JP6173985B2 - Method for adjusting mold clamping force of toggle type injection molding machine for performing heat and cool molding method - Google Patents

Description

  The present invention relates to a mold clamping force adjusting method in a toggle type injection molding machine that performs a heat and cool molding method.

  As is well known in the art, an electric injection molding machine equipped with a toggle type mold clamping device includes a stationary platen fixed on a bed, a mold clamping housing slidably provided on the bed, a fixed platen and a mold clamping housing. 4 tie bars, a movable platen inserted through the tie bar, a toggle mechanism provided between the mold clamping housing and the movable platen, and the like. A toggle mechanism is also well known, and is composed of a crosshead and a plurality of toggle links. The cross head is provided with a ball nut, and when the ball screw is rotated by a mold opening / closing motor, the cross head can be driven in the axial direction. Thus, the toggle type mold clamping device can be driven. Incidentally, the tie bar is coupled to the mold clamping housing as follows. That is, the mold clamping housing has through holes, and tie bars are inserted into the through holes. Male screws are formed at the ends of the inserted tie bars, and tie bar nuts are screwed into these male screws. These tie bar nuts are rotatably provided in the mold clamping housing, and movement in the axial direction is restricted. These tie bar nuts can be rotated by a predetermined mold thickness adjusting mechanism. Since the tie bar is coupled to the mold clamping housing in this way, when the mold thickness adjusting mechanism is driven to rotate the tie bar nut, the effective length of the tie bar, that is, the connection length between the fixed platen and the mold clamping housing can be adjusted. The mold thickness between the fixed platen and the movable platen can be adjusted.

  In the toggle type mold clamping device, the process of clamping the fixed side mold and the movable side mold includes a mold closing process until these molds touch and a mold clamping process in which a mold clamping force is generated after the touch. Can be divided. If the crosshead position when the mold touches when the mold closing process is completed, that is, the mold touch position is an appropriate position, a desired mold clamping force can be obtained at the time of mold clamping. This is because when the mold opening / closing motor is further driven in the mold clamping process to reach the position where the crosshead position is set, that is, when the mold clamping completion position is reached, the extension due to elastic deformation of the tie bar becomes a desired length and tension is obtained. . Thus, it is necessary to adjust the mold thickness so that the mold touch position is appropriate.

JP 2004-122579 A

  The mold thickness adjustment is generally performed only once when the mold is replaced, but an appropriate mold clamping force may not be obtained. Although there are various causes for this, it can be said that the change in the apparent mold thickness due to the thermal expansion / contraction of the mold clamping device or the mold due to the temperature change is the main cause. Therefore, as in the adjustment method described in Patent Document 1, there is also proposed an adjustment method corresponding to a change in the apparent mold thickness by performing mold thickness adjustment every predetermined number of molding cycles. The adjustment method described in Patent Document 1 detects the peak current of the mold clamping motor, that is, the peak torque at the time of mold clamping in the last molding cycle, after the molding cycle is performed a prescribed number of times S. If the peak torque is not within an appropriate range, the mold thickness adjustment is performed after the mold clamping process is completed, so that the mold clamping force can be appropriately obtained in the subsequent molding cycles. In the method described in Patent Document 1, mold thickness adjustment is performed for each of a plurality of molding cycles, but a method of adjusting the mold thickness for each molding cycle is also well known. Even when the mold thickness is adjusted for each molding cycle, the torque of the clamping motor in the clamping process or the clamping force obtained from the detection of distortion of the tie bar is detected. After completion of the process, the mold thickness is adjusted to prepare for the next molding cycle.

  By the way, a so-called heat and cool molding method is well known as a molding method for obtaining a molded product excellent in surface transferability such as a glossy molded product or a molded product having a fine shape. The heat and cool molding method is a molding method in which a molten resin is injected while a mold is heated, and then the mold is cooled to obtain a molded product. The molten resin injected into the mold cavity has a high mold temperature, and maintains a high fluidity without cooling and solidifying, and smoothly flows along the surface of the cavity. Since the molten resin is then cooled in a state where the molten resin is properly filled in the cavity, a molded product having excellent surface transferability can be obtained.

  The heat and cool molding method is excellent as a molding method because it can obtain a molded product with excellent transferability. However, when the mold is heated or cooled, the mold and the clamping device are heated by the temperature change. It expands and shrinks. The apparent mold thickness changes with this thermal expansion and contraction. In the heat and cool molding method, since the mold is injected while being sufficiently heated and clamped, the mold thickness is adjusted so that the clamping force at this time becomes a desired magnitude. In the heat and cool molding method, a heating medium is supplied to the mold during heating or cooling to control the mold to a desired temperature. That is, the temperature at the time of high temperature and low temperature of the mold is almost constant. However, since the temperature of the mold clamping device is not particularly controlled, the temperature change of the mold clamping device varies. That is, the change in temperature is not always constant. As a result, the apparent mold thickness changes with each molding cycle. FIG. 3 schematically shows a change in mold clamping force when the heat and cool molding method is performed. In the first molding cycle 51, when the mold is heated to a desired temperature and the mold is clamped, an optimal mold clamping force 53 is generated as indicated by reference numeral 52. Injection is performed at reference numeral 52. Thereafter, when the mold is cooled, the clamping force decreases as indicated by reference numeral 54. The mold is opened after cooling and solidification to obtain a molded product. Similarly, the mold is heated to a desired temperature in the second molding cycle 55, but an optimum mold clamping force 53 may not be reached as indicated by reference numeral 56 during mold clamping. Even if the mold is cooled after injection, it may be less than the clamping force in the first molding cycle, as indicated by reference numeral 57. In this graph, in the third molding cycle 58, the optimum mold clamping force 53 is exceeded when the mold is heated and clamped. Thus, in the heat and cool molding method, the mold clamping force at the time of mold clamping is likely to change for each molding cycle. This is because the temperature of the mold clamping device tends to vary in the heat-and-cool molding method in which the mold is forcibly heated or cooled as compared to a general molding method in which the temperature of the mold clamping device is relatively stable. Because there is. In the heat and cool molding method, the variation in mold clamping force increases in each molding cycle as described above. Therefore, if the mold clamping force exceeds the optimum mold clamping force 53 as indicated by reference numeral 59, the mold clamping motor is used. May detect an abnormality and stop the mold clamping process. That is, the problem that the molding cycle stops tends to occur. Therefore, for example, mold thickness adjustment is performed for each molding cycle, or mold thickness adjustment is performed for several molding cycles as in the method described in Patent Document 1, so that an apparent mold thickness change can be prevented. It is possible to respond. However, the mold thickness adjustment in these conventional methods is only performed to prepare for the mold clamping process in the next and subsequent molding cycles. That is, even if it is detected that the clamping force is inappropriate in the clamping process of a predetermined molding cycle, the mold thickness cannot be adjusted in the molding cycle. Then, as described above, the problem that the mold clamping motor detects an abnormality and the molding cycle stops cannot be solved. In the first place, with the heat and cool molding method, the temperature of the mold clamping device varies with each molding cycle, so even if you perform mold thickness adjustment in preparation for the next and subsequent molding cycles, the optimal mold clamping force can be obtained at the next mold clamping. There is no guarantee to be done.

  An object of the present invention is to provide a mold clamping force adjusting method that solves the above-described problems. Specifically, the present invention provides a heat and cool molding method in an injection molding machine equipped with a toggle type mold clamping device. It is an object of the present invention to provide a method for adjusting a mold clamping force, in which a desired mold clamping force can be stably obtained and an abnormal mold clamping force is detected and a molding cycle is not interrupted.

  To achieve the above object, the present invention provides a toggle type injection molding machine in which mold opening and closing can be performed by driving a crosshead of a toggle mechanism, and mold thickness can be adjusted by driving a tie bar nut provided on a tie bar. When performing a heat and cool molding method in which the temperature is raised to a predetermined temperature and injected, and then the mold is cooled, the clamping force is adjusted in the clamping process. Specifically, the mold clamping process includes a first stage in which the mold is closed and the mold thickness is adjusted so that the crosshead is driven to the mold closing position and the mold clamping force is in a minute contact state. And a third stage in which a desired clamping force is generated by driving the cross head to the clamping completion position. The temperature rise of the mold is completed before the second stage, and the second stage is when the mold clamping force in the contact state deviates from a predetermined reference range. Adjust the mold thickness to within the standard range. Thereafter, when the third stage is performed, a desired clamping force can be obtained.

Thus, in order to achieve the above object, the invention according to claim 1 connects the fixed platen, the movable platen, the mold clamping housing, and the fixed platen and the housing with the movable platen interposed therebetween. It consists of a tie bar and a toggle mechanism provided between the movable platen and the mold-clamping housing, and drives the crosshead of the toggle mechanism with a mold attached to the fixed platen and the movable platen. Then, in a toggle type injection molding machine that can open and close the mold and adjust the mold thickness by driving the tie bar nut provided on the tie bar, the mold is heated to a predetermined temperature and then injected. When the heat and cool molding method for cooling the mold is performed, the mold clamping step is a process of driving the cross head to the mold closing position and closing the mold so that the mold clamping force is in a minute contact state. Stage 1 And a second stage for performing mold thickness adjustment, and a third stage for driving the cross head to a mold clamping completion position to generate a desired mold clamping force. It is completed before the second stage, and the second stage performs mold thickness adjustment when the mold clamping force of the mold in the contact state deviates from a predetermined reference range set in advance. Thus, the method is configured as a method for adjusting the clamping force of a toggle type injection molding machine.
According to a second aspect of the present invention, in the mold clamping force adjusting method according to the first aspect, in the second step, the mold thickness is adjusted in a state where the crosshead is maintained at the mold closed position. It is configured as a mold clamping force adjusting method for a toggle type injection molding machine.
According to a third aspect of the present invention, in the mold clamping force adjusting method according to the first or second aspect, the mold clamping force in the second stage is detected by a strain sensor provided on the tie bar. It is configured as a mold clamping force adjustment method for a toggle type injection molding machine.
According to a fourth aspect of the present invention, in the mold clamping force adjusting method according to the first or second aspect, the mold clamping force in the second stage is detected by torque of a motor that drives the crosshead. It is configured as a mold clamping force adjustment method for a toggle type injection molding machine.

  As described above, the present invention is configured as a mold clamping force adjustment method for a general toggle type injection molding machine. That is, the toggle type injection molding machine is provided between the movable platen and the mold clamping housing, the fixed platen, the movable platen, the mold clamping housing, the tie bar connecting the fixed platen and the housing with the movable platen interposed therebetween. When the toggle mechanism crosshead is driven with the mold attached to the fixed plate and movable plate, the die opens and closes, and when the tie bar nut on the tie bar is driven, the die thickness Since it can be adjusted, it is general. Then, the present invention is configured as a mold clamping force adjusting method when a heat and cool molding method in which the mold is heated to a predetermined temperature and injected and then the mold is cooled in such a toggle type injection molding machine. Is done. Specifically, the mold clamping process includes a first stage in which the mold is closed and the mold thickness is adjusted so that the crosshead is driven to the mold closing position and the mold clamping force is in a minute contact state. And a third stage in which the crosshead is driven to the mold clamping completion position to generate a desired mold clamping force, and the mold temperature rise is completed at least before the second stage. The second stage is configured such that when the mold clamping force of the mold in the contact state deviates from a predetermined reference range that is set in advance, the mold thickness is adjusted to be within the reference range. ing. Accordingly, the mold thickness adjustment is performed when the temperature rise of the mold is completed and the mold is in contact, but this is just before the third stage, which can be called a substantial mold clamping process. is there. That is, according to the present invention, the mold thickness is accurately adjusted immediately before mold clamping in the molding cycle currently being carried out. Then, it can be guaranteed that the desired clamping force can be obtained accurately when clamping in the third stage. Generally, in the heat and cool molding method, the temperature of the mold clamping device may change with each molding cycle, which may result in unstable mold clamping force. In some cases, the molding cycle is stopped upon detecting the abnormality, but these problems can be solved by implementing the mold clamping force adjusting method of the present invention.

It is a figure which shows typically the toggle type injection molding machine which concerns on embodiment of this invention. It is a flowchart explaining the mold clamping force adjustment method which concerns on embodiment of this invention. It is a graph which shows the change of the mold clamping force at the time of implementing a heat and cool molding method.

  The mold clamping force adjusting method according to the present embodiment is carried out in a molding cycle consisting of a so-called heat and cool molding method, and the toggle injection molding machine 1 to be used is a general toggle injection molding machine. That is, the toggle injection molding machine 1 used in the present embodiment is also composed of an injection device 2 and a mold clamping device 3 as shown in FIG. The mold clamping device 3 includes a stationary platen 5, a movable plate 6 that is opened and closed with respect to the stationary platen 5, a mold clamping housing 7, and the stationary platen 5 that penetrates the movable platen 6. Are connected to the mold clamping housing 7 and a toggle mechanism 11 provided between the stationary platen 5 and the mold clamping housing 7. The toggle mechanism 11 is provided with a cross head 12 for driving the toggle mechanism 11, and a ball nut 13 is fixed to the cross head 12. A ball screw 14 is screwed onto the ball nut 13. The mold clamping housing 7 is provided with a mold opening / closing motor 16 formed of a servo motor, and the mold opening / closing motor 16 can rotate the ball screw 14 with a desired rotation angle with high accuracy. When the ball screw 14 is rotated by driving the mold opening / closing motor 16, the crosshead 12 can be driven in the axial direction, the toggle mechanism 11 can be driven to open / close the mold, and the mold can be clamped. Although not shown in FIG. 1, the tie bars 9, 9,... Are connected to the mold clamping housing 7 as follows. That is, the tie bars 9, 9,... Pass through the mold clamping housing 7, and a male screw is formed in the inserted portion. A tie bar nut is screwed to the male screw, and the tie bar nut is rotatably provided in the mold clamping housing 7 in a state where movement in the axial direction is restricted. These tie bar nuts are rotated by a predetermined mold thickness adjusting mechanism. When the tie bar nuts are rotated, the effective length of the tie bars 9, 9,..., That is, the connection length between the fixed platen 5 and the mold clamping housing 7 is adjusted. be able to. Thereby, the mold thickness between the fixed platen 5 and the movable platen 6 can be adjusted. A fixed-side mold 18 is attached to the fixed plate 5 of the mold clamping device 3 configured as described above, and a movable-side die 19 is attached to the movable plate 6.

  In the present embodiment, the mold clamping device 3 is provided with a sensor for detecting the mold clamping force. That is, the strain sensor 20 is provided on the tie bar 9, and the strain sensor 20 detects the elastic deformation of the tie bar 9. The strain sensor 20 is connected to the controller 21 via a signal line. The mold opening / closing motor 16 is also connected to the controller 21 via a signal line. Although not shown in FIG. 1, a mold thickness adjusting mechanism is also connected to the controller 21. Therefore, the controller 21 can accurately detect the position of the crosshead 12, and can detect the mold clamping force by the strain sensor 20, and drive the mold thickness adjusting mechanism based on this to adjust the mold thickness. Yes.

The injection device 2 is well known in the art and will not be described in detail. The injection device 2 includes a heating cylinder 22 and a screw provided in the heating cylinder 22, and an injection nozzle 23 is provided at the tip of the heating cylinder 22. . And the heating cylinder 22, and a band heater wound on the outer peripheral surface thereof, the rear end toward which hopper for supplying resin material is provided in the heating cylinder 22. The screw, band heater, and hopper are not shown in FIG. The injection nozzle 23 of such an injection apparatus 2 is inserted into an opening provided in the fixed platen 5 and touches the sprue of the fixed mold 18. The sprue is not shown in FIG.

  Next, the molding cycle performed in the injection molding machine 1 will be described with reference to the flowchart of FIG. 2. The molding cycle according to the present embodiment includes a molding cycle for performing a so-called heat and cool molding method. As is well known, the heat and cool molding method uses molds 18 and 19 that can be heated or cooled by a heat medium or the like, and the molds 18 and 19 are heated to a predetermined temperature. This is a molding method in which an injection process is performed and a mold is cooled to solidify a resin after the injection process to obtain a molded product. In general, when performing the heat and cool molding method, the temperature rise and cooling of the molds 18 and 19 are controlled in synchronization with the molding cycle. By the way, the mold clamping force adjusting method according to the present embodiment is characterized in that it is performed every molding cycle. More specifically, the mold clamping process is performed by adjusting the mold thickness by adjusting the mold thickness. There is a feature in a certain point.

  Specifically, each step of the molding cycle according to the present embodiment will be described in order. In the molding cycle, first, a measuring step (step S1) for measuring the molten resin in the injection device 2 is performed. When the measuring step S1 is completed, a high-temperature heat medium is supplied to the dies 18 and 19 to raise the temperature thereof (step S2). Or in parallel with implementation of measurement process S1, temperature rise of the metal mold | die of step S2 is started. Next, a mold clamping process is performed. In the molding cycle according to the present embodiment, the mold clamping process is composed of first to third stages. In the first stage, as indicated by step S3, the mold opening / closing motor 16 is driven to drive the crosshead 12 to a predetermined position, that is, the mold closed position, whereby the mold 18, It is made to be in the contact state which 19 contacts. In this specification, the contact state of the dies 18 and 19 means a state in which the mold clamping force is substantially not generated or is sufficiently small even if it is generated. The second stage of the mold clamping process is a stage for adjusting the mold thickness, and at least the temperature increase of the molds 18 and 19 is completed immediately before the second stage. That is, at the start of the second stage, the temperatures of the molds 18 and 19 are stabilized and reach a predetermined target temperature. In a state where the position of the cross head 12 is maintained at the mold closed position, the second stage is performed, and the mold clamping force is detected by the strain sensor 20 (step S4). It is confirmed in step S5 whether or not the detected mold clamping force is within a preset reference range. If it is within the reference range, proceed to the next third stage. On the other hand, if it is not within the reference range, the mold thickness adjusting mechanism is driven in step S6 to adjust the mold thickness so that the mold clamping force falls within the reference range. By the way, in general, since the motor in the mold thickness adjusting mechanism has a small output, the mold thickness cannot be adjusted in a state where the mold clamping force is generated. However, in the embodiment of the present invention, since the mold thickness adjustment is performed in a contact state where the mold clamping force is sufficiently small, even if the motor has a small output, the mold thickness can be adjusted without any problem. When it is confirmed that the mold clamping force is within the reference range when the cross head 12 is in the mold closed position, the third stage is performed. That is, the mold opening / closing motor 16 is driven to drive the cross head 12 to the mold clamping completion position (step S7), and a mold clamping force is generated. Since it is guaranteed that the mold thickness is optimal immediately before the third stage, the generated clamping force is guaranteed to be constant for each molding cycle. An injection process (step S8) of injecting molten resin by driving a screw in the injection apparatus 2 is performed. A cold heat medium is supplied to the molds 18 and 19 to cool them, and the molten resin is cooled and solidified (step S9). Moreover, the pressure holding process which applies pressure holding is implemented as needed. When the resin in the cavities of the molds 18 and 19 is solidified, the mold clamping device 3 is driven to open the mold (step S10), and the molded product is ejected (step S11). The molding cycle is complete. Subsequently, the process returns to step S1 to carry out the next molding cycle.

  The mold clamping force adjusting method or the molding cycle according to the present embodiment can be variously modified. For example, in the present embodiment, it has been described that the mold thickness adjustment is performed in a state where the crosshead 12 is maintained at the mold closed position in the second stage of the mold clamping process. However, if the mold clamping force is detected only once in step S4 when the crosshead 12 is in the mold closed position, the mold is adjusted by temporarily retracting the crosshead 12 when performing mold thickness adjustment in step S6. 18 and 19 may be opened to adjust the mold clamping force to zero. This is because if it is known how much the mold clamping force obtained in step S4 deviates from the reference range, it can be determined how much the mold thickness should be adjusted. If mold thickness adjustment is performed with the mold clamping force zero, the load on the motor of the mold thickness adjustment mechanism can be reduced. Other variations are possible. Although the mold clamping force has been described as being detected by the strain sensor 20 in the present embodiment, it may be detected by the torque of the mold opening / closing motor 16. Since the torque can be detected by the current supplied to the mold opening / closing motor 16, the detection is easy. Further, the present embodiment can be modified in other ways. Although the specification does not particularly describe the mold thickness adjusting mechanism, the motor that drives the mold thickness adjusting mechanism can be configured by a servo motor having a relatively large output. In the case of such a motor, the second stage can be executed in parallel with the first stage of the mold clamping process. More specifically, when the first stage is performed and the mold is closed in the contact state, the mold clamping force is monitored at the same time, and the mold thickness is maintained so that the mold clamping force keeps within the reference range during this period. Controls the servo motor of the adjustment mechanism. Even in this case, the mold thickness can be adjusted appropriately, and a desired mold clamping force can be obtained in the third stage thereafter.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Injection apparatus 3 Mold clamping apparatus 5 Fixed board 6 Movable board 7 Mold clamping housing 9 Tie bar 11 Toggle mechanism 12 Cross head 14 Ball screw 16 Mold opening / closing motor 18 Fixed side mold 19 Movable side mold 20 Strain sensor 22 Heating cylinder 21 Controller

Claims (4)

A fixed platen, a movable platen, a mold clamping housing, a tie bar connecting the fixed platen and the housing with the movable platen interposed therebetween, and the movable platen and the mold clamping housing. And when the tie bar nut provided on the tie bar is driven, the die is opened and closed when the cross head of the toggle mechanism is driven in a state where the mold is attached to the fixed plate and the movable plate. In a toggle type injection molding machine capable of adjusting the thickness, when performing a heat and cool molding method in which the mold is heated to a predetermined temperature and injected, and then the mold is cooled,
The mold clamping process includes a first stage in which the mold is closed so that the cross head is driven to a mold closing position so that the mold clamping force is in a minute contact state, and a mold thickness adjustment is performed. And a third stage for driving the cross head to a mold clamping completion position and generating a desired mold clamping force,
The temperature rise of the mold is completed at least before the second stage,
In the second step, when the mold clamping force of the mold in the contact state deviates from a predetermined reference range set in advance, mold thickness adjustment is performed so that the mold is within the reference range. A method for adjusting a clamping force of a toggle type injection molding machine.   2. The toggle type injection molding machine according to claim 1, wherein in the second stage, the mold thickness is adjusted in a state where the cross head is maintained at the mold closed position. 3. Mold clamping force adjustment method.   The mold clamping force adjusting method according to claim 1 or 2, wherein the mold clamping force in the second stage is detected by a strain sensor provided on the tie bar. Force adjustment method.   3. The mold clamping force adjustment method according to claim 1 or 2, wherein the mold clamping force in the second stage is detected by a torque of a motor that drives the cross head. Force adjustment method.

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