resin pressure reaches the first threshold value TH1 in the third molding cycle. The required time τ3 for the third molding cycle is the elapsed time from time t0 to time t3. The statistic ST calculated by the statistic calculation unit 88 using the three required times (τ1, τ2, τ3) in FIG. 5 is, for example, ST=(τ1+τ2+τ3) / 3.

[0094] Considering the possibility that outliers (abnormal values) may be accidentally included in multiple required times, it is preferable to use the mean, mode, or weighted median as the representative value, which reduces the risk of an outlier being selected as the representative value (maximum or minimum value).

[0095] The range determination unit 90 determines an allowable range AR of the motion information INF (required time). The allowable range AR is determined based on a statistic ST (representative value). The range determination unit 90 determines the allowable range AR, for example, by adding a predetermined offset to the representative value.

[0096] For example, the operation information acquisition unit 86 acquires the required time for each of the first to Mth molding cycles (M: natural number, where M≧2). The statistics calculation unit 88 then calculates the average of the required times acquired during the first to Mth molding cycles as a representative value. In this case, the range determination unit 90 adds a predetermined offset to the representative value to calculate an upper limit value greater than the representative value and a lower limit value less than the representative value. This determines the allowable range AR. The storage unit 76 may store the allowable range AR determined by the range determination unit 90.

[0097] The range determination unit 90 may use different offsets depending on the type of representative value. For example, the range determination unit 90 may use different offsets when the representative value is the maximum value and when the representative value is the mode.

[0098] Furthermore, for example, if the representative value is a maximum value, the range determination unit 90 may use that maximum value as the upper limit of the allowable range AR. Similarly, if the representative value is a minimum value, the range determination unit 90 may use that minimum value as the lower limit of the allowable range AR. In relation to this, the aforementioned statistics calculation unit 88 may calculate multiple types of statistics ST (representative values) as necessary.

[0099] Alternatively, the range determination unit 90 may determine only one of the upper and lower limits of the motion information INF. When only the upper limit is determined, the entire range below the upper limit is the allowable range AR. When only the lower limit is determined, the entire range above the lower limit is the allowable range AR.

[0100] The determination unit 92 determines whether the state of the weighed resin is good or bad by using the allowable range AR based on the statistics ST. The determination unit 92 determines whether the state of the resin weighed in a molding cycle is good or bad based on a comparison between the allowable range AR and the operation information INF acquired by the operation information acquisition unit 86 in the molding cycle performed after the allowable range AR is determined.

[0101] For example, the range determination unit 90 determines the allowable range AR based on the required times acquired during the first through Mth molding cycles. Then, in the Nth molding cycle, the operation information acquisition unit 86 acquires the required time (N: natural number, where N>M). The determination unit 92 compares the allowable range AR with the required time acquired in the Nth molding cycle.

[0102] There are cases where the time required for the Nth molding cycle falls within the allowable range AR. In such cases, the judgment unit 92 judges that the state of the resin in the Nth molding cycle is good. In other words, compared to the states of the resin measured in the first through Mth molding cycles, the state of the resin measured in the Nth molding cycle is stable and does not vary.

[0103] On the other hand, there are cases where the time required for the Nth molding cycle does not fall within the allowable range AR. In such cases, the judgment unit 92 judges that the state of the resin in the Nth molding cycle is not good. In other words, compared with the states of the resin measured in the first to Mth molding cycles, the state of the resin measured in the Nth molding cycle varies greatly and is not stable.

[0104] The correction command unit 94 outputs a correction signal based on the determination result of the determination unit 92. The correction signal is a signal for correcting the measurement condition value CV. When the determination unit 92 determines that the resin condition is poor, the correction command unit 94 outputs the correction signal to the control device 18.

[0105] If the required time compared with the allowable range AR is greater than the allowable range AR, the correction command unit 94 outputs a correction signal to correct the measurement condition value CV to be smaller than the current measurement condition value CV.

[0106] In this case, the control device 18 corrects the measurement condition value CV to be smaller than the current measurement condition value CV based on the input correction signal. That is, the control device 18 reduces at least one of the target temperature of the cylinder 26, the target rotational speed of the screw 34, and the target pressure of the resin from the current value based on the input correction signal.

[0107] The reason why the time required for the Nth molding cycle exceeds the allowable time is because the viscosity of the resin in the Nth molding cycle is excessively lower than the viscosities of the resin in the 1st to Mth molding cycles. In other words, because the viscosity of the resin metered in the Nth metering step is low, it takes a long time for the load LO to reach the first threshold value TH1 in the Nth injection step.

[0108] Therefore, if the required time for the Nth molding cycle exceeds the allowable time, the measurement condition value CV is corrected as described above so that the viscosity of the resin in the (N+1)th and subsequent molding cycles will be greater than the viscosity of the resin in the Nth molding cycle. This makes it possible to reduce variations in the state of the resin in the (N+1)th and subsequent molding cycles.

[0109] On the other hand, if the required time compared with the allowable range AR is smaller than the allowable range AR, the correction command unit 94 outputs a correction signal to correct the measurement condition value CV to a value larger than the current measurement condition value CV.

[0110] In this case, the control device 18 corrects the measurement condition value CV based on the input correction signal to be larger than the current measurement condition value CV. In other words, the control device 18 increases at least one of the target temperature of the cylinder 26, the target rotational speed of the screw 34, and the target pressure of the resin based on the input correction signal.

[0111] The reason why the required time for the Nth molding cycle is less than the allowable time is because the viscosity of the resin in the Nth molding cycle is excessively greater than the viscosity of the resin in the first to Mth molding cycles. In other words, because the viscosity of the resin metered in the Nth metering step is high, the load LO reaches the first threshold value TH1 in a short time in the Nth injection step.

[0112] Therefore, if the required time for the Nth molding cycle is less than the allowable time, the measurement condition value CV is corrected as described above so that the viscosity of the resin in the (N+1)th molding cycle and thereafter is smaller than the viscosity of the resin in the Nth molding cycle. This makes it possible to reduce the variation in the state of the resin in the (N+1)th molding cycle and thereafter.

[0113] The correction command unit 94 may include a correction amount for the measurement condition value CV in the correction signal. In this case, the control device 18 corrects the measurement condition value CV based on the correction amount included in the correction signal.

[0114] The correction amount of the measurement condition value CV is determined, for example, according to the deviation amount from the allowable range AR over a predetermined period of time. In this case, the correction command unit 94 may determine the correction amount using, for example, a data table that stores multiple correction amounts according to the deviation amount. However, the correction amount may be a fixed amount that is not dependent on the deviation amount from the allowable range AR over a predetermined period of time.

[0115] The display control unit 96 controls the display unit 72 to display on the display screen 72d various data stored in the storage unit 76. The display control unit 96 displays various data on the display screen 72d in response to, for example, an instruction from an operator.

[0116] Preferably, the display control unit 96 controls the display unit 72 to display the determination result of the determination unit 92 on the display screen 72d, thereby enabling the operator to know whether the state of the resin is good or bad.

[0117] The operator may instruct the determination device 70 (correction command unit 94) whether or not to correct the measurement condition value CV based on the determination result displayed on the display screen 72d. Furthermore, the operator may instruct the determination device 70 (correction command unit 94) on the amount of correction of the measurement condition value CV described above based on the determination result displayed on the display screen 72d.

[0118] FIG. 6 is a flowchart illustrating the flow of a determination method according to the embodiment.

[0119] The determination device 70 can execute the determination method illustrated in Fig. 6. The determination method includes a load acquisition step S1, a load determination step S2, an operation information acquisition step S3, and a process selection step S4. The determination method of Fig. 6 also includes a calculation feasibility determination step S5, a statistics calculation step S6, a range determination step S7, a state determination step (determination step) S8, and a correction command step S9.

[0120] In the load acquisition step S1, the load acquisition unit 82 acquires the load LO of the screw 34. This load LO is the load LO applied to the screw 34 in response to the screw 34 performing the injection operation in the injection process. The load LO is, for example, the pressure of the resin.

[0121] The load LO increases as the injection operation is performed. In the load determination step S2, for example, the operation information acquisition unit 86 determines whether the load LO exceeds a first threshold value TH1.

[0122] The first threshold value TH1 is determined by the threshold value determination unit 84 based on the type of screw 34 and the type of resin before the load determination step S2 is started. The timing at which the threshold value determination unit 84 determines the first threshold value TH1 is not particularly limited as long as it is before the load determination step S2 is performed. Therefore, the threshold value determination unit 84 may determine the first threshold value TH1, for example, before the injection molding machine 10 starts operating.

[0123] If the load LO does not exceed the first threshold TH1 (LO≦TH1), the load acquisition step S1 continues. If the load LO exceeds the first threshold TH1 (LO>TH1), the operation information acquisition step S3 starts.

[0124] In the motion information acquisition step S3, the motion information acquisition unit 86 acquires the motion information INF (required time). The acquired motion information INF is stored in the storage unit 76.

[0125] In the process selection step S4, whether or not the allowable range AR has been determined is determined, for example, by the range determination unit 90. This determination is made by checking whether or not the storage unit 76 stores the allowable range AR.

[0126] If the allowable range AR has not been determined (S4: NO), the calculation possibility determination step S5 is started. If the allowable range AR has been determined (S4: YES), the state determination step S8 is started.

[0127] In the calculation possibility determination step S5, for example, the statistics calculation unit 88 determines whether or not the statistics ST can be calculated. In the example of Fig. 6, the statistics ST is calculated using a predetermined number of pieces of motion information INF. Therefore, the statistics calculation unit 88 determines that the statistics ST can be calculated when the number of pieces of motion information INF stored in the storage unit 76 has reached the predetermined number.

[0128] If it is possible to calculate the statistics ST (S5: YES), the statistics calculation step S6 is started. If it is not possible to calculate the statistics ST (S5: NO), the flow from the load acquisition step S1 to the calculation possibility determination step S5 is executed again in response to the start of the next molding cycle of the injection molding machine 10. Note that since the operation information acquisition step S3 is executed every time a molding cycle is executed, the number of pieces of acquired operation information INF will eventually reach a predetermined number.

[0129] In the statistic calculation step S6, the statistic calculation unit 88 calculates the statistic ST. In the example of FIG. 6, the calculated statistic ST is a representative value of a predetermined number of pieces of motion information INF (required time). The calculated statistic ST is stored in the storage unit 76.

[0130] In the range determination step S7, the range determination unit 90 determines the allowable range AR based on the statistics ST. The determined allowable range AR is stored in the storage unit 76.

[0131] In the state determination step S8, the determination unit 92 determines whether the state of the resin is good or bad based on the allowable range AR and the operation information INF.

[0132] If the operation information INF (required time) falls within the allowable range AR, the determination unit 92 determines that the resin condition is good. In this case, the determination method of Fig. 6 ends. However, as long as the injection molding machine 10 repeats the molding cycle, the determination device 70 may repeatedly execute the determination method of Fig. 6 (RETURN → START).

[0133] If the required time included in the operation information INF is outside the allowable range AR, the determination unit 92 determines that the condition of the resin is not good. In this case, the correction command step S9 is started.

[0134] In the correction command step S9, the correction command unit 94 outputs a correction signal to the control device 18. This enables the control device 18 to correct the measurement condition value CV based on the correction signal.

[0135] Completion of the correction command step S9 ends the determination method of Fig. 6. However, as described above, the injection molding machine 10 can repeat the molding cycle even after the determination method of Fig. 6 ends. In the molding cycle executed after the correction command step S9 is performed, control is performed based on the corrected measurement condition value CV.

[0136] As described above, according to this embodiment, it is possible to determine whether the condition of the measured resin is good or bad. Moreover, according to this embodiment, if the condition of the resin is determined to be poor, the measurement condition value CV can be automatically corrected. This allows stable production to be continued. Therefore, productivity is improved. Furthermore, the operator of the injection molding machine 10 is no longer required to take the time to adjust the measurement condition value CV. This reduces the workload on the operator.

[0137] Resins used in the production of molded products include recycled resins and fiber-reinforced resins. Recycled resins are resins containing recycled materials. Fiber-reinforced resins are resins containing reinforcing fibers, such as glass fibers. The physical properties of recycled resins and fiber-reinforced resins are less stable than those of virgin materials made from new materials. Therefore, when the injection molding machine 10 produces molded products using recycled resins, fiber-reinforced resins, etc., the state of the resin accumulated in the metering area during the metering process may fluctuate during production. According to this embodiment, even when using recycled resins, fiber-reinforced resins, etc., the determination device 70 can determine whether the state of the resin measured during production is good or bad. Furthermore, the injection molding machine 10 can automatically correct the metering condition value CV based on the correction signal output in accordance with the determination result. Therefore, the injection molding machine 10 can continue to perform good molding even when using recycled resins, fiber-reinforced resins, etc.

[0138] [Modifications] Modifications of the above embodiment are described below. However, descriptions that overlap with the above embodiment will be omitted as much as possible in the following description. Elements that have already been described in the embodiment will be assigned the same reference numerals as in the embodiment unless otherwise specified.

[0139] (Variation 1) The operation information INF is not limited to the required time. For example, the operation information acquisition unit 86 may include in the operation information INF the amount of movement of the screw 34 from when the screw 34 starts the injection operation for injecting resin into the mold 20 until the load LO exceeds the first threshold TH1.

[0140] In addition, when the screw 34 rotates during the injection process, the operation information acquisition unit 86 may include in the operation information INF the amount of rotation of the screw 34 from the time the screw 34 starts the injection operation to inject resin into the mold 20 until the load LO exceeds the first threshold value TH1.

[0141] The above-mentioned case in which the screw 34 rotates during the injection process includes not only the case in which the control device 18 controls the rotation of the first motor 52a to rotate the first shaft 60a, but also the case in which the excitation of the first motor 52a is de-energized and the first shaft 60a is in a free state. In other words, when the first shaft 60a is in a free state during the injection process, the first shaft 60a rotates in response to the viscous resistance of the resin acting on the flight portion 42 of the screw 34.

[0142] According to this modified example, the operation information acquisition unit 86 includes in the operation information INF at least one of the movement amount, rotation amount, and required time of the screw 34 from the time the screw 34 starts the injection operation until the load LO exceeds the first threshold value TH1.

[0143] The statistics calculation unit 88 calculates at least one of the required time statistics ST, the movement amount statistics ST, and the rotation amount statistics ST according to the content of the operation information INF. The operator may instruct the determination device 70 (the operation information acquisition unit 86 and the statistics calculation unit 88) as to which item of the required time, movement amount, and rotation amount to use to calculate the statistics ST. The operator's instruction is given, for example, via the operation unit 74. Furthermore, the manufacturer of the injection molding machine 10 may preset in the determination device 70 which item of the required time, movement amount, and rotation amount to use to calculate the statistics ST.

[0144] According to this modification, multiple statistics ST are calculated. The range determination unit 90 may determine multiple allowable ranges AR according to each of the statistics ST. For example, the range determination unit 90 may determine an allowable range AR based on a representative value of multiple amounts of movement and an allowable range AR based on a representative value of multiple amounts of rotation.

[0145] When a plurality of allowable ranges AR are determined, the determining unit 92 may determine whether the state of the resin is good or bad using each allowable range AR.

[0146] For example, an allowable range AR for the required time is determined based on the required time acquired during each of the first to Mth molding cycles. The determination unit 92 compares the required time acquired during the Nth molding cycle with the allowable range AR for the required time to determine whether the state of the resin during the Nth molding cycle is good or bad.

[0147] Furthermore, an allowable range AR for the movement amount is determined based on the movement amount of the screw 34 obtained during each of the first to Mth molding cycles. The determination unit 92 also compares the movement amount obtained during the Nth molding cycle with the allowable range AR for the movement amount, and further determines whether the state of the resin during the Nth molding cycle is good or bad.

[0148] Furthermore, an allowable range AR for the amount of rotation is determined based on the amount of rotation of the screw 34 obtained during each of the first to Mth molding cycles. The determination unit 92 also compares the amount of rotation obtained during the Nth molding cycle with the allowable range AR for the amount of rotation, and further determines whether the state of the resin during the Nth molding cycle is good or bad.

[0149] According to the above example, the quality of the resin state in the Nth molding cycle is determined based on three types of operation information INF: the required time, the movement amount of the screw 34, and the rotation amount of the screw 34. In this case, there is a possibility that the results of the three types of determinations made regarding the resin state in the Nth molding cycle will differ from one another.

[0150] For example, the resin condition in the Nth molding cycle may be determined to be good when the allowable range AR for the required time and the allowable range AR for the amount of movement are used. On the other hand, the resin condition in the Nth molding cycle may be determined to be bad when the allowable range AR for the amount of rotation is used.

[0151] When the results of multiple determinations made regarding the resin condition in the same molding cycle differ from one another, the final determination result is determined, for example, by majority vote. For example, in the above example, the resin condition in the Nth molding cycle is determined based on three types of operation information INF. Furthermore, the number of times that the resin condition in the Nth molding cycle is determined to be good is two of the three types of operation information INF, which is the majority. In this case, the determination unit 92 ultimately determines that the resin condition in the Nth molding cycle is good.

[0152] However, if the results of multiple judgments made regarding the resin condition in the same molding cycle differ from one another, it is more preferable for the judgment unit 92 to judge that the resin condition is good only if it is determined that the resin condition is good in all of the multiple judgments.

[0153] For example, in the above example, the state of the resin in the Nth molding cycle is determined based on three types of operation information INF. In the determination of one type (amount of rotation) of the three types of operation information INF, it is determined that the state of the resin in the Nth molding cycle is not good. In this case, the determination unit 92 ultimately determines that the state of the resin in the Nth molding cycle is not good.

[0154] The determination unit 92 determines that the resin is in good condition only if it determines that the resin is in good condition in all multiple determinations, thereby reducing the risk of overlooking resin that is not in good condition.

[0155] (Variation 2) The judgment unit 92 may judge whether the state of the resin weighed in the molding cycle is good or bad based on a comparison between the allowable range AR and the operation information INF acquired by the operation information acquisition unit 86 in the molding cycle performed before the allowable range AR was determined.

[0156] For example, the range determination unit 90 determines the allowable range AR based on the required times acquired during the first to Mth molding cycles. The determination unit 92 may compare the allowable range AR with the required time acquired during the Lth molding cycle performed before the Mth molding cycle (L: natural number, where L≦M). This makes it possible to determine whether the state of the resin weighed during the first to Mth molding cycles used to calculate the allowable range AR is good or bad.

[0157] (Modification 3) In the embodiment, an example has been described in which the statistics ST is calculated based on a plurality of required times acquired during the first to Mth molding cycles. However, the plurality of required times does not have to include the required time acquired during the first molding cycle.

[0158] For example, the statistics calculation unit 88 may calculate the statistics ST based on a plurality of required times acquired during the Kth to Mth molding cycles (K: natural number, where 2≦K<M). The allowable range AR is determined based on a plurality of required times acquired during the Kth to Mth molding cycles. Immediately after starting operation of the injection molding machine 10, the operating state may not be stable. In this regard, according to this modified example, the statistics ST can be calculated excluding the required times acquired during molding cycles performed while the operating state of the injection molding machine 10 is not stable.

[0159] (Variation 4) The operator may specify the first threshold value TH1 to the determination device 70. In this case, the threshold value determination unit 84 may be omitted. However, the operator may change the first threshold value TH1 determined by the threshold value determination unit 84 via the operation unit 74.

[0160] The operator inputs the first threshold value TH1 to the determination device 70 via, for example, the operation unit 74. The operation information acquisition unit 86 acquires operation information INF based on a comparison between the input first threshold value TH1 and the load LO applied to the screw 34.

[0161] (Variation 5) The load obtaining unit 82 may obtain at least one of the torque of the first motor 52a (first torque) and the torque of the second motor 52b (second torque) as the load LO applied to the screw 34. The first threshold value TH1 compared with the torque of the first motor 52a may be different from the first threshold value TH1 compared with the torque of the second motor 52b.

[0162] The operation information acquisition unit 86 may acquire the shorter of the time required for the first torque to reach the first threshold value TH1 and the time required for the second torque to reach the first threshold value TH1 as operation information INF.

[0163] However, the operation information acquisition unit 86 may acquire the longer of the time required for the first torque to reach the first threshold value TH1 and the time required for the second torque to reach the first threshold value TH1 as operation information INF.

[0164] The first torque may be the disturbance load torque of the first motor 52 a. Similarly, the second torque may be the disturbance load torque of the second motor 52 b. In this case, the disturbance load torque of the first motor 52 a or the second motor 52 b may be estimated using a disturbance estimation observer.

[0165] (Modification 6) FIG. 7 is a diagram showing the configuration of a determination device 701 (70) according to Modification 6. In FIG.

[0166] The determination device 701 differs from the embodiment (see also FIG. 3) at least in that it includes a control limiting unit 98 instead of the correction command unit 94 .

[0167] The control limiting unit 98 outputs a predetermined control signal based on the determination result of the determining unit 92. This control signal is a signal that limits the operation of the injection molding machine 10. When the determining unit 92 determines that the condition of the resin is not good, the control limiting unit 98 outputs a control signal to the control device 18.

[0168] When a control signal is input from the control limiting unit 98, the control device 18 stops the operation of the injection molding machine 10. As a result, if it is determined that the resin condition is poor, the production of molded products is temporarily suspended. While the production of molded products is suspended, the operator can inspect the injection molding machine 10, adjust the measurement condition value CV, etc.

[0169] The determination device 701 may include both the control limiting unit 98 and the correction command unit 94. In this case, the correction command unit 94 and the control limiting unit 98 may be selectively used based on, for example, the amount of deviation of the operation information INF (required time) from the allowable range AR.

[0170] For example, if the deviation amount is less than a predetermined deviation amount, the correction command unit 94 outputs a correction signal to correct the measurement condition value CV. In this case, the control limiting unit 98 does not output a control signal. On the other hand, if the deviation amount is equal to or greater than the predetermined deviation amount, the control limiting unit 98 outputs a control signal to restrict the operation of the injection molding machine 10. In this case, the correction command unit 94 does not output a correction signal. This makes it possible to suppress an increase in the frequency with which the operation of the injection molding machine 10 is restricted.

[0171] (Seventh Modification) FIG. 8 is a diagram showing the configuration of a determination device 702 (70) according to a seventh modification.

[0172] The statistics calculation unit 88 may calculate the degree of dispersion based on the plurality of pieces of motion information INF as the statistics ST. For example, the statistics calculation unit 88 may calculate a dispersion, a deviation, or a coefficient of variation based on the plurality of pieces of motion information INF. The deviation is, for example, a standard deviation. However, the statistics calculation unit 88 may also calculate an average deviation as the deviation.

[0173] The degree of dispersion indicates the degree of dispersion of the plurality of pieces of operation information INF. For example, if the operation information INF includes required times, the degree of dispersion indicates the degree of dispersion of the required times among the plurality of molding cycles.

[0174] The determination unit 92 compares the degree of dispersion with a predetermined threshold (second threshold) TH2. The second threshold TH2 is stored in advance in the storage unit 76. The second threshold TH2 is determined in advance based on experiments. Similar to the first threshold TH1, the second threshold TH2 may be determined depending on the type of screw 34 and the type of resin.

[0175] If the degree of dispersion is equal to or less than the second threshold value TH2, the determination unit 92 determines that the resin is in a good state. On the other hand, if the degree of dispersion exceeds the second threshold value TH2, the determination unit 92 determines that the resin is in a poor state.

[0176] The resin determined based on the degree of dispersion is the resin measured in the molding cycle in which the multiple pieces of operation information INF for calculating the degree of dispersion were acquired.

[0177] For example, a degree of dispersion is calculated based on multiple pieces of operation information INF acquired during the Kth to Mth molding cycles (K: natural number, where 1≦K<M). The determination unit 92 uses the degree of dispersion to determine whether the state of the resin metered during the Kth to Mth molding cycles is good or bad. If the degree of dispersion is equal to or less than the second threshold value TH2, it is determined that the state of the resin metered during all of the Kth to Mth molding cycles is good. If the degree of dispersion exceeds the second threshold value TH2, it is determined that the state of the resin metered during all of the Kth to Mth molding cycles is poor.

[0178] FIG. 9 is a flowchart illustrating the flow of a determination method according to the seventh modification.

[0179] The determination device 702 can execute the determination method exemplified in Fig. 9. The determination method includes a load acquisition step S1, a load determination step S2, an operation information acquisition step S3, a calculation feasibility determination step S5, a statistics calculation step S6, a state determination step S8, and a correction command step S9.

[0180] The load acquisition step S1, the load determination step S2, the operation information acquisition step S3, the calculation feasibility determination step S5, and the correction instruction step S9 will not be described (see the embodiment).

[0181] The statistic calculation step S6 is the same as in the embodiment in that it is a step in which the statistic calculation unit 88 calculates the statistic ST. However, in the statistic calculation step S6 in Fig. 9, the dispersion is calculated as the statistic ST.

[0182] The state determination step S8 is the same as in the embodiment in that it is a step in which the determination unit 92 determines whether the state of the resin is good or bad using the statistics ST. However, the statistics ST used by the determination unit 92 in the statistics calculation step S6 in Fig. 9 is not a representative value but a dispersion. Also, in the state determination step S8 in Fig. 9, it is determined whether the state of the resin weighed between the start of the determination method and the start of the statistics calculation step S6 is good or bad.

[0183] The statistics calculation unit 88 may calculate the degree of dispersion once and then recalculate the degree of dispersion each time the molding cycle is repeated.

[0184] For example, the statistics calculation unit 88 calculates the degree of dispersion based on the multiple required times acquired during the Kth to Mth molding cycles. The degree of dispersion is used to determine whether the state of the resin measured during the Kth to Mth molding cycles is good or bad.

[0185] Thereafter, the statistics calculation unit 88 recalculates the degree of dispersion based on the required times acquired during the (K+1)th to (M+1)th molding cycles. The degree of dispersion can be used to determine whether the state of the resin weighed during the (K+1)th to (M+1)th molding cycles is good or bad.

[0186] However, the state of the resin measured in the (K+1)th to Mth molding cycles has already been determined. In this case, the determination based on the recalculated dispersity is performed as a double check for the range of the (K+1)th to Mth molding cycles. Alternatively, the determination result based on the recalculated dispersity may be ignored for the range of the (K+1)th to Mth molding cycles.

[0187] In the above example, the dispersibility is recalculated every time the molding cycle is repeated after the Mth cycle. That is, in the above example, the dispersibility is calculated once per cycle. However, the dispersibility may be calculated twice or more times.

[0188] (Modification 8) The statistics calculation unit 88 may calculate both the representative value and the variance value (see Modification 7). The determination unit 92 may determine whether the state of the resin is good or bad based on both the representative value and the variance value.

[0189] For example, the statistical quantity calculation unit 88 calculates the deviation (degree of dispersion) of the required times acquired during the Kth to Mth molding cycles. The determination unit 92 uses the deviation to determine whether the state of the resin weighed during the Kth to Mth molding cycles is good or bad.

[0190] The statistical calculation unit 88 also calculates the average (representative value) of the required times obtained during the Kth to Mth molding cycles. The range determination unit 90 determines the allowable range AR based on the average value. The judgment unit 92 uses the allowable range AR to judge whether the state of the resin weighed in the Nth molding cycle is good or bad.

[0191] The determining unit 92 may perform both a determination based on the degree of dispersion and a determination based on the representative value in order to determine whether the state of the resin weighed in the same molding cycle is good or bad.

[0192] For example, a deviation and an average value are calculated based on multiple required times acquired during the first through Mth molding cycles. An allowable range AR is determined based on the average value. The determination unit 92 determines the state of the resin weighed during the first through Mth molding cycles based on the deviation. The determination unit 92 also determines the state of the resin weighed during the Lth molding cycle based on the allowable range AR (L: natural number, where L≦M). Thus, the state of the resin during the Lth molding cycle is determined based on both the degree of dispersion and the representative value.

[0193] Here, there is a possibility that the judgment result based on the degree of dispersion and the judgment result based on the representative value may differ. In such a case, it is preferable that the judgment unit 92 finally judges that the resin state in the Lth molding cycle is good only when the judgment based on both the degree of dispersion and the judgment based on the representative value are good. This reduces the risk of overlooking resin in a poor state.

[0194] (Modification 9) In order to reduce the pressure of the resin, the control device 18 may control the second motor 52b to perform a suck-back operation, which moves the screw 34 backward from the metering position.

[0195] (Modification 10) The threshold value table TB may store a plurality of threshold values ​​according to the type of nozzle 32 as well as the type of screw 34 and the type of resin.

[0196] (Variation 11) A system in which the axis LA of the cylinder 26 and the axis of the screw 34 overlap is also called an inline (inline screw) system. An injection molding machine 10 to which the inline system is applied is also called an inline type injection molding machine. The injection unit 14 of the inline type injection molding machine 10 is easier to maintain than injection units of other types.

[0197] However, the determination device 70 may be provided in an injection molding machine 10 that is not of the inline type. An example of a type that is not of the inline type is a pre-plasticization type.

[0198] (Modification 12) The determination device 70 may be incorporated into the control device 18. In this case, the control device 18 and the determination device 70 are provided as a single integrated electronic device.

[0199] (Modification 13) FIG. 10 is a configuration diagram of an injection molding system SYS1 (SYS) according to Modification 13.

[0200] The injection molding system SYS1 includes a plurality of injection molding machines 10 and a management device 100. The number of injection molding machines 10 included in the injection molding system SYS1 is not particularly limited.

[0201] The management device 100 is, for example, an electronic device for managing a plurality of injection molding machines 10. The management device 100 is communicably connected to the control devices 18 (181, 182, 183, ...) of each injection molding machine 10. The management device 100 communicates with the plurality of control devices 18 via a predetermined network. An operator can issue instructions to, for example, the plurality of control devices 18 collectively via the management device 100.

[0202] The determination device 70 may be incorporated into the management device 100. In this case, the determination device 70 and the management device 100 are provided to the operator as a single integrated electronic device.

[0203] The determination device 70 acquires a plurality of pieces of operation information INF from each of the plurality of injection molding machines 10. For example, the determination device 70 acquires a plurality of pieces of operation information INF from each of the control devices 181, 182, and 183 via a predetermined network.

[0204] Furthermore, the determination device 70 determines whether the state of the resin measured is good or bad for each injection molding machine 10. For example, the determination device 70 determines whether the state of the resin measured by the injection molding machine 10 equipped with the control device 181 is good or bad based on a plurality of pieces of operation information INF acquired from the control device 181. Similarly, the determination device 70 determines whether the state of the resin measured by the injection molding machine 10 equipped with the control device 182 (183) is good or bad based on a plurality of pieces of operation information INF acquired from the control device 182 (183).

[0205] According to this modification, the quality of the resin metered by each of the multiple injection molding machines 10 can be determined using a single electronic device (determination device 70).

[0206] FIG. 11 is a configuration diagram of another injection molding system SYS2 (SYS) according to Modification 13.

[0207] The determination device 70 may be incorporated into one of a plurality of control devices provided in the injection molding system SYS (see also Modification 12).

[0208] For example, the injection molding system SYS2 includes at least three control devices 18 (185, 186, 187, ...). The determination device 70 is incorporated into, for example, the control device 185. The determination device 70 communicates with the other control devices 18 (187, 188) via a predetermined network. This allows the determination device 70 to determine the quality of the resin metered not only in the injection molding machine 10 equipped with the control device 185, but also in each of the injection molding machines 10 equipped with the control device 186 and the control device 187, for example.

[0209] [Inventions Obtained from the Embodiments] Inventions that can be understood from the above-described embodiments and modifications will be described below.

[0210] <First Invention> The first invention is a determination device (70) for determining whether a resin measured in an injection molding machine (10) is good or bad, the determination device (70) including a cylinder (26) and a screw (34) for injecting the resin measured in the cylinder into a mold (20), the determination device including a load acquisition unit (82) for acquiring a load (LO) applied to the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles, and a load acquisition unit (82) for acquiring a load (LO) applied to the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles after the screw starts an injection operation for injecting the resin into the mold in a plurality of molding cycles. the load exceeds a first threshold (TH1); a statistical quantity calculation unit (88) that calculates at least one statistical quantity (ST) of the movement amount, the rotation amount, and the required time of the screw based on the plurality of pieces of operation information acquired during the plurality of molding cycles; and a judgment unit (92) that judges whether the state of the weighed resin is good or bad based on the statistical quantity.

[0211] This makes it possible to determine whether the state of the weighed resin is good or bad.

[0212] The load acquisition unit may acquire, as the load, at least one of a first torque of a first motor (52 a) that rotates the screw and a second torque of a second motor (52 b) that advances the screw. This allows the load of the screw to be detected based on a current torque sensor originally provided in the motor, thereby suppressing an increase in equipment costs for load detection.

[0213] The load acquisition unit may acquire the pressure of the resin in the cylinder as the load, thereby detecting the load on the screw based on a pressure sensor originally provided in the injection molding machine, thereby suppressing an increase in equipment costs for load detection.

[0214] The first invention may further include a threshold value determining unit (84) that determines the first threshold value based on a threshold value table (TB) that stores a plurality of first threshold values ​​according to at least one of a plurality of types of the screw and a plurality of types of the resin, and the operation information acquiring unit may acquire the operation information using the first threshold value determined by the threshold value determining unit. In this way, the operation information is acquired based on an appropriate threshold value according to the screw, resin, etc. used in injection molding.

[0215] The first invention may further comprise an operation unit (74) for an operator to specify the first threshold value, thereby allowing the operator to arbitrarily set the first threshold value.

[0216] The statistical calculation unit may calculate at least one of a degree of dispersion of the plurality of movement amounts, a degree of dispersion of the plurality of rotation amounts, and a degree of dispersion of the plurality of required times based on the acquired operation information, and if the calculated degree of dispersion exceeds a second threshold (TH2), the determination unit may determine that the state of the resin metered during the plurality of molding cycles is not good. This makes it possible to determine whether the state of the metered resin is good or bad.

[0217] The statistical calculation unit may calculate at least one of a plurality of representative values ​​of the movement amounts, a plurality of representative values ​​of the rotation amounts, and a plurality of representative values ​​of the required times, and the judgment device may further include a range determination unit (90) that determines an allowable range (AR) based on the calculated representative value, and in the molding cycle after the allowable range has been determined, the judgment unit may determine whether the state of the metered resin is good or bad based on the operation information and the allowable range. This makes it possible to determine whether the state of the metered resin is good or bad.

[0218] The injection molding machine includes a control device (18) that controls the injection molding machine to measure the resin based on a measurement condition value (CV) including at least one of a target temperature of the cylinder, a target rotational speed of the screw, and a target pressure of the resin, and the judgment device further includes a correction command unit (94) that outputs a correction signal for correcting the measurement condition value based on the judgment result of the judgment unit, and the control device corrects the measurement condition value based on the correction signal, and the correction signal may be a signal to correct the measurement condition value to be smaller than the current measurement condition value if the movement amount, the rotation amount, or the required time is larger than the allowable range, or a signal to correct the measurement condition value to be larger than the current measurement condition value if the movement amount, the rotation amount, or the required time is smaller than the allowable range. This automatically corrects the measurement condition value to stabilize the quality of the molded product.

[0219] The first invention further includes a control limiting unit (98) that outputs a predetermined control signal to a control device of the injection molding machine when the determining unit determines that the resin is in a poor condition, and the predetermined control signal may be a signal that limits operation of the injection molding machine. This automatically limits operation of the injection molding machine when there is a risk that the quality of the molded product will be unstable.

[0220] The first invention may further include a display control unit (96) that controls the display device (72) to display information indicating the judgment result of the judgment unit on the display device, thereby notifying an operator of the judgment result of whether the resin condition is good or bad.

[0221] In the first invention, the load and the plurality of pieces of operation information may be acquired from each of the plurality of injection molding machines, thereby determining the quality of the state of the metered resin for each of the plurality of injection molding machines, thereby enabling a single determination device to determine the quality of the state of the resin metered by each of the plurality of injection molding machines.

[0222] The determination device may be incorporated into a management device (100) that manages the multiple injection molding machines, thereby enabling a single determination device (management device) to determine whether the state of the resin metered by each of the multiple injection molding machines is good or bad.

[0223] <Second Invention> The second invention is a method for determining whether the state of a resin metered in an injection molding machine (10) is good or bad, the method comprising: a load acquisition step (S1) for acquiring a load (LO) applied to the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles; an operation information acquisition step (S3) for acquiring operation information (INF) including at least one of a movement amount, a rotation amount, and a required time of the screw from when the screw starts an injection operation for injecting the resin into the mold until the load exceeds a threshold in a plurality of the molding cycles; a statistics calculation step (S6) for calculating at least one statistics (ST) of the movement amount, the rotation amount, and the required time based on the plurality of pieces of operation information acquired in the plurality of molding cycles; and a determination step (S8) for determining whether the state of the metered resin is good or bad based on the statistics.

[0224] This makes it possible to determine whether the state of the weighed resin is good or bad.

[0225] REFERENCE SIGNS LIST 10... injection molding machine 18... control device 20... mold 26... cylinder 34... screw 52a... first motor 52b... second motor 70... determination device 72... display unit (display device) 74... operation unit 82... load acquisition unit 84... threshold value determination unit 86... operation information acquisition unit 88... statistics calculation unit 90... range determination unit 92... determination unit 94... correction command unit 96... display control unit 98... control limit unit 100... management device AR... allowable range INF... operation information LO... load ST... statistics TB... threshold value table TH1... first threshold value TH2... second threshold value

Claims

1. A judgment device (70) for judging whether a resin measured by an injection molding machine (10) is good or bad, the judgment device (70) comprising: a cylinder (26); and a screw (34) for injecting the resin measured in the cylinder into a mold (20), a load acquisition unit (82) that acquires a load (LO) applied to the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles; an operation information acquisition unit (86) that acquires operation information (INF) including at least one of a movement amount, a rotation amount, and a required time of the screw from when the screw starts an injection operation for injecting the resin into the mold until the load exceeds a first threshold value (TH1) in a plurality of the molding cycles; a statistics calculation unit (88) that calculates at least one statistics (ST) of the movement amount, the rotation amount, and the required time based on a plurality of pieces of operation information acquired during a plurality of molding cycles; A determination unit (92) that determines whether the measured resin is in a good or bad state based on the statistics; A determination device comprising:

2. The determination device according to claim 1 , The load acquisition unit acquires, 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.

3. The determination device according to claim 1 , The load acquisition unit acquires the pressure of the resin in the cylinder as the load.

4. The determination device according to any one of claims 1 to 3, Further provided is a threshold value determination unit (84) that determines the first threshold value based on a threshold value table (TB) in which a plurality of first threshold values ​​are stored according to at least one of a plurality of types of the screw and a plurality of types of the resin, The motion information acquisition unit acquires the motion information by using the first threshold determined by the threshold determination unit.

5. The determination device according to any one of claims 1 to 3, The determination device further comprises an operation unit (74) for an operator to specify the first threshold value.

6. The determination device according to any one of claims 1 to 3, the statistics calculation unit calculates at least one of a degree of dispersion of the plurality of movement amounts, a degree of dispersion of the plurality of rotation amounts, and a degree of dispersion of the plurality of required times based on the acquired motion information; When the calculated dispersity exceeds a second threshold (TH2), the judgment unit judges that the state of the resin metered during the multiple molding cycles is not good.

7. The determination device according to any one of claims 1 to 3, the statistics calculation unit calculates at least one of a representative value of a plurality of the movement amounts, a representative value of a plurality of the rotation amounts, and a representative value of a plurality of the required times; The determination device further includes a range determination unit (90) that determines an acceptable range (AR) based on the calculated representative value, A determination device, in the molding cycle after the allowable range is determined, the determination unit determines whether a state of the weighed resin is good or bad based on the operation information and the allowable range.

8. The determination device according to claim 7, the injection molding machine includes a control device (18) that controls the injection molding machine based on a metering condition value (CV) including at least one of a target temperature of the cylinder, a target rotational speed of the screw, and a target pressure of the resin to meter the resin; The determination device further includes a correction command unit (94) that outputs a correction signal for correcting the measurement condition value based on the determination result of the determination unit, The control device corrects the measurement condition value based on the correction signal, The correction signal is a signal to correct the measurement condition value to be smaller than the current measurement condition value when the movement amount, the rotation amount, or the required time is larger than the allowable range; a determination device that outputs a signal to the effect that the measurement condition value is to be increased from the current measurement condition value when the movement amount, the rotation amount, or the required time is smaller than the allowable range.

9. The determination device according to any one of claims 1 to 3, a control limiting unit (98) that outputs a predetermined control signal to a control device of the injection molding machine when the determining unit determines that the state of the resin is not good; The predetermined control signal is a signal to limit the operation of the injection molding machine.

10. The determination device according to any one of claims 1 to 3, The determination device further comprises a display control unit (96) that controls a display device (72) to cause the display device to display information indicating the determination result of the determination unit.

11. The determination device according to any one of claims 1 to 3, a determining device that obtains the load and a plurality of pieces of the operation information from each of the plurality of injection molding machines, and determines whether the state of the metered resin is good or bad for each of the injection molding machines.

12. The determination device according to claim 11, The determination device is incorporated in a management device (100) that manages a plurality of the injection molding machines.

13. A method for determining whether a resin measured by an injection molding machine (10) is good or bad, the method comprising: a cylinder (26) and a screw (34) for injecting the resin measured in the cylinder into a mold (20), the method comprising the steps of: A load acquisition step (S1) of acquiring a load (LO) applied to the screw in response to the resin being injected from the cylinder into the mold in a plurality of molding cycles; An operation information acquisition step (S3) for acquiring operation information (INF) including at least one of the movement amount, rotation amount, and required time of the screw from when the screw starts an injection operation for injecting the resin into the mold until the load exceeds a threshold value in a plurality of the molding cycles; A statistics calculation step (S6) of calculating at least one statistic (ST) among the movement amount, the rotation amount, and the required time based on the plurality of pieces of operation information acquired in the plurality of molding cycles; A determination step (S8) of determining whether the measured resin is in a good or bad state based on the statistics; A method for determining whether or not a