JP3930373B2 - Method for controlling mold clamping device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control method for smoothly moving and displacing a movable plate without being affected by external force when opening and closing a mold clamping device such as an injection molding machine.
[0002]
[Prior art]
According to the conventional control method of the mold clamping apparatus shown in FIG. 1, after the mold is aligned by the opening / closing means 2, the half nut 19 is engaged with the engaging portion 20, and the mold is clamped by the pressure clamping means 3. Then, since the movable platen 5 moves further to the fixed platen 4 side from the die alignment position by the mold clamping force, the servo motor 15 is forcibly rotated. At this time, when a spring 8 that acts to push open the fixed mold 6 and the movable mold 7 is provided, the mold is clamped by the pressing means 3 after the mold is matched by the opening / closing means 2. Alternatively, in the step of releasing the mold clamping force by the pressure-clamping means 3 and opening the strong mold, a phenomenon occurs in which the movable mold 7 is separated from the fixed mold 6 by the spring 8. In order to prevent this abnormal phenomenon, the servo motor 15 is positioned and controlled at the mold alignment position to prevent the spring 8 from separating the movable mold 7 from the fixed mold 6. In the conventional control method, the servo motor 15 is controlled to be positioned at the mold alignment position as described above. Therefore, when the servo motor 15 is rotated by the mold clamping force or the strong mold opening force, the servo motor 15 returns to the original positioning position. Thus, the servo motor 15 is over-heated, so that an excessive current flows through the servo motor 15 and power loss occurs and the servo motor 15 overheats.
[0003]
[Problems to be solved by the invention]
The present invention has been proposed to solve the problems of power loss and overheating of the servo motor in the mold clamping apparatus as described above.
[0004]
[Means for Solving the Problems]
That is, a mold comprising opening / closing means for opening and closing the movable platen by a servo motor, and pressure clamping means for performing mold clamping and / or strong mold opening of the movable plate to the fixed plate by means different from the servo motor. In the method of controlling the clamping device, after the molds attached to the fixed platen and the movable platen are matched with each other by the opening and closing means, the mold clamping process is released, or the mold clamping force is released and the process proceeds to strong mold opening. In the step, when the movable platen positioned by the servomotor is displaced by an external force, the positioning target position of the movable platen is moved according to a displacement amount of the movable plate displaced by the external force. More specifically, the positioning target position of the movable plate is moved to a position where the movable plate is displaced by an external force.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional plan view schematically showing a mold clamping apparatus for carrying out the present invention and a block diagram of a control apparatus, and FIGS. 2 and 3 are flowcharts showing a control method of the present invention.
[0006]
The mold clamping device 1 includes an opening / closing means 2, a pressure clamping means 3, and a control device 22. The opening / closing means 2 is attached to both side surfaces of the movable plate 5 by screwing with the servo motor 15 attached to both side surfaces of the fixed platen 4, the encoder 16 coupled to the drive shaft of the servomotor 15, the ball screw 17, and the ball screw 17. It consists of a ball nut 18. In the vicinity of the four corners of the fixed platen 4 and the movable platen 5, through-holes through which the four tie bars 9 are slidably inserted are provided, and the movable platen 5 to which the movable die 7 is attached is the fixed platen to which the fixed die 6 is attached. 4, the servomotor 15 can be moved close to and away from each other. The end of the ball screw 17 opposite to the fixed plate is supported by the support plate 10 so as to be rotatable and reciprocating.
[0007]
The pressing means 3 is detachably connected to the engaging portion 20 by a driving device such as a cylinder provided on the side of the movable plate 5 opposite to the engaging portion 20 engraved on the outer peripheral surface of the tie bar 9. The mold includes a half nut 19 and a mold clamping cylinder 11 that is provided on the side of the fixed platen 4 opposite to the movable plate and pushes and pulls the tie bar 9. The internal space of the mold clamping cylinder 11 is divided into a mold clamping chamber 13 and a strong mold opening chamber 14 by a piston 12 fixed to the end face of the tie bar 9, and the engaging portion 20 of the tie bar 9 is movable by a half nut 19. When engaged with 5, pressure oil is supplied to the mold clamping chamber 13 to clamp and mold the mold, and pressure oil is supplied to the strong mold opening chamber 14 to release the molded product from the mold. Therefore, strong mold opening is performed. The pressing means 3 is an example, and there are various other forms. For example, the mold clamping cylinder may be provided on the movable platen 5 instead of the fixed platen 4, or the mold clamping cylinder and the half nut may be provided on the support plate 10 so that the movable platen and the support plate move together. Moreover, the form provided in the member which protruded in the anti-fixed board side of the movable board instead of the tie bar may be sufficient.
[0008]
The control device 22 is a servo comprising an input unit 24, an output unit 25, a setting / display unit 26 and a storage unit 27, and a speed control unit 28 and a current / power control unit 29, which are connected to a CPU 23 comprising a microprocessor via a bus line. An amplifier 31 is included. The control device 22 is responsible for sequence control of the mold clamping device 1 and an injection device (not shown) and servo motor control. The control device 22 is input to the input unit 24 based on the set values such as the position, speed, force, etc. of the movable platen 5 set by the setting / display unit 26 and the operation program or constant stored in the storage unit 27. A speed signal is output from the output unit 25 to the hydraulic device 30 and the servo amplifier 31 that drive the clamping cylinder 11 so that the position of the tie bar 9 from the position sensor 21 and the position of the movable platen 5 from the encoder 16 become the set positions. And control. The output unit 25 outputs a torque command for limiting the output torque of the servo motor 15 to the speed control unit 28 in addition to the speed signal.
[0009]
The control device 22 and the servo amplifier 31 are configured by known devices, and the portion related to the positioning control of the servo motor 15 will be described. The positioning target position of the movable platen 5 set by the setting / display unit 26 is stored in the storage unit 27 and the position signal of the movable platen 5 input to the input unit 24 from the encoder 16 fixed to the shaft of the servomotor 15. These are collated by the calculation of the CPU 23 based on the control program, and are calculated to be a speed signal and input to the speed control unit 28 of the servo amplifier 31. The speed control unit 28 matches the speed signal with the speed value detected by the encoder 16, and outputs a control signal PID-calculated so that the speed value matches the speed signal to the current / power control unit 29. The current / power control unit 29 generates a current accurately corresponding to the control signal by a constant current circuit, further amplifies the current and supplies it to the servo motor 15. According to such a servo system which is a positioning control system by the control device 22, the servo amplifier 31 and the servo motor 15, the movable platen 5 always reaches the target position set by the setting / display unit 26. Positioning is controlled by
[0010]
Next, the mold clamping operation in the mold clamping apparatus 1 will be described with reference to FIG. This control is performed by the control unit 22 based on the control program stored in the storage unit 27 and a constant, so that the CPU 23 and the output unit 25 and the servo are controlled so that the position of the movable platen 5 becomes the target position set by the setting / display unit 26. The calculation is performed through the amplifier 31 and the servo motor 15 is controlled. In a mold open state where the movable mold 7 is separated from the fixed mold 6 as shown in FIG. 1, the half nut 19 is not engaged with the tie bar 9, and the servo motor 15 is driven to move the movable platen 5. Close to the fixed platen 4. The movable mold 7 is matched with the fixed mold 6 (S1) and abuts to complete the mold closing. At this time, the encoder 16 that detects the separation distance from the mold closing completion position of the movable mold 7 detects the zero position. The servo motor 15 is positioned and controlled with the zero position as the target position, and is in a servo lock state (S2). In this state, even when the movable mold 7 has the spring 8, the movable mold 7 is not separated from the fixed mold 6 by the elastic force of the spring 8. Next, each half nut 19 is driven in proximity to the tie bar 9 to engage the half nut 19 and the tie bar 9. Thereafter, pressure oil is supplied to the mold clamping chamber 13 of the mold clamping cylinder 11 and the movable platen 5 is pulled toward the fixed platen 4 to clamp the mold. At this time, the movable platen 5 is further moved in the direction of the fixed platen 4 from the zero positioning position by the clamping force, so that the servo motor 15 that is servo-locked moves the movable platen 5 from the zero target position (several mm). Is forcibly rotated to the negative side by an amount corresponding to (S3). For this reason, a relatively large current flows through the servomotor 15 that is positioned and controlled to return to the original zero position. If this state continues, the servomotor 15 generates heat and power is lost. Therefore, the torque command to the servomotor 15 is changed to a lower predetermined value (S4), and the target position for the positioning control of the servomotor 15 that has been zero is displaced by the external force that is the mold clamping force of the pressing means 3. The position is moved by sequentially changing to a given position every predetermined time (2 msec in this example) (S5). This step S5 is repeated until the mold clamping is completed (S6). When the mold clamping is completed, the torque command changed to a lower value is returned to the original value (S7). Steps S4 and S7 are executed as necessary, and are not essential.
[0011]
The operation in the strong mold opening, which is another embodiment of the present invention, will be described with reference to FIG. After the mold is clamped by the pressing means 3 as described above, the molten resin injected and filled into the mold cavity from an injection device (not shown) is cooled and solidified to form a molded product. Then, the movable mold 7 is separated from the fixed mold 6 in order to release the molded product. At this time, when the molded product has a large shape in the moving axis direction of the movable mold 7, the force required to release the molded product against the adhesive force between the molded product and the mold cavity surface is the servo motor 15. There may be a shortage. Therefore, the strong mold is opened by the oil pressure of the clamping means 3.
[0012]
Prior to the powerful mold opening, first, in step S11, the hydraulic pressure supplied to the mold clamping chamber 13 of the mold clamping cylinder 11 which is a pressure clamping means is released to release the mold clamping pressure. At this time, the half nut 19 is kept engaged with the tie bar 9 and further prevents the movable mold 7 from moving due to the elastic force of the spring 8 when the spring 8 is built in the movable mold 7. Then, the servo motor 15 is servo-locked so that the movable platen 5 can be positioned at the zero position which is the mold closing completion position (S12). At this time, the encoder 16 that detects the separation distance from the mold closing completion position of the movable mold 7 detects the zero position. Next, when the strong mold opening is performed by supplying pressure oil to the strong mold opening chamber 14 of the mold clamping cylinder 11, the servo motor 15 that is servo-locked moves the mold opening to the positive side of several mm of the movable platen 5. Along with this, it is forcibly rotated from the zero target position (S13). For this reason, the servo motor 15 that is servo-locked is positioned and controlled so that it returns to the original zero position. Therefore, a relatively large current flows through the servo motor 15, and when this state continues, the servo motor 15 generates heat and generates electric power. Loss. Therefore, the torque command to the servomotor 15 is changed to a lower predetermined value (S14), and the target position for positioning control of the servomotor 15 which has been zero is set by an external force which is a strong mold opening force of the pressing means 3. The position is moved to the displaced position by sequentially changing every predetermined time (in this example, 2 milliseconds) (S15). This step S15 is repeated until the strong mold opening force is completed (S16). When the powerful mold opening is completed, the torque command changed to a lower value is returned to the original value (S17). Thereafter, the engagement of the half nut 19 with the tie bar 9 is released, and the movable platen 5 is opened by the servo motor 15. Steps S14 and S17 are executed as necessary, and are not essential.
[0013]
Although the embodiment of the present invention has been illustrated and described above, this is merely an example, and the present invention is not construed as being limited by the specific description in the embodiment.
[0014]
For example, it has been described that the torque command of the servo motor 15 is changed to a lower predetermined value after the movable platen 5 is moved by the external force and the servo motor 15 in the servo lock state is forcibly rotated. When the movable platen 5 is moved by this and the servo motor 15 in the servo lock state is forcibly rotated, the servo lock is released, that is, the servo system of the servo motor 15 is disabled and power is supplied to the servo motor 15. You may make it cut off.
[0015]
Further, it has been described that when the servo motor 15 that is servo-locked is forcibly displaced by an external force, the target position of the servo motor 15 is moved to the displaced position, but within the displaced amount. Then, it may be moved to a target position where the speed signal is within a predetermined value range.
[0016]
Further, as means for detecting that the servo motor 15 that is servo-locked is forcibly displaced by an external force, the following may be mentioned. (1) When the speed signal increases beyond the specified value. (2) When the position value of the encoder 16 changes. (3) When the speed or acceleration value calculated based on the position value of the encoder 16 exceeds a predetermined value.
[0017]
【The invention's effect】
Since the present invention is implemented as described above, even in a mold with a built-in spring, the mold does not open at the time of switching from the completion of mold closing to mold clamping or depressurization to strong mold opening. The movable plate can be operated smoothly without loss of power.
[Brief description of the drawings]
FIG. 1 is a plan view of a partial cross section showing an outline of a mold clamping device for carrying out the present invention, and a block diagram of a control device.
FIG. 2 is a flowchart showing a method of controlling a mold clamping process in the present invention.
FIG. 3 is a flowchart showing a control method of a powerful mold opening process in the present invention.
[Explanation of symbols]
1 ......... Clamping device 2 ......... Opening / closing means 3 ......... Pressure clamping means 4 ......... Fixed plate 5 ......... Movable plate 6 ......... Fixed mold 7 ......... Movable mold 8 ......... Spring 9 ... Tie bar 10 ... Support plate 11 ... Clamping cylinder 12 ... Piston 13 ... Clamping chamber 14 ... Powerful mold opening 15 ... Servo motor 16 ... Encoder 17 ... Ball screw 18 ... Ball nut 19 ... Half nut 20 ... Engagement part 21 ... Position sensor 22 ... Control device 23 ... CPU
24 ...... Input unit 25 ...... Output unit 26 ...... Setting / display unit 27 ...... Storage unit 28 ...... Speed control unit 29 ...... Current / power control unit 30 ...... Hydraulic device 31 ...... Servo amplifier

Claims (4)

A mold clamping device comprising: opening / closing means for opening / closing the movable board by a servo motor; and pressure clamping means for performing mold clamping and / or powerful mold opening of the movable board to the fixed board by means different from the servo motor In the control method of
After the molds attached to the fixed platen and the movable platen are matched by the opening / closing means and positioned by the servo motor, the process is shifted to mold clamping, or the mold clamping force of the pressure clamping means is released to strengthen the mold. in the process of transition to mold opening said that, when the movable platen being positioned by the servo motor has been displaced by external force, the target position of a positioning servo system by the servo motor of the movable plate is displaced by an external force A method for controlling a mold clamping device, wherein the movable platen is moved in accordance with a displacement amount of the movable platen . When the movable plate positioned by the servo motor is displaced by an external force, the positioning target position of the movable plate is moved to the position of the movable plate displaced by an external force. The method for controlling a mold clamping device according to claim 1.  When moving the positioning target position of the movable plate to a position where the movable plate is displaced by an external force, the torque command of the servo motor is changed to a lower value, and the movement of the positioning target position is completed 3. The method for controlling a mold clamping device according to claim 1, wherein the original torque command value is returned to the original value. A mold clamping device comprising: opening / closing means for opening / closing the movable board by a servo motor; and pressure clamping means for performing mold clamping and / or powerful mold opening of the movable board to the fixed board by means different from the servo motor In the control method of
After the molds attached to the fixed platen and the movable platen are matched by the opening / closing means and positioned by the servo motor, the process is shifted to mold clamping, or the mold clamping force of the pressure clamping means is released to strengthen the mold. In the process of shifting to mold opening, when the movable platen positioned by the servo motor is displaced by an external force, the servo system of the servo motor is disabled and the current is cut off. Control method.

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