JP2772587B2 - Mold protection control method and apparatus for electric injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling and protecting a metal mold in an electric injection molding machine.

[0002]

BACKGROUND OF THE INVENTION In an injection molding machine, when the mold closing foreign object there of molded articles molded between the step middle mold Ru, since they may damage the intact mold closing performing the mold itself, usually A mold protection section is provided, during which the movable mold is driven at low speed and low pressure to perform mold protection control.

[0003] A method generally used for this mold protection control is to start a mold protection timer at the time of starting the mold protection, and before the timer expires,
If a sensor such as a proximity switch provided at the mold touch position is turned on, it is assumed that no foreign matter is present, and the mold is clamped as it is. A method of operating an abnormality detection circuit to generate an alarm or the like and stopping the movement of the movable mold is employed.

Further, in the electric injection molding machine, when the movable mold reaches the mold protection start position, the output torque of the servo motor for driving the movable mold is limited, the motor is driven at a low torque, and the mold is driven within a predetermined time. A mold protection control method that outputs an alarm or the like when the mold touch position is not reached is also employed (Japanese Patent Application Laid-Open Nos. 61-1148354 and 63).
-286315).

[0005]

In the above-described conventional mold protection control method, even if the pressure is low, the mold clamping force is applied to both molds via a foreign matter for a predetermined time measured by a timer. Therefore, when the mold protection abnormality detecting circuit operates, unnecessary pressure is applied to the cavity of the mold, and the mold may be damaged depending on the cavity structure of the mold.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mold protection control method and apparatus capable of achieving a mold protection function without applying as much pressure as possible to the mold.

[0007]

Means for Solving the Problems The position of the movable mold is detected.
Position detecting means, load detecting the load applied to the movable mold
Detecting means (servo rotation of the servo motor that drives the movable mold)
Means for detecting the position deviation detected on the road,
Means for detecting the drive current of the servo motor or tie bar
Alternatively, the mold clamping force detection sensor attached to a part of the mold clamping mechanism
Capacitors) is provided, at least mold protection section performs mold closing in the absence foreign material between the mold and to a plurality set movable mold position, to detect the load exerted on the movable mold Symbol
憶means stores in, each time the mold closing is started, the position
The position detection means and the load detection means detect the position of the movable mold and the load, and the detected load corresponding to the set position is compared with the stored load by the comparison means, and the detected load is stored. The above-mentioned problem has been solved by operating the mold protection abnormality detecting means at a predetermined value or more.

[0008]

If there is no foreign matter between the molds, the pattern of the load applied to the movable mold with respect to the position of the movable mold during the mold closing process is substantially the same. That is, the load applied to the movable mold until the mold is touched is about the frictional resistance with the tie bar when the movable platen to which the movable mold is attached moves, and there is a slight variation in the mold closing speed, speed switching, and the like. It is almost constant. The load applied to the movable mold can 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 servomotor that drives the movable mold so as to overcome the above load outputs the output torque, it can also be detected by detecting the drive current of the servomotor. Further, the change in the load is accompanied by a change in the follow-up of the servomotor with respect to the movement command to the servomotor for driving the movable mold, and thus can be detected by detecting the position deviation. Therefore, the position deviation according to the position of the movable mold,
If the drive current of the servo motor and the value detected from the mold clamping force sensor are stored, the above-described positional deviation in the mold clamping process when there is no foreign matter between the dies, the drive current value of the servo motor or the mold clamping The value detected by the force sensor is substantially the same as the pattern corresponding to the stored position of the movable mold. However, when foreign matter is present, the load increases and each of the above values becomes larger than the stored value. Therefore, if these detected values become more than a predetermined value than the stored value, it is determined that the foreign matter is present. Activate the mold abnormality detecting means. Thereby, if the load becomes larger than normal (the state where there is no foreign matter between the molds), at that time, the mold abnormality detecting means is activated, an alarm is issued and the operation is stopped,
Protects the mold and minimizes unnecessary pressure on the mold.

[0009]

FIG. 3 is a schematic view of a main part of an electric injection molding machine according to an embodiment of the present invention. A mold 4 is fixed between a fixed platen 1 and a movable platen 2 and a movable platen 2 is fixed. A toggle mechanism 5 is disposed between the movable platen 2 and the rear platen 3 so that the movable platen 2 can be moved right and left in FIG. 3 along a tie bar (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. 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 supposed to be. The rotational position of the servo motor 11 is detected by a pulse encoder 12. The toggle-type mold clamping mechanism driven by the servomotor as described above is not different from the conventional one, so that only the outline is shown.

In the figure, reference numeral 20 denotes a numerical control device (hereinafter referred to as an NC device) as a control device for controlling an injection molding machine.
The NC device 20 is a microprocessor for NC (hereinafter, referred to as NC).
A CPU 21 for a programmable machine controller (hereinafter referred to as a PMC), and a ROM for storing a sequence program for controlling a sequence operation of the injection molding machine in the CPU 22 for the PMC.
26 is connected to a bus, and a RAM 27 used for temporary storage of data and the like is connected to the bus. CPU for NC
Reference numeral 21 denotes a ROM 24 storing a management program for controlling the entire injection molding machine, a RAM 25 used for temporarily storing data, etc., and each axis for injection, clamping, screw rotation, and ejector. A servo circuit for driving and controlling the servomotor is connected via a servo interface 28. In FIG. 3, only the servomotor 11 for mold clamping and the servo circuit 29 are shown. C for NC
The PU 21 and the PMC CPU 22 are bus-connected by a bus arbiter controller (hereinafter referred to as BAC) 23, and the BAC 23 has a nonvolatile shared RAM 30 composed of a bubble memory or a CMOS memory, an input circuit 31,
The output circuit 32 is connected to a bus, and controls the bus used by the BAC 23.

The shared RAM 30 has a memory for storing an NC program for controlling each operation of the injection molding machine, and a memory for storing various set values, parameters, and macro variables. A signal from each sensor provided in the injection molding machine is input to the input circuit 31.
Numeral 2 is connected to various actuators provided in the injection molding machine. In particular, the output circuit 32 outputs a torque limit value to the servo circuit 29, and applies a limit to the torque command value output from the servo circuit 29 to limit the servo motor 11. Only the circuit for limiting the output torque of FIG. The servo circuit 29 receives an output signal of a pulse encoder 12 as a position detector for detecting the rotational position of the servomotor 11 attached to the servomotor 11 and controls the position, speed, etc. of the servomotor 11. It is supposed to.

The servo circuit for driving and controlling each servo motor is the same as the conventional servo circuit. In particular, an error register (not shown) for storing the position deviation of the servo circuit 29 of the mold clamping servo motor 11 is provided. Are read from the NC CPU 21 via the servo interface 28. That is, the 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
Since the position deviation amount is always stored by subtracting the feedback pulse generated from, the position deviation can be read by reading the value of this error register.

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

When operating the injection molding machine, a CRT /
Various molding conditions are set by the MDI 34 and the shared RAM 3
Store to 0. Then, in order to carry out the mold protection control of the present invention, in the present embodiment, a registration process for storing a position deviation according to the position of the movable mold (the rotational position of the servomotor 11) is started.

First, the operator inputs a die protection registration command from the CRT / MDI 34, and inputs the position Pi (i = 1 to n) of the movable die for storing the position deviation. Since there is a fixed relationship between the position of the movable mold and the rotational position of the servo motor for clamping which drives the movable die, the rotational position of the servo motor for clamping is set to set the movable position of the movable mold. The position is set. Also, the coordinate system of the position of the movable mold is usually a position at which the set mold clamping force is obtained,
That is, the lock-up position where the link of the toggle mechanism 5 is fully extended is set as the origin, and the mold opening direction is set as the plus direction.

When the die protection registration command is input, the CPU 21 for NC stores the table TB as shown in FIG.
25, and the position Pi of the movable die to be input next is sequentially stored in the table TB. The flowchart of the process for 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 sets the pointer i to “0” in the initial setting.
And the registration process shown in the flowchart of FIG. 1 is started at predetermined intervals.

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

Next, the setting position Pi corresponding to the pointer i
Is compared with the current position P read from the table TB and detected (step S3), and the detected current position P is
If it is larger than i, that is, if it has not reached the set position Pi, the processing of the cycle ends. If the detected current position P is equal to or smaller than 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 position deviation Ei is written to the address corresponding to the set position Pi, and the pointer i is incremented by "1" (steps S4 and S5). Next, it is determined whether or not the movable mold has reached the position of the set mold clamping force and the toggle mechanism 5 has reached the position where the lock-up state has been reached (step S6). Is terminated. Thereafter, by performing the above-described processing in each cycle, the position deviation Ei when the position is reached for each set position Pi is calculated as shown in FIG.
B will be stored.

Thus, when it is detected in step S6 that the mold clamping process has been completed and lock-up has been completed, the NC C
The PU 21 displays a message as to whether or not to register on the CRT screen of the CRT / MDI 34 (step S7), and the operator performs the mold clamping process normally without any foreign matter 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
Sharing data of table TB stored in M25
The information is stored in the AM 30 (step S10), and the registration process ends.

FIG. 4 shows an example of the relationship between the mold clamping speed, the position deviation, and the position of the movable mold (rotational position of the servomotor). The relationship depends on the set mold clamping speed and its speed fluctuation. And the position deviation fluctuates. Therefore, the position deviation Ei is stored according to the set movable mold position Pi arbitrarily determined by the above-described processing, and the pattern of the position deviation with respect to the movable mold position is stored.

FIG. 4 shows an example in which the set movable mold position Pi is set to a position from the start of mold clamping to lock-up. However, the movable mold position P0 to be set first 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 FIG. 4, the position deviation greatly changes in a section in which the mold clamping force is generated after the mold touches. Therefore, the set position Pi is set in consideration of the point that the position deviation greatly changes. There must be.

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

The position deviation pattern is registered in this way, and then the continuous molding operation is started. When the mold clamping process is started, the NC CPU 21 executes the processing shown in FIG. 2 at predetermined intervals.

First, the mold clamping process is performed on the basis of the set mold clamping conditions as in the prior art (step S20). Next, the current position P of the movable mold is read, and the position P and the pointer i (this pointer i is The setting position Pi corresponding to the initial setting at the start of the molding operation (set to “0”) is shared RAM.
30 is read out from the table TB stored in the table 30 and compared (step S22). If the current position P is larger than the set position Pi, the processing of the cycle ends, and the current position P is
If i or less, the position error E at that time is
(Step S23), and compares the position deviation E with a value obtained by adding a predetermined amount α to the storage position deviation E corresponding to the pointer i (step S2).
4) If the detected position deviation E is large, the die protection abnormality detecting device is activated to output an alarm or the like, and the operation of the injection molding machine is stopped (steps S28 and S29). If the detected position deviation E is not larger, the pointer i is incremented by "1" (step S25), and if the lock-up is not completed (step S26), the processing of the cycle is ended. In this manner, the above-described processing is performed for each predetermined period, and when the detected position deviation E at each set position Pi does not exceed the value obtained by adding a predetermined amount α to the stored position deviation Ei, and lockup is completed, the pointer i is set to “0”. The mold clamping process ends, and the process proceeds to the next process.

FIGS. 6 and 7 are flowcharts of a registration process and a mold protection control process according to another embodiment of the present invention. In this embodiment, a mold protection section (or a process from the start of mold closing to the touch of a mold) is performed. In this case, the position deviation pattern is stored only in the section (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.
The mold clamping process is performed for each 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 equal to or less than the set mold touch position PT (step S31). S32), current movable mold position P
Is larger than the mold touch position PT, it is determined whether or not the current movable mold position P is below the set position Pi corresponding to the pointer i (step S33), and if not, the processing of the cycle is ended. If the current movable mold position P is equal to or smaller than the set position Pi, the position deviation E at that time is read (step S34), and the position deviation E is stored in the table TB corresponding to the set position Pi, and the pointer i Is incremented by "1" (step S35), and the process in the cycle ends.

Hereinafter, the set position P until the mold touches.
The position deviation Ei at that time for i is stored in the table TB, and after the die touch, the process proceeds from step S32 to step S36, and the processing of each cycle is completed as it is until lockup is completed. When the lockup is completed, whether or not to register is displayed (step S37). 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). The registration processing ends.

Thus, the pattern of the positional deviation from the movable die position up to the touch of the die is registered and stored.

On the other hand, when the continuous molding operation is started, the process shown in FIG. Conventional performs similarly mold clamping process, greater than then read the movable mold position P (step S40, S4 1), the position P is the mold touch position PT and set position Pi (i is initially "0") If this is the case (steps S42, S43), the process ends. If the position does not reach the die touch position PT and becomes equal to or less than the position Pi corresponding to the set pointer i, the position deviation E is read, and the position deviation E is added to the storage position deviation Ei corresponding to the pointer i by a predetermined amount α. It is determined whether the value is equal to or greater than the set value (steps S44 and S45). If not, the pointer i is incremented by "1" (step S46). If the detected position deviation E is greater than Ei + α, the mold protection abnormality detecting device is operated to stop the operation of the injection molding machine (steps S49 and S50). When the position 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 position deviation is not compared from the subsequent processing cycle until lockup. Steps S40, S41, S4
Steps S2 and S47 are performed. When the lock-up is completed, the pointer i is set to "0" (step S48), the process of the mold clamping process is completed, and the process proceeds to the next process.

In each of the above-described embodiments, the position deviation Ei is registered for the set position Pi by one operation of the mold clamping process. And the position deviation Ei of each position in each mold clamping operation.
May be stored, and the averaged position deviation Ei may be obtained, and the averaged position deviation Ei may be stored.

In this case, the index n is first set to "0" in response to the mold protection registration start command, and the processing in FIGS. 1 and 6 is started at each processing cycle. When the lock-up is completed in S36, the mold opening process is performed next. When the mold opening process is completed, the index n is incremented by "1". If the index does not reach the set number, FIGS. And the above index n
Reaches a set number, the processing of steps S7 and S9 or steps S37 and S38 is performed. When a registration command is input, the average of the stored positional deviations of the respective positions Pi is calculated, and this average value is calculated for each position. May be stored in the shared RAM 30 after the position deviation Ei with respect to.

Further, in each of the above embodiments, the load applied to the movable mold is detected based on the position deviation. If there is a foreign substance between the molds and the load pattern differs from the load pattern of the mold clamping process in a normal state, the mold protection abnormality occurs. However, the drive current of the mold clamping servomotor 11 may be used instead of the position deviation. That is, if the load applied to the movable mold fluctuates, the drive current of the servomotor also fluctuates.Therefore, the pattern of the drive current for the movable mold position is stored during the normal mold clamping process, and the pattern is stored during continuous molding. The detected drive current at each set movable mold position to be detected may be compared with a stored value. In this case, the torque command value (proportional to the drive current) output from the servo circuit 29 to the servomotor may be detected, or the drive current is actually detected by the detector and A / D conversion is performed. Input circuit 3
1 may be input.

Further, a load applied to the movable mold is detected by attaching a pressure sensor such as a strain sensor to a tie bar or a toggle mechanism, for example, a crosshead, and A / D converting the input to an input circuit to detect the load. You may.

Although the toggle type clamping mechanism has been described in the above embodiment, a crank type clamping mechanism or a direct-acting type clamping mechanism (a type of clamping which converts the rotating motion of the motor into a linear motion to perform the clamping). Needless to say, the present invention can be applied to an injection molding machine using the mechanism.

[0035]

According to the present invention, the load (at least at the set movable mold position in the mold protection section) when normal mold clamping is performed without foreign matter such as a molded product interposed between the molds. The position load, the drive current of the servomotor for mold clamping, and the value detected by the pressure sensor attached to the tie bar or toggle mechanism) are stored. Then, the load is compared with the stored load, and when the detected load is equal to or more than the predetermined value from the stored load, the mold protection abnormality detecting means is activated, an alarm is generated, and the operation of the injection molding machine is stopped. Therefore, even if there is a foreign substance between the molds, the foreign matter is immediately found and the mold clamping operation is stopped, so that the cavity of the mold is not damaged.

[Brief description of the drawings]

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

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

FIG. 3 is a main part block diagram of an electric injection molding machine for carrying out the embodiment.

FIG. 4 is a diagram illustrating an example of a relationship among a mold clamping speed, a position deviation, and a movable mold position (a rotational position of a servomotor).

FIG. 5 is an explanatory diagram of a table for storing a position deviation with respect to a set movable mold position in the embodiment.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Movable platen 4 Die 5 Toggle mechanism 11 Servo motor 12 Pulse coder 20 Numerical controller

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-19425 (JP, A) JP-A-2-147222 (JP, A) JP-A-2-54943 (JP, A) JP-A 62-19443 130819 (JP, A) JP-A-4-54120 (JP, A) JP-A-63-136918 (JP, U) JP-A-1-139520 (JP, U) JP-B-1-52165 (JP, B2) (58) Fields surveyed (Int.Cl. ⁶ , DB name) B29C 45 / 04,45 / 26-45/38 B29C 45/64-45 / 70,45 / 76 B22D 17/26 B29C 33 / 22,33 /twenty four

Claims (8)

(57) [Claims] 1. A mold is closed in a state where there is no foreign matter between molds, and loads applied to the movable mold are stored at least for a plurality of movable mold positions set in a mold protection section, and the mold is closed. 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 load is equal to or more than a predetermined value from the stored load. A mold protection control method for an electric injection molding machine that sometimes activates a mold protection abnormality detection unit and stops operation. 2. The method according to claim 1, wherein the load is a value of a position deviation detected by a servo circuit of a servomotor that drives the movable mold. 3. The method according to claim 1, wherein the load is a value of a drive current of a servomotor for driving the movable mold. 4. The method according to claim 1, wherein the load is a value detected by a mold clamping force detection sensor attached to a tie bar or a part of a mold clamping mechanism. 5. A load detector for detecting a load applied to a movable mold.
Ejecting means, position detecting means for detecting the position of the movable mold,
Close the mold with no foreign matter between the molds and
The above load detection is performed for the set movable mold position detected in the step.
Storage means for storing the load detected by the ejection means, and mold closing
Every time is started, the position detection means and load detection means
The position of the moving die and the load are detected, and the set position is detected.
Ratio of comparing the detected load corresponding to the position with the stored load
Comparing the detected load with a predetermined value or more from the stored load.
Electric gun equipped with a mold protection abnormality detecting means that operates when
Die protection control device for the outgoing molding machine. 6. The load detecting means drives a movable mold.
The position deviation value detected by the servo circuit of the servo motor is
6. The gold of the electric injection molding machine according to claim 5, which is means for detecting.
Mold protection control device. 7. The load detecting means drives a movable mold.
A means for detecting the value of the drive current of the servomotor.
Item 6. A die protection control device for an electric injection molding machine according to Item 5. 8. The load detecting means is a tie bar or a mold.
A mold clamping force detection sensor attached to a part of the clamping mechanism
A mold protection control device for an electric injection molding machine according to claim 5.