JP2015033793A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine which allows accurate determination of the timing of replacement of a check valve, independently of the viscosity of a resin.SOLUTION: In a storage section of a controller 1, the relationship between the viscosity of a molten resin stored in the tip part of a heating cylinder 21 and the limit value of the injection speed at which back flow does not occur when a specified injection pressure is applied to the molten resin by using an injection device appropriate in the clearance between the inner surface of the heating cylinder 21 and the outer surface of a screw 23. In response to an instruction of an operator or automatically at predetermined specified timing, measurement of the viscosity of a molten resin stored in the tip part of the heating cylinder 21 and measurement of the injection speed are carried out, and the timing of replacement of a check valve is determined by comparing the measurements with the viscosity of the molten resin and the limit value of the injection speed stored in the storage section.

Description

  The present invention relates to an in-line screw type injection molding machine, and more particularly to a technique for automatically determining the replacement time of a backflow prevention valve provided in a screw.

  The screw of an in-line screw type injection molding machine is generally provided with a backflow prevention valve for preventing the molten resin stored in the heating cylinder from flowing backward to the rear side of the screw head during injection. .

  The function of the check valve provided in the screw will be described with reference to FIG. In FIG. 9, reference numeral 51 denotes a heating cylinder, reference numeral 52 denotes a screw disposed in the heating cylinder 51 so as to be able to rotate and move forward and backward, and reference numeral 57 denotes a backflow prevention valve. A band heater (not shown) is wound around the outer periphery of the heating cylinder 51 to heat the inside of the heating cylinder 51 at a predetermined temperature. The screw 52 includes a screw main body 53 having a screw portion formed on the outer periphery and a screw head 54 attached to the front end portion of the screw main body 53. The backflow prevention valve 57 is loosely inserted between the screw main body 53 and the screw head 54, and can move by a predetermined amount in the axial direction of the screw 52 while being in contact with the inner peripheral surface of the heating cylinder 51. It consists of a check ring 55 that rotates integrally with the screw 52, and a check sheet 56 that is sandwiched between the front end surface of the screw body 53 and the screw head 54. A groove-shaped resin passage 54 a is formed in the loose insertion portion of the check ring 55 in the screw head 54.

  In the configuration shown in FIG. 9, during the weighing process, the screw 52 is rotationally driven in a predetermined direction by a driving force of a not-shown measuring servo motor. Thus, the pellet-shaped raw material resin supplied to the rear side of the screw 52 is transferred forward by the screw feeding action of the screw 52 while being kneaded and plasticized. At this time, as shown in FIG. 9A, the check ring 55 is separated from the check sheet 56 by the pressure of the resin transferred forward, and the molten resin is separated from the check ring 55 and the check sheet 56. And a resin passage 54 a formed between the screw head 54 and the check ring 55, and sent to the front side of the screw head 54. Then, the screw 52 moves backward under the pressure of the molten resin sent to the front side of the screw head 54. At this time, the screw 52 is given a predetermined backward resistance (back pressure) by the driving force of an injection servo motor (not shown) that is driven and controlled by pressure feedback control, and is thereby stored in the front side of the screw head 54. A predetermined pressure is applied to the molten resin.

  After the completion of the weighing process, the process proceeds to the injection process. The injection process includes a primary injection process and a pressure holding process. In the primary injection process, the screw 52 is driven forward by the driving force of the injection servo motor driven and controlled by speed feedback control, and the molten resin stored in the front side of the screw head 54 in the metering process is injected into the mold. -Filled. At this time, the check ring 55 is retracted by the pressure accompanying the injection operation of the molten resin located in front of the screw head 54, and is in close contact with the check sheet 56 as shown in FIG. Thereby, the reverse flow (back flow) of the molten resin to the rear side of the screw head 54 is prevented. In the pressure holding process following the primary injection process, the driving force (holding pressure) of the injection servomotor that is driven and controlled by pressure feedback control is added to the screw 52. Thereby, an amount of molten resin corresponding to the cooling shrinkage of the resin in the mold is replenished in the mold. Also in this pressure holding process, the check ring 55 receives the pressure in the backward direction, and the check ring 55 is maintained in a state of being in close contact with the check sheet 56.

  By the way, the wear of the check ring 55 progresses with time with the operation of the injection molding machine. When the wear proceeds to a certain extent, the clearance between the inner surface of the heating cylinder 51 and the check ring 55 becomes excessive, and a backflow occurs during filling. Even if a backflow occurs, if the degree is small, it is often not reflected in the appearance of the molded product, so it is difficult for the operator to notice that a backflow has occurred, and back up to the extent that a short shot occurs in the molded product. It is not uncommon for an operator to notice for the first time when the flow amount increases.

  In order to prevent such a problem, the applicant of the present application first monitors the measured injection speed data in the pressure-holding process, and if the time during which the measured injection speed data maintains a substantially constant speed exceeds a predetermined time, It has been determined that a backflow has occurred in the prevention valve, and an injection molding machine that automatically displays on the display screen that the backflow prevention valve has reached the replacement time has been proposed (see, for example, the abstract of Patent Document 1). ). According to the present invention, since it is possible to notify the operator that the backflow prevention valve has reached the replacement time, it is possible to prevent the production of a molded product with insufficient quality, and to prevent unnecessary replacement of the backflow prevention valve. The operating rate of the molding machine can be increased.

Japanese Patent No. 5199639

  However, since the invention described in Patent Document 1 is configured to determine the presence or absence of backflow by monitoring measured injection speed data during the pressure-holding process, the backflow is applied to resin materials having a medium or higher resin viscosity. Although it is possible to accurately determine the presence or absence of backflow, for resin materials with low resin viscosity, backflow is likely to occur even when wear of the backflow prevention valve is minimal, so accurately determine when to replace the backflow prevention valve. It turned out to be difficult.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to accurately determine that the backflow prevention valve has reached the replacement time regardless of the resin viscosity level. Is to provide a simple injection molding machine.

In order to achieve the above-mentioned object, the present invention includes a screw housed in a heating cylinder so as to be rotatable and capable of moving forward and backward, a backflow prevention valve attached to the screw, and a controller for controlling the drive of the screw. A metering step of rotating the screw to store a predetermined amount of molten resin at the tip of the heating cylinder, and driving the screw forward after the metering step to store it at the tip of the heating cylinder. In an in-line screw type injection molding machine that continuously manufactures a molded product of a predetermined shape by repeating the injection process of injecting the molten resin into the mold cavity, the storage unit of the controller includes the heating unit wherein the viscosity of the molten resin is stored in the distal end portion of the cylinder, the inner surface of the heating cylinder of the tip the heating cylinder to the molten resin that has been stored in unit subscriptions The clearance between the outer surface when the applying a predetermined pressure by using an appropriate injection device, the correlation is stored in the limit value of the forward speed of the screw does not cause backflow, the controller, the operator In response to an instruction or automatically at a predetermined timing set in advance, the viscosity of the molten resin stored at the tip of the heating cylinder and the measurement of the injection speed are measured, and these measured values are stored in the storage unit. In comparison with the limit values of the viscosity of the molten resin and the forward speed of the screw stored in the table, it is determined whether or not the backflow prevention valve has reached the replacement time.

  Various resin materials having different viscosities at the time of melting are used for manufacturing molded articles. When the operation of the injection molding machine is started, the weighing conditions and the injection conditions suitable for the resin material to be used are set in the injection molding machine, and the automatic operation for continuously producing the molded product is executed. The automatic operation of the injection molding machine is performed by repeating the resin material measurement process and the injection process of the molten resin plasticized in the measurement process. By the way, when the automatic operation is performed for a long period of time, the check valve is worn, and the clearance between the inner surface of the heating cylinder and the outer surface of the check valve increases with time. Therefore, when the injection pressure at the time of primary injection and the holding pressure at the holding pressure are received, the molten resin in the heating cylinder easily flows backward to the end side of the heating cylinder beyond the backflow prevention valve. This phenomenon is called backflow. If backflow occurs, molding defects such as sink marks and insufficient weight will occur in the molded product and the yield of non-defective products will decrease.Therefore, replace the check valve immediately with a new one, and replace the inner surface of the heating cylinder with the check valve. It is necessary to optimize the clearance with the outer surface. For this purpose, it is desirable to detect the occurrence of backflow as needed and to notify the operator that the backflow prevention valve has reached the replacement time.

  Backflow occurs during the forward drive of the screw, but in the primary injection process, the screw is driven by speed feedback control, so the forward speed of the screw is the same regardless of whether or not backflow occurs. Follow the preset speed control pattern. On the other hand, in the pressure holding process, since the product exists in the cavity of the mold and the screw is driven by pressure feedback control, the screw hardly advances when no backflow occurs. When a backflow occurs, the screw moves forward at a speed corresponding to the backflow amount. As described above, when the holding pressure is constant, when the backflow occurs, the forward speed of the screw becomes faster than when the backflow does not occur. Therefore, it is possible to detect the occurrence of backflow by monitoring the forward speed of the screw in a state where a predetermined pressure corresponding to the holding pressure is applied. Even if the clearance between the inner surface of the heating cylinder and the outer surface of the check valve is constant, the lower the viscosity of the molten resin at the time of injection, the easier the backflow occurs. Therefore, in order to accurately detect the occurrence of backflow, it is necessary to consider the viscosity at the time of injection of the resin material used for manufacturing the molded product.

  According to the first aspect of the present invention, the relationship between the viscosity of the molten resin stored in the heating cylinder and the limit value of the forward speed of the screw that does not cause backflow is stored in advance in the storage unit of the controller, The viscosity of the molten resin stored at the tip of the machine and the screw advance speed during the injection operation are measured as needed, and each measured value is compared with each recorded value, regardless of the viscosity of the molten resin. It is possible to appropriately determine whether or not a flow has occurred and, in turn, whether or not the backflow prevention valve has reached the replacement time. Specifically, if the measured screw advance speed exceeds the limit value of the screw advance speed stored corresponding to the measured viscosity of the molten resin, the backflow is occurring. Judgment can be made to prompt the operator to replace the check valve.

  Note that the viscosity of the molten resin stored in the heating cylinder is known for various resin materials used in the injection molding machine or can be obtained by experiments. In addition, the limit value of the forward speed of the screw that does not cause backflow is determined by using an injection device in which the clearance between the inner surface of the heating cylinder and the outer surface of the backflow prevention valve is adjusted within the allowable value at the time of shipment. By performing the injection operation with the pressure set to a constant value, various resin materials having different viscosities can be experimentally obtained. Therefore, the viscosity of the molten resin and the limit value of the forward speed of the screw that does not cause backflow can be stored in the storage unit of the controller in association with each other. On the other hand, the viscosity measurement of the molten resin using an actual machine can be performed by the method described in Japanese Patent No. 3732821. The advance speed of the screw during the automatic operation is determined by the sensor provided in each part of the injection molding machine. It can be calculated from the output signal.

  In the injection molding machine having the above-described configuration, the viscosity measurement of the molten resin may be performed by performing nozzle back after completion of the metering operation, and separating the nozzle provided at the tip of the heating cylinder from the mold, In this state, the screw is driven forward to perform an injection operation of the molten resin stored at the tip of the heating cylinder.

  The viscosity of the molten resin can be measured by the method described in Patent Document 1. The method described in Patent Document 1 is to calculate the resin viscosity from the injection pressure value when the injection speed during the injection operation is constant. Therefore, the resin viscosity can be calculated even when the injection nozzle is touched to the mold as long as the injection speed during the injection operation is constant, but when the injection nozzle is touched to the mold, the mold cavity The injection pressure easily varies depending on the shape. Therefore, if the resin viscosity is calculated in a nozzle back state in which the injection nozzle is separated from the mold, the influence of the cavity shape and the like can be avoided, and the calculation of the resin viscosity can be performed easily and with high accuracy.

  In the injection molding machine having the above-described configuration, the injection speed may be measured when the product is in the mold and the nozzle provided at the tip of the heating cylinder is touched to the mold. It was configured to run on.

  2. Description of the Related Art Conventionally, in an injection molding machine, a screw forward speed during an injection process, that is, an injection speed is measured, and drive control of an injection servo motor is performed based on the measurement result. Therefore, according to the above configuration, since it is not necessary to measure the injection speed by a special method in order to detect the backflow, it is possible to easily determine the replacement time of the check valve.

  According to the present invention, in the injection molding machine having the above-described configuration, the controller displays a determination result as to whether or not the backflow prevention valve has reached a replacement time on a display screen of a display device.

  According to this configuration, the operator can be notified of the replacement time of the backflow prevention valve by a visually visible method, so that it is difficult for the operator to miss the replacement time of the backflow prevention valve, and the backflow prevention valve can be replaced appropriately.

  Further, the present invention is the injection molding machine having the above-described configuration, wherein the controller determines whether or not the backflow prevention valve has reached an exchange time, and an execution program for an automatic operation mode for continuously manufacturing a molded product. An inspection mode execution program to be stored in the storage unit, and when the operator operates the input device to instruct the transition to the inspection mode during execution of the automatic operation mode, from the automatic operation mode It shifted to the said inspection mode, and it was set as the structure which determines whether the said backflow prevention valve has reached the replacement time.

  According to such a configuration, it is possible to inspect whether or not the backflow prevention valve has reached the replacement time at any time according to an instruction from the operator, so that compared with the case where the periodic inspection is performed every predetermined time, injection molding Detailed inspection according to the operating status of the machine becomes possible, and it is possible to appropriately determine the replacement time of the check valve.

  Further, the present invention is the injection molding machine having the above-described configuration, wherein the controller determines whether or not the backflow prevention valve has reached an exchange time, and an execution program for an automatic operation mode for continuously manufacturing a molded product. An inspection mode execution program to be performed and an execution timing of the inspection mode are stored in a storage unit, and the automatic operation is automatically performed when the execution timing of the inspection mode stored in the storage unit is reached. The mode is changed from the mode to the inspection mode, and it is determined whether or not the backflow prevention valve has reached the replacement time.

  According to such a configuration, the controller automatically checks whether or not the backflow prevention valve has reached the replacement time, so unlike the case of an instruction from the operator, the backflow prevention valve is not forgotten. Can be reliably determined.

  In the injection molding machine of the present invention, the controller performs viscosity measurement of the molten resin stored in the heating cylinder and measurement of the advance speed of the screw in accordance with an operator instruction or automatically at a predetermined timing, Since it is determined whether or not the backflow prevention valve has reached the replacement time, it is possible to appropriately determine whether or not the backflow prevention valve has reached the replacement time regardless of the viscosity of the molten resin.

It is explanatory drawing which shows typically the structure of the measurement system of the injection molding machine which concerns on embodiment, and an injection system. It is a block block diagram of the system controller with which the injection molding machine which concerns on embodiment is equipped. It is a figure which shows the determination table of the exchange time of a backflow prevention valve. It is a flowchart which shows the determination processing procedure of the exchange time of a backflow prevention valve. It is a figure which illustrates the display content of the display apparatus when it determines with with a backflow. It is a graph which shows the relationship between resin viscosity and a shear rate. It is principal part sectional drawing of the heating cylinder with which the injection molding machine which concerns on embodiment is equipped. It is a table | surface figure which shows an example of the relationship between the preset temperature of a band heater and resin viscosity. It is operation | movement explanatory drawing of a backflow prevention valve.

  Embodiments of an inline screw type injection molding machine according to the present invention will be described below with reference to the drawings. The technical features of the present invention are not limited to the embodiments described below, and appropriate modifications can be made without departing from the scope of the present invention.

  FIG. 1 schematically shows a configuration of a measuring system and an injection system of an inline screw type injection molding machine according to the present invention. In this figure, 31 is a metering servo motor, 31a is an output pulley of the metering servo motor 31, 32 is a timing belt for transmitting the rotation of the output pulley 31a to a pulley 33 coupled to the rear end of the screw 23, and 34 is an injection. Servo motor 34a, the output pulley 34a of the injection servo motor 34, the rotation of the output pulley 34a rotation → timing belt that transmits to the pulley 36a of the linear motion conversion mechanism 36, 36 to convert the rotational motion into linear motion Rotation → linear motion conversion mechanism comprising a ball screw mechanism or the like for transmission to the screw 23, 37 an encoder for detecting the rotation of the measuring servo motor 31, and 38 for detecting the pressure applied to the screw 23 (detecting the actually measured injection pressure value) The load cell 39 is an encoder that detects the rotation of the servo motor 34 for injection. That. Note that the measuring servo motor 31 and the timing belt 32 move forward and backward integrally with a screw 23 that is housed in the heating cylinder 21 so as to be rotatable and forward and backward. A check valve 24 is attached near the tip of the screw 23.

  Also, 41 is a screw rotation speed feedback control unit, 42 is a speed feedback control unit, 43 is a pressure feedback control unit, 44 is a switch unit that switches between the output of the speed feedback control unit 42 and the output of the pressure feedback control unit 43, These feedback control units 41 to 43 and the switch unit 44 are provided in the operation process control unit 4 of FIG. Reference numeral 45 denotes a servo amplifier that drives and controls the metering servo motor 31, and 46 denotes a servo amplifier that drives and controls the injection servo motor 34. These servo amplifiers 45 and 46 are provided in the driver group 14 shown in FIG. It is done.

  During the weighing process, the screw rotation speed feedback control unit 41 that receives the command value of the weighing process drives and controls the measuring servo motor 31 via the servo amplifier 45, the screw 23 rotates, and the molten resin is placed on the tip side of the screw 23. Is stored, the screw 23 moves backward. At this time, the screw rotation speed feedback control unit 41 monitors the actual screw position obtained from the output A3 of the encoder 39, and also sets the set screw rotation speed data and the actual screw rotation speed data obtained from the output A1 of the encoder 37. In contrast, a control signal is generated so that the section from the measurement start position until the screw 23 reaches the predetermined retraction position is set to the set screw rotation speed, and this is output to the servo amplifier 45, and the measurement servo The motor 31 is driven and controlled. Further, during the weighing process, the injection servo motor 34 is driven and controlled by the pressure feedback control via the servo amplifier 46 by the pressure feedback control unit 43 that receives the command value of the weighing process. Thus, back pressure is applied to the screw 23. At this time, the pressure feedback control unit 43 monitors the actually measured screw position obtained from the output A3 of the encoder 39, and compares the set pressure data with the actually measured pressure data obtained from the output A2 of the load cell 38 to start measurement. A control signal is generated so that the resin pressure set corresponding to the screw retreat position from the position is generated, and this is output to the servo amplifier 46, and the injection servo motor 34 is driven and controlled.

  When the primary injection process of the injection process is performed by speed feedback control, the injection servomotor 34 is controlled by speed feedback control via the servo amplifier 46 by the speed feedback control unit 42 that receives the command value of the primary injection process. Is controlled so that the forward speed of the screw 23 is controlled to reach the set injection speed. At this time, the speed feedback control unit 42 monitors the actually measured screw position obtained from the output A3 of the encoder 39, and calculates the set speed data set according to the position and the position data obtained from the output A3 of the encoder 39. The control signal is generated so that the injection speed set in accordance with the screw advance position is obtained from the injection start position by comparing with the actually measured speed data obtained in this way, and this is output to the servo amplifier 46 to be injected. The servo motor 34 for driving is controlled.

  1 can move to a nozzle touch position or a nozzle back position with respect to a mold apparatus (not shown). In the resin viscosity measurement mode described later, the measurement system of FIG. The system and the injection system are moved to the nozzle back position to perform free injection. Further, in the measurement mode and the measurement speed measurement mode, the measurement system and the injection system shown in FIG. 1 are moved to the nozzle touch position, and the required measurement operation and injection operation are performed with the product in the mold. The injection pressure value (actually measured injection pressure value) can be measured by the load cell 38 or can be calculated from a torque value obtained from the actually measured drive current value of the injection servomotor 34.

  FIG. 2 shows the configuration of the system controller 1 provided in the injection molding machine according to the embodiment. The system controller 1 of the injection molding machine controls the entire injection molding machine, and the entire molding process such as weighing operation, suck back operation, injection (primary injection and pressure holding) operation, mold opening / closing operation, ejection operation, etc. Control, calculation / storage processing of measured data during molding operation, non-defective / defective product determination processing, abnormality determination processing, calculation / storage processing of molten resin viscosity, or output of display device 3 Various processes such as an image display control process are executed. The system controller 1 is actually composed of various I / O interfaces, ROM, RAM, CPU, and the like, and executes various processes by various programs created in advance. In this example, the system controller 1 includes an operation condition setting storage unit 2, a measurement value storage unit 3, an operation process control unit 4, a backflow determination unit 5, a resin viscosity calculation unit 6, a measured resin viscosity storage unit 7, and a display process. The unit 8 is configured to be included.

  Further, the system controller 1 includes, as external devices, an input device 11 such as a keyboard input device operated by an operator, a display device 12 such as a color liquid crystal display device that displays various image data to the operator, and injection molding. Connected is a sensor group 13 composed of various sensors disposed in each part of the machine and a driver group 14 composed of various drivers for driving actuators such as motors and heaters disposed in each part of the injection molding machine. Has been. Note that the input device 11 and the display device 12 can be configured to be built in the system controller 1 instead of being externally attached to the system controller 1. Examples of the sensor constituting the sensor group 13 include a position sensor, a speed sensor, a pressure sensor, a rotation amount detection sensor, and a temperature sensor. The driver group 14 includes a motor driver that drives a motor such as a weighing servo motor or an injection servo motor, a heater driver that drives a band heater wound around the outer surface of the heating cylinder, and the like. .

  In the operation condition setting storage unit 2, operation control conditions in each operation mode are stored in a rewritable manner. The operation control condition can be input to the operation condition setting storage unit 2 using the input device 11 or a memory card (not shown). In the injection molding machine of this example, at least an automatic operation mode for automatically and continuously producing a molded product and a backflow prevention valve replacement timing determination mode to be described later are stored as operation modes. The operation mode can be switched as appropriate. Switching from the other operation mode to the check timing for the check valve replacement time can be performed by an operator instruction or automatically by setting the switching time in the operation condition setting storage unit 2. You can also do it. When switching to the check mode for the backflow prevention valve is performed according to the operator's instruction, it is possible to determine whether the backflow prevention valve has reached the replacement time at any time during automatic operation. Can be prevented or minimized. On the other hand, if the switching to the replacement time determination mode of the backflow prevention valve is automatically performed according to the instruction of the system controller 1, the replacement time is not neglected due to carelessness of the operator, etc. The replacement time can be reliably determined. As described above, by appropriately switching the operation mode of the injection molding machine to the replacement time determination mode of the backflow prevention valve, the cause of the molding failure is caused by the backflow due to wear of the backflow prevention valve 24 without disassembling the screw 23. It can be judged whether it is a thing.

  As shown in FIG. 3, the operating condition setting storage unit 2 does not cause backflow of the viscosity of the molten resin stored in the heating cylinder 21 in the weighing process and the molten resin stored in the heating cylinder 21. The relationship with the limit value of the screw forward speed when injecting at a predetermined injection pressure is also stored.

  For resin materials commonly used in the manufacture of molded articles, the viscosity of the molten resin stored in the heating cylinder in the metering process is known. Further, an unknown resin material can be measured using a resin viscosity measuring instrument such as a capillary rheometer or a melt indexer, or can be measured by the method described in Japanese Patent No. 3732821. In the example of FIG. 3, the viscosity of the molten resin is divided into five stages of 1 to 20 Pa · sec, 21 to 50 Pa · sec, 51 to 75 Pa · sec, 76 to 100 Pa · sec, and 101 Pa · sec or more.

  On the other hand, the limit value of the forward speed of the screw that does not cause backflow when the molten resin stored in the heating cylinder is injected at a predetermined injection pressure is the clearance between the inner surface of the heating cylinder and the outer surface of the check valve. However, it is calculated | required by using the injection apparatus adjusted to the appropriate value before the replacement | exchange of a backflow prevention valve was required, for example, the injection apparatus at the time of shipment. In this example, as shown in FIG. 2, the limit value of the forward speed of the screw that does not cause backflow with an injection pressure of 100 MPa is obtained, and the resin material having a molten resin viscosity of 1 to 20 Pa · s is 0.5 mm. / Sec for resin materials of 21-50 Pa · sec, 0.4 mm / sec, for resin materials of 51-75 Pa · sec, 0.3 mm / sec, for resin materials of 76-100 Pa · sec, 0.2 mm / sec For a resin material of 101 Pa · sec or higher, 0.1 mm / sec was obtained.

  Measurement information (position information, speed information, pressure information, rotation angle information, rotation speed information, temperature information, etc.) of each part of the injection molding machine detected by the sensor group 13 is captured in the measurement value storage unit 3 in real time. Stored. The measurement information taken in and stored in the measurement value storage unit 3 includes actual injection speed data and actual injection pressure data in the injection process (primary injection process and pressure holding process). The actually measured injection speed data is obtained based on measurement information and time information of an encoder attached to an injection servo motor (not shown) and stored in the measurement value storage unit 3. The actually measured pressure data is measured by a load cell (not shown) attached to the rear side of the screw and stored in the measured value storage unit 3.

  The operation process control unit 4 stores an operation control program for each process prepared in advance for each operation mode. The operation process control unit 4 is based on the operation control program prepared in advance and the operation condition setting values stored in the operation condition setting storage unit 2 and in the measurement value storage unit 3. The driver group 14 is driven and controlled with reference to the measurement information, the state confirmation information from each part, and the own time information, and the operation of each process according to each operation mode is executed by the injection molding machine.

  In the injection molding machine of this example, the procedure for determining the replacement time of the check valve shown in FIG. 4 is stored in the operation process control unit 4 as an operation control program. As shown in FIG. 4, the procedure for determining the replacement time of the backflow prevention valve of the present example is that when it is determined in step S1 that switching to the replacement time determination mode of the backflow prevention valve is instructed (Yes), the measuring step (step S2 ) And the nozzle back operation (procedure S3) are performed in this order, and then the process proceeds to procedure S4 to measure the resin viscosity. The switching instruction to the replacement time determination mode in step S1 can be performed by the operator operating the input device 11, or the switching time to the replacement time determination mode is set in the operation condition setting storage unit 2 in advance. Can also be done. In order to perform accurate weighing, the weighing process in step S2 is performed in a state where the product is in the mold and the nozzle is touched, as in the weighing process during automatic operation. The nozzle back operation in step S3 is performed in order to carry out the resin viscosity measurement in step S4 easily and with high accuracy without being affected by the cavity shape of the mold. A specific method for measuring the resin viscosity in step S4 will be described in detail later.

  After the resin viscosity is measured, the nozzle touch operation (procedure S5) and the metering step (procedure S6) are performed in this order, and then the process proceeds to step S7 to measure the injection speed. The nozzle touch operation in step S5 is performed in order to accurately perform the weighing process in step S6 in accordance with the automatic operation mode. The measurement of the injection speed in step S7 is obtained by differentiating the output change of the position sensor that detects the position of the screw 23 with respect to time.

  Next, the process proceeds to step S8, where the measured resin viscosity and the injection speed are compared with the determination table shown in FIG. 3, and the measured injection speed is set according to the measured resin viscosity. It is determined whether it is below the limit value. In step S8, when it is determined that the measured injection speed is equal to or less than the limit value of the injection speed at which no backflow occurs (Yes), the process proceeds to step S9 and automatic operation is resumed. On the other hand, if it is determined that the measured injection speed exceeds the limit value of the injection speed at which no backflow occurs (No), the process proceeds to step S10, and the check valve has reached the replacement time. A message is displayed on the display device to notify the operator.

  The resin viscosity calculation unit 6 calculates the resin viscosity based on the actually measured injection pressure value (measured value of the injection pressure measuring sensor in the sensor group 13) when the injection speed is constant. The measured injection pressure value when the injection speed is constant is the same as the resin viscosity measurement mode, which will be described later, with the injection nozzle provided at the tip of the heating cylinder nozzle back from the mold device. It is calculated | required by injecting the stored molten resin free. As another method, the resin is actually injected into the mold with the injection nozzle touching the mold apparatus and the injection range is guaranteed to be constant (or within time). It is also obtained by selecting the actual injection pressure value at.

  The measured resin viscosity storage unit 7 is an operator from the input device 11 such as the resin material name, the resin material manufacturer name, the resin material type number, and the lot number, which is calculated by the resin viscosity calculating unit 6. Are stored in the form of an appropriate storage table in association with the input information according to the above, the set temperature condition of the band heater at the time of resin viscosity measurement, the measurement date and time, and the like.

  The backflow determination unit 5 stores the determination table of FIG. 3 stored in the operating condition setting storage unit 2, the measured speed (injection speed) of the screw 23 stored in the measurement value storage unit 3, and the measured resin viscosity storage unit 7. The stored measured resin viscosity is compared, and it is determined whether the measured speed of the screw 23 exceeds the injection speed set for the resin viscosity corresponding to the measured resin viscosity. For example, when injection molding is performed using a polyamide resin and the measured resin viscosity is 25 Pa · sec, the injection speed set corresponding to 21 to 50 Pa · sec recorded in the determination table of FIG. The limit value 0.4 mm / sec is compared with the measured speed of the screw 23. If the measured speed of the screw 23 is 0.35 mm / sec, for example, it is determined that there is no back flow, and the measured speed of the screw 23 is determined. Is, for example, 0.45 mm / sec, it is determined that “there is a back flow”. If it is determined that there is a backflow, the backflow prevention valve has reached the replacement time.

  The display processing unit 8 displays display image data in a designated display mode based on a display image creation / control program created in advance in response to a call instruction for a desired display image performed by an operator operating the input device 11. Create The created image data is transferred to a frame buffer (not shown) and temporarily stored. The output of the frame buffer is sent to the display device 12 according to a command from the display processing unit 8, and the image data is displayed on the display screen of the display device 12. Is displayed. When the backflow determination unit 5 determines that “there is a backflow”, the display screen 12a of the display device 12 has a “backflow has occurred. As shown in FIG. Is displayed. From this, the operator can recognize that the backflow prevention valve 24 has reached the replacement time, so that the operator can quickly start the replacement work of the backflow prevention valve 24, and prevent or minimize the occurrence of defective products. Can be suppressed. Moreover, since the backflow prevention valve 24 can be replaced at an appropriate timing, it is possible to avoid unnecessary replacement work and increase the operating rate of the injection molding machine.

  Hereinafter, a specific method of resin viscosity measurement shown in step S4 of FIG. 4 will be described.

The viscosity of the molten resin stored in the heating cylinder in the weighing process is η (Pa · sec), the shear stress acting on the molten resin in the injection process is τ (Pa), the shear rate of the molten resin in the injection process (in-line screw type In an injection molding machine, when γ (sec ⁻¹ ) is an injection speed indicated by the screw advance speed, the shear stress τ is expressed by the following equation (1) using the resin viscosity η and the shear speed γ. It is represented by

τ = η × γ (1) Equation (1) Here, it has been confirmed that there is a relationship as shown in FIG. 6 between the shear rate γ in the equation (1) and the viscosity η of the molten resin. That is, as apparent from FIG. 6, when the shear rate γ is in the range of 10 ¹ to 10 ⁵ , the viscosity η changes with the change of the shear rate γ, but the shear rate γ is less than 10 ^1. In the case of (1) and exceeding 10 ⁵ , the viscosity η shows a substantially constant value regardless of the change in the shear rate γ. Therefore, when the shear rate (injection rate) is a predetermined constant value within the range of 10 ¹ to 10 ⁵ , the viscosity of the molten resin can be calculated from the equation (1). For example, the shear rate γ obtained from the injection speed of 10 mm / sec is approximately γ = 10 ³ to 10 ⁴ regardless of the size of the injection molding machine, and satisfies the above-described viscosity calculation conditions satisfactorily. It becomes. Meanwhile, the shear rate gamma obtained from the injection speed 100 mm / sec, at 100 tons or more of the injection molding machine can also indicate the value of gamma = 10 ⁵ neighborhood, no longer a parameter of appropriate speed settings. Therefore, in the present invention, the resin viscosity is measured in a range that satisfies the above-described viscosity calculation condition by controlling the injection speed to be a certain value within the range of 5 to 50 mm / sec. ing.

In an in-line screw type injection molding machine, the shear stress τ and shear rate γ are JIS K7199, injection pressure is P (Pa), nozzle hole diameter is r (mm), nozzle land length is L (mm), flow rate Is represented by the following formulas (2) and (3), where Q (mm ³ / sec).

τ = (P × r) / (4 × L) (2) Formula γ = (32 × Q) / (π × r ³ ) (3) Here, the flow rate Q is the screw cross-sectional area. When A (mm ² ) and the injection speed (screw advance speed) are V (mm / sec),
Q = A × V ...... Since it is expressed by equation (4), if the screw diameter is D, equation (4) is
Q = (π × D ² × V) / 4 (represented by equation (5)), and substituting equation (5) into equation (3),
γ = (8 × D ² × V) / r ³ (6)

Therefore, after all, the viscosity η of the molten resin is
η = (r ⁴ × P) / (32 × L × D ² × V) (7) is obtained by the equation (7). That is, if the injection speed is constant, if the injection pressure P is actually measured, the value of the injection speed and the mechanical dimension that are controlled to be constant are known. Therefore, the resin viscosity can be calculated based on the actually measured injection pressure value. It becomes possible.

  The resin viscosity measurement method according to the present embodiment is configured based on such knowledge, and the measured resin viscosity has a highly accurate value that is substantially equivalent to the value presented by the resin material manufacturer. It was confirmed by experiments that it was obtained.

  FIG. 7 illustrates the diameter r of the nozzle hole formed in the injection nozzle 22, the land length L of the injection nozzle 22, and the diameter D of the screw 23. 7 indicate band heaters wound around the outer circumferences of the heating cylinder 21 and the injection nozzle 22.

  As described above, the resin viscosity can be calculated by measuring the injection pressure value during the constant injection speed condition. However, when the molten resin is injected and filled in the mold, the injection pressure may fluctuate depending on the cavity shape of the mold, etc. When performing ultra-high speed injection, the injection speed is calculated as described above. It is also conceivable that the value is out of the range that satisfies the conditions satisfactorily. Therefore, in the present embodiment, when the resin viscosity is measured, the resin viscosity is measured in a state in which the advance speed of the screw 23 is feedback controlled under the condition that the injection nozzle 22 is not touched to the mold and the injection speed is constant. I am trying to measure.

  That is, when switching to the replacement timing judgment mode of the backflow prevention valve is instructed before the automatic operation is performed or when the automatic operation is interrupted, for example, up to 50% of the injection stroke under the mass control conditions during mass production. Weighing is performed, and after the completion of weighing, the nozzle back operation is performed to perform free injection under the condition of a constant injection speed (provided that the injection speed satisfies the range of 5 to 50 mm / sec). Then, the injection pressure value at this time is measured, and the resin viscosity is calculated in the resin viscosity calculation unit 6 based on the actually measured injection pressure value. The calculated resin viscosity is displayed in an appropriate form on the display device 12 and is stored in the measured resin viscosity storage unit 7. At this time, if necessary, information input by the operator from the input device 11 such as a resin material name, a resin material manufacturer name, a resin material type number, and a lot number, and setting of the band heaters BH1 to BH4 at the time of resin viscosity measurement The temperature condition, the measurement date and time, and the like are stored in the measurement resin viscosity storage unit 7 together with the measurement resin viscosity data. If the displayed resin viscosity is out of the desired value (for example, out of the recommended value of the resin material manufacturer), the operator changes the set temperature of the band heaters BH1 to BH4, The heating conditions by the band heaters BH1 to BH4 are changed so that the resin viscosity falls within a desired range. At this time, when the relational data between the resin viscosity and the set temperature of each band heater, which has been obtained through a case study in advance, is stored in an appropriate database managed by the measured resin viscosity storage unit 7 or the system controller 1 It is also possible to display the band heater temperature of each part for changing the resin viscosity to prompt the change of the set temperature of each of the band heaters BH1 to BH4. FIG. 8 shows the relationship between the set temperature of each band heater BH1 to BH4 and the resin viscosity when PPS (polyphenylene sulfide) resin is used as the raw material resin and injection is performed with the injection speed set to 10 mm / sec. It is a table. If such a table is prepared in advance, it becomes possible to display the band heater temperature of each part for changing and correcting the resin viscosity as described above.

If the resin viscosity is measured with an injection molding machine during mass production in this way , the resin viscosity can be measured on the injection molding machine itself, immediately and under the same measurement conditions as in mass production. Can be performed with high accuracy, and is very convenient. On the other hand, if resin viscosity is measured using a dedicated measuring instrument as in the past, it takes time and effort, and there is a possibility of plasticizing conditions different from mass production. There was also a risk of data differing from the viscosity. Furthermore, if the resin viscosity is measured with an injection molding machine during mass production operation, the set temperature of each band heater can be changed easily and easily by the guidance display of the set temperature instruction. It becomes.

  It should be noted that the viscosity of the molten resin stored at the tip of the heating cylinder 21 at the completion of the metering process can be measured independently regardless of the molding operation. In this case as well, the same measurement as in mass production, which is set according to the resin material, for example, up to 50% of the injection stroke, similar to the measurement of resin viscosity before automatic operation or when automatic operation is interrupted Weighing under control conditions, and after completion of weighing, let free injection be performed under the condition of constant injection speed (however, the injection speed shall be within the range of 5-50mm / sec), and the injection pressure value at this time The resin viscosity is calculated based on this measurement. At this time, measurement and injection are repeated a plurality of times arbitrarily, and the resin viscosity measured in each injection and the result of statistical calculation thereof are displayed and stored. When storing, if necessary, information input by the operator from the input device 2 such as a resin material name, a resin material manufacturer name, a resin material type number, a lot number, or a set temperature of the band heater when measuring the resin viscosity Conditions, measurement date and time, etc. are also stored.

  In this way, if you just want to know the viscosity of the resin regardless of the molding operation, you can compare the resin viscosity for each lot of the same manufacturer and the same resin material, or the resin viscosity of the same manufacturer but different manufacturers. Comparison and the like can be easily performed. In addition, even if the same resin material is used, it is possible to compare the viscosities of resins that are considered to have different storage conditions and different degrees of drying, and thus it is possible to grasp the drying state of the resin material. In this case, the resin viscosity can be accurately measured under the same measurement conditions as in mass production, and there is no need to prepare a dedicated measuring instrument as in the prior art.

  In addition, when switching to the replacement time determination mode of the backflow prevention valve is instructed when changing the resin, an automatic purging operation for changing the resin from the resin A to the resin B is executed. The resin viscosity of each free injection is measured and monitored, and when the viscosity of the resin B stored in advance is measured, it can be considered that the resin replacement has been completed and the automatic purging operation can be automatically stopped. .

  In this way, conventionally, the operator is clearly attached to the injection molding machine, and compared with the case where the resin replacement completion is confirmed visually, the burden on the operator is eliminated, and the resin replacement completion can be accurately determined. It is also possible to reduce the amount of resin when changing the resin.

  The injection molding machine according to the above-described embodiment performs the measurement of the viscosity of the molten resin stored in the heating cylinder 21 and the measurement of the advance speed of the screw 23 in accordance with an operator instruction or automatically at a predetermined timing. Thus, since it is determined whether or not the backflow prevention valve has reached the replacement time, it is possible to appropriately determine whether or not the backflow prevention valve 24 has reached the replacement time regardless of the viscosity of the molten resin.

  In the above-described embodiment, the viscosity of the molten resin and the limit value of the injection speed are stored in the determination table. However, the resin material name can be stored instead of the viscosity of the molten resin. According to such a configuration, the operator can easily recognize the limit values of the resin viscosity and the injection speed intuitively, so that it is possible to more smoothly determine the replacement time of the backflow prevention valve 24.

DESCRIPTION OF SYMBOLS 1 System controller 2 Operation condition setting storage part 3 Measured value storage part 4 Operation process control part 5 Back flow determination part 6 Resin viscosity calculation part 7 Measurement resin viscosity memory | storage part 8 Display processing part 11 Input device 12 Display apparatus 12a Display screen 13 Sensor Group 14 Driver group 21 Heating cylinder 22 Injection nozzle 23 Screw 24 Backflow prevention valve 31 Servo motor for metering 32 Timing belt 34 Servo motor for injection 35 Timing belt 36 Rotation → Linear motion conversion mechanism 37 Encoder 38 Load cell 39 Encoder 41 Screw rotation speed feedback Control unit 42 Speed feedback control unit 43 Pressure feedback control unit 44 Switch unit BH1 to BH4 Band heater

Claims (6)

A screw housed in a heating cylinder so as to be rotatable and capable of moving back and forth; a backflow prevention valve attached to the screw; and a controller for controlling driving of the screw; and rotating the screw to drive the heating A metering process for storing a predetermined amount of molten resin at the tip of the cylinder, and after the metering process, the screw is driven forward to inject the molten resin stored at the tip of the heating cylinder into the cavity of the mold. In an inline screw type injection molding machine that continuously manufactures a molded product of a predetermined shape by repeating the injection process to
The storage unit of the controller, the a viscosity of the molten resin is stored in the distal end portion of the heating cylinder, between the outer surface of the inner surface and the screw of the heating cylinder into a molten resin is stored in the distal end portion of the heating cylinder The correlation with the limit value of the forward speed of the screw that does not cause backflow when a predetermined pressure is applied using an injection device with an appropriate clearance is stored,
The controller performs viscosity measurement of the molten resin stored in the tip of the heating cylinder and measurement of injection speed according to an operator's instruction or automatically at a predetermined timing set in advance. Injection in which the measured value is compared with the limit value of the viscosity of the molten resin and the forward speed of the screw stored in the storage unit to determine whether or not the backflow prevention valve has reached the replacement time. Molding machine.   The viscosity of the molten resin is measured by performing nozzle back after completion of the metering operation, separating the nozzle provided at the tip of the heating cylinder from the mold, and driving the screw forward in this state, The injection molding machine according to claim 1, wherein the injection molding machine is performed by performing an injection operation of molten resin stored in a tip portion of the cylinder.   The measurement of the injection speed is performed in a state where a product is in the mold and a nozzle provided at a tip portion of the heating cylinder is in nozzle touch with the mold. Item 3. The injection molding machine according to any one of Items 2.   The injection according to any one of claims 1 to 3, wherein the controller displays a determination result of whether or not the backflow prevention valve has reached a replacement time on a display screen of a display device. Molding machine.   The controller stores an execution program for an automatic operation mode for continuously manufacturing a molded product and an execution program for an inspection mode for determining whether or not the backflow prevention valve has reached a replacement time. And when the operator operates the input device to instruct to shift to the inspection mode during execution of the automatic operation mode, the automatic flow control mode shifts to the inspection mode, and the backflow prevention valve The injection molding machine according to any one of claims 1 to 4, wherein it is determined whether or not a replacement time has been reached.   The controller includes an execution program for an automatic operation mode for continuously manufacturing a molded product, an execution program for an inspection mode for determining whether or not the backflow prevention valve has reached a replacement time, and the inspection mode. Is stored in the storage unit, and when the execution timing of the inspection mode stored in the storage unit is reached, the automatic operation mode is automatically shifted to the inspection mode, and the backflow prevention is performed. The injection molding machine according to any one of claims 1 to 4, wherein it is determined whether or not the valve has reached a replacement time.

Images