JPS63286314A - Motor-driven injection molding machine - Google Patents

Abstract

PURPOSE:To reduce dispersion in weights of molded products, by constituting the title machine so that there is no deceleration in a forward movement speed of a screw in the vicinity of a dwell changeover position by controlling by a numerical control device a torque limit changeover device controlling output torque of a servomotor into dwell torque by discriminating that the dwell changeover position is attained by discriminating device. CONSTITUTION:A place where a screw is at present is detected by a position detecting device E and the detected position and a dwell changeover position set up by a dwell changeover position setting device D are compared by a discriminating device F with each other. When the place where the screw is at present arrives at the dwell changeover position, an output signal is applied to a torque limit changeover device G, output torque of a servomotor is controlled to that corresponding to dwell and dwell control is performed. Consequently, when it is discriminated by a discriminating device that a screw position detected by the screw position detecting device E has arrived at the dwell changeover position, a torque limiting value is converted into and the output torque of the servomotor is controlled to that corresponding to the dwell. Therefore, it does not happen that an advance movement speed of the screw is decelerated in the vicinity of the dwell changeover position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an injection molding machine. In particular, a servo motor is used as the drive source of the injection mechanism, and II
The present invention relates to an electric injection molding machine that moves from an injection process to a pressure holding process without decelerating near a holding pressure switching position.

IIIJtI with conventional technology numerical control equipment (hereinafter referred to as NG equipment)
In an electric injection molding machine, the screw advance command for the injection process and the screw advance command for the holding pressure process are issued separately, and when the screw reaches the holding pressure switching position,
It is known to perform υ1111 by switching from the injection process to the pressure holding process. For example, JP-A-61-12582
See Publication No. 6, etc. In this case, the N of the injection process and pressure holding process is
The G program consists of 210 steps as shown below.

N210G31.1 G90 X X F
11M12;N220 G90 GOlX
F f2M13: In the above NG program, N210°210 is the sequence number, G31.1 is the G code that commands to switch the speed by override, G90 is the G code that indicates the absolute command, GOl
is a G code indicating the cutting feed (linear interpolation), and X indicates the injection axis, which means a command to the servo motor that drives the screw in the axial direction. Further, F is a speed command, M12. M13
means M code. The injection speed of each stage during injection is set and controlled by the switching screw position of each stage and an override value that determines the injection speed of each stage. As a result, in sequence number N210, which is the 10th step of the injection process, the screw is moved at the injection speed equal to the command speed f, multiplied by the override value of each stage, up to the holding pressure switching position x, which is set by a macro variable, etc. After confirming that the injection and holding pressure switching position x 1 has been reached, sequence number N, which is the block for the next pressure holding process, is pressed.
Start processing 220 and move the screw to the most optimal position x2
(Normally, the value of x2 is taken as the origin "0") until the speed f
2 (normally set to maximum speed).

With the injection and pressure holding control as described above, as shown in FIG. 5, the pressure applied to the advancing speed of the screw charcoal and resin changes. That is, when switching from the injection process to the holding pressure process, the forward speed of the screw is decelerated to confirm that the screw has reached the holding pressure switching position, and the screw position has entered the in-position width of the holding pressure switching position. After this is confirmed, a movement command for the next pressure holding is output and the screw moves forward, so the forward speed of the screw becomes slower than the set speed at the pressure holding switching position, and as a result, the resin There was also a change in the pressure applied to the

Problems to be Solved by the Invention In conventional electric injection molding machines, as shown in Figure 5, the forward speed of the screw is reduced at the pressure holding switching position, resulting in variations in the weight of the molded products. It had the disadvantage of being large.

Therefore, an object of the present invention is to prevent the forward speed of the screw from being slowed down near the holding pressure switching position, and to reduce the weight variation of molded products. An object of the present invention is to provide a blocked injection molding machine.

Means for Solving the Problems Figure 1 is a block diagram of the means adopted by the present invention to solve the problems of the prior art. A drive control means A that drives a servo motor C that drives the mechanism to perform injection and pressure holding, a pressure holding switching position setting means that sets a pressure holding switching position, and a screw position detection means E that detects the screw position. a determining means F for determining whether or not the screw position detected by the detecting means E has reached the holding pressure switching position set by the setting means; and a torque provided in the servo circuit B of the servo motor C. When the limit means Ba and the discrimination means F determine that the holding pressure switching position has been reached, the torque limit means Ba is switched to the holding pressure torque limit value to limit the output torque of the servo motor to the holding pressure torque. The above problem was solved by providing a torque limit switching means G in an electric injection molding machine controlled by a numerical control device.

Operation When the injection/pressure holding process begins, the drive control means A outputs a screw advance command to the most advanced position of the screw, advances the screw, and starts injection. On the other hand, the position detecting means E detects the current position of the screw, and the discriminating means F compares this detected position with the holding pressure switching position set by the holding pressure switching position setting means, and determines the current position of the screw. When the position reaches the holding pressure switching position, an output signal is sent to the torque limit switching means G, and upon receiving the signal,
The torque limit switching means G outputs a torque limit value corresponding to the set pressure holding to the torque limit means Ba in the servo circuit B, limits the output torque of the servo motor to the torque corresponding to the pressure holding, and performs pressure holding control. . As a result, the screw driven by the driving means 11J is driven at the set speed to the most forward screw position, and the above determination determines that the screw position detected by the screw position detection means E has reached the holding pressure switching position. When the determination is made by means F, the torque limit value is simply converted and the output torque of the servo motor is limited to the torque corresponding to the holding pressure, so the forward speed of the screw is changed as shown in FIG. is not decelerated near the holding pressure switching position.

Embodiment FIG. 2 is a block diagram of main parts of an embodiment of the present invention, in which 1 is a screw, and 2 is a servo of an injection shaft that drives the screw 1 in the axial direction via a transmission ff (not shown). motor,
A position detector 3 is attached to the motor shaft of the servo motor 2 and detects the position of the screw 1 from the rotational position of the servo motor.

Further, 10 is an NG device, and the NG device 10 includes a microprocessor (hereinafter referred to as CPU) 11 for NG and a CPU for a programmable controller (hereinafter referred to as PMC).
The PMC CPLJ 12 is connected to a ROM 15 that stores sequence programs such as a program for switching from an injection process to a pressure holding process, which will be described later.
Also connected is a RAM 22 used for temporary storage of data. The NG CPU 11 has a ROM 14 that stores a management program for controlling the entire injection molding machine, and is used for injection, clamping, and screw rotation.

Drive servo motors for each axis such as for ejectors! 1t11
A servo circuit for controlling the control is connected via a servo interface 16. In addition, FIG. 2 shows a servo motor 2 for injection. Only the servo circuit 17 is shown. Also, 18
is a nonvolatile shared RAM composed of bubble memory or CMOS memory, and is used to store NG programs, various setting values, parameters, etc. that control each operation of the injection molding machine. 13 is a bus arbiter controller (hereinafter referred to as BAC)
2. Shared RAM18. Each bus of input circuit 19 and output circuit 20 is connected, and WABAC
13 controls the bus used by 111. In addition, 24 is the operator panel controller 2
This is a manual data input device with a CR1 display device (hereinafter referred to as CRT/MDI) connected to the BAC 13 via CRT 3. Note that 21 is a RAM connected to NCJ'l1CPtJ11 by bus, and is used for temporary storage of data.

In the above configuration, among the NG programs stored in the shared RAM 18, the injection and pressure holding process programs are instructed in one block as shown below.

N210 G31.1 G90 X X F
flMll: In this block, the movement position x1 commanded to the '+-bo motor 2 as the injection axis X is the most advanced position of the screw, and this position is normally the origin "0". In addition, as in the past, the injection speed is the command speed f1 commanded in the above block multiplied by the override value of each stage of the injection process, and the particular switching screw position of the injection process and the override value of each stage and The switching position of each stage and the override value of each stage during pressure holding are CR.
It is set in advance from the T/MDI 24 and stored in the shared RAM 18. In addition, the holding pressure switching position 1Fff, the torque limit value corresponding to the maximum injection pressure at 04 exit, the torque limit value HP corresponding to the holding pressure of each stage in the pressure holding process, the pressure holding time HT of each stage and the injection process Setting values such as the maximum injection time Ti are also set and stored in the shared RAM 18 via the CRT/MDI 24.

Therefore, we started the injection molding machine, started the injection process, and
When the above-mentioned injection and pressure holding block is read from the program, the NCI CPU 11 distributes pulses at the commanded speed up to the most suitable screw position fiX1 (-0) commanded by the block, at the first stage of the injection process. Starting at the speed multiplied by the override value, the servo interface 16. The servo motor 2 is driven via the servo circuit 17 to start injection, and the M code M11 commanded by the block is written to the shared RAM 18 via the BAC 13.
1 code is detected, the torque limit value corresponding to the set maximum injection pressure is set to BAC13,
The output torque is sent to the torque limit circuit in the servo circuit 17 via the output circuit 20, and the output torque of the servo motor 2 is limited to that corresponding to the maximum injection pressure, and the injection timer ■i
is set to the set maximum injection time and started (step 81). Then, the 8MC CPU 12 determines whether or not the injection timer Ti has timed up (step S2), and also transmits the signal from the position detector 3 to the servo circuit 17. The current screw position is determined by the current value register provided in the RAM 21 of the NO CPtJ 11 which stores the screw position using the signal obtained through the servo interface 16.
The SC is detected via the BAC 13 and the shared RAM 18, and it is monitored whether the screw position *SC has reached the set holding pressure switching position TR (step 83). Note that speed control at each stage of the injection process is performed during this period, but the explanation will be omitted since it is not directly related to the gist of the present invention. Thus,
Before the injection timer Ti times up, the screw position [
When the SG reaches the holding pressure switching position, the PMC CPU 12 sets the torque limit flHP1 corresponding to the first stage holding pressure of the set holding pressure process to the BAC 13 and the torque limit circuit in the servo circuit 17 via the output circuit 20. The output torque of the servo motor 2 is limited to the torque corresponding to the first stage pressure holding, and the pressure holding time of the first stage is set and started in the pressure holding timer HT1 (step 84). In this example, the pressure holding process is a two-stage process.

Then, it waits for the pressure holding timer HTI to time up (step S5), and when the time has expired, it outputs the torque limit value HP2 for holding pressure in the second stage to the torque limit circuit in the servo circuit 17 as described above, and the servo motor 2
The output torque is set to a torque corresponding to the second-stage holding pressure, and the second-stage set pressure holding time is set and started in the holding pressure timer HT2 (step 36). Then, when the timer HT2 times up (step S7), the position command indicates the screw most advanced position X, which is the target position, (-
NC#ICPL1 when reaching O) and completing distribution.
11 is written to the shared RAM 18 via the BAC 13.
8) If the distribution completion signal has been written, write the completion signal FIN corresponding to the M11 code into the shared RAM 18 via the BAC 13 (step 89). As a result, N
The G CPU 11 reads the next block and starts the next metering cycle.

On the other hand, in steps 82 and 83, if the injection timer 1 times up before the screw position SC reaches the pressure holding switching position TR due to some reason such as the high viscosity of the molten resin to be injected, the pressure holding process is started immediately. , the pressure holding control is started from step S4. In addition, i in the pressure holding process
Even if lIJlm is completed, the distribution completion signal is sent to the NG CPU.
11 (step 88), the PC
The CPU 12 starts the follow-up function, turns on the dry run function, turns on the rapid feed rate, and outputs a manual fast forward command (step 5).
10). As a result, NCjllCPLJll is the speed command value in the servo circuit 17 and the position detector 3 of the servo motor 2.
Reads the value of the error register that stores the difference between the signals from The pulse is output to the error register, and pulse distribution is forcibly performed even though the screw position has not reached the screw most forward position. (The device cannot proceed to the next block.)

In this way, even though the pulse distribution is forced and the screw position does not move to the screw most advanced position, it follows up and sets the value of the error register to zero, that is, as if the screw had reached the screw most advanced position. Therefore, the NG CPU 11 sends out a distribution completion signal and sends this to P.
When MC#JCPLJI2 detects (step 511)
. Stop the follow-up function, turn off dry run and rapid feed rate (step 512),
Out.

End signal F for M11 code as end of pressure holding process
Send IN (Step S9) to move on to the next weighing cycle.

Since the operation is as described above, pulse distribution is performed continuously from the injection process to the pressure holding process without being positioned at the pressure holding switching position TR, so the injection speed of the screw 1 is adjusted to the holding pressure as shown in Fig. 4. There is no deceleration near switching position TR.

In the above embodiment, the injection and pressure holding processes are configured as a program formed in one block, but the injection process and the pressure holding process may be separated and configured in two blocks. In this case, the pressure holding switching position Instructions and screws for the injection process up to! Fi is a command for the pressure holding process up to the forward position, but if the injection process block is not provided with an M code and the injection process is performed with a cutting feed command, the cutting feed command will not decelerate successive blocks and will distribute pulses. is performed, so there is no deceleration near the holding pressure switching position.

Effects of the Invention As described above, in the present invention, since the injection speed is not slowed down near the holding pressure switching position, uniform products can be molded with less variation in mold opening of molded products. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the means adopted by the present invention to solve the problems of the prior art, FIG. 2 is a block diagram of a main part of an embodiment of the present invention, and FIG. 3 is a block diagram of the same embodiment. FIG. 4 is an explanatory diagram showing the relationship between injection speed, injection pressure, holding pressure and screw position in the same embodiment. FIG. It is an explanatory view showing the relationship between pressure holding pressure and screw position. 1...screw, 2...servo motor, 3...
Position d detector, 10... Numerical control device (NC6 position). Figure 1

Claims (3)

[Claims] (1) In an electric injection molding machine in which a servo motor is controlled by a numerical control device and the servo motor drives an injection mechanism to perform injection, the servo motor is driven by commanding the movement of the screw to its most advanced position. A drive control means for performing injection and pressure holding, a pressure holding switching position setting means for setting a pressure holding switching position, a screw position detection means for detecting the screw position, and a screw position detected by the detection means is set by the setting means. a determining means for determining whether the holding pressure switching position set in is reached; a torque limit means provided in the servo circuit of the servo motor; and a determining means for determining whether the holding pressure switching position has been reached. an electric injection molding machine comprising: a torque limit switching means that switches the torque limit means to a holding pressure torque limit value when the torque limit value is set, and limits the output torque of the servo motor to the holding pressure torque; (2) Provide a timer to measure the time from the start of injection,
If the timer reaches the set time before the determining means determines that the screw position has reached the holding pressure switching position, the torque limit switching means sets the torque limit value of the torque limiting means to the holding pressure. An electric injection molding machine according to claim 1, wherein the torque limit value is changed to . (3) After switching to the holding pressure torque limit value, a timer is provided to measure the holding pressure time, and when the timer reaches the set time,
When the screw is not positioned at the most advanced screw position by the drive control means, the drive control means distributes the pulses of the movement command to the most advanced position of the screw, and follows up and completes the movement command to the most advanced position of the screw. An electric injection molding machine according to claim 1 or 2.