JP2009172923A - Injection molding machine having function of adjusting mold clamping force - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine that has the function of controlling a toggle type mold clamping device to an optimum mold clamping force. <P>SOLUTION: The injection molding machine, which has a toggle mechanism 6 disposed between a rear platen 2 and a movable platen 3 mounted with a movable die to reciprocate the movable platen by means of a mold clamping motor, is provided with a mold clamping force adjusting motor 10 for moving the position of the rear platen 2 at a predetermined speed to adjust a mold clamping force, a mold clamping force sensor 13 for measuring the mold clamping force, a mold clamping force correction amount calculation means for calculating a mold clamping force correction amount that is the difference between the mold clamping force measured by the mold clamping force sensor 13 and a target mold clamping force, and a rear platen movement time calculation means for calculating a movement time of the rear platen 2 from a rear platen movement time calculating proportional constant that is the rate of change in rear platen movement time relative to mold clamping force and the calculated mold clamping force correction amount. A mold clamping force adjustment means is driven according to the calculated rear platen movement time to adjust the mold clamping force. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection molding machine, and more particularly to an injection molding machine having a function of adjusting a clamping force of an injection molding machine.

  Keeping the mold clamping force of the injection molding machine during automatic operation constant is important for stabilizing the thickness of the molded product and the state of outgassing. In the toggle type mold clamping mechanism provided in the injection molding machine, the mold clamping force changes due to the temperature change of the mold. Therefore, the injection molding machine having the toggle type mold clamping mechanism has a function of automatically correcting the mold clamping force by moving the rear platen as disclosed in Patent Documents 1 to 4.

Patent Document 1 discloses a technique for adjusting the mold clamping force using a correspondence relationship between the amount of movement of the movable mold obtained from the actually measured mold clamping force value and the magnitude of the mold clamping force.
In Patent Document 2, an actual mold clamping force during a test mold clamping operation is measured, a constant value for calculating an extension amount of a tie bar corresponding to a desired mold clamping force is obtained, and a rear platen adjustment motor is moved by a predetermined amount. A technique for automatically adjusting the mold clamping force is disclosed.
Patent Document 3 discloses a technique for automatically correcting play of a drive system and adjusting the play to a predetermined mold thickness.
Patent Document 4 discloses a technique for adjusting a mold clamping force by obtaining a change amount of a mold clamping force and an adjustment amount of a rear platen from a change in a peak current value during mold clamping of a servo motor for mold clamping.

JP 2007-261059 A JP-A-5-69465 JP-A-1-221217 JP 2004-122579 A

In the techniques disclosed in Patent Documents 1 to 3 for correcting the mold clamping force by adjusting the position of the rear platen, a sensor for accurately measuring the position of the rear platen (a motor for adjusting the mold clamping force, a pulse coder, or a linear on the rear platen). It is necessary to further provide a scale) in the injection molding machine, and there is a problem that the injection molding machine becomes expensive.
By providing the pulse coder, the accurate rotation amount of the mold clamping force adjusting motor can be detected, but the influence of backlash cannot be solved. In addition, the arrangement of the linear scale complicates the structure of the injection molding machine.
Further, in the technique disclosed in Patent Document 4 in which the movement time obtained by multiplying the adjustment amount of the rear platen by a constant is commanded and controlled, the backlash of the gear portion and the mold clamping force adjustment when the rear platen is moved by a minute amount are used. There was a problem that the influence of the delay time of the motor torque rise was not taken into consideration.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an injection molding machine that controls an optimal clamping force even if the molding machine or the mold is changed, without newly providing a sensor for measuring the position of the rear platen.

    The invention according to claim 1 of the present application is an injection molding machine having a toggle type mold clamping device that is disposed between a movable platen to which a rear platen and a movable mold are attached, and moves the movable platen back and forth with a mold clamping motor. The mold clamping force adjusting means for adjusting the clamping force by moving the position of the rear platen at a predetermined speed, the clamping force measuring means for measuring the clamping force, and the clamping force measuring means. A mold clamping force correction amount calculating means for calculating a mold clamping force correction amount that is a difference between a mold clamping force and a target mold clamping force, and a proportional constant for calculating a rear platen moving time that is a rate of change of the rear platen moving time with respect to the mold clamping force. And a rear platen moving time calculating means for calculating a moving time of the rear platen based on the mold clamping force correction amount calculated by the mold clamping force correction amount calculating means, and based on the calculated rear platen moving time. An injection molding machine having a function of adjusting the mold clamping force, characterized by adjusting the clamping force to drive the adjusting means clamping force.

  According to a second aspect of the present invention, the mold clamping force adjusting means is driven to mold clamping based on the calculated rear platen moving time and the non-response time from when the rear platen moving command is output until the rear platen starts moving. The injection molding machine having a function of adjusting the clamping force according to claim 1, wherein the force is adjusted.

  According to a third aspect of the present invention, there is provided a mold clamping force change amount calculating means for calculating a change amount of the mold clamping force before and after the rear platen is moved when the rear platen is moved for a predetermined time, and the predetermined time and the mold clamping. The mold clamping according to claim 1, further comprising: a rear platen moving time calculation proportional constant calculating unit that calculates a rear platen moving time calculating proportional constant from the amount of change in force. This is an injection molding machine having a function of adjusting the force.

  According to a fourth aspect of the present invention, there is provided a non-response time calculation means for calculating a non-response time from when a rear platen movement command is output until the rear platen starts to move, and the mold clamping force adjusting means for the rear platen movement time and 4. The injection having a function of adjusting a mold clamping force according to claim 2, wherein the mold clamping force adjusting means is driven based on the non-response time to adjust the mold clamping force. It is a molding machine.

  According to a fifth aspect of the present invention, the proportional constant calculating means for calculating the rear platen moving time and the non-response time calculating means include the amount of change in mold clamping force measured during mold clamping force adjustment and the rear platen measured during mold clamping force adjustment. 5. The injection molding machine having a function of adjusting a mold clamping force according to claim 4, wherein the proportional constant for calculating the rear platen moving time and the no-response time are calculated based on the moving time of the rear platen.

  The invention according to claim 6 is characterized in that the non-response time is obtained individually in the case where the rear platen is moved in the same direction as in the previous movement and in the case where the rear platen is moved in the opposite direction. An injection molding machine having a function of adjusting the clamping force described in any one of the above.

  According to a seventh aspect of the present invention, the mold clamping force measuring means includes a mold clamping force sensor, a peak current of the mold clamping motor during mold clamping or mold loosening, a current of the mold clamping motor at the time of mold touch, The mold clamping force according to any one of claims 1 to 6, wherein the mold clamping force is at least one of means for measuring a movable platen movement amount after the mold is touched on the mold until the mold clamping is completed. It is an injection molding machine having a function of adjusting.

  According to the present invention, the mold clamping force can be corrected without providing a new sensor for measuring the position of the rear platen by controlling the amount of movement of the rear platen by the movement time of the rear platen.

  Further, the present invention can command an optimal rear platen moving time even if the molding machine or the mold is changed, and can quickly and accurately correct the clamping force of the injection molding machine to the target clamping force.

  Hereinafter, an embodiment of an injection molding machine according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an embodiment of an injection molding machine according to the present invention. The stationary platen 1 and the rear platen 2 are connected by a plurality of tie bars 4. A movable platen 3 is disposed along the tie bar 4 between the fixed platen 1 and the rear platen 2. A fixed mold 5a is attached to the fixed platen 1, and a movable mold 5b is attached to the movable platen 3 so as to face the fixed mold 5a.

  A toggle mechanism 6 is disposed between the rear platen 2 and the movable platen 3, and a nut (not shown) provided on the cross head 6 a of the toggle mechanism 6 is attached to the rear platen 2 so as to be rotatable and not movable in the axial direction. The ball screw 7 is screwed. The ball screw 7 is driven by a mold clamping servo motor 8 through a transmission mechanism, whereby the movable platen 3 is moved forward and backward in the direction of the fixed platen 1 to open and close the molds 5a and 5b, and thereby perform the toggle. Forms a mold clamping device. The mold clamping servomotor 8 is provided with a position / speed detector 11 for detecting the rotational position and speed of the servomotor such as a pulse encoder. Thus, the position of the cross head 6a, that is, the state of the toggle mechanism 6 and the position of the movable platen 3 (movable side mold 5b) can be detected.

  Further, a mold clamping force adjusting means is constituted by a transmission mechanism (not shown) composed of a mold clamping force adjusting motor 10, a tie bar nut 9 and a gear. The end of the tie bar 4 on the rear platen 2 side is threaded. The tie bar nut 9 screwed with the screw is rotated by a mold clamping force adjusting motor 10 via the transmission mechanism (not shown), so that the rear platen 2 can be moved forward and backward along the tie bar 4.

  The mold clamping force sensor 13 is disposed at a position near the fixed platen 1 on at least one of the four tie bars 4. The mold clamping force sensor 13 is a sensor that measures distortion (mainly elongation) of the tie bar 4. When the mold is clamped, a tensile force is applied to the tie bar 4 corresponding to the mold clamping force, and the tie bar 4 extends slightly in proportion to the mold clamping force. Therefore, by measuring the extension amount of the tie bar 4 with the mold clamping force sensor 13, the mold clamping force actually applied to the molds 5a and 5b can be known.

  Reference numeral 20 denotes a control device for controlling the injection molding machine. FIG. 1 shows only the main part of the control device 20. An axis control circuit 22, an input / output circuit 24, a memory 26, an A / D converter 27 for controlling the position, speed, and current (torque) of the servo motor via a bus 30 to a processor (CPU) 21 that controls the whole. The interface circuit 28 of the display device 29 is connected.

  The axis control circuit 22 includes a processor, a memory, an interface, and the like. The position / speed feedback signal from the position / speed detector 11 attached to the mold clamping servomotor 8 is fed back. A current feedback signal from the current detector 12 that detects the drive current is fed back. A mold clamping servomotor 8 is connected to the shaft control circuit 22 via a servo amplifier 23. Further, the mold clamping force adjusting motor 10 is connected to the input / output circuit 24 via the inverter 25, and the display device 29 is connected to the interface 28.

  The memory 26 stores a program for controlling the injection molding machine. A program created based on a flowchart shown in an algorithm for adjusting the clamping force described later is also stored in the memory 26. The processor 21 controls the injection molding machine based on these programs. Regarding the mold clamping operation, the processor 21 outputs a movement command to the axis control circuit 22 based on the program. A processor (not shown) built in the axis control circuit 22 determines the position and speed based on the movement command and the position / speed feedback signal from the position / speed detector 11 and the current feedback signal from the current detector 12. , And feedback control of current, and drive control of the mold clamping servomotor 8 via the servo amplifier 23 is performed.

  When the mold clamping servomotor 8 is driven, the ball screw 7 is rotated, and the crosshead 6a of the toggle mechanism 6 having a nut (not shown) screwed to the ball screw 7 moves along the ball screw 7, so that the toggle mechanism 6 Is driven, the movable platen 3 moves forward, the movable mold 5b contacts the fixed mold 5a, further moves the movable platen 3, the link of the toggle mechanism 6 extends, and the movable platen 3 reaches a predetermined position. When the lockup position is reached, the mold clamping servomotor 8 is positioned at this position, and the position of the rear platen 2 is adjusted so that the target mold clamping force is generated.

  That is, since the fixed platen 1 and the rear platen 2 are connected by the tie bar 4, when the fixed mold 5a and the movable mold 5b come into contact with each other and the movable platen 3 and the movable mold 5b move forward, the fixed platen 1 and the rear platen 2 are connected by a tie bar 4, so that the tie bar 4 is stretched and a clamping force is obtained by a reaction force of the tie bar 4, and the link of the toggle mechanism 6 is stretched to extend the tie bar. It is adjusted to obtain a tightening force.

  Because of such a structure, when the molds 5a and 5b are replaced with different mold thicknesses or when the mold clamping force is changed, the position of the rear platen 2 must be changed to adjust the mold clamping force. Don't be. When changing the position of the rear platen 2, the processor 21 drives the mold clamping force adjusting motor 10 via the input / output circuit 24, and rotates the tie bar nut 9 via a transmission mechanism (not shown) to The position can be changed.

  In such an injection molding machine that drives the toggle type mold clamping mechanism with the mold clamping servomotor 8, the mold clamping force varies due to thermal expansion of the molds 5a and 5b during the automatic operation of the injection molding machine. Therefore, in an injection molding machine having a toggle type mold clamping device, it is necessary to suppress fluctuations in the mold clamping force and obtain a stable mold clamping force.

  In the present invention, without providing a sensor for specifying the position on the rear platen 2 or a sensor for specifying the rotational position on the mold clamping force adjusting motor 10, the driving time of the mold clamping force adjusting motor 10 (in other words, The die height is adjusted by changing the position of the rear platen 2 by controlling the movement time of the rear platen 2. The die height means a distance between the fixed platen 1 and the rear platen 2. The adjustment of the die height means that the position of the rear platen 2 is changed by driving the mold clamping force adjusting motor 10 for an appropriate time, and the distance between the fixed platen 1 and the rear platen 2 is changed.

FIG. 2 is a graph showing the relationship between the movement time of the rear platen 2 and the mold clamping force correction amount in one embodiment of the present invention. The meanings of symbols used in the graph are as follows.
Fdiff represents the difference between the current mold clamping force and the target mold clamping force. K is a proportional constant for calculating the rear platen travel time. C ′ is a constant for calculating the rear platen movement time when correcting in the same direction as the direction in which the rear platen was moved last time. This constant C ′ is a constant for correcting the rising delay of the torque, and is called a no response time. C is the rear platen moving time for eliminating the difference between the current mold clamping force and the target mold clamping force. The rear platen movement time C also corrects the non-response time C ′ from the movement command start to the rear platen movement start caused by the torque rising delay time of the mold clamping force adjusting motor 10.

  D 'is a constant for calculating the rear platen movement time in the case of correcting in the direction opposite to the direction in which the rear platen was moved last time. The constant D 'is a constant for correcting the torque rise delay and the delay due to backlash, and is referred to as no response time. The α component shown in FIG. 2 indicates a delay in the movement time of the rear platen due to backlash caused by the movement of the rear platen in the direction opposite to the previous movement direction. D is the rear platen moving time for eliminating the difference between the current mold clamping force and the target mold clamping force. This rear platen movement time D is also corrected for the non-response time D ′ until the start of the rear platen movement caused by the backlash generated in the power transmission means for transmitting power from the mold clamping force adjusting motor 10 to the tie bar nut 9 provided in the rear platen 2. is doing.

  Backlash generated in a gear portion (not shown) which is a power transmission means for moving the rear platen 2 forward and backward by the mold clamping force adjusting motor 10 moves the rear platen 2 in the direction opposite to the previous rear platen movement direction. Occurs when adjusting the tightening force. Table 1 summarizes the above description.

  The moving time of the rear platen 2 is a variable, and the amount of change in mold clamping force is a variable. These two variables have a linear function relationship. A proportional constant K for calculating the rear platen moving time, which is the rate of change of the rear platen moving time with respect to the amount of change in the clamping force when the rear platen 2 moves, can be obtained. The proportional constant K for calculating the rear platen moving time is the proportional constant of the linear function.

  Further, a backlash at a gear portion (not shown) which is a power transmission means for moving the rear platen 2 forward and backward by the mold clamping force adjusting motor 10 and torque of the mold clamping force adjusting motor 10 for moving the rear platen 2. The no-response time due to the rise time is an intercept of the linear function. This section is C ′ and D ′.

  The linear function can be identified by obtaining two points of the movement time of the rear platen 2 and the actual amount of change in the mold clamping force and solving the simultaneous equations. A solution method using simultaneous equations will be described later. The proportionality constant that is the rate of change of the mold clamping force is not affected by the moving direction of the rear platen 2. Therefore, the same value can be used when the mold clamping force is adjusted in the positive direction and when it is adjusted in the negative direction.

  Further, it is also possible to use combination data in which the mold clamping force correction direction is reverse as the two values of the movement time of the rear platen 2 and the amount of change in the mold clamping force to obtain the simultaneous linear equations. When the mold clamping force exceeds an appropriate range, the rear platen 2 is moved for the movement time of the rear platen 2 obtained from the linear function, and the mold clamping force is adjusted.

  The non-response time differs depending on whether the rear platen 2 is moved in the same direction as the previous movement direction or in the opposite direction due to the influence of the backlash of the gear portion which is a driving force transmission means of the mold clamping force adjusting motor 10. . The change rate of the mold clamping force is not affected by backlash, and the same value can be used. The previous moving direction of the rear platen 2 is always stored, including during manual or automatic mold thickness adjustment.

  In addition, the mold clamping force is replaced with the method of directly measuring using the mold clamping force sensor 13, and the maximum value of the drive current of the mold clamping servo motor 8 during the mold clamping process or the molds 5a and 5b are actually measured. It can also be obtained by measuring the amount of movement of the movable platen 3 from the position in contact with the mold until the mold clamping is completed.

  Further, the change rate and non-response time of the mold clamping force are stored in a memory 26 such as a RAM or ROM of the control device 20 of the injection molding machine in a molding condition file for each mold, so that these can be changed even if the mold changes. If a molding condition file that stores the variables is stored, it is possible to set a stable mold clamping force immediately after the start of molding by calling it.

3 to 6 are examples of flowcharts showing an algorithm for adjusting the clamping force in one embodiment of the present invention. Hereinafter, each flowchart will be described according to each step. The meanings of symbols and abbreviations used in the flowchart are summarized in Table 2.
Data such as K, T, n, Aj, Bk, Cj, and Dk shown in Tables 1 and 2 are stored in time series as necessary.

  FIG. 3 is a flowchart showing an algorithm for performing mold clamping force adjustment based on the rate of change of mold clamping force in one embodiment of the present invention. Hereinafter, the flowchart will be described according to each step. [Step SA1] The number S of molding shots is set. For example, the number of shots S, which is the number of moldings, is set from input means (not shown) provided in the control device 20. Similarly, a proportional constant K ′ for calculating the rear platen movement time, which is a change rate of the mold clamping force, a non-response time T ′ from the start of the movement command to the start of movement, and the target mold clamping force Fset are input to the input means (not shown). Set from. Alternatively, the rear platen moving time calculation proportional constant K ′, the non-response time T ′ from the movement command start to the movement start, and the target mold clamping force Fset that are stored in advance in the memory are read.

  [Step SA2] The molding cycle count R is reset to zero. [Step SA3] A molding cycle is started. [Step SA4] A value Fact of the mold clamping force when the mold clamping is completed is measured and stored in the memory. [Step SA5] It is determined whether or not the current mold clamping force Fact is within an appropriate mold clamping force range (a range larger than Fmin and smaller than Fmax). If it is not within the proper range, the process proceeds to step SA6, and if it is within the proper range, the process proceeds to step SA11. [Step SA6] A difference Fdiff between the current mold clamping force Fact and the target mold clamping force Fset is calculated. [Step SA7] A rear platen moving time T for eliminating the difference between the current mold clamping force and the target mold clamping force Fset is obtained. T is calculated by T = K ′ * | Fdiff | + T ′.

  [Step SA8] It is determined whether or not Fdiff is greater than zero. If Fdiff is greater than zero, the process proceeds to step SA9. If Fdiff is not greater than zero, the process proceeds to step SA10. [Step SA9] This means that the mold clamping force Fact is larger than the target mold clamping force Fset. Therefore, in this case, the rear platen is moved backward for T time (in a direction away from the fixed platen). [Step SA10] This means that the mold clamping force Fact is smaller than the target mold clamping force Fset. Therefore, in this case, the rear platen is advanced by T time (direction approaching the fixed platen).

  [Step SA11] The injection molding process is terminated. The movement of the rear platen is performed simultaneously with ejector ejection or the like for shortening the cycle time, and is performed until the injection molding process is completed. [Step SA12] If it is determined whether or not the set number of moldings has been reached, the process ends. If not, the process proceeds to step SA13. [Step SA13] The molding number R is increased by 1, and the process returns to Step SA3 to start the next injection molding process.

  FIG. 4 is a flowchart showing an algorithm for adjusting the mold clamping force based on the rate of change of the mold clamping force in one embodiment of the present invention. In the flowchart of this algorithm, the influence of the change rate of the clamping force was taken into account. In the flowchart showing this algorithm, the change rate of the clamping force is a fixed value.

  Hereinafter, the flowchart will be described according to each step. [Step SB1] The number S of molding shots is set. For example, the number of shots S, which is the number of moldings, is set from an input means (not shown) provided in the control device 20. Similarly, the rear platen moving time calculation proportional constant K ′, the non-response time T ′ from the start of the movement command to the start of movement, and the target mold clamping force Fset are set from the input means (not shown). Alternatively, the rear platen moving time calculation proportional constant K ′, the non-response time T ′ from the movement command start to the movement start, and the target mold clamping force Fset that are stored in advance in the memory are read.

  [Step SB2] The molding cycle count R is reset to zero. Further, K ′ is set to the proportional constant K for calculating the rear platen moving time. [Step SB3] A molding cycle is started. [Step SB4] A value Fact of the mold clamping force when the mold clamping is completed is measured and stored in the memory. [Step SB5] It is determined whether or not 1 is set in the rear platen movement monitoring flag F. When the flag F is 1, the process proceeds to step SB6. If the flag F is not 1 (0), the process proceeds to step SB8. The rear platen movement monitoring flag F can use a memory, a register, or the like. Normally, the rear platen movement monitoring flag F is set to 0. When the rear platen is moved, 1 is set in the flag F. [Step SB6] An actual mold clamping force variation Fcng is obtained. Fcng is a difference between the current mold clamping force Fact and the mold clamping force Fbef of the previous cycle. Fcng is calculated by Fcng = Fact−Fbef.

  [Step SB7] A change rate K of the rear platen moving time with respect to the mold clamping force is obtained. K is calculated by K = (T−T ′) / | Fcng |. [Step SB8] The value of the mold clamping force Fbef in the previous cycle is replaced with the current mold clamping force Fact. [Step SB9] It is determined whether or not the current mold clamping force Fact is within an appropriate mold clamping force range (a range larger than Fmin and smaller than Fmax). If not in the proper range, the process proceeds to step SB10. If it is within the appropriate range, the process proceeds to step SB18. [Step SB10] A difference Fdiff between the current mold clamping force Fact and the target mold clamping force Fset is calculated. [Step SB11] A rear platen moving time T for eliminating the difference between the current mold clamping force and the target mold clamping force Fset is obtained. T is calculated by T = K * | Fdiff | + T ′. As K, an initial value K ′ or a value of K calculated by this algorithm is used.

  [Step SB12] It is determined whether or not Fdiff is greater than zero. If Fdiff is greater than zero, the process proceeds to step SB14. On the other hand, if Fdiff is not greater than zero (small), the process proceeds to step SB13. [Step SB13] This means that the mold clamping force Fact is smaller than the target mold clamping force Fset. Therefore, in this case, the rear platen is advanced by T time. [Step SB14] This means that the mold clamping force Fact is larger than the target mold clamping force Fset. Therefore, in this case, the rear platen is moved backward for T time.

[Step SB15] The rear platen movement monitoring flag F is set to 1, and the process proceeds to step SB16. [Step SB16] The injection molding process is terminated. The movement of the rear platen is performed simultaneously with ejector ejection or the like for shortening the cycle time, and is performed until the injection molding process is completed. [Step SB17] It is determined whether or not the set number of moldings has been reached. If not, the process proceeds to step SB19. [Step SB18] The rear platen movement monitoring flag F is reset to 0, and the process proceeds to Step SB16. [Step SB19] The molding number R is increased by 1, and the process returns to Step SB3 to start the next injection molding process.
In addition, if the cycle operation has already been performed and the rear platen moving time calculation proportional constant K has been calculated and the mold has not been replaced, the calculated K is used instead of K ′ as the initial value. Also good.

  FIG. 5 is a flowchart showing an algorithm for performing mold clamping force adjustment based on the rate of change of mold clamping force in one embodiment of the present invention. This algorithm flowchart is a flowchart of the algorithm that takes into account the change rate of the mold clamping force, the backlash, and the rise delay time of the torque of the mold clamping force adjusting motor. In the flowchart showing this algorithm, values related to the influence of the change rate of the clamping force, the backlash, and the rise delay time of the torque are fixed values.

  Hereinafter, the flowchart will be described according to each step. [Step SC1] The number S of molding shots is set. For example, the number of shots S, which is the number of moldings, is set from an input means (not shown) provided in the control device 20. Similarly, the proportional constant K ′ for calculating the rear platen movement time, the non-response time C ′ from the start of the movement command to the start of the rear platen movement, the non-response time D ′ until the start of the rear platen movement considering backlash, and the target clamping force Fset is set from the input means (not shown). Or, a proportional constant K ′ for calculating the rear platen movement time stored in the memory in advance, a non-response time C ′ from the start of the movement command to the start of the rear platen movement, a non-response time D ′ until the start of the rear platen movement considering backlash, and Read the target mold clamping force Fset.

  [Step SC2] The molding cycle count R is reset to zero. [Step SC3] Initial values of Fdiffbef and Fdiff are set to zero. [Step SC4] A molding cycle is started. [Step SC5] The value Fact of the mold clamping force when the mold clamping is completed is measured and stored in the memory. [Step SC6] The value of the mold clamping force Fbef in the previous cycle is replaced with the current mold clamping force Fact. [Step SC7] It is determined whether or not the current mold clamping force Fact is within an appropriate mold clamping force range (a range larger than Fmin and smaller than Fmax). If it is within the proper range, the process proceeds to step SC18. If it is not within the proper range, the process proceeds to step SC8. [Step SC8] A difference Fdiff between the current mold clamping force Fact and the target mold clamping force Fset is calculated.

  [Step SC9] The previously calculated product of Fdiffbef, which is the difference between the current mold clamping force Fact and the target mold clamping force Fset, and Fdiff, which is the difference between the current mold clamping force Fact and the target mold clamping force Fset, If greater than 0, the process proceeds to step SC10, and if not greater than 0, the process proceeds to step SC14. Here, the case where the product is larger than 0 means that Fdiff and Fdiffbef have the same sign value. In other words, it means that both the value of Fdiff and the value of Fdiffbef are “positive numerical values” or, conversely, both values are “negative numerical values”. In these cases, when adjusting the mold clamping force between the previous time and this time, it is necessary to make the same adjustment whether the mold clamping force is increased in the previous time and this time or whether the mold clamping force is decreased in the previous time and this time. Therefore, when the value of the product is larger than 0, the process proceeds to step SC10 which is a process for executing the adjustment operation of the mold clamping force in the same direction. On the other hand, if the value of the product is not larger than 0, it is necessary to make an adjustment that is strong last time and weak this time, weak last time and strong this time. Therefore, if the value of the product is not greater than 0, the process proceeds to step SC14, which is a process for executing the adjustment work in the opposite direction.

  [Step SC10] When the movement direction of the rear platen is the same between the previous time and the current time, the influence of the backlash can be ignored. Therefore, the movement time C of the rear platen is calculated by C = K ′ * | Fdiff | + C ′. [Step SC11] It is determined whether or not Fdiff is greater than 0. If it is greater than 0 (when the current mold clamping force is greater than the target mold clamping force), the rear platen is moved backward for C hours so as to weaken the mold clamping force. If it is not larger than 0 (when the current mold clamping force is smaller than the target mold clamping force), the rear platen is advanced for C hours to increase the mold clamping force. [Step SC14] When the moving direction of the rear platen is different between the previous time and the current time, the influence of backlash must be taken into consideration. The moving time D of the rear platen is calculated by D = K ′ * | Fdiff | + D ′.

  [Step SC15] It is determined whether or not Fdiff is greater than 0. If not, the process proceeds to step SC16. [Step SC16] (When the current mold clamping force is smaller than the target mold clamping force), the rear platen is advanced by D hours to increase the mold clamping force. If greater than 0 (when the current mold clamping force is greater than the target mold clamping force), the process proceeds to step SC17. [Step SC17] The rear platen is moved backward for D hours so as to weaken the mold clamping force.

  [Step SC18] The value of Fdiffbef is replaced with Fdiff. [Step SC19] The injection molding process is terminated. The movement of the rear platen is performed simultaneously with ejector ejection or the like for shortening the cycle time, and is performed until the injection molding process is completed. [Step SC20] It is determined whether or not the set number of moldings has been reached. If not, the process proceeds to step SC21.

  In step SC9, determination may be made based on whether the product of Fdiffbef and Fdiff is 0 or more. In this case, the process of step SC10 is performed when the mold clamping force adjustment is performed for the first time. If it is determined whether or not it is greater than 0, the process of step SC11 is performed for the first time of mold clamping force adjustment.

  FIGS. 6A and 6B are flowcharts illustrating an algorithm for adjusting the mold clamping force based on the rate of change of the mold clamping force according to the embodiment of the present invention. This algorithm flowchart is a flowchart of the algorithm that takes into account the effects of the rate of change of mold clamping force, backlash, and the rise delay time of the torque of the mold clamping force adjusting motor. In the flowchart showing this algorithm, values related to the influence of the mold clamping force, backlash, and torque rise delay time are assumed to change.

  Hereinafter, the flowchart will be described according to each step. [Step SD1] The molding shot number S is set. For example, the number of shots S, which is the number of moldings, is set from an input means (not shown) provided in the control device 20. Similarly, the proportional constant K ′ for calculating the rear platen movement time, the non-response time C ′ from the start of the movement command to the start of the rear platen movement, the non-response time D ′ until the start of the rear platen movement considering backlash, and the target mold clamping force Fset It sets from the input means (not shown). Or, a proportional constant K ′ for calculating the rear platen movement time stored in the memory in advance, a non-response time C ′ from the start of the movement command to the start of the rear platen movement, a non-response time D ′ until the start of the rear platen movement considering backlash, and Read the target mold clamping force Fset.

  [Step SD2] The molding cycle count R is reset to zero. Further, K ′ is set to the proportional constant K for calculating the rear platen moving time. [Step SD3] The values of the rear platen movement number n, the rear platen movement number j in the same direction as the previous time, and the rear platen movement number k in the opposite direction to the previous time are set to zero. Similarly, the initial values of Fdiffbef and Fdiff are set to zero. [Step SD4] A molding cycle is started. [Step SD5] The value Fact of the mold clamping force when the mold clamping is completed is measured and stored in the memory.

[Step SD6] It is determined whether or not the rear platen movement monitoring flag F is set to 1. If 1 is set in the flag F, the process proceeds to step SD7. If the flag F is 0 instead of 1, the process proceeds to step SD13 (see FIG. 6-2). Normally, the rear platen movement monitoring flag F is set to 0. When the rear platen is moved, the rear platen movement monitoring flag F is set to 1.
[Step SD7] It is determined whether or not the number of rear platen movements in the same direction as the previous time is 2 or more. If the number of movements is 2 or more, the process proceeds to step SD8. (See FIG. 6-2).

  [Step SD8] It is determined whether or not the exclusive logic between the previous movement direction Mn-1 of the rear platen and the current movement direction Mn is "0". When the exclusive OR is “0”, the process proceeds to step SD9. When the exclusive OR is “1”, the process proceeds to step SD12. In this flowchart, the forward movement of the rear platen is represented by “1”, and the backward movement of the rear platen is represented by “0”. The exclusive OR of the previous movement direction Mn-1 of the rear platen and the current movement direction Mn is "0" when both Mn-1 and Mn are "1" or "0". In other words, when the exclusive OR is “0”, it means that the previous movement direction and the current movement direction of the rear platen are the same direction. The exclusive OR is “1” when one of Mn−1 and Mn is “1” and the other is “0”. In other words, when the exclusive OR is “1”, it means that the previous movement direction of the rear platen is different from the current movement direction. The exclusive OR will be described later using Table 3.

  [Step SD9] An actual mold clamping force change amount Aj when the mold clamping force is corrected in the same direction in the previous and present times is obtained. Aj is calculated by Aj = Fact−Fbef. [Step SD10] A proportional constant K for calculating the rear platen moving time, which is a change rate of the mold clamping force, is calculated. K is calculated by K = (Cj−Cj−1) / (| Aj | − | Aj−1 |). [Step SD11] A constant C ′ for calculating the rear platen movement time C ′ (no response time from the movement start command to the start of the rear platen movement) in the case of correcting in the same direction as the previous time is obtained. C ′ is calculated by C ′ = (| Aj | * Cj−1− | Aj−1 | * Cj) / (| Aj | − | Aj−1 |). The process of deriving these K and C ′ will be described later.

  [Step SD12] A constant D ′ for calculating the rear platen movement time when correcting in the direction opposite to the previous time D ′ (no response time until the start of rear platen movement considering backlash) is obtained. An example of calculating D 'will be described. The backlash of the driving force transmission mechanism from the mold clamping force adjustment motor is large. If the backlash component by the driving force transmission mechanism is α, the non-response time from the start of command to the start of rear platen movement can be expressed as D ′ = C ′ + α. α is measured in advance as a value unique to the injection molding machine and stored in the memory of the injection molding machine, or a proportional constant K for calculating the rear platen movement time, which is a change rate of the mold clamping force, is calculated. D ′ taking into account α can also be calculated using Dk and Bk which are data at the time of actual mold clamping force correction. D ′ = Dk− | Bk | * K and Bk = Fact−Fbef.

[Step SD13] The value of the mold clamping force Fbef in the previous cycle is replaced with the current mold clamping force Fact. [Step SD14] It is determined whether or not the current mold clamping force Fact is within an appropriate mold clamping force range (a range larger than Fmin and smaller than Fmax). If not in the proper range, the process proceeds to step SD15. If it is within the appropriate range, the process proceeds to step SD16.
[Step SD15] A difference Fdiff between the current mold clamping force Fact and the target mold clamping force Fset is calculated. [Step SD16] The rear platen movement monitoring flag F is set to zero. Then, the process proceeds to step SD34.

  [Step SD17] The rear platen movement count n is incremented by 1, and the flow proceeds to Step SD18. [Step SD18] The previously calculated product of Fdiffbef, which is the difference between the current mold clamping force Fact and the target mold clamping force Fset, and Fdiff, which is the difference between the current mold clamping force Fact and the target mold clamping force Fset, If greater than 0, the process proceeds to step SD19, and if not greater than 0, the process proceeds to step SD26. Here, the case where the product is larger than 0 means that Fdiff and Fdiffbef have the same sign value. In other words, it means that both the value of Fdiff and the value of Fdiffbef are “positive numerical values” or, conversely, both values are “negative numerical values”. In these cases, when adjusting the mold clamping force between the previous time and this time, it is necessary to make the same adjustment whether the mold clamping force is increased in the previous time and this time or whether the mold clamping force is decreased in the previous time and this time. Therefore, when the value of the product is larger than 0, the process proceeds to step SD19 which is a process for executing the adjustment operation of the mold clamping force in the same direction. On the other hand, if the value of the product is not larger than 0, it is necessary to make an adjustment that is strong last time and weak this time, weak last time and strong this time. Therefore, when the value of the product is not larger than 0, the process proceeds to step SD26 which is a process for executing the adjustment work in the opposite direction.

  [Step SD19] The rear platen movement count j in the same direction as the previous time is incremented by 1, and the process proceeds to Step SD20. [Step SD20] If the movement direction of the rear platen is the same between the previous time and the current time, the influence of backlash can be ignored. Therefore, the movement time Cj of the rear platen is calculated by Cj = K * | Fdiff | + C ′. C ′ is an initial value or the value calculated in step SD11.

  [Step SD21] It is determined whether or not Fdiff is greater than 0. If it is greater than 0 (when the current mold clamping force is greater than the target mold clamping force), the process proceeds to step SD22. If it is smaller than 0, the process proceeds to step SD24. [Step SD22] The rear platen is moved backward for Cj so as to weaken the clamping force. [Step SD23] The index Mn indicating the moving direction of the rear platen is set to zero. In this flowchart, when Mn is “0”, it means that the rear platen moves backward. [Step SD24] Since Fdiff is smaller than 0 (when the current mold clamping force Fact is smaller than the target mold clamping force Fset), the rear platen is advanced in the direction of increasing the mold clamping force by Cj. [Step SD25] The index Mn representing the rear platen movement direction is set to “1”. In this flowchart, when Mn is “1”, it means that the rear platen moves forward.

  [Step SD26] The rear platen movement count k in the direction opposite to the previous time is incremented by 1, and the process proceeds to Step SD27. [Step SD27] When the movement direction of the rear platen is different between the previous time and the current time, the influence of backlash must be taken into consideration. In this case, the movement time D of the rear platen is calculated by Dk = K * | Fdiff | + D ′. D 'is an initial value or the value calculated in step SD12.

[Step SD28] It is determined whether or not Fdiff is greater than 0. If it is greater than 0 (if the current mold clamping force Fact is greater than the target mold clamping force Fset), the process proceeds to step SD29, and if smaller than 0 ( If the current mold clamping force Fact is smaller than the target mold clamping force Fset), the process proceeds to step SD31.
[Step SD29] The rear platen is moved backward for Dk time so as to weaken the mold clamping force. [Step SD30] The index Mn indicating the moving direction of the rear platen is set to “0”. [Step SD31] The rear platen is advanced by Dk time to increase the clamping force. [Step SD32] The index Mn indicating the moving direction of the rear platen is set to “1”.

[Step SD33] The rear platen movement monitoring flag F is set to 1, and the process proceeds to step SD34. [Step SD34] The value of Fdiffbef is replaced with Fdiff, and the process proceeds to step SD35. [Step SD35] One molding cycle process of injection molding is terminated.
Note that the movement of the rear platen for adjusting the mold clamping force in the present invention is performed at the same time as the ejection of the ejector to shorten the cycle time, and is performed until the injection molding process is completed. Yes. [Step SD36] It is determined whether or not the set number of moldings S has been reached. If not, the process proceeds to step SD37. [Step SD37] Add 1 to the number of molding cycles R and return to step SD4.
In addition, if the cycle operation has already been performed and the proportional constant K for calculating the rear platen moving time has been calculated and the mold has not been replaced, the calculated K is used instead of K ′ as the initial value. Also good.

  As described above, the index Mn indicating the movement direction of the rear platen is time-series data representing forward and backward movements of the rear platen as 1 and 0 when the mold clamping force is adjusted, for example, 10001111110010110000. Then, based on the exclusive OR of Mn and the previous Mn-1, it can be determined whether or not the moving direction of the rear platen has changed. Table 3 is a table explaining exclusive OR of Mn-1 and Mn.

Here, the derivation process of the rear platen movement time calculation proportional constant K calculated in step SD10 and the rear platen movement time calculation constant C ′ calculated in step SD11 will be additionally described. Assuming that the relationship between the rear platen movement time and the amount of change in mold clamping force can be expressed by a linear function, the following two formulas (1) and (2) are established when the mold clamping force correction is performed for the second time.
Cj = Aj * K + C '(1)
Cj-1 = Aj-1 * K + C '(2)
From the expressions (1) and (2), Cj = Aj * K + (Cj−1−Aj−1 * K) (3)
Solving equation (3) for K,
K = (Cj−Cj−1) / (Aj−Aj−1) (4)
In equation (4), the rate of change in mold clamping force can be calculated regardless of whether Aj and Aj-1 are positive or negative. Therefore, if Aj and Aj-1 are absolute values,
K = (Cj−Cj−1) / (| Aj | − | Aj−1 |) (5)
Substituting (5) into (2) and setting Aj-1 to an absolute value as in (5),
Cj−1 = | Aj−1 | * (Cj−Cj−1) / (| Aj | − | Aj−1 |) + C ′ (6)
Solving (6) for C ',
C ′ = Cj−1− | Aj−1 | * (Cj−Cj−1) / (| Aj | − | Aj−1 |)
= Cj-1 * (| Aj |-| Aj-1 |) / (| Aj |-| Aj-1 |)
− | Aj−1 | * (Cj−Cj−1) / (| Aj | − | Aj−1 |)
= (Cj-1 * | Aj | -Cj * | Aj-1 |) / (| Aj |-| Aj-1 |) (7)
By using these formulas, K ′ and C ′ can be obtained.

It is a schematic diagram of one embodiment of an injection molding machine which is the present invention. It is a graph showing the relationship between the rear platen moving time and the mold clamping force correction amount in one embodiment of the present invention. It is a flowchart which shows the algorithm which performs mold clamping force adjustment based on the change rate of mold clamping force in one Embodiment of this invention. It is a flowchart which shows the algorithm which performs mold clamping force adjustment based on the change rate of mold clamping force in one Embodiment of this invention. In the flowchart of this algorithm, the change rate of the clamping force is a changing value. It is a flowchart which shows the algorithm which performs mold clamping force adjustment based on the change rate of mold clamping force in one Embodiment of this invention. This algorithm flowchart is a flowchart of the algorithm that takes into account the change rate of the mold clamping force, the backlash, and the rise delay time of the torque of the mold clamping force adjusting motor. In the flowchart showing this algorithm, the values related to the effects of mold clamping force, backlash, and torque rise delay time are fixed. It is a flowchart which shows the algorithm which performs mold clamping force adjustment based on the change rate of mold clamping force in one Embodiment of this invention. This algorithm flowchart is a flowchart of the algorithm that takes into account the change rate of the mold clamping force, the backlash, and the rise delay time of the torque of the mold clamping force adjusting motor. In the flowchart showing this algorithm, the values related to the influences of the clamping force, backlash, and torque rise delay time are assumed to change (part 1). It is a flowchart which shows the algorithm which performs mold clamping force adjustment based on the change rate of mold clamping force in one Embodiment of this invention. This algorithm flowchart is a flowchart of the algorithm that takes into account the change rate of the mold clamping force, the backlash, and the rise delay time of the torque of the mold clamping force adjusting motor. In the flowchart showing this algorithm, the values related to the influence of the clamping force, backlash, and torque rise delay time are assumed to change (part 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Rear platen 3 Movable platen 4 Tie bar 5a, 5b Mold 6 Toggle mechanism 6a Crosshead 7 Ball screw 8 Mold clamping servo motor 9 Tie bar nut 10 Mold clamping force adjustment motor 11 Position / speed detector 12 Current detector 13 Clamping force sensor 20 Control device 21 CPU (processor)
22 Axis control circuit 23 Servo amplifier 24 Input / output circuit (DI / DO)
25 Inverter 26 Memory 27 A / D converter 28 Interface 29 Display device 30 Bus

Claims (7)

In an injection molding machine having a toggle type mold clamping device that is disposed between a rear platen and a movable platen to which a movable mold is attached, and moves the movable platen back and forth with a mold clamping motor.
Mold clamping force adjusting means for adjusting the mold clamping force by moving the position of the rear platen at a predetermined speed;
Mold clamping force measuring means for measuring the mold clamping force;
Mold clamping force correction amount calculating means for calculating a mold clamping force correction amount which is a difference between a mold clamping force measured by the mold clamping force measuring means and a target mold clamping force;
Rear platen moving time for calculating the rear platen moving time based on a proportional constant for calculating the rear platen moving time, which is a rate of change of the rear platen moving time with respect to the mold clamping force, and the mold clamping force correction amount calculated by the mold clamping force correction amount calculating means. A calculating means,
An injection molding machine having a function of adjusting a mold clamping force, wherein the mold clamping force adjusting means is driven to adjust the mold clamping force based on the calculated rear platen moving time.   The mold clamping force adjusting means is driven to adjust the mold clamping force based on the calculated rear platen moving time and the non-response time from when the rear platen moving command is output until the rear platen starts moving. An injection molding machine having a function of adjusting the mold clamping force according to claim 1. Mold clamping force change amount calculating means for calculating a change amount of the mold clamping force before and after the rear platen movement when the rear platen is moved for a predetermined time;
A rear platen moving time calculating proportional constant calculating means for calculating a rear platen moving time calculating proportional constant from the predetermined time and the amount of change in the clamping force;
An injection molding machine having a function of adjusting a clamping force according to any one of claims 1 and 2.   Based on the rear platen movement time and the non-response time, the non-response time calculation means for calculating the non-response time until the rear platen starts moving after the rear platen movement command is output. 4. The injection molding machine having a function of adjusting the mold clamping force according to claim 2, wherein the mold clamping force adjusting means is driven to adjust the mold clamping force.   The proportional constant calculating means for calculating the rear platen moving time and the non-response time calculating means are configured to move the rear platen based on a change amount of the mold clamping force measured at the time of adjusting the mold clamping force and a moving time of the rear platen measured at the time of adjusting the mold clamping force. 5. The injection molding machine having a function of adjusting a clamping force according to claim 4, wherein a proportional constant for time calculation and the non-response time are calculated.   6. The mold clamping according to claim 4, wherein the non-response time is obtained individually when the rear platen is moved in the same direction as when the rear platen is moved in the opposite direction and when the rear platen is moved in the opposite direction. Injection molding machine with the function of adjusting force.   The mold clamping force measuring means includes a mold clamping force sensor, a peak current of the clamping motor during clamping or loosening, a current of the clamping motor when touching the mold, and after actually touching the mold. The injection molding having the function of adjusting the clamping force according to any one of claims 1 to 6, wherein the injection molding function is at least one of means for measuring a moving amount of the movable platen until the clamping is completed. Machine.

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