JPH072334B2 - Automatic clamping force setting method for toggle type clamping device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically setting a mold clamping force of a toggle mold clamping device of an injection molding machine. [Prior Art] The method of setting the mold clamping force of a toggle type mold clamping device is such that the extension of the tie bar at the time of mold clamping acts as the mold clamping force due to the characteristics of the mechanism. It was a method of subtly adjusting the position of the pressure receiving plate so that the amount of expansion of the mold was almost the set mold clamping force. Various methods have been devised for automatically setting the mold clamping force, but in each method, the mold clamping force is set by finely adjusting the position of the pressure receiving plate, and the mold clamping force is set there. Although there are differences in the detection method or the method of moving the pressure receiving plate to the set position, the mold clamping force is detected or predicted, and the correction amount is fed back to the mold thickness adjusting means of the toggle device to make the position of the pressure receiving plate subtle. It was a method of setting the mold clamping force by adjusting the mold clamping force. [Problems to be Solved by the Invention] However, when setting the mold clamping force, it is not easy to accurately move the entire toggle device by the mold thickness adjusting means, and the operation is complicated. An object of the present invention is to provide a new automatic mold clamping force setting method capable of automatically and accurately setting the mold clamping force only by giving a mold thickness and a set value of the mold clamping force. [Means for Solving the Problems] The feature of the present invention according to the above object is that a toggle type in which a rotary motion by a servomotor is converted into a linear motion and transmitted to a crosshead of a toggle mechanism, and the movable mechanism is moved by the toggle mechanism. The servomotor of the mold clamping device is provided with a control device having a torque limit function for limiting the upper limit value of the output torque, and a sensor for detecting the position of the crosshead from the rotation amount of the servomotor, and at a predetermined position. When setting the mold clamping force by providing the pressure platen position control means together with the position detector of the pressure platen, the mold platen and the mold clamping force are set, and the set mold clamping force is generated from the set values. The setting position is calculated and set, the pressure receiving platen position control means moves the pressure receiving platen, and when the set value is reached, the movement of the pressure receiving platen is stopped and the stop position of the pressure receiving platen is detected. Then, the detected value and the pressure receiving plate setting position are compared, and it is determined whether or not the value is an allowable value.If the value is an allowable value, the mold clamping force setting step is terminated, and if the value is not an allowable value, The purpose is to calculate the position of the crosshead that generates the set mold clamping force, and set that value as the mold clamping clamp position. [Operation] Assuming that the crosshead position is at a position where the pressure receiving plate can freely move, when the mold clamping force setting process is started, the central controller determines the set mold clamping force from the set values of the mold thickness and the mold clamping force. Calculate and set the setting position of the pressure receiving plate that generates force,
A command is given to the motor means for controlling the pressure receiving platen to move the pressure receiving platen, and when the set position is reached, the movement of the pressure receiving platen is stopped, and the stop position of the pressure receiving platen is detected. Compare with the panel setting position, judge whether the value is the allowable value, and if it is the allowable value, terminate the mold clamping force setting process,
If it is not the allowable value, the position of the crosshead that generates the set mold clamping force is calculated, and the value is set as the mold clamping clamp position, and the mold clamping force setting step is ended. [Example] In the figure, 1 is a pressure receiving plate, 2 is a fixed plate, and both plates are connected by tie bars 3, 3 provided over four corners. Reference numeral 4 denotes a movable plate which is inserted between the tie bars 3 and 3 and is provided between the pressure receiving plate 1 and the fixed plate 2, and is connected to the pressure receiving plate 1 with a toggle mechanism 5. The crosshead 6 at the center of the toggle mechanism 5
A ball nut 7 is internally installed in the pressure bearing plate 1, and a ball screw shaft 8 is rotatably attached to the pressure receiving plate 1. The ball screw shaft 8 and the ball nut 7 are screwed together, and the rotational movement of the ball screw shaft 8 at a fixed position is converted into a linear movement by the ball nut 7, and the links 5a, 5a are expanded and contracted by the movement of the crosshead 6. The movable platen 4 is the fixed plate 2
On the other hand, the mold 9 is moved back and forth, and the mold 9 attached to the opposite side surfaces of the fixed plate 2 and the movable plate 4 is opened and closed and clamped. The driving of the toggle mechanism 5 is performed by a servo motor 10 attached to the pressure receiving plate side. The servo motor 10 and the ball screw shaft 8 are connected via a drive belt 11,
Further, the servomotor 10 includes a control device 12 having a torque limit function for limiting the upper limit of the output torque of the servomotor, and a sensor 13 (encoder) for detecting the position of the crosshead 6 from the rotation amount of the servomotor. Is provided. Furthermore, the sensor 13 and the control device 12 are connected to a central controller 14. This central controller 14 is a control device that controls the entire injection molding machine with a CRT device as a display equipped with a micro computer, and a ROM that stores a control program, a temporary storage of data, and a calculation process. RAM,
It is equipped with an input / output device for controlling a servomotor and is capable of numerical calculation processing. Reference numeral 15 is a nut for controlling the position of the pressure receiving plate, which is screwed together with the sprocket 16 to the screw portion 3a of each of the tie bars 3, 3 located on the side of the pressure receiving plate. An encoder detector 20 is provided which is rotated by a chain 19 wound around a sprocket 18 of a control motor 17 and which knows the position of the pressure receiving plate 1 from the amount of rotation. The position detector 20 and the motor 17 are connected to the central controller 14. In the above configuration, assuming that the crosshead position is at a position where the pressure receiving plate 1 can freely move, when the mold clamping force setting process is started, the central controller 14 sets the mold thickness and the mold clamping force based on the set values. The set position of the pressure receiving platen 1 for generating the mold clamping force is calculated, and after setting it, a command is issued to the motor 17 for controlling the pressure receiving platen position. The motor 17 rotates in accordance with the command to drive the chain 19, and rotates the nut 15 together with the sprocket 16 by a predetermined amount to move the pressure receiving plate 1 to the set position. When the pressure receiving plate 1 reaches the set position, the motor 17 is stopped and the position is detected. This detection position is compared with the setting position of the pressure receiving plate 1 to determine whether or not the value is an allowable value. If the value is an allowable value, the mold clamping force setting step is ended, and if it is not the allowable value, The position of the crosshead 6 that generates the set mold clamping force is calculated. Then, that value is set as the mold clamping clamp position, and the mold clamping force setting step is completed. FIG. 2 is a flowchart showing the above process. When setting the thickness of the mold, if the exact value of the mold thickness is unknown, or if the machine is not accurately controlled in absolute dimensions, the thickness of the mold is determined by the machine's specific dimensions. It is necessary to set the height. In such a case, the mold thickness detection step may be performed before the mold clamping force setting step to allow the machine to detect the mold thickness. As an example of the method, after the pressure receiving plate is finally withdrawn,
After moving the crosshead and positioning it at the mold clamping clamp position, move the pressure receiving plate forward and touch the mold to detect the position where the pressure receiving plate stops moving, and then detect the mold from the position of the pressure receiving plate at that time. It suffices to calculate the thickness. FIG. 3 is a flow chart showing the mold thickness detecting step. An increment encoder may be used as the pressure platen position detection sensor. In this case, the mold thickness detection step is first provided to perform the mold touch. Since the mold touch position is also the mold thickness position, the amount of tie bar extension required with the mold touch position as the reference point. The mold clamping force setting control may be performed by setting to the setting position of the pressure receiving plate. [Effect of the Invention] In the present invention having the above-described configuration, since the extension of the tie bar at the time of mold clamping is proportional to the mold clamping force, the mold clamping force can be generated by controlling the elongation of the tie bar. If the correct thickness is given, the extension dimension of the tie bar required to generate the mold clamping force can be calculated, and the relative distance between the pressure receiving plate and the moving plate during the mold clamping clamp can be calculated from the crosshead position during the mold clamping clamp. Since it can be calculated, the set position of the pressure receiving plate that generates the set mold clamping force can be calculated by subtracting the extension amount of the tie bar from the mold thickness position. Therefore, if the pressure receiving plate is positioned at the set position, the set mold clamping force is set. When the pressure receiving platen position is different from the set position, it is calculated from the error value of the pressure receiving platen position and the crosshead position at the time of mold clamping is changed to change the moving amount of the movable platen for the above error. The amount of extension of the tie bar can be corrected to be the same as the set value, and the mold clamping force and the set value can be matched. Furthermore, the position control of the pressure receiving plate and the control of the mold clamping clamp position can be performed by digital control, and the mold clamping force can be easily set, so work efficiency is good, and a device for measuring the mold clamping force is not required. It does not require delicate adjustment and has the advantage that a general-purpose induction motor can be used as the motor of the pressure platen position control means.

[Brief description of drawings]

FIG. 1 is an explanatory view of an automatic mold clamping force correcting method of the present invention, and FIG.
FIG. 3 is a flowchart thereof, and FIG. 3 is a flowchart of a die thickness inspection process. 1 ... Pressure receiving plate, 2 ... Fixed plate, 3 ... Tie bar, 4 ... Movable plate, 5 ... Toggle mechanism, 6 ... Crosshead, 7 ... Ball nut, 8 ... Ball screw shaft, 9 ... Mold, 10 ... … Servomotor, 11 …… Drive belt 12 …… Servomotor control device 13 …… Crosshead position detection sensor 14 …… Center control 15 …… Mold thickness adjusting nut 17 …… Pressure platen position control motor 20 ... Position detector on pressure plate

Claims (1)

[Claims] 1. An upper limit of output torque to the servo motor of a toggle type mold clamping device, which converts a rotary motion of a servo motor into a linear motion and transmits the linear motion to a cross head of a toggle mechanism, and the toggle mechanism moves a movable plate. A control device having a torque limit function for limiting the value and a sensor for detecting the position of the crosshead from the rotation amount of the servo motor are provided, and a pressure receiving plate position control means is provided at a predetermined position together with a position detecting device of the pressure receiving plate. When setting and setting the mold clamping force,
Set the mold thickness and mold clamping force, calculate and set the setting position of the pressure receiving plate that generates the set mold clamping force from those set values, and move the pressure receiving plate by the pressure receiving plate position control means. , When the set value is reached, the movement of the pressure receiving platen is stopped to detect the stop position of the pressure receiving platen, and the detected value and the pressure receiving platen setting position are compared to determine whether or not the value is an allowable value. If the allowable value is reached, the mold clamping force setting process is terminated, and if it is not the allowable value, the position of the crosshead that generates the set mold clamping force is calculated, and that value is set as the mold clamping clamp position. Automatic clamping force setting method for toggle type clamping device.