Injection molding machine and program

Abstract

To provide an injection molding machine that can more accurately grasp the molten state of the resin. [Solution] The injection molding machine comprises a mold clamping device for opening and closing and clamping the mold, an injection device for injecting molten resin into the cavity of the clamped mold, and a control device for controlling the mold clamping device and the injection device. The injection device comprises a heating cylinder whose tip moves toward and away from the clamped mold, and a screw that moves back and forth inside the heating cylinder. The control device performs a plasticization process in which the resin supplied to the heating cylinder is plasticized by rotating and retracting the screw, an discharge process in which the molten resin plasticized in the plasticization process is discharged by advancing the screw inside the heating cylinder, a measurement process in which waveform data showing the change in resin viscosity of the molten resin in the discharge process is measured, and an output process in which the waveform data measured in the measurement process is output.

Description

Technical Field

[0001] The present invention relates to an injection molding machine and a program.

Background Art

[0002] Conventionally, an injection molding machine that advances a screw in a heating cylinder and injects molten resin into a cavity of a clamped mold is known. In such an injection molding machine, it is important to grasp the molten state of the resin in the heating cylinder in order to inject the molten resin under appropriate molding conditions.

[0003] Therefore, for example, in Patent Documents 1 and 2, a technique is disclosed in which the resin viscosity is determined based on the injection speed and injection pressure of the molten resin, and when the determined resin viscosity does not fall within a predetermined range, the molding conditions (for example, the temperature of the heater) are adjusted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the injection speed and injection pressure vary as the screw moves, it is difficult to say that the molten state of the resin can be grasped over the entire movement range of the screw in the techniques of Patent Documents 1 and 2 in which the resin viscosity is determined only at a predetermined position within the movement range of the screw.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide an injection molding machine capable of more appropriately grasping the molten state of the resin.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides an injection molding machine comprising a mold clamping device for opening and closing and clamping a mold, an injection device for injecting molten resin into the cavity of the clamped mold, and a control device for controlling the mold clamping device and the injection device, wherein the injection device comprises a heating cylinder whose tip moves toward and away from the clamped mold, and a screw that moves back and forth inside the heating cylinder, and the control device is characterized in that it performs a plasticization process in which the resin supplied to the heating cylinder is plasticized by rotating and retracting the screw, a discharge process in which the molten resin plasticized in the plasticization process is discharged by advancing the screw inside the heating cylinder, a measurement process in which waveform data showing the change in the resin viscosity of the molten resin in the discharge process is measured, and an output process that outputs the waveform data measured in the measurement process. [Effects of the Invention]

[0008] According to the present invention, the melting state of the resin can be understood more appropriately. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of the injection molding machine according to this embodiment. [Figure 2] This is a hardware configuration diagram of an injection molding machine. [Figure 3] This is a flowchart of the reference waveform generation process. [Figure 4] This is a flowchart of the injection control process. [Figure 5] This figure shows examples of reference waveform data (A) and comparison waveform data (B). [Figure 6] This is a flowchart for the differential waveform display process. [Figure 7] This figure shows an example of differential waveform data. [Figure 8] This is a hardware configuration diagram of an information processing device. [Modes for carrying out the invention]

[0010] The injection molding machine 10 according to the present invention will be described below with reference to the drawings. The injection molding machine 10 is a device that injects a measured molding material (molten resin) into a mold to form a molded product.

[0011] [Configuration of injection molding machine 10] Figure 1 is a side view of the injection molding machine 10 according to this embodiment. Figure 2 is a hardware configuration diagram of the injection molding machine 10. As shown in Figures 1 and 2, the injection molding machine 10 mainly comprises a mold clamping device 20, an injection device 30, and a control device 60.

[0012] The mold clamping device 20 opens and closes the mold 21 and clamps it. Specifically, the mold clamping device 20 mainly comprises a fixed die plate 23 that supports the fixed side mold 22 and a movable die plate 25 that supports the movable side mold 24. The fixed side mold 22 and the movable side mold 24 are supported so as to face each other in the left-right direction (horizontal direction) of the injection molding machine 10.

[0013] The movable die plate 25 moves left and right along the tie bar 27 as the driving force of the mold opening / closing motor 28 is transmitted through the toggle link mechanism 26. When the movable die plate 25 moves to the left, the fixed mold 22 and the movable mold 24 separate. On the other hand, when the movable die plate 25 moves to the right, the fixed mold 22 and the movable mold 24 come into contact, forming a cavity (internal space) inside the mold 21. When further pressure is applied in the direction that moves the movable die plate 25 to the right, the fixed mold 22 and the movable mold 24 are clamped together.

[0014] The injection device 30 plasticizes, measures, and injects the molding material. In this embodiment, the injection device 30 is positioned opposite the clamping device 20 in the horizontal direction (to the right of the clamping device 20). The injection device 30 mainly comprises a heating cylinder 31, a screw 32, a hopper 33, and a hopper block 34.

[0015] The heating cylinder 31 is a cylindrical member extending in the left - right direction of the injection molding machine 10. The heating cylinder 31 mainly includes a resin passage 35 and a nozzle 36. Further, a band heater 39 for heating the heating cylinder 31 is attached to the outer peripheral surface of the heating cylinder 31.

[0016] The resin passage 35 is a cylindrical space extending in the axial direction (longitudinal direction) inside the heating cylinder 31. The resin passage 35 communicates with the outside of the heating cylinder 31 (the cavity of the mold 21) through a nozzle 36 provided at the tip (front end) of the heating cylinder 31. In other words, the resin passage 35 is a space extending axially from the nozzle 36.

[0017] The screw 32 is a cylindrical member. On the outer peripheral surface of the screw 32, a groove extending spirally along the longitudinal direction of the screw 32 (hereinafter referred to as "spiral groove") is formed. The screw 32 is accommodated in the internal space of the heating cylinder 31 in a state where it can move (hereinafter referred to as "advance and retreat") and rotate in the left - right direction of the injection molding machine 10. Further, the screw 32 in the heating cylinder 31 is configured to be replaceable. In other words, screws 32 with different specifications (for example, material, shape of the spiral groove, volume of the spiral groove) can be inserted into the heating cylinder 31.

[0018] The driving force of the injection motor 37 is transmitted to the screw 32 to cause it to advance and retreat, and the driving force of the metering motor 38 is transmitted to cause it to rotate. More specifically, when the injection motor 37 rotates forward, the screw 32 moves (advances) toward the tip of the heating cylinder 31 (that is, the nozzle 36). On the other hand, when the injection motor 37 rotates in reverse, the screw 32 moves (retreats) toward the base end of the heating cylinder 31 (that is, the side opposite to the nozzle 36).

[0019] Hereinafter, within the range that the tip of the screw 32 can reach within the heating cylinder 31, the position closest to the nozzle 36 will be referred to as the "forward limit," and the position furthest from the nozzle 36 will be referred to as the "reverse limit." Furthermore, the terms "forward rotation" and "reverse rotation" for the injection motor 37 do not specify an absolute direction of rotation, but merely specify a relative relationship (i.e., forward rotation and reverse rotation are rotations in opposite directions).

[0020] The hopper 33 is a funnel-shaped component that stores granular resin, which is the raw material. The hopper block 34 is a component that supports the heating cylinder 31 and the hopper 33. The hopper 33 communicates with the resin passage 35 through the hopper block 34, on the base side of the tip of the heating cylinder 31. The granular resin stored in the hopper 33 is supplied to the resin passage 35 of the heating cylinder 31 through an opening provided at the lower end. The granular resin used in this injection molding machine 10 is, for example, a so-called "pellet" that is molded into a cylindrical shape.

[0021] The injection device 30 rotates the injection motor 37 in the reverse direction and the metering motor 38, causing the screw 32 to rotate and retract. As a result, the pellets supplied through the hopper 33 are plasticized and filled (metered) into the resin passage 35 in front of the screw 32. The injection device 30 also rotates the injection motor 37 in the forward direction, causing the screw 32 to move forward.

[0022] Furthermore, the heating cylinder 31 receives the driving force from the nozzle touch motor 40, which allows the nozzle 36 to move toward and away from the clamped mold 21. When the screw 32 is advanced with the nozzle 36 in contact with the clamped mold 21 (nozzle touch), the plasticized molten resin in front of the screw 32 is injected through the nozzle 36 into the cavity of the mold 21. On the other hand, when the screw 32 is advanced with the nozzle 36 separated from the mold 21, the plasticized molten resin in front of the screw 32 is discharged to the outside through the nozzle 36 (purge).

[0023] The hopper 33 is supplied with different types of resin (e.g., different degrees of plasticity) depending on the molded product. The particle size of the pellets supplied to the hopper 33 varies depending on the raw material supply device (not shown) that supplies the raw materials to the hopper 33. In addition to pellets, recycled resin may also be supplied to the hopper 33. Recycled resin refers to unwanted parts (runners) separated from the molded product, resin discharged (purged) from the heating cylinder 31, etc. The ratio of pellets and recycled resin supplied to the hopper 33 gradually changes during the injection control process, which will be described later with reference to Figure 4.

[0024] [Configuration of the control device 60] As shown in Figure 2, the control device 60 comprises a CPU (Central Processing Unit) 61 and memory 62. The memory 62 is composed of, for example, ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or a combination thereof. The control device 60 performs the processing described later by having the CPU 61 read and execute program code stored in the ROM or HDD. RAM is used as a work area when the CPU 61 executes the program.

[0025] However, the specific configuration of the control device 60 is not limited to this and may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array).

[0026] The control device 60 controls the operation of the entire injection molding machine 10. More specifically, the control device 60 controls the mold opening / closing motor 28, injection motor 37, metering motor 38, band heater 39, nozzle touch motor 40, and communication interface (IF) 68 based on various signals output from the rotary encoder 64, load cell 65 (pressure sensor), multiple temperature sensors 66a, 66b, 66c, and display input device 67.

[0027] The mold opening / closing motor 28, injection motor 37, metering motor 38, and nozzle touch motor 40 are servo motors that, for example, generate driving force to open and close the mold 21, driving force to move the screw 32 forward and backward, driving force to rotate the screw 32, and driving force to bring the heating cylinder 31 (nozzle 36) into and out of contact with the mold 21, according to the control of a servo amplifier (not shown).

[0028] The rotary encoder 64 is a sensor that detects the speed and tip position of the screw 32. More specifically, the rotary encoder 64 outputs pulse signals to the control device 60 corresponding to the rotation of the injection motor 37. The control device 60 then determines the speed of the screw 32 based on the number of pulse signals output per unit time. The control device 60 also determines the tip position of the screw 32 based on the cumulative value of the pulse signals.

[0029] The load cell 65 is a sensor that detects the pressure applied to the screw 32. More specifically, the load cell 65 outputs a pressure signal (voltage value) corresponding to the pressure applied to the screw 32 to the control device 60. The control device 60 then determines the pressure applied to the screw 32 based on the pressure signal output from the load cell 65.

[0030] The temperature sensors 66a, 66b, and 66c detect the temperature of each region in the longitudinal direction of the heating cylinder 31 (for example, tip region A, intermediate region B, and base region C) and output a temperature signal indicating the detected temperature to the control device 60. In other words, the band heater 39 is configured so that the temperature of each of the tip region A, intermediate region B, and base region C can be set individually. The temperature sensors 66a, 66b, and 66c then detect the temperature of each of the tip region A, intermediate region B, and base region C.

[0031] The display input device 67 is a user interface that includes a display (display device) for displaying various information to be notified to the operator, and buttons, switches, dials, etc. (input devices) for receiving input operations from the operator. The display input device 67 may also include a touch panel superimposed on the display. The display input device 67 receives input operations from the operator and outputs an input signal corresponding to the received input operation to the control device 60.

[0032] The communication IF68 is an interface for communicating with an external device (e.g., an information processing device 70) via a communication network. The control device 60, for example, transmits information to the external device via the communication IF68 and receives information from the external device via the communication IF68. The communication network consists of, for example, the Internet, a public network, a wired LAN, a wireless LAN, or a combination thereof.

[0033] [Information to be set in memory 62] Memory 62 stores the molding conditions for injection molding. The molding conditions are the operating conditions for the injection molding machine 10 that molds the molded product. In the processes shown in Figures 3 and 4, the control device 60 operates the injection molding machine 10 according to the molding conditions stored in memory 62. The molding conditions according to this embodiment include a number of parameters (for example, mold opening / closing speed, cooling time, removal time, injection speed, injection pressure, injection stroke, heater temperature, screw rotation speed, screw back pressure). However, the parameters included in the molding conditions are not limited to these.

[0034] The parameter "mold opening / closing speed" is the speed (mm / s) at which the mold 21 switches from one state (open) to the other (closed). The parameter "cooling time" is the waiting time (sec) from when the molten resin is injected into the mold 21 until the mold 21 is opened. The molten resin injected into the cavity of the mold 21 solidifies during this cooling time to form a molded product. The parameter "removal time" is the time (sec) required for the robot arm (not shown) to remove the molded product from the opened mold 21.

[0035] The parameter "injection speed" is the forward speed (mm / s) of the screw 32 during the injection process. The parameter "injection pressure" indicates the maximum pressure (MPa) applied to the screw 32 during the injection process. In other words, during the injection process, speed control based on the parameter "injection speed" takes precedence, but if the pressure indicated by the parameter "injection pressure" is reached, the speed is controlled so that the injection speed approaches the set value, within a range that does not exceed that pressure. Note that the parameters "injection speed" and "injection pressure" may be the same value throughout the entire injection stroke, or they may be different values ​​in each of the multiple regions included in the injection stroke.

[0036] The parameter "injection stroke" is the forward distance (mm) of the screw 32 during the injection process. The parameter "heater temperature" is the temperature (°C) of the band heater 39 that heats the heating cylinder 31. The parameter "screw rotation speed" is the rotation speed (rpm) of the screw 32 during the plasticization process. The parameter "screw back pressure" is the pressure (MPa) applied to the screw 32 as it rotates and retracts during the plasticization process.

[0037] [Reference waveform generation process] Figure 3 is a flowchart of the reference waveform generation process. Figure 5(A) shows an example of reference waveform data. The reference waveform generation process is a process that generates waveform data (hereinafter referred to as "reference waveform data") that shows the change in resin viscosity when molten resin is discharged with the heating cylinder 31 (nozzle 36) separated from the mold 21.

[0038] The control device 60 executes a reference waveform generation process, for example, when the molding conditions stored in the memory 62 are changed. The control device 60 may also update (overwrite) the molding conditions stored in the memory 62 with molding conditions input by the operator through the display input device 67, or molding conditions received from an external device through the communication IF 68. At the start of the reference waveform generation process, the molten resin to be discharged next into the space in front of the screw 32 of the heating cylinder 31 has been measured by the plasticization process described later, and the helical groove of the screw 32 on the tip side of the hopper 33 is filled with resin (pellets, semi-molten resin, molten resin).

[0039] First, the control device 60 deletes from memory 62 the reference waveform data stored in memory 62 during past reference waveform generation processes and the comparison waveform data stored in memory 62 during past injection control processes (S11).

[0040] Next, the control device 60 drives the nozzle touch motor 40 to separate the nozzle 36 from the mold 21 (S12). Next, the control device 60 advances the screw 32 by rotating the injection motor 37 in the forward direction according to the molding conditions "injection speed", "injection pressure", and "injection stroke" (S13). As a result, the molten resin metered in the area in front of the screw 32 in the heating cylinder 31 is discharged (purged) to the outside of the heating cylinder 31. The process in step S13 is an example of a purging process. Furthermore, the purging process and the injection process (described later) are examples of discharge processes.

[0041] Furthermore, during the purging process, the control device 60 acquires the velocity (injection velocity) of the screw 32 detected by the rotary encoder 64 and the pressure (injection pressure) detected by the load cell 65, in correspondence with the position of the screw 32 detected by the rotary encoder 64 (hereinafter referred to as "screw position") (S13). The control device 60 acquires the injection velocity and injection pressure for each control cycle throughout the entire injection stroke of the purging process. The screw position can be expressed as the distance from the forward limit (0 mm) toward the base end of the heating cylinder 31.

[0042] Next, the control device 60 measures waveform data showing the change in resin viscosity of the molten resin during the purging process based on the injection speed and injection pressure acquired in step S13, and stores the measured waveform data in the memory 62 as reference waveform data (S14). The reference waveform data shows the change in resin viscosity of the molten resin corresponding to the screw position throughout the entire injection stroke of the purging process. In step S13, the process of measuring waveform data is an example of a measurement process, and the process of storing the waveform data in the memory 62 is an example of an output process.

[0043] The viscosity of molten resin can be expressed as a function of injection speed and injection pressure, as described in Patent Documents 1 and 2. More specifically, the viscosity of molten resin is inversely proportional to the injection speed and proportional to the injection pressure. The function for measuring (calculating) the viscosity of molten resin is pre-stored in memory 62. The control device 60 can measure the viscosity of molten resin over the entire injection stroke by inputting the injection speed and injection pressure obtained at the same screw position (same control cycle) into the aforementioned function. The viscosity measured by this function is, for example, a representative value of the viscosity of molten resin present in the space in front of the screw 32 of the heating cylinder 31 when the screw 32 is at the position detected by the rotary encoder 64. However, the specific method for measuring the viscosity is not limited to the example described above, and any well-known method can be used.

[0044] Next, the control device 60 drives the nozzle touch motor 40 to bring the nozzle 36 into contact with the mold 21 (S15), and terminates the reference waveform generation process. Alternatively, the control device 60 may repeatedly execute steps S13 to S14 to measure multiple waveform data and generate reference waveform data by averaging the measured multiple waveform data.

[0045] As another example of output processing, the control device 60 may display the waveform shown by the reference waveform data on the display input device 67. Furthermore, the control device 60 may display straight lines indicating predetermined upper and lower limits of resin viscosity, for example, as shown by the dashed lines in Figure 5(A). The upper and lower limits are the permissible range of resin viscosity that allows for proper molding of the molded product. As yet another example of output processing, the control device 60 may transmit the reference waveform data to the information processing device 70 via the communication IF 68.

[0046] The operator may adjust the molding conditions based on the reference waveform data displayed on the display input device 67. For example, if a portion of the waveform shown in the reference waveform data exceeds the upper limit, the heater temperature may be lowered. As another example, if a portion of the waveform shown in the reference waveform data falls below the lower limit, the heater temperature may be increased. The control device 60 or the information processing device 70 may also change the molding conditions stored in the memory 62 based on the relationship between the reference waveform data and the upper and lower limits.

[0047] [Injection control processing] Figure 4 is a flowchart of the injection control process. Figure 5(B) shows an example of comparison waveform data. The injection control process is the process of injecting molten resin filled in the heating cylinder 31 into the cavity of the clamped mold 21 to form a molded product. The control device 60 starts the injection control process in response to a molding instruction being input, for example, through the display input device 67. The molding instruction includes, for example, the number of molded products to be molded (hereinafter referred to as "number of molded products").

[0048] At the start of the injection control process, the mold 21 is open, the nozzle 36 is in contact with the mold 21, the molten resin to be injected next is metered into the space in front of the screw 32 of the heating cylinder 31, and the helical groove of the screw 32 on the tip side of the hopper 33 is filled with resin (pellets, semi-molten resin, molten resin). Furthermore, at the start of the injection control process, the reference waveform data is already stored in the memory 62. In addition, the molding conditions stored in the memory 62 are the same as those at the time the reference waveform generation process is executed.

[0049] First, the control device 60 rotates the mold opening / closing motor 28 according to the molding condition "mold opening / closing speed" to close and clamp the mold 21 (S21). This forms a cavity inside the mold 21. The process in step S21 is an example of a mold clamping process.

[0050] Next, after the mold clamping process (S21) is completed, the control device 60 advances the screw 32 by rotating the injection motor 37 in the forward direction according to the molding conditions "injection speed", "injection pressure", and "injection stroke" (S22). As a result, the molten resin metered in the area in front of the screw 32 within the heating cylinder 31 is injected into the cavity of the mold 21. The process in step S22 is an example of the injection process (ejection process). Hereinafter, one injection process may be referred to as a "shot".

[0051] Furthermore, during the injection process, the control device 60 acquires the speed of the screw 32 (injection speed) detected by the rotary encoder 64 and the pressure (injection pressure) detected by the load cell 65, in correspondence with the screw position detected by the rotary encoder 64 (S22). The control device 60 acquires the injection speed and injection pressure for each control cycle throughout the entire injection stroke of the injection process.

[0052] Next, the control device 60 measures waveform data showing the change in resin viscosity of the molten resin during the injection process based on the injection speed and injection pressure acquired in step S22, and stores the measured waveform data in the memory 62 as comparison waveform data (S23). The comparison waveform data shows the change in resin viscosity of the molten resin corresponding to the screw position throughout the entire injection stroke of the injection process. In step S23, the process of measuring waveform data is an example of a measurement process, and the process of storing the waveform data in the memory 62 is an example of an output process.

[0053] Next, after the injection process (S22) is completed, the control device 60 rotates and retracts the screw 32 to plasticize the granular resin supplied to the heating cylinder 31 through the hopper 33, thereby metering the molten resin to be injected next into the space in front of the screw 32 in the heating cylinder 31 (S24). The process in step S24 is an example of a plasticization process.

[0054] Furthermore, after the injection process (S22) is completed, the control device 60 cools the molten resin in the cavity according to the molding condition "cooling time" in parallel with the plasticizing process (S24) (S25). As a result, the molten resin is cooled in the mold 21 and the molded product is formed. At this time, the control device 60 may circulate cooling water in the cooling water channel provided in the mold 21. The process in step S25 is an example of a cooling process.

[0055] Next, in response to the completion of both the plasticization process (S24) and the cooling process (S25) (S25: Yes), the control device 60 opens the mold 21 by rotating the mold opening / closing motor 28 according to the molding condition "mold opening / closing speed", and causes the robot arm to remove the molded product from the opened mold 21 according to the molding condition "removal time" (S26). The process in step S26 is an example of the removal process.

[0056] Next, the control device 60 determines whether the number of molded products formed in the injection control process has reached the number of products to be molded as indicated in the molding instruction (S27). If the number of molded products formed has not reached the number of products to be molded (S27: No), the control device 60 repeats the process from step S21 onwards. In other words, the control device 60 repeatedly executes the process from steps S21 to S26 until the number of molded products formed reaches the number of products to be molded.

[0057] Then, the control device 60 terminates the injection control process when the number of molded products reaches the number of molded products (S27: Yes). In other words, in the repeatedly executed steps S22 to S23, the control device 60 stores multiple comparison waveform data in the memory 62. That is, at the end of the injection control process, one reference waveform data and one or more (typically multiple) comparison waveform data measured under the same molding conditions are stored in the memory 62.

[0058] As another example of output processing, the control device 60 may display the waveform shown in the comparison waveform data on the display input device 67. The control device 60 may also display straight lines indicating predetermined upper and lower limits of resin viscosity, for example, as shown by the dashed lines in Figure 5(B). Furthermore, the control device 60 may superimpose the waveforms shown in each of the multiple comparison waveform data stored in the memory 62 onto the display input device 67. In addition, the control device 60 may superimpose the waveforms shown in the reference waveform data and the comparison waveform data stored in the memory 62 onto the display input device 67. "Superimposed display" refers to displaying multiple waveforms simultaneously with the same scale for the horizontal and vertical axes. As yet another example of output processing, the control device 60 may transmit the comparison waveform data to the information processing device 70 via the communication IF 68.

[0059] The operator may adjust the molding conditions based on the comparison waveform data displayed on the display input device 67. For example, if a portion of the waveform shown in the comparison waveform data exceeds the upper limit, the heater temperature may be lowered. As another example, if a portion of the waveform shown in the comparison waveform data falls below the lower limit, the heater temperature may be increased. The control device 60 or the information processing device 70 may also change the molding conditions stored in the memory 62 based on the relationship between the comparison waveform data and the upper and lower limits.

[0060] The reference waveform data and comparison waveform data are, for example, data showing waveforms on a two-dimensional plane with the screw position as the first axis (horizontal axis) and resin viscosity as the second axis (vertical axis), as shown in Figure 5. More specifically, the reference waveform data and comparison waveform data are a collection of plots (points) of resin viscosity for each control cycle, and are typically curves. Furthermore, the comparison waveform data differs from the reference waveform data in parts due to the influence of the shape of the mold 21.

[0061] As one example, before the leading edge of the injected molten resin enters the mold 21 (the right-hand region in Figure 5), the resin viscosity shown in the comparative waveform data is roughly the same as the resin viscosity shown in the reference waveform data. As another example, when the leading edge of the injected molten resin passes through a section with a large cross-sectional area (the passage) (the central region in Figure 5), the resin viscosity shown in the comparative waveform data is lower than the resin viscosity shown in the reference waveform data. As yet another example, when the leading edge of the injected molten resin passes through a section with a small cross-sectional area (the passage) (the left-hand region in Figure 5), the resin viscosity shown in the comparative waveform data is higher than the resin viscosity shown in the reference waveform data.

[0062] [Differential waveform display processing] Figure 6 is a flowchart of the differential waveform display process. Figure 7 is a diagram showing an example of differential waveform data. The differential waveform display process is a process that outputs (displays) differential waveform data generated based on the reference waveform data and comparison waveform data stored in memory 62. The control device 60 executes the differential waveform display process when instructed by an operator, for example, through the display input device 67. It is assumed that the reference waveform generation process shown in Figure 3 and the injection control process shown in Figure 4 have already been executed at the start of the differential waveform display process.

[0063] First, the control device 60 generates differential waveform data based on the reference waveform data stored in memory 62 and one of the multiple comparison waveform data stored in memory 62 (S31). The differential waveform data is data that shows the deviation of the comparison waveform data from the reference waveform data. As an example, the control device 60 may generate differential waveform data by subtracting the resin viscosity of the reference waveform data from the resin viscosity of the comparison waveform data at the same screw position throughout the entire injection stroke. As another example, the control device 60 may generate differential waveform data by dividing the resin viscosity of the comparison waveform data at the same screw position throughout the entire injection stroke by the resin viscosity of the reference waveform data.

[0064] Next, the control device 60 determines whether other comparison waveform data is stored in the memory 62 (S32). If the control device 60 determines that other comparison waveform data is stored in the memory 62 (S32: Yes), it generates difference waveform data using that comparison waveform data (S31). That is, the control device 60 generates multiple difference waveform data based on the reference waveform data stored in the memory 62 and each of the multiple comparison waveform data stored in the memory 62. The control device 60 may generate difference waveform data using all the comparison waveform data stored in the memory 62, or it may generate difference waveform data using only the comparison waveform data selected by the operator through the display input device 67.

[0065] Next, as shown in FIG. 7 for example, the control device 60 superimposes and displays a plurality of differential waveform data generated in step S31 that is repeatedly executed on the display input device 67 (S33). Further, the control device 60 may further display the position of the value of the reference waveform data (the straight line of "reference value" indicated by the broken line in FIG. 7) on the display input device 67. In the example of FIG. 7, the differential waveform data (solid line) generated from the comparison waveform data of the M-th shot and the differential waveform data (dashed-dotted line) generated from the comparison waveform data of the N-th shot are shown, but the number of differential waveform data to be superimposed and displayed is not limited to the example of FIG. 7. Note that M < N. The process of step S33 is an example of output processing. As another example of output processing, the control device 60 may transmit the differential waveform data to the information processing device 70 through the communication IF 68.

[0066] Then, the operator who has seen the screen displayed in step S33 may estimate the state of the mold 21 based on the plurality of differential waveform data superimposed and displayed on the display input device 67. As an example, as shown in FIG. 7(A), the operator may estimate that a part of the mold 21 has been shaved and the cross-sectional area has increased when, in the section where the comparison waveform data is below the reference value, the value obtained by subtracting the resin viscosity of the N-th shot from the resin viscosity of the M-th shot is equal to or greater than the threshold value (that is, the resin viscosity of the N-th shot has decreased from the resin viscosity of the M-th shot). As another example, as shown in FIG. 7(B), the operator may estimate that a foreign object has clogged a part of the mold 21 and the cross-sectional area has decreased when, in the section where the comparison waveform data is above the reference value, the value obtained by subtracting the resin viscosity of the M-th shot from the resin viscosity of the N-th shot is equal to or greater than the threshold value (that is, the resin viscosity of the N-th shot has increased from the resin viscosity of the M-th shot).

[0067] Furthermore, the control device 60 may estimate the state of the mold 21 based on multiple differential waveform data, as described above. As another example, the control device 60 may transmit differential waveform data to an AI server (not shown) via the communication IF 68 to estimate the state of the mold 21. These processes are examples of estimation processes. The control device 60 may then further output the state of the mold 21 estimated in the estimation process (for example, by displaying it on the display input device 67 or transmitting it to the information processing device 70 via the communication IF 68).

[0068] [Effects of the Embodiment] According to the above embodiment, by displaying (outputting) the waveform data shown in Figure 5 on the display input device 67, the operator can grasp the change in resin viscosity of the molten resin throughout the entire injection stroke. This allows for faster attainment of appropriate molding conditions.

[0069] Furthermore, by referring to the reference waveform data shown in Figure 5(A), it is possible to grasp the neutral resin viscosity transition, excluding the influence of the mold 21. On the other hand, by referring to the comparison waveform data shown in Figure 5(B), it is possible to grasp the resin viscosity transition specific to the mold 21 mounted on the clamping device 20. In the above embodiment, an example in which both reference waveform data and comparison waveform data are measured has been described, but it is also possible to measure only one of them.

[0070] Furthermore, according to the above embodiment, by displaying (outputting) the difference waveform data generated from the reference waveform data and the comparison waveform data, it is possible to extract and understand only the portion of the change in the viscosity of the molten resin that is influenced by the mold 21. This makes it possible to quickly reach appropriate molding conditions.

[0071] Furthermore, according to the above embodiment, by displaying multiple differential waveform data overlaid on each other, the state of the mold 21 can be estimated from the change in resin viscosity due to repeated injection processing. This makes it possible to easily understand the state of the mold 21, which previously could not be determined without removing it from the clamping device 20.

[0072] Furthermore, according to the above embodiment, the control device 60 estimates the state of the mold 21 from multiple differential waveform data, allowing even an inexperienced operator to appropriately understand the state of the mold 21.

[0073] [Differentiation] A modified example of the above embodiment will be described with reference to Figure 8. The present invention can be conceived as a system comprising an injection molding machine 10 and an information processing device 70 connected to the injection molding machine 10 via a communication network. The injection molding machine 10 and the information processing device 70 constituting this system may share the processing shown in Figures 3, 4, and 6.

[0074] [Configuration of the information processing device 70] Figure 8 is a hardware configuration diagram of the information processing device 70. The information processing device 70 is, for example, a tablet terminal, a smartphone, or a laptop computer. As shown in Figure 8, the information processing device 70 mainly comprises a CPU 71, memory 72, storage 73, input device 74, display 75 (display device), and communication IF 77. Each component of the information processing device 70 is connected to the communication bus 79.

[0075] The CPU 71 performs the processing described later by executing a series of instructions contained in the program 78 loaded into memory 72. Memory 72 is implemented as, for example, RAM or other volatile memory. Storage 73 is implemented as, for example, ROM, a hard disk drive, flash memory, or other non-volatile storage device. Program 78 is stored in storage 73 and is loaded into memory 72 as needed and executed by the CPU 71.

[0076] The input device 7 is an input interface that accepts input operations from the administrator of the information processing device 70, such as a keyboard or pointing device. The display 75 is an output interface that outputs (displays) information to the administrator of the information processing device 70. The communication interface 77 is a communication interface that sends and receives data to and from an external device (for example, an injection molding machine 10) via a communication network.

[0077] The program stored in the memory 62 of the injection molding machine 10 causes the control device 60 (computer) to execute some of the processes shown in Figures 3, 4, and 6. The program 78 also causes the information processing device 70 (computer) to execute other parts of the processes shown in Figures 3, 4, and 6. Examples of processes executed by program 78 are listed below, but the division of roles between the injection molding machine 10 and the information processing device 70 is not limited to these examples.

[0078] As an example, program 78 may receive the injection speed and injection pressure acquired in step S13 of Figure 3 from the injection molding machine 10 via communication IF 77 and have the information processing device 70 execute the process in step S14. As another example, program 78 may receive the injection speed and injection pressure acquired in step S22 of Figure 4 from the injection molding machine 10 via communication IF 77 and have the information processing device 70 execute the process in step S23. As yet another example, program 78 may have the information processing device 70 execute the process in Figure 6.

[0079] Furthermore, the program according to the present invention is not limited to a single program, but may be a collection of multiple programs. Also, some or all of the means implemented by the program may be implemented by hardware such as integrated circuits. Moreover, the program may be provided by being recorded on a non-transient recording medium readable by a computer. Recording mediums include, for example, hard disks, SD cards, DVDs, and servers on the Internet.

[0080] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the invention. [Explanation of Symbols]

[0081] 10…Injection molding machine, 20…Clamping device, 21…Mold, 22…Fixed mold, 23…Fixed die plate, 24…Movable mold, 25…Movable die plate, 26…Toggle link mechanism, 27…Tie bar, 28…Mold opening / closing motor, 30…Injection device, 31…Heating cylinder, 32…Screw, 33…Hopper, 34…Hopper block, 35…Resin passage, 36…Nozzle, 37…Injection motor, 38…Measuring motor, 39…Band heater, 40…Nozzle touch motor, 50…AI server, 51…Trained model, 60…Control device, 61,70…CPU, 62,72…Memory, 64…Rotary encoder, 65…Load cell, 66a,66b,66c…Temperature sensor, 67…Display input device, 68,77…Communication interface, 78…Program, 79…Communication bus

Claims

1. A mold clamping device that opens and closes the mold and clamps it, An injection device for injecting molten resin into the cavity of the clamped mold, In an injection molding machine comprising a clamping device and a control device for controlling the injection device, The injection device is, A heating cylinder whose tip moves in and out of the mold that is clamped, The heating cylinder comprises a screw that moves back and forth inside the heating cylinder, The control device is A plasticizing process is performed by rotating and retracting the screw to plasticize the resin supplied to the heating cylinder, A discharge process is performed by advancing the screw within the heating cylinder to discharge the molten resin that has been plasticized in the plasticization process, A measurement process for measuring waveform data showing the change in resin viscosity of the molten resin in the discharge process, An injection molding machine characterized by performing an output process that outputs the waveform data measured in the measurement process.

2. In the injection molding machine according to claim 1, The aforementioned discharge treatment is, With the heating cylinder separated from the mold, a purging process is performed to discharge the molten resin to the outside of the heating cylinder, The process includes an injection process in which the molten resin is injected into the cavity while the heating cylinder is connected to the mold, The control device is characterized in that, in the measurement process, it measures the waveform data in at least one of the purging process and the injection process.

3. In the injection molding machine according to claim 2, The control device is In the measurement process described above, the reference waveform data, which is the waveform data in the purging process, and the comparison waveform data, which is the waveform data in the injection process, are measured. An injection molding machine characterized in that, in the output processing, it outputs difference waveform data, which is waveform data showing the deviation of the comparison waveform data from the reference waveform data.

4. In the injection molding machine according to claim 3, Equipped with a display device that shows information, The control device is In the measurement process, the reference waveform data in the purging process and the comparison waveform data in each of the multiple injection processes performed under the same molding conditions as the purging process are measured. An injection molding machine characterized in that, in the output processing, the difference waveform data of each of the multiple comparison waveform data with respect to the reference waveform data is superimposed and displayed on the display device.

5. In the injection molding machine according to claim 3, The control device is In the measurement process, the reference waveform data in the purging process and the comparison waveform data in each of the multiple injection processes performed under the same molding conditions as the purging process are measured. Further estimation processing is performed to estimate the state of the mold based on the difference waveform data of each of the multiple comparison waveform data with respect to the reference waveform data. An injection molding machine characterized in that, in the output processing, it further outputs the state of the mold estimated in the estimation processing.

6. The injection molding machine comprises a clamping device for opening and closing and clamping the mold, and an injection device for injecting molten resin into the cavity of the clamped mold, wherein the injection device comprises a heating cylinder whose tip moves toward and away from the clamped mold, and a screw that moves back and forth inside the heating cylinder, and is connected to a computer. A plasticizing process is performed by rotating and retracting the screw to plasticize the resin supplied to the heating cylinder, A discharge process is performed by advancing the screw within the heating cylinder to discharge the molten resin that has been plasticized in the plasticization process, A measurement process for measuring waveform data showing the change in resin viscosity of the molten resin in the discharge process, A program characterized by causing the program to execute an output process that outputs the waveform data measured in the measurement process.

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