JP3366921B2 - Compression molding control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression molding method, and more particularly to an electric compression molding method in an electric injection molding machine. 2. Description of the Related Art Injection compression molding methods for compressing a molded article, that is, an injected resin, after or during injection to improve the pressure transferability of the molded article are already known. [0003] This is because when a molten resin is injected into a mold,
Pressure is applied along the path through which the resin passes, and pressure is applied to the resin only in a certain direction. For example, when molding a disk-shaped molded product, a radial line may be generated in the molded product because pressure is applied radially. Therefore,
As a method of applying pressure to the injected resin after or during the injection to make the direction of the pressure applied to the resin uniform, an injection compression molding method of moving a mold and compressing the injected resin is employed. . [0004] In the compression step of the injection compression molding, it is desirable that the timing of starting the compression of the resin can be arbitrarily set. It is desirable to be able to perform the operation of the shaft. In addition, in order to activate the means for compressing the resin in the mold that has been injected after the injection and to apply compression, both the moving position of the means for compressing the resin and the force applied to the resin must be precisely controlled. However, in the case of an injection molding machine using a hydraulic pressure, it has been difficult to precisely control both the position of the means for compressing the resin and the force applied to the resin in order to compress the resin. Accordingly, an object of the present invention is to provide a compression molding control method in an electric injection molding machine which is capable of performing an operation of compressing a resin in a mold at an arbitrary timing after injection by a compression servomotor. Is to do. SUMMARY OF THE INVENTION The present invention controls an injection servomotor to perform one of injection, dwelling and weighing operations.
At any given time, the compression servomotor
Can compress the resin in the mold.
Control, and perform any of injection, holding pressure, or weighing.
At times, compression of the resin is controlled. FIG. 3 is a schematic view of a main part of an electric injection molding machine embodying an embodiment of the present invention. In the figure,
Reference numerals 1 and 2 denote dies, and a movable die 1 is a movable platen 3
The fixed mold 2 is fixed to a fixed platen 4.
Reference numeral 6 denotes a heating cylinder. A screw 5 is fitted in the heating cylinder 6, and the screw 5 is driven in the axial direction by an injection servomotor 7.
Although not shown, it is rotated by a screw rotation motor to measure and knead the resin. In the drawing, reference numeral 8 denotes a compression servomotor. The compression servomotor 8 is one of a clamp shaft and an ejector shaft servomotor depending on the structure of the molds 1 and 2. The above example shows an example in which the drive motor of the clamp shaft also serves as the compression servomotor. Then, the rotary motion of the compression servomotor (servomotor for the clamp shaft) is converted into a linear motion, and
A load cell 9 as a pressure detector is disposed on a member that presses the (movable platen 3). When the resin is compressed by the ejector shaft, a load cell is disposed on a member that converts the rotational motion of the servo motor that drives the ejector shaft into a linear motion and presses the molded product. Reference numeral 20 denotes an NC unit (numerical control unit) for controlling the injection molding machine. The NC unit 20 includes a central processing unit (hereinafter, referred to as CPU) 21 for NC and a programmable machine controller (hereinafter, referred to as PMC). CPU2 for
The NC CPU 21 has a RO storing a control program for controlling the entire injection molding machine.
M24 and a RAM 25 used for temporary storage of data are connected to the bus. A servo interface 26 is connected to the NC CPU 21 via a bus. The servo interface 26 has a servo for driving and controlling a servomotor for each axis such as injection, clamping (compression), screw rotation, and ejector. Circuit is connected,
FIG. 3 shows only the servo circuit 27a for the injection axis and the servo circuit 27b for the clamp axis (for compression). Although not shown in the servo circuits 27a and 27b, a feedback pulse from a pulse coder serving as a position detector attached to the servomotor is input to control the position and speed of each axis. Has become. A ROM 28 which stores a sequence program for controlling the sequence operation of the injection molding machine and a RAM 29 which is used for temporary storage of data in the course of arithmetic processing by the PMC CPU 22 are connected to the PMC CPU 22 via a bus. . The NC CPU 21 and the PMC CPU 2
2 is a bus arbiter controller (hereinafter referred to as BAC)
23, and the BAC 23 further has a shared RA.
M30, input circuit 31, and output circuit 32 are bus-coupled. The shared RAM 30 is composed of a writable nonvolatile memory such as a bubble memory and a CMOS memory, and stores an NC program for controlling the operation of the injection molding machine, various setting values such as molding conditions, parameters, macro variables, and the like. It has become. Various sensors provided in the injection molding machine are connected to the input circuit 31. In particular, according to the present invention, the output signal of the load cell 9 is converted to the A / D converter 1
The pressure signal converted into a digital signal at 0 is input. Various actuators of the injection molding machine are connected to the output circuit 32. In connection with the present invention, the output circuit 32 has a torque for limiting the output torque of the servomotor of each axis. A D / A converter for converting the limit value into an analog signal is connected, and in FIG.
Servo circuit 27b for driving and controlling compression servomotor 8
The torque limit value is output via the D / A converter 35. It should be noted that a torque limit value for holding pressure and back pressure is also input to the servo circuit 27a of the injection servomotor 7, but is omitted in FIG. Further, a manual data input device with a CRT display device (hereinafter, referred to as CRT / MDI) 34 is connected to the BAC 23 via an operator panel controller 33. In the above configuration, various molding conditions are input and set from the CRT / MDI 34 and stored in the shared RAM 30 before operating the injection molding machine. In particular, in the present invention, a clamp axis as a step feed axis, a step feed speed, and a step feed amount, that is, a step feed position of the clamp shaft and a torque limit value during compression are set as a step feed command in the compression step. Next, when the injection molding machine is operated, the NC device 20 controls the injection molding machine in accordance with the sequence program stored in the ROM 28 and the NC program stored in the shared RAM 30 to close the mold, close the mold, perform injection, Each process of compression, holding pressure, cooling, weighing, mold opening, and removal of the molded product is repeated to produce a molded product. The NC CPU 21 receives a command from the PMC CPU 22 and
The C program is read, and the process shown in FIG. 2 is performed at predetermined intervals. One block of the NC program is read, the pulse distribution amount for one distribution cycle is calculated, and the pulse distribution amount calculated for the specified axis is output to the servo circuit of the specified axis via the servo interface 26. (Step S
200). Then, it is determined whether or not the mode is the step mode (step S201). If the mode is not the step mode, the process proceeds to step S208 to determine whether or not the pulse distribution to the predetermined axis specified by one block of the NC program is completed (step S208). ), If not completed, the process of the cycle is terminated, and steps S200, S201, and S are performed in the next cycle.
When the distribution is determined to be completed in step S208, the process proceeds to the next block (step S20).
9) Hereinafter, the same processing as described above is repeated, and in a normal operation (when not in the step mode), the above-described operation is repeatedly performed. On the other hand, the PMC CPU 22 has a ROM 28
Are controlled in accordance with the sequence program stored in the injection start command (step S) as shown in FIG.
100) is output via the BAC 23 and the shared RAM 30, the NC CPU 21 receives this signal and distributes pulses to the injection servomotor to start injection as described above. at the same time,
A timer T for determining the start of compression is started (step S101). Then, after waiting for the timer T to time out (step S102), a step mode output is output, and the step feed axis (clamp axis), step feed speed, and step feed rate set together with the step mode signal in the shared RAM 30 via the BAC 23 are output. The feed position (direction and movement amount) is written to a predetermined address (step S103).
Then, the torque limit value TLS at the time of compression set in the shared RAM 30 is read, and the servo circuit 27b of the compression servomotor (servomotor for clamp shaft) 8 is output via the output circuit 32 and the D / A converter 35. And the output torque of the motor is limited (step S104). On the other hand, as a result of the step mode signal being written in the shared RAM 30, the NC CPU 21 reads from the shared RAM 30 that the step mode is selected in step S201 in the flowchart of FIG. Is determined (step S20).
2) Since the manual feed flag is not set in the first cycle in which the step mode is detected, the manual feed flag is set (step S203), and the PMC CPU 22 writes the program at a predetermined address of the shared RAM 30. (Clamp axis), step feed speed, and step feed position (feed direction and feed amount) are read (step S204),
The distribution amount of the step feed shaft (clamp shaft) is calculated and output (step S205). As a result, the servo motor 8 for compressing the step feed shaft, that is, the clamp shaft, is driven to compress the injected resin. Then, it is determined whether or not the pulse distribution of the step feed axis (clamp axis) has been completed (step S206).
Then, in the next cycle, steps S200 to S
Since the mode is shifted to 201 and the mode is the step mode, it is next determined whether or not the manual feed flag is set (step S202). Since the manual feed flag is already set,
In step S205, pulse distribution is performed to the step feed axis (clamp axis), and thereafter, pulse distribution is performed to the axis specified by the NC program in each cycle (injection to the injection axis and holding pressure control). (Step S200) together with the step feed axis.
That is, the pulse distribution of the step feed is performed in parallel to the servomotor of the clamp shaft as the compression servomotor. When the pulse distribution to the step feed axis is completed (step S206), the manual feed flag is lowered, the step mode is reset, and the step feed position arrival signal is written in the shared RAM 30 (step S207). On the other hand, the PMC CPU 22 outputs a step mode output (step S103) and outputs the torque limit value TLS to the servo circuit 27b of the compression servomotor (servomotor of the clamp shaft) 8 (step S1).
04), the feedback pressure PF from the load cell 9 is read via the input circuit 31 and the A / D converter 10 (step S105), and the feedback pressure PF is compared with the set torque limit value TLS (step S106). If the limit value TLS is larger than the feedback pressure PF, the torque limit value TL output to the servo circuit 27b is increased by a predetermined amount Δα (step S10).
7) If the feedback pressure PF is larger, the output torque limit value TL is reduced by a predetermined amount Δα (step S108).
Until the step feed position arrival signal is written in step S109, the processing from step S105 is repeated. That is, the set torque limit value TLS is output to the servo circuit 27b of the servo motor for the clamp axis of the compression servo motor 8, and the torque output by the compression servo motor 8, that is, the resin in the mold is reduced. The applied compression pressure (PF) is limited to the set torque limit value TLS,
If the feedback pressure PF, which is the compression pressure actually applied to the resin in the mold, does not reach or exceeds the set torque limit value TLS due to the characteristics of the machine or other reasons, the servo control is performed in steps S107 and S108. By changing the torque limit value TL output to the circuit 27b, the feedback pressure PF becomes equal to the set torque limit value TLS. (The accuracy of matching between the set torque limit value TLS and the feedback pressure PF depends on the resolution of the A / D converter 10 and the D / A converter 35). Then, the NC CPU 21 ends the pulse distribution of the step feed, and transfers the position arrival signal to the shared RAM.
30 and is detected (step S109).
The compression molding process ends. In this manner, while the injection and holding pressure are being performed by the injection servomotor, and furthermore, while the metering is being performed, the resin injected into the mold is subjected to compression and compression. The servo motor 8 (servo motor for the clamp shaft in this embodiment) is step-feeded, and is set while being controlled so that the compression pressure on the resin by the compression servo motor 8 is maintained at the set value. The resin is compressed to the position, and both the position and the pressure for resin compression are simultaneously and precisely controlled. As described above, according to the present invention, the compression of the resin in the mold is performed by the compression servomotor at any time during which any one of the operation control of the injection shaft is performed such as injection, holding pressure, or measurement. Since the operation can be performed, the resin in the mold can be compressed at an optimal time, and a high-quality molded product having good pressure transfer properties can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a C for PMC according to an embodiment of the present invention.
FIG. 2 is an operation processing flowchart related to a compression molding process performed by a PU; FIG. 2 is an operation processing flowchart performed by an NC CPU according to the embodiment; FIG. 3 is an electric injection molding according to the embodiment; FIG. 2 is a schematic view of a main part of the machine. [Description of Signs] 1, 2 Mold 5 Screw 7 Injection Servo Motor 8 Compression Servo Motor 20 NC Device

Continuation of front page (72) Inventor Kazuo Kubota 3-5-1 Asahigaoka, Hino-shi, Tokyo FANUC CORPORATION Product Development Laboratory (56) References JP-A-60-174623 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claims] [Claim 1] At any time during which injection, holding pressure, or measurement is performed by controlling an injection servomotor.
Of the resin in the mold by the compression servomotor
Control so that injection can be performed,
Controls resin compression while performing pressure or metering
Compression molding control method to be performed .