JPH04259523A - Protecting and controlling method of mold of motor-driven injection molding machine - Google Patents

Abstract

PURPOSE:To fulfil mold protective function without applying excessive pressure to a mold as much as possible. CONSTITUTION:A load (positional deviation) pattern to be applied to a movable mold to a movable mold position at least at a mold protective section at a normal mold clamping process is stored. At the time of molding, when the load at an established movable mold position is higher than the stored load by at least a fixed value, operation is suspended by deciding it as a disorder in mold protection (S22, S23, S24, S28, S29). With this construction, when a foreign matter is interposed within a space between the molds, the operation is suspended immediately and it does not happen that the mold is hurted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold protection control method for an electric injection molding machine.

0002

[Prior Art] In an injection molding machine, there is a foreign object such as a molded product between the molds during the mold closing process, and if the mold is closed as it is, there is a risk of damaging the mold itself. A protection zone is provided, during which the movable mold is driven at low speed and low pressure to perform mold protection control.

[0003] A method generally adopted for this mold protection control is to start a mold protection timer at the time when mold protection starts, and before the timer times out,
If a sensor such as a proximity switch installed at the mold touch position turns on, it is assumed that there is no foreign object and the mold is clamped. If the sensor does not turn on and the timer times out, the mold is protected. A method is adopted in which an abnormality detection circuit is activated to generate an alarm or the like, and the movement of the movable mold is stopped.

Furthermore, in an electric injection molding machine, when the movable mold reaches the mold protection start position, the output torque of the servo motor that drives the movable mold is limited and driven at low torque, and the mold is finished within a predetermined time. A mold protection control method that outputs an alarm, etc. if the mold touch position is not reached is also adopted (Japanese Patent Application Laid-open No. 1148354/1983, Japanese Patent Application Laid-Open No. 63-1988).
(See Publication No. 286315).

[0005]

[Problems to be Solved by the Invention] In the conventional mold protection control method described above, even if the pressure is low, mold clamping force is applied to both molds through foreign objects for a predetermined time measured by a timer. Therefore, when the mold protection abnormality detection circuit is activated, unnecessary pressure is applied inside the mold cavity, and depending on the mold cavity structure, the mold may be damaged.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mold protection control method that can achieve the mold protection function without applying as much extra pressure to the mold as possible.

[0007]

[Means for solving the problem] The mold is closed with no foreign matter between the molds, and the load applied to the movable mold (movable mold or the value of the drive current of the servo motor, or the value detected from the mold clamping force detection sensor attached to the tie bar or part of the mold clamping mechanism) Each time mold closing is started, the position of the movable mold and the load are detected, the detected load corresponding to the set position is compared with the stored load, and the detected addition is memorized. The above problem was solved by activating the mold protection abnormality detection means when the load exceeds a predetermined value.

[0008]

[Operation] If there is no foreign material between the molds, the pattern of the load applied to the movable molds relative to the position of the movable molds during the mold closing process will be approximately the same pattern. In other words, until the mold touches the movable mold, the load on the movable mold is just the frictional resistance with the tie bar when the movable platen with the movable mold attached moves, and it varies somewhat depending on the mold closing speed and speed switching, etc. However, it is almost constant. The load applied to the movable mold can also be detected by attaching a mold clamping force detection sensor to a tie bar or a part of the mold clamping mechanism. Also,
Since the servo motor that drives the movable mold so as to overcome the load outputs an output torque, it can also be detected by detecting the drive current of the servo motor. Further, since load fluctuations are accompanied by fluctuations in the follow-up delay of the servo motor with respect to the movement command to the servo motor that drives the movable mold, it can also be detected by detecting positional deviation. Therefore, if you memorize the above position deviation, servo motor drive current, and value detected from the mold clamping force sensor according to the position of the movable mold, you can easily perform the mold clamping process without foreign objects between the molds. The positional deviation, the drive current value of the servo motor, or the value detected from the mold clamping force sensor has almost the same pattern as the stored pattern for the position of the movable mold. However, if a foreign object is present, the load will increase and each of the above values will be larger than the stored values, so if these detected values exceed the stored values by a predetermined value,
The mold abnormality detection means is activated as a result of the presence of foreign matter. As a result, if the load becomes larger than normal (when there is no foreign material between the molds), the mold abnormality detection means will be activated, issue an alarm, and stop the operation to protect the mold. and minimize the amount of time that unnecessary pressure is applied to the mold.

[0009]

[Embodiment] Fig. 3 is a schematic diagram of the main parts of an electric injection molding machine implementing an embodiment of the present invention.A mold 4 is fixed between a fixed platen 1 and a movable platen 2, respectively. A toggle mechanism 5 is disposed between the rear platen 3 and the movable platen 2 so that the movable platen 2 can be moved left and right in FIG. 3 along tie bars (not shown). A ball nut is fixed to the crosshead 7 of the toggle mechanism 5, and the ball nut is screwed into a ball screw 6, and the ball screw 6 is driven by a servo motor 11 for mold clamping via a pulley 8, a timing belt 10, and a pulley 9. It is now possible to do so. Further, the rotational position of the servo motor 11 is detected by a pulse encoder 12. The toggle type mold clamping mechanism driven by a servo motor as described above is the same as the conventional one, so only an outline thereof is shown.

In the figure, 20 is a numerical control device (hereinafter referred to as an NC device) as a control device for controlling the injection molding machine.
The NC device 20 is an NC microprocessor (hereinafter referred to as
It has a CPU 21 (hereinafter referred to as CPU) and a CPU 22 for a programmable machine controller (hereinafter referred to as PMC), and the PMC CPU 22 has a ROM 2 that stores sequence programs etc. for controlling sequence operations of the injection molding machine.
6 is connected to the bus, and a RAM 27 used for temporary storage of data is also connected to the bus. CPU2 for NC
1 includes a ROM 24 that stores a management program that controls the injection molding machine as a whole, a RAM 25 that is used for temporary storage of data, and axes for injection, clamping, screw rotation, ejector, etc. A servo circuit that drives and controls the servo motor is connected via a servo interface 28. In addition, in FIG. 3, only the servo motor 11 and the servo circuit 29 for mold clamping are shown. CP for NC
The U21 and the PMC CPU 22 are bus-coupled by a bus arbiter controller (hereinafter referred to as BAC) 23, and
A nonvolatile shared RAM 30 composed of bubble memory or CMOS memory, an input circuit 31, and an output circuit 32 are connected to the BAC 23 via a bus, and the BAC 23 controls the bus used.

The shared RAM 30 has a memory section that stores NC programs and the like for controlling each operation of the injection molding machine, and a memory section that stores various setting values, parameters, and macro variables. The input circuit 31 is configured to receive signals from each sensor provided in the injection molding machine, and the output circuit 3
2 is connected to various actuators provided in the injection molding machine, and in particular outputs a torque limit value from the output circuit 32 to the servo circuit 29, and limits the torque command value output from the servo circuit 29 to drive the servo motor 11. Only the circuit that limits the output torque of is shown. Note that the servo circuit 29 receives an output signal from a pulse encoder 12 as a position detector that detects the rotational position of the servo motor 11 attached to the servo motor 11, and controls the position, speed, etc. of the servo motor 11. It is supposed to be done.

[0012] The above-mentioned servo circuit for driving and controlling each servo motor is the same as a conventional servo circuit, and particularly includes an error register (not shown) for storing the position deviation of the servo circuit 29 of the mold clamping servo motor 11. The value can be read from the NC CPU 21 via the servo interface 28. That is, the above error register is N
The C CPU 21 adds the movement command (distribution pulse) output to the servo circuit 29 of the mold clamping servo motor 11 via the servo interface 28, and adds the movement command (distribution pulse) to the pulse encoder 12.
Since the amount of positional deviation is always stored by subtracting the feedback pulse generated from the error register, the positional deviation can be read by reading the value of this error register.

A manual data input device with a CRT display (hereinafter referred to as CRT/MDI) 34 is connected to the BAC 23 via an operator panel controller 33.

[0014] When operating the injection molding machine, the CRT/
Various molding conditions are set using MDI34, and shared RAM3
Store at 0. In order to carry out the mold protection control of the present invention, in this embodiment, a registration process is started to store a positional deviation according to the position of the movable mold (rotational position of the servo motor 11).

First, the operator inputs a mold protection registration command from the CRT/MDI 34, and inputs the position Pi (i=1 to n) of the movable mold whose positional deviation is to be stored. Note that there is a certain relationship between this movable mold position and the rotational movement position of the mold clamping servo motor that drives the movable mold, so by setting the rotational movement position of this mold clamping servo motor, the movable mold I'm trying to set the location. In addition, the coordinate system of the position of the movable mold is usually the position where the set mold clamping force is obtained,
That is, the lock-up position in which the link of the toggle mechanism 5 is fully extended is the origin, and the mold opening direction is the positive direction.

When the mold protection registration command is input, the NC CPU 21 stores the table TB as shown in FIG. 5 in the RAM.
The positions Pi of the movable molds created in 25 and input next are sequentially stored in the table TB. Note that a flowchart of the process of storing the position Pi of the movable mold is omitted. Next, when the operator inputs a mold protection registration start command, the NC CPU 21 initializes the pointer i to "0".
, and the registration process shown in the flowchart in FIG. 1 is started at predetermined intervals.

The NC CPU 21 is based on the conditions of the mold clamping process such as mold closing speed, mold protection start position, mold protection speed, mold protection torque limit value, mold touch position, etc. of the set molding conditions. Then, the same process as the conventional mold clamping process is performed (step S1). When the processing of the mold clamping process of the cycle is completed, in this embodiment, the movable mold position P, that is, the rotational position of the mold clamping servo motor is further read out (step S2). A current value register for integrating the amount of movement distributed by the NC CPU 21 in pulses to the servo circuit 29 of the mold clamping servo motor 11 is provided in the shared RAM 25 in the same manner as before, and the movement can be performed by reading the value of this current value register. The mold position P can be read out. Furthermore, a more accurate movable mold position P may be obtained by subtracting the positional deviation amount stored in an error register in the servo circuit from the value of this current value register.

Next, set position Pi corresponding to pointer i
is read out from the table TB and compared with the detected current position P (step S3), and the detected current position P is the set position P.
If it is larger than i, that is, if the set position Pi has not been reached, the processing for the cycle ends. Furthermore, if the detected current position P is less than or equal to the set position Pi and has reached the set position Pi, the position deviation E at that time is read from the error register in the servo circuit 29, and the read position deviation E is stored in the table TB. The positional deviation Ei is written to the address corresponding to the set position Pi, and the pointer i is incremented by "1" (steps S4, S5). Next, it is determined whether the movable mold has reached the position of the set mold clamping force and the toggle mechanism 5 has reached the lock-up state (step S6), and if the lock-up has not been completed, the corresponding cycle The process ends. Hereinafter, by performing the above-mentioned processing for each period, the position deviation Ei when the position is reached for each set position Pi is calculated in the table T as shown in FIG.
It will be stored in B.

[0019] When it is detected in step S6 that the mold clamping process is completed and the lock-up is completed, the NC C
The PU 21 displays a message asking whether to register or not on the CRT screen of the CRT/MDI 34 (step S7), and the operator confirms that the mold clamping process is performed normally without any foreign matter intervening between the molds during the mold clamping process described above. When a registration command is input to register the data (positional deviation) at this time (step S9), the NC CPU 21 registers the RA.
Share the data of table TB stored in M25 R
The information is stored in the AM 30 (step S10), and the registration process ends.

FIG. 4 shows an example of the relationship between mold clamping speed, position deviation, and movable mold position (servo motor rotational position). The position deviation fluctuates. Therefore, the positional deviation Ei is stored in accordance with the set movable mold position Pi arbitrarily determined by the process described above, and the pattern of positional deviation with respect to the movable mold position is stored.

Although FIG. 4 shows an example in which the set movable mold position Pi is set between the mold clamping start point and the lock-up time, the first set movable mold position P0 is set after the mold protection start position. It is sufficient to set the position from the start of mold protection to lock-up. especially,
As shown in Figure 4, the positional deviation fluctuates greatly in the section where mold clamping force is generated after the mold touches, so the set position Pi should be set taking into consideration the fact that this positional deviation fluctuates greatly. There must be.

Alternatively, the position Pi may be set only in the mold protection section, and the positional deviation pattern of this mold protection section may be stored. An example in this case will be described later.

After the positional deviation pattern is registered in this way, the continuous molding operation is started, and when the mold clamping process begins, the NC CPU 21 executes the process shown in FIG. 2 at predetermined intervals.

First, the mold clamping process is performed based on the set mold clamping conditions as in the past (step S20), then the current position P of the movable mold is read, and the position P and pointer i (this pointer i is continuously The setting position Pi corresponding to (set to "0" in the initial setting at the start of molding operation) is shared in the RAM.
30 and compare them (step S22), and if the current position P is larger than the set position Pi, the processing for the cycle is ended, and the current position P is set as the set position P.
If it is less than or equal to i, then the position deviation E is determined by the servo circuit 29.
(step S23), and compares this positional deviation E with the value obtained by adding the set predetermined amount α to the stored positional deviation E corresponding to pointer i (step S24).
If the detected positional deviation E is large, the mold protection abnormality detection device is activated to output an alarm or the like, and the operation of the injection molding machine is stopped (steps S28, S29). Further, if the detected position deviation E is not larger, the pointer i is incremented by "1" (step S25), and if the lockup is not completed (step S26), the processing for the cycle is ended. In this way, the above-mentioned process is performed every predetermined period,
When the detected positional deviation E at each set position Pi does not exceed the value obtained by adding a predetermined amount α to the stored positional deviation Ei and the lockup is completed, the pointer i is set to "0", the mold clamping process is completed, and the next process is started. Move to processing.

FIGS. 6 and 7 are flowcharts of registration processing and mold protection control processing in another embodiment of the present invention. In this embodiment, the mold protection period (or the period from the start of mold closing to the mold touch) The position deviation pattern is stored only in the section), and the mold protection control is performed only in the mold protection section (or the section from the start of mold closing to the mold touch).

In the registration process, as shown in FIG.
A mold clamping process is performed every processing cycle (step S30), the movable mold position P is read (step S31), and it is determined whether the read current movable mold position P is less than or equal to the set mold touch position PT (step S32), current movable mold position P
When is larger than the mold touch position PT, it is determined whether the current movable mold position P is less than or equal to the set position Pi corresponding to the pointer i (step S33), and if it is not less than the set position Pi, the process for the cycle is ended. Further, if the current movable mold position P is below the set position Pi, the position deviation E at that time is read (step S34), this position deviation E is stored in the table TB in correspondence with the set position Pi, and the pointer i is incremented by "1" (step S35), and the processing for the period is ended.

[0027] From now on, until the mold is touched, the set position P
The positional deviation Ei at that time with respect to i is stored in the table TB, and after the mold is touched, the process moves from step S32 to step S36, and the processing of each cycle is ended as it is until the lockup is completed. When the lockup is completed, it is displayed whether or not to register (step S37), and when a registration command is input (step S38), the data of the table TB stored in the RAM 25 is stored in the shared RAM 30 (step S39), Finish the registration process.

In this way, the pattern of positional deviation with respect to the movable mold position up to the mold touch is registered and stored.

On the other hand, when the continuous molding operation is started, the process shown in FIG. 7 is carried out at predetermined intervals when the mold clamping process begins. Perform the mold clamping process in the same way as before, then read the movable mold position P (steps S40, S40), and if this position P is larger than the mold touch position PT and the set position Pi (i is "0" at the beginning), (Steps S42, S43) The process ends immediately. In addition, when the mold touch position PT is not reached and the position becomes below the position Pi corresponding to the set pointer i, the position deviation E is read and this position deviation E is added by a predetermined amount α to the memorized position deviation Ei corresponding to the pointer i. It is determined whether or not the value is greater than or equal to the specified value (steps S44, S45), and if it is not greater than the value, the pointer i is incremented by "1" (step S46). Further, if the detected positional deviation E is larger than Ei+α, the mold protection abnormality detection device is activated to stop the operation of the injection molding machine (steps S49 and S50). When the positional deviation E detected for each set position Pi is smaller than Ei+α and the movable mold position P reaches the mold touch position PT, the positional deviation will not be compared from the subsequent processing cycle until lockup. Steps S40, S41, S42,
The process of S47 is performed. Then, when the lockup is completed, pointer i is set to "0" (step S4
8) Finish the mold clamping process and move on to the next process.

In each of the above-described embodiments, the positional deviation Ei with respect to the set position Pi is registered in one mold clamping operation, but the mold protection registration start command causes multiple mold clamping operations to be performed. The positional deviation Ei at each position is determined by each mold clamping operation.
may be stored, the average positional deviation Ei may be determined, and each of the average positional deviations Ei may be stored.

In this case, first, the index n is set to "0" by the mold protection registration start command, and the processes shown in FIGS. 1 and 6 are started for each processing cycle, but step S6 in FIG. When the lock-up is completed in S36, the mold opening process is performed next, and when the mold opening process is completed, the index n is set to "1".
If the index does not reach the set number, the process of FIGS. 1 and 6 is performed again, and when the index n reaches the set number, step S7, S9 or step S
37 and S38, and when a registration command is input, the average value of the positional deviation of each stored position Pi is taken, and this average value is set as the positional deviation Ei for each position, and then it is stored in the shared RAM 30. Just do it.

Furthermore, in each of the above embodiments, the load applied to the movable mold is detected based on positional deviation, and when there is a foreign object between the molds and the load pattern differs from the normal mold clamping process load pattern, a mold protection abnormality is detected. However, the drive current of the mold clamping servo motor 11 may be used instead of the positional deviation. In other words, if the load on the movable mold changes, the drive current of the servo motor will also change.
The pattern of this drive current for the movable mold position during the normal mold clamping process may be stored, and the detected drive current at each set movable mold position detected during continuous molding may be compared with the stored value. In this case, the servo circuit 29
The torque command value (proportional to the drive current) output from the servo motor may be detected, or the drive current may actually be detected by a detector, A/D converted, and input to the input circuit 31. You can do it like this.

Furthermore, the load applied to the movable mold is detected by attaching a pressure sensor such as a strain sensor to the tie bar or the cross head of the toggle mechanism, and this is A/D converted and inputted to the input circuit for detection. It's okay.

In addition, although the toggle type mold clamping mechanism was explained in the above embodiment, a crank type mold clamping mechanism or a direct acting type mold clamping mechanism (mold clamping mechanism that performs mold clamping by converting the rotary motion of a motor into linear motion) It goes without saying that the present invention can also be applied to an injection molding machine using a mechanism).

[0035]

Effects of the Invention In the present invention, the load (
During continuous molding, the load is detected every time the movable mold position reaches the set position. Then, this load is compared with the stored load, and when the detected load is higher than the stored load by a predetermined value, the mold protection abnormality detection means is activated, an alarm etc. is generated, and the operation of the injection molding machine is stopped. Therefore, even if there is a foreign object between the molds, it is immediately detected and the mold clamping operation is stopped, so that the mold cavity will not be damaged.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of position deviation registration processing according to an embodiment of the present invention.

FIG. 2 is a flowchart of mold protection control processing in the same embodiment.

FIG. 3 is a block diagram of main parts of an electric injection molding machine implementing the same embodiment.

FIG. 4 is a diagram showing an example of the relationship among mold clamping speed, positional deviation, and movable mold position (rotational position of a servo motor).

FIG. 5 is an explanatory diagram of a table that stores positional deviations with respect to set movable mold positions in the same embodiment.

FIG. 6 is a flowchart of position deviation registration processing according to another embodiment of the present invention.

FIG. 7 is a flowchart of mold protection control processing in another embodiment.

[Explanation of symbols]

1 Fixed platen 2 Movable platen 4 Mold 5 Toggle mechanism 11 Servo motor 12 Pulse coder 20 Numerical control device

Claims (4)

[Claims] Claim 1: The mold is closed with no foreign matter between the molds, and the load applied to the movable mold is memorized for a plurality of movable mold positions at least in the mold protection zone, and the mold is closed. Each time the movable mold is started, the position of the movable mold and the load are detected, and the detected load corresponding to the set position is compared with the stored load, and if the detected load is greater than the stored load by a predetermined value or more. A mold protection control method for an electric injection molding machine that sometimes activates a mold protection abnormality detection means and stops operation. 2. The mold protection control method for an electric injection molding machine according to claim 1, wherein the load is a positional deviation value detected by a servo circuit of a servo motor that drives the movable mold. 3. The mold protection control method for an electric injection molding machine according to claim 1, wherein the load is a value of a drive current of a servo motor that drives the movable mold. 4. The mold protection control method for an electric injection molding machine according to claim 1, wherein the load is a detected value from a mold clamping force detection sensor attached to a tie bar or a part of the mold clamping mechanism.