JP5485192B2 - Method for determining propriety of mold clamping force and method for adjusting mold clamping force - Google Patents

Description

  The present invention relates to a method for determining whether or not a mold clamping force is appropriate in an electric injection molding machine equipped with a toggle type mold clamping device, and to determine whether or not the mold clamping force is appropriate. The present invention relates to a mold clamping force adjusting method for adjusting a clamping force.

  As is well known in the art, the electric injection molding machine is composed of a pair of molds, a mold clamping device for clamping these molds, an injection device for melting a resin material and injecting it into the mold, etc. Each device is driven by a servo motor. A so-called toggle type clamping device that opens and closes by a toggle mechanism is also well known. The toggle type clamping device includes a stationary platen to which a fixed side die is fixed, a movable platen to which a movable side die is fixed, and A mold clamping housing, a plurality of tie bars that connect the fixed platen and the mold clamping housing and through which the movable platen is inserted, and a toggle mechanism provided between the mold clamping housing and the movable platen Has been. The toggle mechanism includes long and short links and a cross head that are connected to each other, and the cross head is provided on a ball screw or a ball nut. Therefore, when the ball nut or ball screw is rotated by the servo motor for opening and closing the mold, the crosshead can be driven in the axial direction, and the toggle type mold clamping device is opened and closed. When the mold is clamped by driving the crosshead, the pair of molds touches first, and then the tie bar extends due to elastic deformation. A mold clamping force is generated by the tension of the elongation. Since the crosshead position touched by the mold by the servo motor and the position of the crosshead when the mold clamping is completed can be accurately detected, the mold clamping force can be calculated by calculating the extension of the tie bar from these positions. . In such a toggle type mold clamping device, the tie bar is connected to the mold clamping housing by a tie bar nut. Therefore, when the tie bar nut is rotated when the mold is opened, the connection length between the fixed platen and the tie bar of the mold clamping housing, that is, the tie bar effective length can be adjusted, and the crosshead position where the mold touches can be adjusted. As a result, the mold clamping force can be adjusted.

JP 2005-138447 A JP 2001-277248 A JP 2008-49694 A

For example, Patent Documents 1 to 3 propose a method for detecting the mold clamping force or a method for adjusting the mold clamping force so as to obtain a desired mold clamping force.
Patent Document 1 describes a method of detecting a mold clamping force periodically in an operating injection molding machine and correcting it. According to the method described in Patent Document 1, the torque of the servo motor that drives the toggle mechanism at a predetermined cycle is monitored, and the crosshead position touched by the pair of molds is detected. Then, the movable platen position when the mold touches from the crosshead position, that is, the closed position is calculated, and it is checked whether it is within an appropriate range. If the closed position is not within an appropriate range, it is determined that a desired mold clamping force cannot be obtained when the mold is clamped, and the closed position is adjusted to be within an appropriate range. As a result, even in an injection molding machine in operation, the mold clamping force can be corrected so that a desired mold clamping force is generated.

  Patent Document 2 describes a method of calculating a mold clamping force using a position sensor. That is, in the mold clamping process, when the mold is not touched and no load is applied and the mold clamping housing reaches a reference position, this is set as the first position. The position of the mold clamping housing when the mold clamping is completed is set as the second position. Then, the elongation of the tie bar is obtained from the first and second positions, and the mold clamping force is calculated. Therefore, the clamping force can be accurately measured without providing a sensor on the tie bar or the like. Further, Patent Document 2 also describes a method of adjusting the clamping force by rotating the tie bar nut when the calculated clamping force is not a desired clamping force. That is, the mold clamping force can be easily adjusted.

  Patent Document 3 describes a method of controlling a mold clamping device that can easily set a so-called low pressure mold clamping force. Low-pressure mold clamping means clamping with a low-pressure mold clamping force at a predetermined mold opening position so that foreign matter can be easily detected even when a mold is closed. In the method described in 3, the mold clamping force in this low pressure mold clamping can be adjusted appropriately. Although this adjustment method is not directly related to the present invention, the clamping device described in Patent Document 3 is provided with a strain sensor on the tie bar. Therefore, the mold clamping force can be detected not only when the mold clamping device is driven but also at the time of injection.

  The mold clamping force can also be calculated by the methods of Patent Documents 1 and 2, and can be adjusted to a desired mold clamping force. However, it cannot be determined by these methods whether the mold clamping force is appropriate. In other words, if the clamping force to be set is known, the clamping force can be adjusted to that level, but how much clamping force is appropriate for injection molding? Cannot be judged. In the present invention, the appropriate mold clamping force is a mold clamping force that does not open the mold by the injection pressure when it is injected, and an excessively large mold clamping force is excluded. By judging whether the mold clamping force is appropriate from this point of view and adjusting the mold clamping force, it is possible to perform injection molding with the minimum amount of power consumption, and to achieve high quality The molded product can be molded with energy saving. However, such determination or adjustment cannot be performed by the methods of Patent Documents 1 and 2. If the sensor described in Patent Document 3 is used, the mold clamping force can be detected even during injection. However, the mold clamping apparatus must be provided with such a sensor, and a controller for processing the sensor signal must be provided. This increases the cost. Furthermore, a specific method for determining whether or not the mold clamping force is appropriate is unknown.

  It is an object of the present invention to provide a mold clamping force suitability determination method and a mold clamping force adjustment method that solve the above-described problems. Specifically, a controller, a controller that processes sensor signals, and the like Therefore, it is possible to carry out the process at a low cost, and to determine whether or not the mold clamping force has an appropriate magnitude. An object of the present invention is to provide a mold clamping force adjusting method for adjusting to a large size.

  In order to achieve the above object, according to the present invention, in an electric injection molding machine equipped with a toggle type mold clamping device, whether or not the mold clamping force is appropriate is determined by monitoring a change in the crosshead position during the injection process or the pressure holding process. . In the toggle type mold clamping device, a predetermined torque is generated by a servo motor that drives the cross head in order to maintain mold clamping. If the crosshead position changes even slightly, the control works to maintain the mold clamping state and the torque changes. Therefore, the change of the crosshead position is monitored by monitoring the torque. Further, in order to easily detect a change in torque, the toggle mechanism is clamped in a slightly bent state before being fully extended. In this way, it is configured to determine whether or not the mold clamping force is appropriate and to adjust the mold clamping force so that the mold clamping force becomes appropriate.

Thus, in order to achieve the above object, the invention according to claim 1 is an electric injection molding machine including a toggle type mold clamping device configured to detect a crosshead position by a servo motor that drives the crosshead. determination of appropriateness clamping force, injection process injecting an injection material into clamping a mold or in the pressure-holding step of applying pressure to the injection material after the injection, so that performed by monitoring changes in the cross head position Configured.
According to a second aspect of the present invention, in the method of the first aspect, the toggle-type mold clamping device is clamped in a folded state before the toggle mechanism is fully extended so that the mold clamping force is appropriate. Is configured to determine.
According to a third aspect of the present invention, in the method according to the first or second aspect, the change in the crosshead position is monitored by monitoring the torque of the servo motor.
According to a fourth aspect of the present invention, in the determination method according to the third aspect, when the torque changes beyond a predetermined threshold, it is determined that the clamping force is insufficient. Is done.
According to a fifth aspect of the present invention, the mold clamping force is adjusted by adjusting the connection length of a plurality of tie bars connecting the fixed plate of the toggle type mold clamping device and the mold clamping housing, and In the electric injection molding machine designed to determine whether the mold clamping force is insufficient by the method described in 1., when the mold clamping force is determined to be insufficient, the connection length of the tie bars is shortened little by little every time injection molding is performed. Thus, it is configured to eliminate the shortage of mold clamping force.
According to a sixth aspect of the present invention, the mold clamping force is adjusted by adjusting the connection length of a plurality of tie bars connecting the fixed plate of the toggle type mold clamping device and the mold clamping housing, and In the electric injection molding machine designed to determine the shortage of the clamping force by the method described in 1., if the shortage of the clamping force is not determined, the connection length of the tie bar is increased slightly each time injection molding is performed. Then, a minimum deficiency determination clamping force that is a mold clamping force when it is first determined that the mold clamping force is insufficient is obtained, and the mold clamping force of the toggle type mold clamping device is the minimum deficiency determination mold clamping force. It is comprised so that it may adjust to the magnitude | size which added the addition type clamping force of predetermined magnitude | size.

  As described above, in the electric injection molding machine including the toggle type mold clamping device that detects the crosshead position by the servo motor that drives the crosshead, the present invention applies the injection material to the mold that has been clamped. In the injection process of injecting or in the pressure holding process of applying pressure to the injected material after injection, the change in the crosshead position is monitored to determine whether the mold clamping force is appropriate. If the mold clamping force is insufficient, the mold will open slightly due to the pressure of the injection material in the injection process or pressure holding process, and the movable plate will retreat. This can be easily done by monitoring the crosshead position. Can be detected. Therefore, according to the present invention, it is unnecessary to provide a sensor or a controller for processing the sensor signal, and it is possible to determine whether the mold clamping force is appropriate at a low cost. According to another invention, the toggle type mold clamping device is configured to determine whether or not the mold clamping force is appropriate by being clamped in a folded state before the toggle mechanism is fully extended. Can be reliably detected by the change of the toggle mechanism, that is, the change of the crosshead position. That is, it is possible to reliably determine whether the mold clamping force is appropriate. According to another invention, the change of the crosshead position is monitored by monitoring the torque of the servo motor. The servo motor is controlled to maintain the mold clamping state by applying a predetermined torque, but if the movable plate moves backward and the cross head position changes even slightly, it is controlled to return the cross head position to the original position. Torque increases. The change in torque is relatively large and easy to detect. If this change is monitored, the change in crosshead position can be easily detected. That is, whether or not the mold clamping force is appropriate can be determined more reliably and easily. According to another invention, in this method, when the torque changes beyond a predetermined threshold value, it is determined that the clamping force is insufficient. The shortage of the clamping force can be reliably determined. According to another invention, in the electric injection molding machine designed to determine whether the mold clamping force is insufficient, when it is determined that the mold clamping force is insufficient, the connection length of the tie bar is slightly reduced each time injection molding is performed. Since it is configured to shorten each time to eliminate the shortage of the mold clamping force, the mold clamping force can be adjusted to an appropriate mold clamping force without adjusting the mold clamping force more than necessary. According to another invention, when the lack of clamping force is not determined, the connection length of the tie bar is gradually increased every time injection molding is performed, and the mold when the lack of clamping force is first determined is determined. Obtaining the minimum deficiency determination clamping force, which is the clamping force, and adjusting the mold clamping force of the toggle type mold clamping device to a value obtained by adding a predetermined amount of additional clamping force to the minimum deficiency determination clamping force Thus, even when the mold clamping force is larger than necessary, the mold clamping force can be adjusted to an appropriate value.

It is a side view which shows a part of injection molding machine concerning embodiment of this invention. It is a block diagram which shows the mold clamping force adjustment method which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. Similarly to the conventional injection molding machine, the electric injection molding machine 1 according to the present embodiment is composed of an injection device 2, a toggle type mold clamping device 3 and the like, part of which is shown in FIG. The toggle type mold clamping device 3 includes a fixed platen 5 fixed to the bed, a movable platen 6 mounted on the bed and configured to be opened and closed with respect to the fixed platen 5, and similarly to the bed. A plurality of tie bars 9, 9,... Passing through the mounted mold clamping housing 8, the movable plate 6 and connecting the fixed plate 5 and the mold clamping housing 8, and the mold clamping housing 8 and the movable plate 6 are connected. And a toggle mechanism 11 provided between the two. The toggle mechanism 11 is also configured as known in the art, and includes long links 13 and 13, short links 14 and 14, cross links 15 and 15, and a cross head 17. One end of the long links 13 and 13 is pivotally attached to the movable platen 6 by toggle pins 18 and 18, and one end of the short links 14 and 14 is pivotally attached to the mold clamping housing 8 by toggle pins 19 and 19, respectively. Has been. The other ends of the long links 13 and 13 and the other ends of the short links 14 and 14 are pivotally attached by toggle pins 20 and 20. Further, the short links 14 and 14 are provided with protrusions on the side portions, and the cross head 17 and these protrusions are connected by the cross links 15 and 15. Such a cross head 17 is fixed to the tip of a ball screw 22, and the ball screw 22 is screwed into a ball nut 23. The ball nut 23 is rotatably provided in the mold clamping housing 8 and is provided with a driven gear 25. The ball nut 23 is rotated by a mold opening / closing servomotor 26 and a drive gear 27. Accordingly, when the mold opening / closing servomotor 26 is driven, the crosshead 17 can be driven in the axial direction, so that the mold can be opened and closed. The mold opening / closing servomotor 26 can detect the rotation angle, and can accurately detect the position of the crosshead 17, that is, the position of the crosshead. The mold opening / closing servomotor 26 is driven by a servo amplifier 29, and the servo amplifier 29 is controlled by a controller 30.

  Although not shown in FIG. 1, the mold clamping housing 8 and the tie bars 9, 9,... Are connected by a conventionally known connection method. That is, the mold clamping housing 8 is formed with four tie bar nut pockets. The tie bar nuts are rotatably accommodated in the tie bar nut pockets in a state in which the movement in the axial direction is restricted. , 9... Are screwed together. The tie bar nut is rotated synchronously by a predetermined drive mechanism. Accordingly, when the tie bar nut is rotated in synchronization, the connection length between the fixed platen 5 and the mold clamping housing 8, that is, the connection length between the tie bars 9, 9,... Can be adjusted. As a result, the mold clamping force can be adjusted. In such a toggle type mold clamping device 3, a fixed side mold 32 is attached to the fixed platen 5, and a movable side die 33 is attached to the movable platen 6.

  In the electric injection molding machine 1 according to the present embodiment, a method for adjusting to an optimum mold clamping force will be described. The optimum mold clamping force in the present invention is a mold clamping force that can reliably maintain the mold clamping state during the injection process or the pressure holding process, and it is not excessively large but has a minimum mold clamping force. That is. In order to adjust to such a mold clamping force, it is necessary to determine whether the mold clamping force is appropriate. When the clamping force is insufficient, the molds 32 and 33 are slightly opened by the pressure of the injection material in the injection process or the pressure holding process, and the movable platen 6 is retracted instantaneously. Then, the position of the crosshead 17, that is, the crosshead position changes. In this embodiment, the change in the crosshead position is monitored to determine whether the mold clamping force is insufficient. More specifically, the torque of the mold opening / closing servomotor 26 is monitored. Yes. This is due to the following reason. That is, the servo amplifier 29 supplies a certain amount of electric power to generate torque in the mold opening / closing servomotor 26 under the control of the controller 30 so that the crosshead position does not change during mold clamping. When the crosshead position slightly changes, control is performed to restore the original position, the power supplied from the servo amplifier 29 is increased, and the torque of the mold opening / closing servomotor 26 is increased. The torque is controlled with a predetermined crosshead position as a target value, and the control includes not only a proportional element but also an integral element. Therefore, even if the crosshead position changes slightly, the torque changes greatly. Therefore, in the method for determining the appropriateness of the mold clamping force according to the present embodiment, this change in torque is monitored.

  By the way, in the present embodiment, the toggle mechanism 11 is adjusted so as to be clamped in a slightly bent state so that when the movable platen 6 moves backward, this is reliably detected as a change in the crosshead position. This is because if the mold is clamped in a state where the toggle mechanism 11 is fully extended, the toggle mechanism 11 is in a self-locking state, so that it is difficult to detect the backward movement of the movable platen 6 due to a change in the crosshead position. Therefore, when the method for adjusting the mold clamping force described below is performed, adjustment is performed so that the mold clamping is completed in a slightly bent state before the toggle mechanism 11 is fully extended.

A method of adjusting the mold clamping force according to the present embodiment will be described with reference to FIG. First, the controller 30 inputs a determination threshold value Ta for determining whether the mold clamping force is insufficient (step S1). Next, the coupling length of the tie bars 9, 9,... Is adjusted, and the mold clamping force is initially adjusted so that a predetermined mold clamping force is generated. For example, a necessary clamping force is calculated from the projected area of the molded product and the injection pressure of the injection material, and adjusted to such a clamping force (step S2). The crosshead 17 is driven in the axial direction by the mold opening / closing servomotor 26 to clamp the mold (step S3). In order to maintain the mold clamping state, a predetermined torque is generated in the mold opening / closing servo motor 26. Stores the initial torque _{T 1} to the controller 30 (step S4). The injection material weighed in the injection apparatus 2 is injected into the cavities in the molds 32 and 33 as conventionally known. Then, the injection device 2 applies pressure to the injection material to hold it. Detecting the maximum torque T ₂ monitors the torque of the mold opening and closing servo motor 26 in such an injection process and the pressure holding step (step S5). The controller 30 determines whether the mold clamping force is appropriate according to the following conditional expression (step S6).
Maximum torque T ₂ −initial torque T ₁ > determination threshold Ta

If the conditional expression is true, it is determined that the crosshead position has changed and it is determined whether the mold clamping force is insufficient. That is, it becomes clear that the mold clamping force initially adjusted in step S2 was insufficient. In this case, the coupling length of the tie bars 9, 9,... Is slightly shortened and the mold clamping force is adjusted so that the mold clamping force is increased by ΔF (step S7). The same procedure as step S3 to step S6 is repeated. I.e. clamping (step S3 '), and stores the initial torque T ₁ of the order to maintain the clamping state to the controller 30 (step S4'), the maximum torque of the mold opening and closing servo motor 26 in the injection process and the pressure holding step T ₂ is detected (steps S5 '). Then, whether or not the mold clamping force is appropriate is determined by the conditional expression described above (step S6 ′). If the conditional expression is true, the process returns to step S7 and steps S3 ′ to S6 ′ are repeated. When the conditional expression becomes false, it is determined that the mold clamping force is optimum, and the adjustment of the mold clamping force is finished.

If the conditional expression is false in step S6, it can be determined that the crosshead position has not changed and the clamping force is sufficient. In this case, the mold clamping force may be excessive. Therefore, the tie bars 9, 9,... Are slightly lengthened and the mold clamping force is adjusted so that the mold clamping force is reduced by ΔF (step S8). A procedure similar to that in steps S3 ′ to S6 ′ is performed. I.e. clamping (step S3 ''), and stores the initial torque T ₁ of the order to maintain the clamping state to the controller 30 (step S4 ''), the mold opening and closing servo motor 26 in the injection process and the pressure holding step detecting the maximum torque _{T 2} (step S5 ''). Then, whether or not the mold clamping force is appropriate is determined by the conditional expression described above (step S6 ″). If the conditional expression is false, the process returns to step S8 to repeat steps S3 ″ to S6 ″. When the conditional expression becomes true, it is determined that the clamping force is insufficient. This slightly insufficient mold clamping force is determined as the minimum insufficient mold clamping force Fs (step S9). As shown in the following equation, an additional mold clamping force Fb, which is a small mold clamping force, is added to the minimum shortage determination mold clamping force Fs to obtain an optimum mold clamping force F (step S10).
Optimum mold clamping force F = Minimum shortage determination mold clamping force Fs + Additional mold clamping force Fb
The mold clamping force is adjusted so that the optimum mold clamping force F is obtained. Finish the adjustment.

  The embodiment of the present invention can be variously modified. For example, in the present embodiment, whether the mold clamping force is appropriate is determined by monitoring the torque of the mold opening / closing servomotor 26. This is because the torque change is larger than the change of the crosshead position and is easy to detect. However, since the mold opening / closing servomotor 26 can accurately detect the crosshead position, the crosshead position can be directly detected. You may make it monitor. Further, in the adjustment of the mold clamping force, the toggle mechanism has been described as adjusted so that the mold is clamped in a slightly bent state, but it is not always necessary to do so. That is, even if the mold is clamped with the toggle mechanism fully extended, the mold clamping force can be adjusted similarly. Furthermore, although it has been described that the torque is monitored in both the injection process and the pressure holding process, it may be monitored only in one of the processes.

DESCRIPTION OF SYMBOLS 1 Electric injection molding machine 2 Injection apparatus 3 Toggle type clamping device 5 Fixed board 6 Movable board 8 Clamping housing 9 Tie bar 11 Toggle mechanism 17 Crosshead 26 Mold opening / closing servo motor 29 Servo amplifier 30 Controller 32 Fixed side mold 33 Movable Side mold

Claims (6)

In an electric injection molding machine equipped with a toggle type mold clamping device adapted to detect a crosshead position by a servo motor that drives the crosshead,
Determination of appropriateness clamping force, injection process injecting an injection material into clamping a mold or in the pressure-holding step of applying pressure to the injection material after injection, it is done by monitoring a change in the cross head position A method for determining whether a mold clamping force is suitable.   2. The method according to claim 1, wherein the toggle type mold clamping device is clamped in a folded state before the toggle mechanism is fully extended to determine whether the mold clamping force is appropriate. A method for determining the appropriateness of the tightening force.   3. The method according to claim 1, wherein the change of the crosshead position is monitored by monitoring a torque of the servo motor.   The determination method according to claim 3, wherein when the torque changes beyond a predetermined threshold value, it is determined that the mold clamping force is insufficient. 5. The mold clamping force is adjusted by adjusting the connecting length of a plurality of tie bars connecting the fixed plate of the toggle type mold clamping device and the mold clamping housing, and the mold clamping force is adjusted by the method according to claim 4. In the electric injection molding machine designed to judge the shortage,
A method for adjusting a clamping force, characterized in that, when it is determined that the clamping force is insufficient, the connection length of the tie bars is gradually shortened every time injection molding is performed to solve the shortage of clamping force. 5. The mold clamping force is adjusted by adjusting the connecting length of a plurality of tie bars connecting the fixed plate of the toggle type mold clamping device and the mold clamping housing, and the mold clamping force is adjusted by the method according to claim 4. In the electric injection molding machine designed to judge the shortage,
If insufficient clamping force is not determined, the tie bar connection length is gradually increased every time injection molding is performed, and the minimum insufficient determination that is the clamping force when the insufficient clamping force is first determined. A mold clamping force is obtained, and a mold clamping force of the toggle type mold clamping device is adjusted to a magnitude obtained by adding a predetermined magnitude of an additional mold clamping force to the minimum shortage determination mold clamping force. Tightening force adjustment method.

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