JPH0321421A - Device for controlling backward speed of screw of injection molder - Google Patents

Abstract

PURPOSE:To stabilize the molding cycle by a method wherein the reference pattern of the backward speed of a screw is stored and the amount of operation of the controller of the backward speed of the screw is determined on the basis of the deviation obtained through the comparison of the reference pattern of the backward speed of the screw with the present backward speed of the screw. CONSTITUTION:The reference pattern of the backward speed of a screw is tabulated by comparing with the backward speeds of the screw in regard to a large number of sampling times. The resultant table is stored in a program setter 22. On the other hand, the present backward speeds of the screw are detected at respective sampling times and compared with the stored backward speed so as to obtain the respective deviations. A controller 32 of the backward speed of the screw is put into actuation on the basis of the deviations so as to determined the amounts of operation of a servo valve 31 in order to send commands to the servo valve 31, resulting in correcting the pattern of the backward speed of the screw to the reference pattern of the backward speed of the screw.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a screw retraction speed control device for an injection molding machine. (Prior art) Conventionally, a shaped material that has been heated and fluidized in a heating cylinder is injected into a mold under high pressure, cooled and solidified or hardened therein, and then the mold is opened to take out the shaped product. There is a screw-type injection molding machine that moves the screw inside the heating cylinder back and forth to form the injection molding. FIG. 5 is a diagram illustrating a control device for the above-mentioned conventional ejection command machine.

In the figure, a screw 2 is supported inside a heating cylinder l of an injection molding machine so as to be freely rotatable and move forward and backward, and is connected to a drive system consisting of a hydraulic cylinder 3 and a hydraulic motor 4, and is rotated and driven by the drive system. It can be moved forward and backward. The screw 2 in Fig. 5 has completed the injection shot, but at this point, prior to the next shot, the work of melting and plasticizing the molding material 5 and storing it at the tip of the head, that is, weighing is performed. ．． In the measuring process, the screw 2 is driven by the hydraulic motor 4 and rotates, and at this time, the large material 5 that has been dropped and supplied from the material supply port 10 moves forward in the groove 6 due to the rotation of the screw 2. While moving, it is melted and plasticized in the heating cylinder 1 and stored at the front end of the screw 2. The pressure of the bulky material 5 in the heating cylinder 1 generated during melting and plasticization becomes a reaction force against the screw 2, and the reaction force causes the screw 2 to retreat to a preset position. In this way, the formidable material 5 stored at the front end of the screw 2
is injected from the nozzle 7 into the cavity 9 of the mold 8 by pushing the screw 2 forward by the hydraulic cylinder 3. In addition, after the injection process is completed, a certain injection hydraulic pressure is applied to compensate for the cooling and shrinkage of the large-sized material 5 in the cavity 9, but when this pressure-holding process is completed, the screw 2 is operated again. It is rotated and weighed. Here, in the conventional injection molding machine, the injection speed of the screw 2 is used during the injection process, the set switching pressure is used when moving from the injection process to the pressure holding process, and the hydraulic cylinder 3 is controlled during the pressure holding process. During the metering process, feedback control is performed using the screw rotation speed and screw back pressure, that is, the oil pressure inside the hydraulic cylinder 3, depending on the preset screw position and time. Note that switching from the injection process to the pressure holding process can be done by setting the cylinder oil pressure in advance as described above;
There is a method of setting the screw position in advance. For this purpose, the control device of the injection molding machine is provided with a screw rotation speed regulator 12, and an injection speed regulator mu13.
, a holding pressure uI4 regulator 14 and a screw back pressure regulator l5 are provided so as to be freely switchable by a switch l6. and,
Each of these regulators 12, 13, 14. 15 is a servo valve 17. 18, the hydraulic motor 4 and hydraulic cylinder 3 are driven. Further, a screw tachometer 19, a speed detector 20, and a pressure detector 2l are provided for feedback control, and the screw rotation speed, screw speed, and oil pressure inside the injection cylinder 3 detected by each are transmitted to each of the above-mentioned regulators 12. ．． 13,14. It is designed to be feedbanked to 15. These controls are performed according to a program set by the program setter 22. In addition, a digital displacement detector 2 is used to control the oil pressure and rotation speed according to the set value of the screw position.
3 are provided. (Problem to be Solved by the Invention) However, in the screw retraction speed control device of Yokoi's injection molding machine, during the metering process, the screw rotation speed and the oil pressure in the injection cylinder 3 are
．． 15 for control, the screw retraction speed is not constant in each cycle, resulting in variations in the screw retraction time, that is, the metering time. As a result, each cycle becomes unstable, making it difficult to operate the injection molding machine stably and continuously. The present invention solves the problems of the conventional screw retraction speed control device of the injection molding machine, and makes the screw retraction speed constant in each cycle so that there is no variation in screw retraction time and metering time. The purpose of this project is to provide a screw retraction speed control device for injection molding machines. (Means for Solving the Problems) For this purpose, in the screw retraction speed control device for an injection molding machine of the present invention, a screw is disposed on one side of the piston, a rod is formed on the other side, and a rod is formed on both sides of the piston. A double-acting injection cylinder forming an oil chamber, a servo valve connected to the screw side oil chamber of the injection cylinder, a screw retraction speed 1g adjuster connected to the servo valve, and a screw retraction speed adjuster connected to the servo valve. a program setting device connected to the device, and a speed detector for detecting the screw retraction speed; the program setting device includes means for storing a reference screw retraction speed pattern; The apparatus includes means for comparing the screw retraction speeds and means for determining the operation amount of the screw retraction speed regulator based on the deviation obtained from the comparison. (Function) According to the present invention, a screw is disposed on one side of the piston,
A double-acting injection cylinder with a rod formed on the other side and oil chambers formed on both sides of the piston, a servo valve connected to the oil chamber on the screw side of the injection cylinder, and a screw retraction cylinder connected to the servo valve. speed regulator and the screw retraction speed 1
It has a program setting device connected to the iI node and a speed detector for detecting the screw retraction speed, and the program setting device has a means for storing a reference screw retraction speed pattern, and a means for storing a reference screw retraction speed pattern. A means to compare the current screw retraction speed and the deviation obtained from the comparison to determine the above screw retraction speed! Since the screw has a means for determining the amount of operation of the adjuster, the screw retraction speed pattern can be made constant in each cycle. Therefore, variations in the screw retraction time, that is, the metering time, can be reduced, making it possible to stabilize the cycle. (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. A screw retraction speed control device for an injection molding machine according to the present invention will be explained with reference to FIGS. 1 to 4.

Fig. 1 is a control block diagram of the screw retraction speed control device of the injection molding machine of the present invention, Fig. 2 is a relation diagram between screw stroke and screw rotation speed, Fig. 3 is a relation diagram between screw stroke and screw retraction speed, and Fig. 4 is a diagram showing the relation between screw stroke and screw retraction speed. is a diagram of the relationship between time and screw retraction speed. In the figure, a screw 2 is moved forward and backward by an injection cylinder 3 and rotated by a hydraulic motor 4, similar to the control method used in conventional injection molding machines. The injection cylinder 3 has a screw 2 disposed in front of a piston 3c, and a rod 3d formed in the rear. There is an oil chamber 3a before and after the IS piston 3c.
3b is formed, and pressure oil is supplied to the oil chamber 3a via a servo valve 31, and pressure oil is supplied to the oil chamber 3b via a servo valve 1B. The injection cylinder 3 is operated by an injection speed 11 moderator 13, a holding pressure regulator 14, a screw back pressure regulator 15, and a screw retraction speed 1i1 moderator 32,
The hydraulic motor 4 is operated by a screw rotation speed regulator 12. Further, the speed of the screw 2 detected by the speed detector 20 is sent to the injection speed regulator l3 as the screw rotation speed IA! If
The screw 2 detected by the screw tachometer 19 is installed in the f unit l2.
The rotation speed of the holding pressure regulator 14 and the screw back pressure regulator 1
5, the injection pressure detected by the pressure detector 21 is fed back, and the screw retraction speed regulator 32 is fed back the retraction speed of the screw 2 detected by the speed detector 20. Here, in the screw retraction speed @ control device of the injection injection machine of the present invention, the servo valve 3l is controlled by the screw retraction speed regulator 32, and the pressure oil adjusted by the servo valve 31 is supplied to the oil chamber 3a. is supplied to As mentioned above, the injection cylinder 3 has oil chambers 3a on both sides of the piston 3c.
, 3b is used. Pressure oil regulated by a screw retraction speed adjustment supply 32 is supplied to the oil chamber 3a on the side where the screw 2 is disposed, and the injection cylinder 3 is actuated by the pressure oil to cause the screw 2 to retract. In the injection molding machine, the screw speed is controlled by the injection speed regulator 13 in the same way as in the conventional control method.
The R clause is 4. Further, during the transition from the injection process to the pressure holding process, nozzle pressure control is performed by the pressure detector 26, and in the pressure holding process, the resin pressure detected by the pressure detector 26 is held! Control is performed by feeding back to the 11-node 14 and the screw back pressure 11-node 15. Furthermore, in the measuring process, the speed detector 2
The backward speed of the screw 2 detected by 0 is fed back to the screw backward speed jjiiff device 32 and set in the program setting device 22. Adjust the screw retraction speed to match the standard screw retraction speed pattern. Next, a method of controlling the screw retraction speed control device for an injection molding machine according to the present invention will be explained.

In the program setting device 22, the screw rotation speed corresponding to the screw stroke is set according to a metering program set by the operator.

That is, the screw rotational speed is set to be N1 between the strokes So and St, the screw speed is set to Na between the strokes S, , S■, and the screw speed is N3 between the strokes Sx and Ss. Note that the stroke S0 indicates the measurement start position, and the stroke S indicates the measurement end position. When measuring using the above measurement program, first obtain the screw retraction speed pattern during barging to test the resin, and then repeat this operation until the barging is stabilized to obtain the standard screw retraction speed pattern. The standard screw retraction speed pattern is shown by the solid line in Figure 3. Figure 3 shows the screw retraction speed (V#') at each stroke. FIG. 4 shows the above standard screw retraction speed pattern created by the screw retraction speed at each time. The reference screw retraction speed pattern includes screw retraction speed v. ' is compared and made into a table, and the table is stored in the RAM H area of the program setter.

On the other hand, the current screw retraction speed is detected at each sampling time (indicated by a broken line in FIG. 4) and compared with the screw retraction speed stored in the table above to obtain the deviation e. The screw retraction speed regulator 32 is actuated by the deviation e, the operation amount U of the servo valve 31 is determined, and a command is sent to the servo valve 31, so that the screw retraction speed pattern shown by the broken line becomes the screw retraction speed pattern shown by the solid line. It is modified to become Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. (Effects of the Invention) As explained above, according to the present invention, a double-acting injection cylinder is provided with a screw disposed on one side of the piston, a rod formed on the other side, and oil chambers formed on both sides of the piston. a servo valve connected to a screw side oil chamber of the injection cylinder; a screw retraction speed regulator connected to the servo valve;
a program setting device connected to the screw retraction speed regulator; and a speed detector for detecting the screw retraction speed; the program setting device includes means for storing a reference screw retraction speed pattern; Means for comparing the speed pattern and the current screw retraction speed, and the deviation obtained from the comparison to determine the screw retraction speed gli ii
Since a means for determining the operating amount of the FF device is provided, the screw retraction speed pattern can be made constant in each cycle.

Therefore, variations in the screw retraction time, that is, the metering time, can be reduced, and the cycle can be stabilized.

In addition, the plasticization measurement for each cycle is stable, and the plasticization measurement characteristics do not change over time even when the injection molding machine is operated continuously.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of the screw retraction speed control device for the injection molding machine of the present invention, Fig. 2 is a relation diagram between screw stroke and screw rotation speed, Fig. 3 is a relation diagram between screw stroke and screw retraction speed, and Fig. 4 is a diagram showing the relation between screw stroke and screw retraction speed. The figure is a diagram showing the relationship between time and screw retraction speed, and Figure 5 is a diagram showing the control device of a conventional injection-forming machine. l... Heating cylinder, 2... Screw, 3... Hydraulic cylinder, 3a, 3b... Oil chamber, 3c... Piston, 3d... Rod, 4... Hydraulic motor, 5...・
・Form material, 6...Groove, 7...Nozzle, 8...Mold, 9...Cavity, 12...Screw rotation speed!
Ilfiff device, 13... Injection speed 11 mode device, 14.
... Holding pressure regulator, l5... Screw back pressure regulator, 17
, 18. 31...Servo valve, l9...Screw rotation meter, 20...Speed detector, 2l...Pressure detector, 22...Program setting device, 32...Screw retraction speed regulator.

Claims (1)

[Scope of Claims] (a) A double-acting injection cylinder in which a screw is disposed on one side of the piston, a rod is formed on the other side, and oil chambers are formed on both sides of the piston; (b) The injection cylinder (c) a screw retraction speed regulator connected to the servo valve; (d) a program setting device connected to the screw retraction speed regulator; ) a speed detector for detecting the screw retraction speed; (f) the program setting device includes a means for storing a reference screw retraction speed pattern; and (g) a means for storing the reference screw retraction speed pattern and the current screw retraction speed. and (h) means for determining the operation amount of the screw retraction speed regulator based on the deviation obtained from the comparison.