Molding machine and program

Abstract

To provide a molding machine that improves the accuracy of estimating the cause of defective products. [Solution] The molding machine is a device that injects molding material into a mold to form a molded product, and comprises a control device that controls the operation of the molding machine and a state quantity sensor that detects a plurality of state quantities indicating the operating state of the molding machine. In the process of causing the molding machine to form a molded product, the control device causes the state quantity sensor to detect a plurality of state quantities belonging to a first group and a plurality of state quantities belonging to a second group different from the first group, calculates a first MD value which is the Mahalanobis distance based on the MT method using the plurality of state quantities belonging to the first group, calculates a second MD value which is the Mahalanobis distance based on the MT method using the plurality of state quantities belonging to the second group, and outputs the calculated first MD value and second MD value.

Description

Technical Field

[0001] The present invention relates to a molding machine and a program capable of determining the quality of molded products.

Background Art

[0002] Conventionally, in a molding machine that injects a molding material into a mold to form a molded product, using an MD value calculated from a plurality of state quantities (for example, injection speed, injection pressure, holding pressure, retreat speed, etc.) detected by sensors, a method for determining whether a molded product is a good product or a defective product (hereinafter referred to as "good product determination") is known (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] A molding machine forms a molded product through a plurality of processes (for example, a metering process, an injection process, a holding pressure process, etc.). However, in Patent Documents 1 to 3, since good product determination is performed using a single MD value, there is a problem that it is difficult to identify the cause of the occurrence of defective products.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a molding machine with improved accuracy in estimating the cause of defective products.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a molding machine for injecting a molding material into a mold to form a molded product, comprising a control device for controlling the operation of the molding machine and a state quantity sensor for detecting a plurality of state quantities indicating the operating state of the molding machine, wherein, in the process of causing the molding machine to form the molded product, the control device causes the state quantity sensor to detect a plurality of state quantities belonging to a first group and a plurality of state quantities belonging to a second group different from the first group, calculates a first MD value which is a Mahalanobis distance based on the MT method using the plurality of state quantities belonging to the first group, calculates a second MD value which is a Mahalanobis distance based on the MT method using the plurality of state quantities belonging to the second group, and outputs the calculated first MD value and second MD value. [Effects of the Invention]

[0007] According to the present invention, a molding machine can be obtained that improves the accuracy of estimating the cause of defective products. [Brief explanation of the drawing]

[0008] [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 molding process. [Figure 4] This is a flowchart for the process of determining whether a product is good or bad. [Figure 5] This is an example of state data and MD values ​​stored in memory. [Figure 6] This is an example of a screen showing the MD value plot with points up to the first M1 measurement plotted. [Figure 7] This is an example of a screen showing the MD value plot with points up to the M2 trial plotted. [Figure 8] This is an example of a screen showing the MD value plot with points up to the 3rd M3. [Figure 9] Figure 8 shows an example of the MD value plot screen when the first threshold is changed. [Figure 10]It is a hardware configuration diagram of an information processing device.

Embodiment for Carrying Out the Invention

[0009] Hereinafter, the injection molding machine 10 according to the present invention will be described based on the drawings. The injection molding machine 10 is a molding machine that injects molten resin (molding material) measured in a mold to form a molded product. However, the specific example of the molding machine is not limited to the injection molding machine 10, and it may also be a die-casting machine that injects molten metal (molding material) into a mold to form a molded product.

[0010] [Configuration of Injection Molding Machine 10] FIG. 1 is a side view of the injection molding machine 10 according to the present embodiment. FIG. 2 is a hardware configuration diagram of the injection molding machine 10. As shown in FIGS. 1 and 2, the injection molding machine 10 mainly includes a mold clamping device 20, an injection device 30, and a control device 60.

[0011] The mold clamping device 20 opens and closes and clamps the mold 21. Specifically, the mold clamping device 20 mainly includes 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.

[0012] The movable die plate 25 moves in the left-right direction along the tie bar 27 when the driving force of the mold opening and closing motor 28 is transmitted through the toggle link mechanism 26. When the movable die plate 25 moves to the left, the fixed-side mold 22 and the movable-side mold 24 are separated. On the other hand, when the movable die plate 25 moves to the right, the fixed-side mold 22 and the movable-side mold 24 come into contact with each other, and a cavity (internal space) is formed inside the mold 21. Then, when a pressure in the direction of moving the movable die plate 25 to the right is further applied, the fixed-side mold 22 and the movable-side mold 24 are clamped.

[0013] The injection device 30 plasticizes, measures, and injects the molding material. The injection device 30 according to the present embodiment is arranged to face the mold clamping device 20 in the horizontal direction (to the right of the mold clamping device 20). The injection device 30 mainly includes a heating cylinder 31, a screw 32, a hopper 33, and a hopper block 34.

[0014] 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. The band heater 39 is a so - called "thermocouple" that generates heat by receiving power supply from the control device 60, for example.

[0015] 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 along the axial direction from the nozzle 36.

[0016] 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 3 (hereinafter referred to as a "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 in the left - right direction (hereinafter referred to as "forward and backward") and rotate of the injection molding machine 10. Also, 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.

[0017] The screw 32 moves forward and backward when the driving force of the injection motor 37 is transmitted to it, and rotates when the driving force of the metering motor 38 is transmitted to it. More specifically, when the injection motor 37 is rotated forward, the screw 32 moves (advance) toward the tip of the heating cylinder 31 (i.e., the nozzle 36). On the other hand, when the injection motor 37 is rotated backward, the screw 32 moves (reverse) toward the base end of the heating cylinder 31 (i.e., the side opposite the nozzle 36).

[0018] 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).

[0019] 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.

[0020] 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. As a result, the molten resin filled into the resin passage 35 in front of the screw 32 is injected into the cavity of the mold 21 through the nozzle 36.

[0021] 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 molding process, which will be described later with reference to Figure 3.

[0022] [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.

[0023] 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).

[0024] 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, and communication interface (IF) 68 based on various signals output from the rotary encoder 64, load cell 65 (pressure sensor), temperature sensor 66, and display input device 67.

[0025] The mold opening / closing motor 28, the injection motor 37, and the metering motor 38 are servo motors that generate driving force to open and close the mold 21, driving force to move the screw 32 forward and backward, and driving force to rotate the screw 32, respectively, according to the control of a servo amplifier (not shown).

[0026] 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.

[0027] 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.

[0028] The temperature sensor 66 detects the temperature of the heating cylinder 31 and outputs a temperature signal indicating the detected temperature to the control device 60. The control device 60 then determines the temperature of the heating cylinder 31 based on the temperature signal output from the temperature sensor 66.

[0029] 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.

[0030] The communication IF68 is an interface for communicating with an external device (for example, the information processing device 70 shown in Figure 10) via a communication network. The communication network consists of, for example, the Internet, a public network, a wired LAN, a wireless LAN, or a combination thereof. The control device 60 transmits data to the external device via the communication IF68 and receives data from the external device via the communication IF68.

[0031] [Explanation of conditional data] Memory 62 stores condition data. Condition data is data indicating the execution conditions for the molding process described later (hereinafter referred to as "molding conditions"). In the molding process shown in Figure 3, the control device 60 operates the injection molding machine 10 according to the condition data stored in the condition storage area of ​​memory 62. The condition data according to this embodiment includes multiple items (for example, injection speed, injection pressure, injection stroke, holding pressure time, holding pressure, metering speed, rotation speed, screw back pressure, heater temperature). However, the items included in the condition data are not limited to these.

[0032] The item "Injection Speed" is the forward speed (mm / s) of the screw 32 during the injection process. The item "Injection Pressure" indicates the maximum pressure (MPa) applied to the screw 32 during the injection process. The item "Injection Stroke" is the forward distance (mm) of the screw 32 during the injection process. In other words, during the injection process (S12), the control device 60 drives the injection motor 37 so that the forward speed of the screw 32 approaches the item "Injection Speed" and the pressure applied to the screw 32 does not exceed the item "Injection Pressure," and stops the screw 32 at a point where it has advanced by the item "Injection Stroke."

[0033] The item "Holding time" indicates the execution time of the holding process. The item "Holding pressure" indicates the maximum pressure (MPa) applied to the screw 32 during the holding process. In other words, during the holding process (S13), the control device 60 drives the injection motor 37 so that the pressure applied to the screw 32 does not exceed the item "Holding pressure" until the "Holding time" has elapsed.

[0034] The item "metering speed" is the retraction speed (mm / s) of the screw 32 during the metering process. The item "rotational speed" is the rotational speed (rpm) of the screw 32 during the metering process. The item "screw back pressure" is the pressure (MPa) applied to the screw 32 during the metering process. In other words, the control device 60 drives the injection motor 37 and the metering motor 38 during the metering process (S14) so ​​that the retraction speed of the screw 32 approaches the item "metering speed", the rotational speed of the screw 32 approaches the item "rotational speed", and the back pressure applied to the screw 32 does not exceed the item "screw back pressure".

[0035] The item "heater temperature" is the temperature (°C) of the heating cylinder 31. In other words, the control device 60 controls the power supply to the band heater 39 so that the temperature of the heating cylinder 31 approaches the item "heater temperature" during the molding process. More specifically, when the temperature of the heating cylinder 31 is lower than the item "heater temperature", the control device 60 increases the power supply time to the band heater 39 as the temperature of the heating cylinder 31 decreases, and decreases the power supply time to the band heater 39 as the temperature of the heating cylinder 31 increases.

[0036] The control device 60 stores new condition data in the condition storage area according to instructions from the operator via the display input device 67, or according to instructions from an external device (e.g., an information processing device 70) via the communication IF 68. The control device 60 also modifies the condition data stored in the condition storage area (i.e., changes the value of each item) according to instructions from the operator via the display input device 67, or according to instructions from an external device (e.g., an information processing device 70) via the communication IF 68. The display input device 67 and the communication IF 68 are interfaces for instructing the modification of condition data.

[0037] [Molding process] Figure 3 is a flowchart of the molding process. The molding process involves injecting molten resin, which has been filled into the heating cylinder 31, into the cavity of the clamped mold 21, in accordance with the condition data stored in the condition memory area, thereby forming a molded product. At the start of the molding process, the mold 21 is open, 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, resin in the process of plasticization, molten resin).

[0038] First, the control device 60 rotates the mold opening / closing motor 28 to close and clamp the mold 21 (S11). This creates a cavity inside the mold 21. Step S11 is an example of the mold clamping process.

[0039] Next, after the mold clamping process (S11) 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" (S12). 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. Step S12 is an example of the injection process.

[0040] Next, after the injection process (S12) is completed, the control device 60 applies pressure to the resin injected into the mold 21 by rotating the injection motor 37 according to the molding conditions "holding time" and "holding pressure" (S13). Step S13 is an example of the holding process.

[0041] Next, after the holding pressure process (S13) is completed, the control device 60 rotates the injection motor 37 and the metering motor 38 according to the molding conditions "metering speed", "rotation speed", and "screw back pressure", thereby rotating and retracting the screw 32 (S14). As a result, the granular resin supplied to the heating cylinder 31 through the hopper 33 is plasticized and metered into the space in front of the screw 32 in the heating cylinder 31. Step S14 is an example of the metering process.

[0042] Next, after the weighing process (S14) is completed, the control device 60 rotates the mold opening / closing motor 28 to open the mold 21, and causes a robot arm (not shown) to remove the molded product from the opened mold 21 (S15). Step S15 is an example of the removal process.

[0043] Furthermore, the control device 60 continuously controls the power supply to the band heater 39 so that the temperature of the heating cylinder 31 approaches the item “heater temperature” during the execution of the molding process.

[0044] Furthermore, the control device 60 acquires state data (monitor data) during the execution of the molding process. State data is data that includes multiple state quantities indicating the operating state of the injection molding machine 10 performing the molding process. The state quantities include, for example, multiple items (e.g., screw forward speed, maximum pressure during injection, actual stroke, maximum pressure during holding pressure, screw retraction speed, maximum back pressure during metering, energization rate). However, the items included in the state data are not limited to these.

[0045] The item “Screw forward speed” is the forward speed of the screw 32 detected by the rotary encoder 64 during the injection process (S12) (for example, the forward speed at a specific position). The item “Maximum pressure during injection” is the maximum value of the pressure detected by the load cell 65 during the injection process (S12). The item “Actual stroke” is the forward distance of the screw 32 detected by the rotary encoder 64 during the injection process (S12) and the holding pressure process (S13).

[0046] The item “Maximum pressure during holding pressure” is the maximum pressure detected by the load cell 65 during the holding pressure process (S13). The item “Energization rate” is the ratio of the power supply time to the band heater 39 to the execution time of the molding process.

[0047] The item “Screw retraction speed” is the retraction speed of the screw 32 detected by the rotary encoder 64 in the metering process (S14) (for example, the retraction speed at a specific position). The item “Maximum back pressure during metering” is the maximum value of the pressure detected by the load cell 65 in the metering process (S14).

[0048] The rotary encoder 64, which detects the items “screw forward speed,” “actual stroke,” and “screw retraction speed,” the load cell 65, which detects the items “maximum pressure during injection,” “maximum pressure during holding,” and “maximum back pressure during metering,” and the control device 60, which detects the item “energy rate,” are examples of state quantity sensors that detect state quantities of the injection molding machine 10. However, specific examples of state quantity sensors are not limited to these.

[0049] [Good product judgment process] Figure 4 is a flowchart of the good product determination process. Figure 5 shows an example of the state data and MD values ​​stored in memory 62. The good product determination process is the process of determining whether the molded product formed in the molding process is a good product or a defective product. Note that in Figure 5, only a portion of the state quantities included in the state data (screw forward speed, maximum pressure during injection, screw retraction speed, and maximum back pressure during metering) are illustrated.

[0050] First, the control device 60 executes the molding process according to the condition data stored in the condition memory area (S21). Then, as shown in Figure 5, the control device 60 stores the state data acquired in the molding process of step S21 in the memory 62 in association with the number of times the molding process is executed i. Note that the state quantities "screw forward speed V1i" and "maximum pressure P1i during injection" acquired in the injection process are examples of state quantities belonging to the first group, and the state quantities "screw retraction speed V2i" and "maximum back pressure P2i during metering" acquired in the metering process are examples of state quantities belonging to the second group. Note that the number i at the end of the symbol indicating the state quantity is an integer (i=1, 2, 3, ...) indicating the number of times the corresponding molding process is executed.

[0051] Next, the control device 60 calculates the MD value MD1i (first MD value) using multiple state variables belonging to the first group, "screw forward speed V1i" and "maximum pressure P1i during injection," and calculates the MD value MD2i (second MD value) using multiple state variables belonging to the second group, "screw retraction speed V2i" and "maximum back pressure P2i during metering" (S22). Then, as shown in Figure 5, the control device 60 stores the calculated MD values ​​MD1i and MD2i in the memory 62, associating them with the corresponding state data.

[0052] The MD value is the Mahalanobis distance based on the MT method. The method for calculating the MD value is already well known, so a detailed explanation will be omitted, but it can be calculated as follows, for example. The control device 60 can calculate the MD value using, for example, equation 1 below. The state variables xi and yi are state variables acquired in step S21. The mean values ​​μx and μy are the mean values ​​of multiple state variables x and y acquired in advance. Inverse covariance matrix Σ -1 is the inverse matrix of the variance-covariance matrix Σ of multiple state variables x and y obtained in advance as samples. k is the number of items (2 in this embodiment).

[0053]

number

[0054] The operator, for example, has the injection molding machine 10 perform a molding process, and if the molded product formed in this process is judged to be a good product by visual inspection, the operator takes samples of state quantities x and y. By repeating this process, multiple samples of state quantities x and y can be taken. The control device 60 then averages the multiple sampled state quantities x and y and stores the average values ​​μx and μy in the memory 62. The control device 60 also calculates a variance-covariance matrix Σ from the multiple sampled state quantities x and y, and its inverse matrix Σ -1 This is stored in memory 62. Note that, in order to ensure the accuracy required for good product determination, the number of state variables x and y needed to calculate the average values ​​μx and μy is approximately 5 to 10, and the inverse covariance matrix Σ -1 The number of state variables x and y required to calculate this is approximately 100 to 150.

[0055] In Equation 1 used to calculate the MD value MD1, for example, the state variable x corresponds to the screw forward speed V1, and the state variable y corresponds to the maximum pressure P1 at injection. Similarly, in Equation 1 used to calculate the MD value MD2, for example, the state variable x corresponds to the screw retraction speed V2, and the state variable y corresponds to the maximum pressure P2 at metering. In other words, the memory 62 according to this embodiment contains the average value μx of the state variable x, the average value μy of the state variable y, and the inverse covariance matrix Σ of the state variables x and y. -1 However, two types of each are stored. Note that the number of state variables required to calculate the MD values ​​MD1 and MD2 is not limited to two (x, y), but can be three or more. The number of state variables required to calculate the MD values ​​MD1 and MD2 can be the same or different.

[0056] Next, the control device 60 compares the MD values ​​MD1 and MD2 calculated in step S22 with the threshold values ​​Th1 and Th2 stored in the memory 62 (S23). The threshold value Th1 (first threshold) is set, for example, to the maximum value of MD1 at which the molded product can be evaluated as a good product. The threshold value Th2 (second threshold) is set, for example, to the maximum value of MD2 at which the molded product can be evaluated as a good product. The control device 60 can also update the threshold values ​​Th1 and Th2 stored in the memory 62 according to the operator's operation on the display input device 67.

[0057] Then, if, for example, the MD value MD1 is greater than or equal to the threshold Th1, or the MD value MD2 is greater than or equal to the threshold Th2 (S23:Yes), the control device 60 determines that the molded product formed in step S21 is a defective product and notifies the display input device 67 of the occurrence of a defective product (S24). On the other hand, if, for example, the MD value MD1 is less than the threshold Th1 and the MD value MD2 is less than the threshold Th2 (S23:Yes), the control device 60 determines that the molded product formed in step S21 is a good product and skips the process in step S24.

[0058] Next, the control device 60 determines whether or not to continue the molding process (S25). The control device 60 can determine whether or not to continue the molding process based, for example, whether or not the number of molded products has reached a predetermined number, or based on the operator's operation on the display input device 67. Next, if the control device 60 determines to continue the molding process (S25: Yes), it determines whether or not the condition data in the condition storage area has been changed since the execution of the previous step S21 (S26).

[0059] Then, if the control device 60 determines that the condition data has changed (S26: Yes), it executes the molding process N (N=5~10) times to recalculate the average values ​​μx and μy, and updates the average values ​​μx and μy stored in memory 62 (S27). The method for calculating the new average values ​​μx and μy is as described above. Meanwhile, in step S27, the control device 60 calculates the inverse covariance matrix Σ -1 The values ​​are not updated. Next, the control device 60 executes the processes from step S21 onwards using the updated average values ​​μx and μy. On the other hand, if the control device 60 determines that the condition data has not been changed (S26: No), it skips the process in step S27 and executes the processes from step S21 onwards.

[0060] [MD Value Plot Screen] Figure 6 shows an example of the MD value plot screen with points plotted up to the first M1. Figure 7 shows an example of the MD value plot screen with points plotted up to the second M2. Figure 8 shows an example of the MD value plot screen with points plotted up to the third M3. Figure 9 shows an example of the MD value plot screen when the first threshold Th1 is changed from Figure 8.

[0061] The control device 60 can display the MD value plot screen on the display input device 67. For example, the control device 60 may display the MD value plot screen on the display input device 67 along with the processing of steps S23 to S24, or in lieu of the processing of steps S23 to S24. As another example, the control device 60 may display the MD value plot screen on the display input device 67 when an instruction from an operator to display the MD value plot screen is input to the display input device 67. As shown in Figures 6 to 9, the MD value plot screen includes, for example, a plot area, a slider bar, text boxes for entering thresholds Th1 and Th2, and an [Update] icon.

[0062] The plotting area is a two-dimensional plane with the MD value MD1 as the horizontal axis (first axis) and the MD value MD2 as the vertical axis (second axis). The first and second axes are not limited to the above example, as long as they are orthogonal to each other. The control device 60 plots points representing the combination of MD values ​​(MD1i, MD2i) calculated in step S22 in the plotting area. That is, the number of points plotted in the plotting area increases as the number of molding processes increases. The control device 60 also displays an ellipse (dashed line) in the plotting area that passes through the threshold Th1 on the vertical axis and the threshold Th2 on the horizontal axis and includes the origin of the plotting area.

[0063] Furthermore, the control device 60 may, for example, instead of step S23, determine that the molded product corresponding to the points plotted inside the ellipse is a good product, and the molded product corresponding to the points plotted outside the ellipse is a defective product. Alternatively, an operator viewing the MD value plot screen may perform the good product determination. In addition, the further a plotted point is from the origin, the higher the degree of defect of the corresponding molded product may be determined.

[0064] The slider bar is a part that the operator drags left or right to adjust the number of points plotted in the plot area. In other words, points representing the MD values ​​(MD1, MD2) for the 1st to Mth molding processes are plotted in the plot area according to the position of the slider bar operated by the operator. The value of M (an integer) decreases as the slider bar is dragged to the left and increases as the slider bar is dragged to the right. That is, as shown in Figures 6 to 8, the control device 60 increases or decreases the number of points displayed in the plot area (i.e., the value of M) according to the operator's operation on the display input device 67. Note that, for example, if the MD value plot screen is updated in real time during the process of repeating the molding process, the slider bar may be omitted.

[0065] As an example, as shown in Figures 6 and 7, if the position of the points plotted in the plotting area moves upward during the M1 to M2 molding processes, it can be inferred that the defective products are being molded due to a problem in the weighing process. Furthermore, if the position of the plotted points moves gradually, it can be inferred that the cause of the defective products is a gradual deviation from the ideal state for molding good products, such as a decrease in the temperature of the heating cylinder 31 due to low ambient temperature.

[0066] As another example, as shown in Figures 7 and 8, if the position of the points plotted in the plotting area moves to the right during the M2 to M3 molding processes, it can be inferred that the cause of the defective product is in the injection process. Furthermore, if the position of the plotted points moves rapidly, it can be inferred that the cause of the defective product is a sudden deviation from the ideal state for molding good products, such as damage to the mold 21.

[0067] The text boxes display the threshold values ​​Th1 and Th2 stored in memory 62. Furthermore, the threshold values ​​Th1 and Th2 in the text boxes are configured to be changeable by the operator via the display input device 67. When the control device 60 receives an operator's input via the display input device 67, pressing the [Update] icon, it overwrites (updates) the threshold values ​​Th1 and Th2 stored in memory 62 with the values ​​entered in the text boxes. The control device 60 also changes the shape and size of the ellipse in the plot area based on the updated threshold values ​​Th1 and Th2, as shown in Figure 9.

[0068] [Effects of the Embodiment] According to the above embodiment, by outputting multiple MD values ​​calculated using state variables for each group, it becomes easier to estimate the cause of defective products. In other words, the accuracy of estimating the cause of defective products molded by the injection molding machine 10 is improved. Note that the number of MD values ​​to be output (i.e., groups of state variables) is not limited to two, but may be three or more. Also, the same state variable may belong to multiple groups.

[0069] Furthermore, "outputting MD values ​​MD1 and MD2" may refer to, for example, displaying an MD value plot screen on the display input device 67, displaying the MD values ​​MD1 and MD2 as numerical values ​​on the display input device 67, or transmitting the MD values ​​MD1 and MD2 to an external device via the communication I / F 68.

[0070] Furthermore, according to the above embodiment, by grouping the state quantities obtained for each molding process into the same group, it becomes easier to estimate which process caused the molding of a defective product. However, the process for calculating the MD value is not limited to the injection process or the metering process. Also, the method of grouping the state quantities is not limited to the example described above. As another example, the state quantities may be grouped by unit (e.g., mm / s, MPa).

[0071] Furthermore, according to the above embodiment, plotting points indicating MD values ​​(MD1, MD2) on a two-dimensional plane makes it easier for the operator to intuitively recognize the state of the molded product (good / defective, cause of defect). If there are three MD values, points indicating the three MD values ​​(MD1, MD2, MD3) may be plotted in a three-dimensional space that the operator can rotate through via the display input device 67. Moreover, if there are three or more MD values, the operator may be allowed to select the MD value for each axis.

[0072] Furthermore, according to the above embodiment, by displaying an ellipse indicating the boundary between good and defective products in the plot area, good product determination can be performed more intuitively. In addition, according to the above embodiment, by making the thresholds Th1 and Th2 changeable, the operator can change the thresholds Th1 and Th2 according to the type of molded product and the required accuracy.

[0073] [Configuration of the information processing device 70] Figure 10 is a hardware configuration diagram of an 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 10, the information processing device 70 mainly comprises a CPU 71, memory 72, storage 73, input device 74, display 75 (display device), and communication I / F 77. Each component of the information processing device 70 is connected to a communication bus 79.

[0074] 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.

[0075] The input device 74 is an input interface that accepts input operations from the operator 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 operator of the information processing device 70. The camera 56 is an imaging device that captures images of the surroundings to generate images (still images, moving images) and stores the image data representing the generated images in the storage 73. 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.

[0076] Program 78 causes the information processing device 70 (computer) to execute a part of the processing performed by the control device 60 in the above embodiment. For example, program 78 may receive the state quantity detected in step S21 from the injection molding machine 10 via the communication I / F 77 and execute the processing in steps S22 to S24. Alternatively, program 78 may display an MD value plot screen on the display 75. As another example, when program 78 receives an operator operation to change the condition data via the input device 74, it may transmit the changed condition data to the injection molding machine 10 via the communication I / F 77.

[0077] 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.

[0078] 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]

[0079] 10…Injection molding machine, 20…Clamping device, 21…Mold, 22…Fixed side mold, 23…Fixed die plate, 24…Movable side 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, 60…Control device, 61,71…CPU, 62,72…Memory, 64…Rotary encoder, 65…Load cell, 66…Temperature sensor, 67…Display input device, 68,77…Communication interface, 70…Information processing device, 73…Storage, 74…Input device, 75…Display, 78…Program

Claims

1. In a molding machine that injects molding material into a mold to form a molded product, A control device for controlling the operation of the molding machine, The system includes a state quantity sensor that detects a plurality of state quantities indicating the operating state of the molding machine, The control device is In the process of forming the molded product using the molding machine, the state quantity sensor is made to detect a plurality of state quantities belonging to the first group and a plurality of state quantities belonging to the second group, which are different from the first group. Using the multiple state variables belonging to the first group, the first MD value, which is the Mahalanobis distance based on the MT method, is calculated. Using the multiple state variables belonging to the second group, the second MD value, which is the Mahalanobis distance based on the MT method, is calculated. A molding machine characterized by outputting the calculated first MD value and the second MD value.

2. In the molding machine according to claim 1, The molding machine described above is A heating cylinder whose tip communicates with 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 metering step in which the molding material supplied to the heating cylinder is metered into the region of the heating cylinder in front of the screw by rotating and retracting the screw within the heating cylinder, An injection step in which the molding material measured in the metering step is injected into the mold by advancing the screw within the heating cylinder, A molding process is performed which includes a holding pressure step in which pressure is applied to the screw in a direction that causes it to move forward, thereby holding the molding material injected in the injection step. In one of the metering step, the injection step, and the holding pressure step, a plurality of state quantities detected by the state quantity sensor are assigned to a first group. A molding machine characterized in that, in one of the metering step, the injection step, and the holding pressure step, a plurality of state quantities detected by the state quantity sensor are assigned to a first group.

3. In the molding machine according to claim 2, It also includes a display device for showing information, The control device is The display device displays a two-dimensional plane in which the first MD value is the first axis and the second MD value is the second axis orthogonal to the first axis. A molding machine characterized by plotting points on the two-dimensional plane that represent combinations of the first MD value and the second MD value calculated in the molding process.

4. In the molding machine according to claim 3, The control device is The molded product corresponding to a point plotted inside an ellipse that passes through the first threshold on the first axis and the second threshold on the second axis and includes the origin of the two-dimensional plane is determined to be a good product. A molding machine characterized by determining that the molded product corresponding to a point plotted outside the ellipse is a defective product.

5. In the molding machine according to claim 4, It is further equipped with an input device that receives input from the operator, The molding machine is characterized in that the control device changes the ellipse on the two-dimensional plane according to the first threshold and the second threshold input to the input device by the operator.

6. In the molding machine according to claim 2, The control device is The molding process is performed according to the molding conditions. The inverse covariance matrix Σ of the state variables x, y, ... obtained in the molding process, the average values ​​μx, μy, ... of the state variables obtained in advance as samples, and the state variables x, y, ... obtained in advance as samples. －１ Substitute this into formula 1 below to calculate the MD value, A molding machine characterized by updating the average values ​​μx, μx, ... based on the state quantities x, y, ... obtained in N (where N is an integer of 2 or more) molding processes performed after the molding conditions have been changed. [Math 1]

7. On the computer, In the process of having a molding machine form a molded product, a plurality of state quantities indicating the operating state of the molding machine are obtained from the molding machine. Using a plurality of state quantities belonging to the first group from among the plurality of state quantities obtained from the molding machine, a first MD value, which is the Mahalanobis distance based on the MT method, is calculated. Using multiple state variables belonging to a second group different from the first group, the second MD value, which is the Mahalanobis distance based on the MT method, is calculated. A program characterized by outputting the calculated first MD value and the second MD value.

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