JP2010111019A - Injection molding machine and control method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine, in which the same measured result (load value) is obtained under the same condition and molding conditions are made to be uniform, and its control method. <P>SOLUTION: The load conversion values of a load cell mounted to the injection molding machine are obtained in advance and are built in the control device of the injection molding machine. On the basis of the load conversion values, the load value measured by the load cell is corrected so as to correct into normal load values. By employing the converted normal load values in the control device, the control of the molding work by the injection molding machine is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an injection molding machine capable of accurately calculating a load applied to a screw and enabling a precise and efficient molding operation, and a control method thereof.

  An injection molding machine having a screw in a cylinder rotates the screw in the cylinder to melt and knead the resin, and advances the screw to inject the resin into a mold to mold a product. Normally, an injection molding machine is equipped with a load cell and other load measuring instruments, and the load applied to the screw is measured by the load cell, and the injection pressure of the resin and the holding pressure after injection are calculated to control the molding operation. Yes.

  Therefore, the load measuring device is installed between, for example, a screw and a drive mechanism that moves the screw back and forth, and measures a load applied to the screw. In addition, an injection molding machine manufacturer purchases a load cell that is a load measuring instrument from the load cell manufacturer, attaches the load cell to the injection molding machine, connects the load cell to the control device of the injection molding machine, and calculates the load value measured by the load cell. It was made to make it input into a control apparatus.

On the other hand, the load cell includes a slight error in the measurement value due to the structure, and the load actually applied to the load cell is not output as an accurate load value. Therefore, in the past, the load cell with the smallest measurement error was selected and attached to the injection molding machine, so that a load value closer to the actual value, that is, the pressure value, was obtained, and various adjustments were made for each injection molding machine to optimize the load cell. A molding operation was to be carried out.
JP 2002-67118 A

  However, conventionally, load cells having different characteristics are incorporated for each injection molding machine. For this reason, individual injection molding machines can perform molding operations normally without any problems by performing control corresponding to the load cells built into them, but the same product can be molded by installing multiple injection molding machines. In such a case, since the characteristics of the load cells incorporated in each injection molding machine are different, the load cells may show different load values even when the same load is actually applied.

  Therefore, when the same product is molded using the same resin under the same conditions with a plurality of injection molding machines, the load value of the screw output from the load cell may be different for each injection molding machine. For this reason, molding conditions cannot be matched in each injection molding machine, and it is difficult to operate each injection molding machine under the same conditions.

  An object of the present invention is to solve the above-mentioned problems, and to provide an injection molding machine in which the same measurement result (load value) is obtained under the same conditions and variations in molding conditions are reduced, and a control method thereof.

  A load conversion value of a load cell attached to the injection molding machine is obtained in advance, and the obtained load conversion value is incorporated into a control device of the injection molding machine. Then, based on the incorporated load conversion value, the load value measured by the load cell is converted into a normal load value, and the control of the molding operation in the injection molding machine is performed by the control device using the converted normal load value. I decided to make it.

  Since the load conversion value of the load cell is built into the control device, the control device corrects the load value measured by the load cell and calculates the full range conversion value for calculating the normal load value over the entire measurement range. Can do. Since the load value output from the load cell is corrected based on the total range converted value, an accurate load value applied to the screw can be obtained, and variation in the load value applied to the screw for each injection molding machine can be reduced. be able to. As a result, when the same product is molded by a plurality of injection molding machines, the molding conditions and the like of each injection molding machine can be unified, and the molding operation can be performed efficiently without variation in settings.

  An embodiment of an injection molding machine and a control method thereof according to the present invention will be described with reference to the drawings. The whole injection molding machine 10 is shown in FIG.

  The injection molding machine 10 includes a base 50, an injection device 12 and a mold clamping device 14 provided on the base 50, and the like. Further, a display means 16 and an input means 18 are provided at a substantially central portion of the injection molding machine 10.

  The base 50 is substantially a rectangular parallelepiped, and a first rail 52 is provided on the upper surface. The first rail 52 is provided along the longitudinal direction of the base 50, and the injection device 12 is movably mounted on the first rail 52. A mold clamping device 14 is provided on the left side of the injection device 12 so as to face the left side portion. The mold clamping device 14 includes a mold clamping mechanism, and opens and closes a mold (none of which is shown) assembled to the mold clamping mechanism. The mold clamping device 14 is preferably a servo motor drive system, but may be a hydraulic drive system. The injection molding machine 10 has a cover on the outside of the injection device 12 and the mold clamping device 14, and each is shown in a state covered with the cover in FIG.

  The injection device 12 is shown in FIGS. Hereinafter, the injection device 12 will be described with the mold clamping device 14 side as viewed from the injection device 12 defined as the front, the front, rear, right, and left are defined as a reference, the direction of gravity is the downward direction, and vice versa.

  The injection device 12 includes a frame 20, a cylinder 22 provided in front of the frame 20 (left side in the figure), a screw 24 provided in the cylinder 22, and a screw that rotates the screw 24 around a central axis. The rotating mechanism 26, the screw forward / reverse mechanism 28 for moving the screw 24 back and forth in the axial direction, the propulsion mechanism 30 for moving the frame 20 on the first rail 52, and the like.

  The frame 20 is formed of a base 32 and an upper frame 34 attached on the base 32. The base 32 is a flat frame, and leg portions 36 are provided on the left and right sides of the base 32. The leg portion 36 is movably mounted on the first rail 52, and thereby the base 32 is slidably supported with respect to the base 50.

  The propulsion mechanism 30 includes a drive motor 38 and a ball screw mechanism 40. The drive motor 38 is attached to the rear wall 39 (right side of the drawing) of the base 32. The drive shaft of the drive motor 38 passes through the rear wall 39 and is connected to the screw portion 42 of the ball screw mechanism 40. The screw portion 42 penetrates substantially the center of the base 32, and the tip side is rotatably supported by the front wall 41 of the base 32. The nut portion 44 of the ball screw mechanism 40 is fixed to the upper surface of the base 50 inside the base 32.

  The upper frame 34 has a rectangular frame shape, and is fixed to the base 32 by support pins 46 and fixing screws 48. The upper frame 34 is configured to be rotatable with respect to the base 32 about the support pin 46 when the fixing screw 48 is released.

  The cylinder 22 is attached to the front wall 35 of the upper frame 34. The cylinder 22 extends to the left in the drawing, and a nozzle portion 54 that is in close contact with the mold is provided at the tip thereof. A hopper 56 is provided on the base end side of the cylinder 22. The hopper 56 communicates with the inside of the cylinder 22 and supplies pellets, which are raw resin, to the cylinder 22. Further, as shown in FIG. 2, the second rail 58 is provided on the left and right side walls 37 in the upper frame 34. The second rail 58 is attached in parallel with the cylinder 22, and a stay 68 described later is movably mounted thereon.

  The screw 24 is slidably and rotatably provided in the cylinder 22. The screw 24 has a spiral groove on the outer periphery on the tip side. Further, the base end side of the screw 24 is connected to a pulley 66 of the rotation mechanism 26 described later.

  The rotation mechanism 26 includes a rotation mechanism main body 60, a driving motor 62, a transmission belt 64, a pulley 66, and the like. The rotation mechanism main body 60 includes a stay 68 and is movably mounted on the second rail 58 via the stay 68.

  A driving motor 62 is attached to the upper part of the rotating mechanism main body 60. A pulley 66 is rotatably provided in front of the rotation mechanism main body 60 via a bearing 61 and is connected to a drive shaft of a drive motor 62 via a transmission belt 64. As described above, the screw 24 is coaxially and integrally fixed to the pulley 66. A forward / reverse mechanism 28 is provided behind the rotation mechanism main body 60 via a load cell 70.

  The forward / reverse mechanism 28 includes a drive motor 72, a transmission belt 74, a pulley 76, a ball screw mechanism 78, and the like. The drive motor 72 is attached to the side of the upper frame 34, and the drive shaft is coupled to the pulley 76 via the transmission belt 74.

  The pulley 76 is rotatably supported on the upper frame 34 by a bearing 77. A threaded portion 80 of a ball screw mechanism 78 is integrally connected to the pulley 76. The screw portion 80 is provided coaxially with the screw 24 and is screwed into the nut portion 82 of the ball screw mechanism 78. The nut portion 82 has a cylindrical shape and is integrally fixed to the rear surface of the load cell 70.

  The load cell 70 is a load measuring device that measures a load applied in the axial direction, and includes a strain generating body and a strain sensor (both not shown) attached to the strain generating body. The load cell 70 has a flat cylindrical shape, and a hole having an inner diameter larger than the outer diameter of the threaded portion 80 is formed at the center. As described above, the left side surface of the load cell 70 in the drawing is fixed integrally with the rotation mechanism main body 60, and the right side surface in the drawing is fixed integrally with the nut portion 82.

  Further, the load cell 70 includes processing means (not shown), and the output value of the strain sensor is processed into an appropriate numerical value by the processing means and sent to the control device 90, and the load conversion value unique to the load cell 70 is stored in the processing means. When the load cell 70 is connected to the control device 90, the load conversion value is sent to the control device 90. The load conversion value indicates the characteristics of the load cell 70. For example, the load cell when several load values are selected as the reference load value from the measurement range of the load cell 70 and the reference load value is actually added to the load cell 70. 70 is formed from the load value output by 70 and the reference load value. It is preferable that the load converted value is measured by the company that manufactured the load cell at the stage where the load cell is manufactured, and is input to the processing means and delivered together with the load cell. The load conversion value may be one inspected by the manufacturer or user of the injection molding machine, or one inspected by a general inspection organization or the like. Further, the processing means may not be provided, and the output value output from the strain sensor may be directly input to the control device 90 of the injection molding machine 10 and processed by the control device 90. In such a case, the load cell 70 is provided with storage means to store the load conversion value, or a separate storage medium is provided, and the load conversion value is stored in the storage medium.

  Furthermore, the stored load conversion value is not limited to the conversion value at the selected reference load value, but may be a continuous value in the entire measurement range or a conversion equation. When continuous values in the entire measurement range are stored in advance, the calculation unit 96 described later is not necessary.

  Next, the control device 90 will be described.

  The control device 90 is inputted with a molding method for the entire molding operation of the injection molding machine 10, and controls the injection molding machine 10 based on the molding method to perform the molding operation. Furthermore, the control apparatus 90 has the correction part 92 regarding the load cell 70 as mainly shown in FIG. 3 as a function.

  The correction unit 92 includes a storage unit 94, a calculation unit 96, and a conversion unit 98. When the load cell 70 is assembled to the injection molding machine 12 and a load conversion value is input to the control device 90, the storage unit 94 stores the load conversion value. The calculation unit 96 estimates the load conversion value in the range measured by the load cell 70 based on the load conversion value of the load cell 70 stored in the storage unit 94, and converts the load value in the entire measurement range. Calculate the value. The entire range converted value calculated by the calculation unit 96 is stored in the storage unit 94.

  When the load unit 70 receives a load from the screw 24 and the load value measured by the load cell 70 is input from the load cell 70, the conversion unit 98 converts the load value to a normal value based on the entire range conversion value stored in the storage unit 94. Convert to load value. Then, the converted normal load value is sent to the main body side of the control device 90.

  That is, the control device 90 controls the injection molding machine 10 based on a normal molding method, and when the load cell 70 receives a load from the screw 24 and measures the load value, sends the load value to the correction unit 92. As described above, the normal load value is calculated by correcting the load value based on the entire range converted value. Such a normal load value is used for control as a normal load value measured by the load cell 70.

  Here, a method for calculating the entire range converted value of the load cell 70 will be described. FIG. 4 shows an example of the load conversion value of the load cell measured by the load cell manufacturer. The four locations A, B, C, and E are reference load values. In the figure, a graph when the load value applied and the load value measured by the load cell accurately correspond to each other is indicated by an oblique straight line drawn by a one-dot chain line. As shown in the figure, according to this, the error of the load value measured and output by the load cell 70 with respect to the actual load value is d1, d2, d3, d4 at points A, B, C, E, respectively. It can be seen that it is.

  Errors d1 to d4 at each point are stored in the load cell 70 as load conversion values. When the load cell 70 is attached to the injection molding machine 10 and the load cell 70 is connected to the control device 90, the control device 90 reads the stored errors d1 to d4 from the load cell 70, and based on this, the calculation unit 96 The load at the measurement point is linearly interpolated, and the difference between the actual load value and the indicated load value among the reference load values A, B, C, E, that is, the converted value of the load cell 70 over the entire measurement range, that is, all The range conversion value is calculated. The calculated entire range converted value is stored in the storage unit 94. Note that the calculation of the entire range conversion value may be performed by complementation by a quadratic curve or other complementation methods instead of linear interpolation. In addition, instead of the errors d1 to d4, the load cell 70 stores both the reference load value and the load value that is output when the reference load value is applied. May be calculated to calculate the entire range conversion value.

  Next, an example of a molding operation by the injection molding machine 10 having the correction value will be described. When the screw 24 is rotated by the rotation mechanism 26, pellets are introduced from the hopper 56 into the cylinder 22. The cylinder 22 is heated by the heating device, and the pellets are melted and kneaded by the heat generated by the rotation of the screw 24. Further, the propulsion mechanism 30 operates, the injection device 12 moves forward, and the nozzle portion 54 of the cylinder 22 is brought into close contact with the mold.

  Then, when the screw back-and-forth mechanism 28 is operated to advance the screw 24, the molten resin is injected from the cylinder 22 into the mold. By the injection of the resin, for example, a reaction force is generated in the screw 24 to the right in the figure. The reaction force is transmitted from the rear end of the screw 24 to the pulley 66 and is transmitted to the rotating mechanism main body 60 via the bearing 61, and the load cell 70 is pressed. Further, a nut portion 82 is provided on the surface of the load cell 70 opposite to the screw 24, and the nut portion 82 is screwed to the screw portion 80, so that the load cell 70 is compressed in the axial direction.

  Therefore, when resin pressure is applied to the screw 24, the load cell 70 is pressed in the axial direction by the reaction force, and the resistance value at the strain sensor changes. A change in resistance value at the strain sensor is read as a voltage change, processed by the processing means, and a load applied to the screw 24 is measured. When the load cell 70 measures the load applied to the screw 24 in this way, the load value is sent to the control device 90.

  The load value sent to the control device 90 is corrected as described above by the correction unit 92 of the control device 90 and converted into a normal load value. Then, the normal load value calculated in this way is output from the correction unit 92 to the control device 90, converted into a pressure value by the control device 90, and used for control of molding operations such as pressure control at injection and holding pressure switching. It is done.

  Therefore, since the control device 90 always uses the load value measured by the load cell 70 after correcting it to a normal load value, the load value applied to the screw 24 can be accurately obtained and the injection molding machine 10 can be accurately controlled. In addition, since the load value measured by the load cell 70 is corrected and converted based on the load conversion value, an inherent error of each load cell 70 is reduced. Thereby, the load value of the screw 24 in the injection molding machine 10 of the same type can be matched, and when a plurality of injection molding machines 10 of the same type are operated, they can be operated under common conditions.

  In the above embodiment, the injection device 12 has been described as an example. However, the present invention is not limited to the injection device having the above configuration. Further, the structure of the load cell 70, the arrangement in the injection device 12, and the like are not limited to the above example.

It is sectional drawing which shows one Embodiment of the injection apparatus of the injection molding machine concerning this invention. It is a top view which shows one Embodiment of the injection apparatus of the injection molding machine concerning this invention. It is a block diagram which shows a control apparatus. It is a graph which shows a load conversion value. It is a perspective view which shows an injection molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Injection molding machine 12 ... Injection apparatus 20 ... Frame 22 ... Cylinder 24 ... Screw 26 ... Screw rotating mechanism 28 ... Screw forward / backward moving mechanism 30 ... Propulsion mechanism 34 ... Upper frame 46 ... Support pin 52 ... First rail 58 ... Second Rail 60: Rotating mechanism main body 70: Load cell 90 ... Control device 92 ... Correction unit 94 ... Storage unit 96 ... Calculation unit 98 ... Conversion unit

Claims (5)

In an injection molding machine that has a screw inside a cylinder and performs a molding operation by injecting resin from the cylinder into a mold,
Load conversion value of the load cell that measures the load applied in the axial direction of the screw is incorporated into the control device of the injection molding machine,
Based on the load conversion value, to correct the load value applied to the screw measured by the load cell,
The corrected load value is a normal load value measured by the load cell, and the control device controls the molding operation of the injection molding machine using the normal load value. Control method of molding machine.   The load conversion value is obtained from a load value output from the load cell and a value of each reference load when a reference load consisting of a plurality of different load values is applied to the load cell. Item 2. A method for controlling an injection molding machine according to Item 1.   The control device calculates an estimated load value estimated to be output from the load cell when a load other than the reference load value is applied based on the load conversion value, and uses the estimated load value to calculate the reference load value. The method for controlling an injection molding machine according to claim 2, wherein a normal load value at a load other than the above is obtained.   The method for controlling an injection molding machine according to any one of claims 1 to 3, wherein the load conversion value of the load cell is obtained before the load cell is incorporated into the injection molding machine. An injection molding machine that performs molding by injecting resin into the mold.
A cylinder,
A screw provided inside the cylinder;
A screw drive mechanism for driving the screw in the cylinder at least in the axial direction;
A load cell that is installed between the screw and the screw drive mechanism and measures the load applied in the axial direction of the screw;
Based on each load conversion value inherent to the load cell, a calculation unit that calculates an entire range conversion value over the entire measurement range of the load cell;
A storage unit for storing the entire range conversion value calculated by the calculation unit;
The load value output by the load cell is corrected based on the entire range converted value, and a conversion unit for obtaining a normal load value,
An injection molding machine comprising: a control unit configured to control the molding operation of the injection molding machine using the normal load value as a load value measured by the load cell.

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