JPH0820052A - Elector control method of injection molding machine - Google Patents

Abstract

PURPOSE:To prevent the damage to an injection mold due to mold clamping operation even when there is an error in the setting of ejection operation related to product release work. CONSTITUTION:When no product release operation is performed, the excitation of a servo motor for an ejector is released to enable an ejector pin to freely retreat. Even if clamping operation is operated in such a state that the ejector pin protrudes from a movable mold a1 and the tip of the ejector pin 37 interferes with a fixed mold a2, the ejector pin 37 is pushed by the fixed mold a2 to freely retreat and, therefore, no serious damage is generated in the jector pin 37 and the fixed mold a2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved ejector control method for an injection molding machine.

[0002]

2. Description of the Related Art FIG. 1 is a partial cross-sectional view schematically showing the construction of a conventionally known injection molding die A. The injection mold A includes a movable mold a1 mounted on a movable platen of the injection molding machine and a fixed mold a2 mounted on a fixed platen of the injection molding machine.
And a fixed platen side injection cylinder 4 in a cavity 40 formed between the core plate 38 of the movable side mold a1 and the cavity plate 39 of the fixed side mold a2.
Molten resin is injected from 1 to form a product having the same shape as the cavity 40. The product release mechanism of injection mold A is
The movable mold a1 includes a large number of ejector pins 37, an ejector plate 33 in which the ejector pins 37 are integrally implanted, a return spring 35 for returning the ejector plate 33 to its original position, and the like. The ejector pin 37 implanted in the ejector plate 33 is provided so as to penetrate the core plate 38 of the movable-side mold a1 so that the tip end thereof is flush with the product surface in the cavity 40, and The ejector plate 33, which is biased toward the original position, is retained at the position shown in FIG. 1 by the original position retaining function. In other words, due to the structure of the movable mold a1, the ejection stroke of the ejector pin 37 depends on the core plate 38 and the movable mounting plate 32.
Is controlled by the thickness of the spacer block 36 for fixing the ejector pin 37 so that the tip of the ejector pin 37 is flush with the product surface when the ejector plate 33 is completely returned to its original position as shown in FIG. The total length or the thickness of the spacer block 36 is precisely adjusted. Otherwise, when the ejector pin 37 returns to its original position, a step is formed between the tip of the ejector pin 37 and the product surface of the cavity 40, which causes undesired unevenness on the product surface.

As the shape of the ejector pin 37, there is a simple rod shape having a relatively large diameter such as that provided in the runner portion, but generally, the shape provided in the cavity 40 portion is the shape and meat of the product. Since it is affected by the thickness, it is often formed with a smaller diameter than that of the runner part.Also, in order to increase the effective pressing area even a little, depending on the case, it may follow the shape of the thick part of the product. It may be formed in a rectangular cross section. Ejector pin 37
Since the buckling strength of the ejector pin 37 itself cannot be sacrificed even when is formed to have a small diameter or a rectangular cross-section, use a rod material that is thicker than is finally needed, and The ejector pin 37 is generally manufactured by cutting into a small diameter or rectangular cross section. As a result of the ejector pin 37 being formed in a stepped shape, the hole formed in the core plate 38 also necessarily has a stepped through hole shape. Needless to say, the core plate 38 has a large hole diameter on the back surface side so as to match the large diameter portion of the ejector pin 37, and has a small hole diameter on the front surface side so as to match the small diameter portion of the ejector pin 37. And may be formed in a rectangular shape in some cases. Ejector pin 3
It has already been described that the protruding stroke of No. 7 is restricted by the thickness of the spacer block 36, but in reality, the large diameter portion of the ejector pin 37 cannot penetrate into the small diameter hole portion of the core plate 38. , Ejector pin 3
The protrusion stroke of 7 will be further limited.

The above is a general configuration example of the injection molding die. In the injection molding machine, the ejector rod 31 is projected through the movable platen and the movable side mounting plate 32 to open the ejector plate 33 when the mold is opened. By pressing to eject the ejector pin 37, a predetermined product release operation is performed. An injection molding machine is already known in which a motor is used to drive the ejector rod 31 to reciprocate between a set return position and a projecting target position to perform product release work.

Naturally, in order to shorten the molding cycle, it is necessary to finish the mold releasing work of the product within a short time. For that purpose, the ejection stroke of the ejector rod 31 on the injection molding machine side should be shortened as much as possible. desirable. First, regarding the set return position of the ejector rod 31, as shown in FIG. 1, whether the tip of the ejector rod 31 contacts the back surface of the ejector plate 33 when the ejector plate 33 is completely returned to the original position. The position such as is the optimum position. This is because if the ejector rod 31 is more protruded than this, the product will be dented if it is set as the setting return position at the time of retracting. Also, the state in which the ejector rod 31 is retracted more than this is set. If you set it as the return position,
This is because, although the ejector plate 33 has already completed the return movement, only the ejector rod 31 performs a meaningless retracting operation and the molding cycle is lengthened. When the optimum return position is to be obtained by manual operation, the ejector rod 31 is once appropriately projected to separate the ejector plate 33 from the movable side mounting plate 32, and then the ejector rod 31 is gradually retracted to eject the ejector rod 31. The position where the movement of the plate 33 stops, that is, the position where the ejector plate 33 completely returns to the original position and the ejector rod 31 starts to separate from the back surface of the ejector plate 33, is determined, and the position is set as the reset position. . However, if this operation is erroneous in an attempt to shorten the molding cycle and the position before the ejector plate 33 is completely returned to the original position is set as the set return position, there is a risk that defective products will be produced. There is. In addition, if the ejector rod 31 is retracted more than necessary due to fear of that, and the ejecting rod 31 is set to the set return position, the molding cycle is increased as described above, and the ejector rod 31 is ejected at the start of projection. The ejector plate 31 may collide with the ejector plate 33 in an impact, which may adversely affect the structure of the mold.

Further, regarding the target position of protrusion of the ejector rod 31, it suffices if the product can be peeled off from the core plate 38 by the ejector pin 37, and the amount of protrusion thereof can be known from a common sense. If the ejector pin 37 is projected more than necessary due to such reasons, the large diameter portion of the ejector pin 37 will rush into the small diameter portion of the hole of the core plate 38, and the injection molding die will be greatly damaged. There is a risk that

Further, when the mold closing operation is performed while the ejector rod 31 is projected while the movable platen is manually moved, the tip of the ejector pin 37 is fixed on the fixed side depending on the amount of projection. It hits against the cavity plate 39 and buckles or damages the hole on the core plate 38 side. Further, if the mold clamping operation is performed as it is, the damage will be extremely serious, and expensive parts such as the cavity block and the core block may be damaged to an unrepairable extent.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to perform a normal injection even if there is some abnormality in the setting of the ejector operation related to the product release work. It is an object of the present invention to provide an ejector control method that makes it possible to perform a molding operation and prevent occurrence of defective molding and damage to an injection molding die.

[0009]

According to the present invention, when the motor for driving the ejector rod is excited only during the releasing work of the product, there is some abnormality in the setting of the ejector operation relating to the releasing work of the product. Even then, it was possible to carry out normal injection molding work.

Further, the return position of the ejector rod at the time of completion of the product release work in the immediately preceding molding cycle is stored, and the ejector rod is set at the set timing after the completion of mold closing in the next molding cycle and before the start of the product release work. The configuration detects the position and outputs the setting abnormality detection signal when the difference between the detection position and the return position exceeds a predetermined value, so that the setting abnormality regarding the ejector can be automatically detected.

Furthermore, the load acting on the ejector rod during the projecting operation is detected, and when the load exceeds the allowable value, a setting abnormality detection signal is output so that damage to the injection molding die can be prevented. did.

[0012]

Since the motor for driving the ejector rod is excited only when the product is released from the mold, the ejector rod can be freely moved during mold closing, mold clamping and injection operations. As a result, forgetting the retracting operation of the ejector rod and manually performing the mold closing mold clamping operation with the ejector pin protruding, or the ejector pin of the injection molding die is insufficient due to an abnormal setting of the ejector rod return position. Even if the mold closing and mold clamping operations are performed with the tip of the ejector pin hitting the fixed-side die without shrinking, the tip of the ejector pin is pushed by the fixed-side die and easily retracts. Therefore, the buckling of the ejector pin and the damage of the injection molding die can be prevented. Further, if the injection pressure holding operation is performed as it is, the ejector pin is at a position defined by the structure of the injection molding die itself due to the pressure increase in the injection molding die cavity, that is,
Since the product can be freely contracted to a position flush with the product surface, a normal product can be molded if a sufficient injection holding pressure is applied.

Also, the return position of the ejector rod at the time of completion of the product release operation in the immediately preceding molding cycle,
In other words, if the difference between the set return position of the ejector rod and the return position of the ejector rod pushed back by the collision with the fixed mold or the injection holding pressure exceeds a predetermined value, the setting abnormality detection signal is output. A setting error related to the ejector rod return position is automatically detected.

Further, if the load acting on the ejector rod during the projecting operation exceeds the allowable value, a setting abnormality detection signal is output, so that even if the projecting target position of the ejector rod is set largely wrongly, It is possible to prevent buckling of the ejector pin and damage to the injection-molding die due to interference with the core plate of the movable-side die caused by excessive protrusion of the ejector pin.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an electric injection molding machine of an embodiment to which an ejector control method of the present invention is applied and a main part of a product release mechanism of a general injection molding die.

A is a two-plate type injection molding die comprising a movable side die a1 mounted on the movable platen of the injection molding machine and a fixed side die a2 mounted on the fixed platen of the injection molding machine. The movable die a1 includes an ejector pin 37, an ejector plate 33, and a return spring 3.
A product release mechanism composed of 5 and the like is provided.
Further, 38 is a core plate of the movable side mold a1, 39 is a cavity plate of the fixed side mold a2, and a cavity 40 having a product shape is formed between them. Three
Reference numeral 4 denotes a columnar supporter provided between the movable side mounting plate 32 and the core plate 38.
Has a total length comparable to the thickness of the core plate 38, and receives a part of the resin pressure acting on the core plate 38 of the movable mold a1 together with the spacer block 36, and prevents the core plate 38 from bending due to the resin pressure acting at the time of holding the injection pressure. To do. The supporter 34 is positioned and fixed to the back surface of the core plate 38 or the front surface of the movable side mounting plate 32. Also, the ejector plate 3
A through hole having a diameter slightly larger than that of the support plate 34 is formed in the support plate 34 at a position corresponding to the arrangement position of the support plate 34, and the return spring 35 fitted on the support plate 34 with a margin is provided on the surface of the ejector plate 33 and the core plate. Both ends are supported by the back surface of 38 and are slightly compressed. That is, the supporter 34 has the function of guiding the movement of the ejector plate 33 along the mold opening / closing direction in addition to preventing the core plate 38 from bending. The components and their functions relating to the injection mold A have already been described in detail in the section "Prior Art" in the present specification, and therefore the description thereof is omitted here. Four
1 is an injection cylinder of the injection molding machine.

Reference numeral 31 is an ejector rod that is standardly equipped on the movable platen of the injection molding machine, and is driven in the mold opening / closing direction by the ejector servomotor M, and is provided with a through hole provided at the center of the movable side mounting plate 32. By ejecting the ejector plate 33 against the return force of the return spring 35 against the original position of the return spring 35, the ejector pin 37 protrudes onto the surface of the core plate 38 at the time of mold opening, so that the product in the cavity 40 is released from the core plate. Release from 38. The return spring 35 itself is not an essential requirement for the product release mechanism in the injection mold A. For example, if the ejector rod 31 on the injection molding machine side is fixed to the ejector plate 33 with a bolt or the like, even if the return spring 35 is eliminated, the ejector rod 31 is removed.
The ejector plate 33 can be reciprocated by the projecting / retracting operation. Servo motor M for ejector
Although a mechanism for converting the rotational movement of the ball into a linear movement of the ejector rod 31, a ball nut &
A screw or the like is preferable, and at least a power transmission mechanism between the ejector servomotor M and the ejector rod 31 is such that a mechanical element such as a worm & wheel, that is, power transmission is unidirectional. Never use things. When an external force is applied to the ejector rod 31, the ejector servomotor M, which is de-excited, easily idles, and the ejector rod 3
This is because 1 can easily move linearly. A pulse coder P is mounted on the ejector servomotor M,
The current position of the ejector rod 31 can be detected appropriately.

The product release mechanism on the injection molding die side and the mechanism on the injection molding machine side, which are required for the product release operation, have been briefly described above. Naturally, known mechanical elements, mechanics and the like are appropriate. It is also possible to adopt other configurations by operating in. The mechanical configuration is not particularly limited, but in the injection molding machine used as the embodiment of the present invention, at least when the ejector rod 31 receives an external force in a state where the ejector servomotor M is de-excited, the ejector rod 3 is used.
It is an essential requirement that 1 moves in the acting direction of the force and the ejector servomotor M easily idles.
According to a broader inventive idea, it is also possible to provide a clutch or the like between the irreversibly operating power transmission mechanism and the ejector rod 31, and to connect the clutch only during product release work. Although included in the concept, although such a configuration complicates the position control and mechanical configuration of the ejector rod 31, it does not mean that a particular effect is obtained, so the ejector rod 31 An injection molding machine using a power transmission mechanism capable of reversible operation for driving is only shown as an optimum embodiment.

Numerical control device 1 for driving and controlling an injection molding machine 1
Reference numeral 0 denotes a CNC CPU 25 which is a numerical control microprocessor, a PMC CPU 18 which is a programmable machine controller microprocessor, a servo CPU 20 which is a servo control microprocessor, and a pressure monitoring CPU 17, and a bus. Information can be transmitted between the microprocessors by selecting mutual input / output via 22. The pressure monitoring CPU 17 is a monitoring CPU for performing sampling processing of injection holding pressure and screw back pressure via the A / D converter 16 and a pressure detector on the injection screw side (not shown). Since it is not directly related to the gist of the present invention, its explanation is omitted.

The PMC CPU 18 is connected to the ROM 13 which stores a sequence program for controlling the sequence operation of the injection molding machine and the RAM 14 which is used for temporary storage of operation data. The CNC CPU 25 is connected to the entire injection molding machine. R storing a program for controlling the program
R used for temporary storage of OM27 and operation data
AM28 is connected.

Each of the servo CPU 20 and the pressure monitoring CPU 17 stores a ROM 21 storing a control program dedicated to servo control, a RAM 19 used for temporary storage of data, and a control program relating to a sampling process of pressure data. The ROM 11 and the RAM 12 used for temporary storage of data are connected. Further, the servo CPU 20 drives the servo motor M for the mold clamping, injection, screw rotation, etc. axes (not shown) and the ejector servo motor M on the basis of a command from the CPU 20. An amplifier 15 is connected, and each output from the pulse coder provided in the servo motor of each axis is fed back to the servo CPU 20, and the servo CPU is based on the feedback pulse from the pulse coder.
The current position and movement speed of each axis calculated by 20 are RA
The current position storage register and the current speed storage register of M19 are successively updated and stored.

The interface 23 is an input / output interface for receiving signals from limit switches and operation panels provided in various parts of the injection molding machine and for transmitting various commands to peripheral equipment of the injection molding machine. is there. On the operation panel of the injection molding machine, operation item selection switches for manual operation, that is, “clamp” (use is forward and backward movement of movable platen), “Ejector” (use is ejector rod 31 protruding and retracting movement), A plurality of "screws" (use is the forward and backward movement of the injection screw), ..., etc. are provided, and only one of the operation item selection switches is operated to further determine forward / reverse movement of each operation. By operating the operation direction selection switch, the movable platen of the injection molding machine, the ejector rod 31, the injection screw, or the like can be appropriately moved in a desired direction.
The ejector servomotor M is excited only when the operation item "Ejector" is selected, and by operating the operation direction selection switch, the ejector servomotor M rotates in the forward and reverse directions according to the operation direction. When other operation items are selected during operation, the non-excitation state is always maintained. Manual data input device 29 with display is C
It is connected to the bus 22 via the RT display circuit 26 so that a monitor display screen, a function menu can be selected and various data input operations can be performed. A numeric keypad for inputting numerical data and various function keys are provided. Has been.

The non-volatile memory 24 is a memory for storing molding data that stores molding conditions related to injection molding work and various set values, parameters, macro variables, etc., and more specifically, setting conditions related to product release work. For example, the projecting target position of the ejector rod 31, the set return position, and the number of times the projecting is performed are also set and stored here.

With the above configuration, the PMC CPU 18 controls the sequence of the entire injection molding machine, while the CNC CPU 25 distributes the pulses to the servo motors of the respective axes based on the control program stored in the ROM 27.
U20 is a position loop control, speed loop control, current loop similar to the conventional one based on the movement command distributed to each axis, the position feedback signal detected by a detector such as a pulse coder, and the speed feedback signal. Servo control such as control is performed, and so-called digital servo processing is executed.

Hereinafter, the PMC CPU 1 shown in FIGS.
The ejector control method in the present embodiment will be described with reference to the sequence control of No. 8. The processes shown in FIGS. 2 to 3 show the sequence operation for one molding cycle, and can be applied during the semi-automatic operation and the automatic operation. The process of 1 molding cycle is the same as the conventional one, mold closing process (including mold clamping) → injection process → pressure holding process → metering process (including cooling) →
The mold opening process and the product releasing process (ejecting process) are performed in this order, and the processing contents of steps S1 to S5 relating to each of these processes are substantially the same as the conventional one.

However, in the case of the present embodiment, the ejector servomotor M is excited only in the step of releasing the product (however, it is also excited when the operation item "Ejector" is selected during manual operation), In other cases, the ejector servomotor M is maintained in a non-excited state, so that there is a big difference in the phenomenological effect from the conventional example.

For example, a molding cycle is started by semi-automatic operation or automatic operation in a state where the ejector rod 31 is extremely protruded by a manual operation for determining a projecting target position or a set return position of the ejector rod 31. In the case where the closing operation (step S1) is executed, or the mold closing operation by the manual operation is inadvertently performed while the ejector rod 31 is projected, the ejector is accompanied by the mold closing operation. The tip of the pin 37 may abut the surface of the cavity plate 39 in the fixed mold a2. However, in the case of the present embodiment, the ejector servomotor M is not excited at the stage when the mold closing operation is performed, and moreover, the rotation of the ejector servomotor M is converted into the linear motion of the ejector rod 31. Since the power transmission mechanism is also configured to be easily reversible, the ejector pin 37 can be easily retracted by being pushed by the cavity plate 39, and each part of the injection mold A including the ejector pin 37. Damage can be prevented. In the example shown in FIG. 1, the return spring 35 is configured to assist the return operation of the ejector pin 37. However, even if the return spring 35 does not exist, the ejector pin 37 can be easily retracted, and the same effect can be obtained. can get. In the conventional device, the ejector servomotor M is constantly excited, and its rotational position is strongly maintained by the position loop control. Therefore, the ejector pin 37 is substantially retracted regardless of the presence of the return spring 35. It is impossible, and the ejector pin 37 is buckled due to the excessive mold closing and clamping action.
In some cases, each part of the injection molding die A may be damaged.

Further, as a means for preventing the injection molding die A from being damaged by pinching or buckling of the ejector pin 37, if the ejector rod 31 is projected beyond the set return position, "the ejector is not retracted. An injection molding machine in which a message such as "is displayed on the display of the manual data input device 29 with a display so as to cancel the execution of the semi-automatic operation or the automatic operation has already been proposed, but this safety measure also applies to the ejector rod 31. If the setting return position itself is set by mistake, the safety of the ejector pin 37 and the injection molding die A cannot be guaranteed. That is, it was designed so that the start of the semi-automatic operation or the automatic operation is automatically permitted if the position of the ejector rod 31 is degenerated from the set return position. In the case where the ejector rod 31 has been set to an extreme protruding position, although the ejector rod 31 is retracted from the set return position, the tip of the ejector rod 37 may still interfere with the fixed side mold a2. is there. In this embodiment, the ejector pin 37 and the ejector rod 31 can be extremely easily retracted. As a result, even if the setting of the return position of the ejector rod 31 is completely incorrect, the ejector rod 37 and the injection molding can be performed. The mold A is not damaged.

Also, in the injection step (step S2) and the pressure holding step (step S3), there is a large difference in action and effect when comparing this embodiment with the prior art. As described above, in the injection molding machine to which the conventional control method is applied, since the ejector servomotor M is always excited and strongly held at the command position at that time, if the set return position of the ejector rod 31 is changed. If it is accidentally set to the front (projecting side), the ejector plate 3 will not be affected even if the injection holding pressure acts on the tip of the ejector pin 37.
3 cannot be retracted sufficiently, resulting in the product being molded with an undesirable recess of the same shape as the tip of the ejector pin 37. This is because the commanded position of the ejector rod 31 in the injection process, the pressure holding process, etc. is exactly the set return position of the ejector rod 31. On the other hand, according to the configuration of the present embodiment in which the ejector pin 37 can be easily retracted, even if the ejector rod 31 is erroneously set to the front position as long as a sufficient injection holding pressure is applied. , Ejector rod 3
There is still room for a normal product to be molded, as 1 may be retracted to the correct position by the resin pressure. As described above, in the injection molding die A, the ejector pin 37 is so arranged that the tip of the ejector pin 37 is flush with the product surface when the ejector plate 33 is completely returned to its original position as shown in FIG. This is because the total length of the above or the thicknesses of the spacer block 36 and the supporter 34 are precisely adjusted. Needless to say, if the ejector pin 37 is finished in a relatively small size due to a design or processing error, the spacer block 36 and the supporter 34 should be ground at the same time, or the ejector plate 33 should be ground. Is generally replaced with a thicker one so that the tip of the ejector pin 37 is adjusted to be flush with the product surface. At least, the return position of the ejector rod 31 is set and changed to an appropriate protruding position, It is not common practice to support the ejector plate 33 with the ejector rod 31 positioned and held at that position to compensate for the insufficient size of the ejector pin 37. There is a risk that the parallelism between the ejector plate 33 and the core plate 38 will not be ensured, or the ejector plate 33 will bend during injection pressure retention, and the uneven portion having the same shape as the ejector pin 37 will be molded in the product. Because. As described above, since the accuracy of the injection molding die is guaranteed by the constituent members of the injection molding die itself, if even the ejector plate 33 can be sufficiently retracted, a normal product can be molded. Yes (Ejector rod 3
Even if 1 degenerates from the set return position for some reason, there is no problem).

With respect to the measuring step (step S4) and the mold opening step (step S5), the processing contents and operational effects are completely the same as those of the conventional one.

Therefore, the PMC CPU 18, which has performed the mold opening process in the same manner as in the prior art, first reads the current position P of the ejector rod 31 from the current position storage register of the RAM 19 and temporarily stores it (step S6). Difference RP between the current value R of the immediately previous position storage register and the current position P
Is determined and whether or not there is an abnormal setting of the return position for the ejector rod 31 is determined by whether or not the value R−P exceeds a predetermined value ε (where ε> 0) (step S).
7).

The immediately preceding position storage register is a register for storing the position at which the ejector rod 31 has returned at the end of the product releasing work performed in the immediately preceding molding cycle.
Until the product release work in the second molding cycle is completed, the operator finds out by the method as described in the section "Prior Art" and restores the setting of the ejector rod 31 stored in the nonvolatile memory 24. The position value is saved as the initial value. Here, if the set return position is set to the front (protruding side) of the correct position, in the mold closing step of step S1 or the injection pressure holding step of steps S2 and S3 in the first molding cycle. The ejector pin 37 contracts due to external force, and R
The value of −P becomes considerably large.

The ejector pin 37 retracts due to the external force received in the mold closing step when the ejector rod 31 retracts due to direct interference with the fixed side mold a2. Only when it is set extremely forward. Further, the ejector pin 37 contracts due to the external force received in the injection pressure maintaining step when the ejector pin 37 contracts due to the injection maintaining pressure acting on the resin and directly interferes with the fixed side mold a2. Even if it is not so much, it can always occur when the set return position of the ejector rod 31 is set forward more than necessary. If the ejector pin 37 is degenerated due to one of these two causes,
The product may be abnormal. Ejector pin 37
This is because although the degeneracy is detected, it is not always guaranteed that the degeneracy is reduced to the original position. Such problems are often caused by the return spring 35.
It is likely to occur in a mold structure not equipped with. Of course, if the biasing force of the return spring 35 is sufficient, the ejector plate 33 may be automatically retracted to an appropriate position even if the external force due to the interference with the fixed side mold a2 or the injection pressure is not applied. Is possible. In this case, before the mold closing operation is started, that is, the product release work in the immediately preceding molding cycle is completed, and the ejector servo motor M is completed.
When the excitation is released, or the ejector rod 3
The ejector plate 33 is automatically retracted to an appropriate position at the time when the ejector servo motor M is de-excited by canceling the operation item selection of "Ejector" after the manual operation of 1 is completed. Therefore, the abnormality of the setting return position will not directly affect the product, but even if the ejector rod 31 can be easily retracted, a certain amount of load is required at the time of the contraction. This is an undeniable fact, and as a result, an abnormality in the set return position may appear as a delay in the return operation of the ejector pin 37. Since the delay in the return operation of the ejector pin 37 hinders the normal reciprocating operation of the ejector pin 37, it becomes a problem when the ejector pin 37 is repeatedly ejected at the time of releasing the product.

The above is the case where the determination result of step S7 is true in the first molding cycle, but the same can be said for the second and subsequent molding cycles. However, in the second and subsequent molding cycles, the return position R at the end of the product release operation in the immediately preceding molding cycle and the position P of the ejector rod 31 at the time of mold opening of the molding cycle executed at that time are always used. Since the determination processing of step S7 is executed, the return position R at the end of the product release operation in the immediately preceding molding cycle
The abnormality can be detected only when the position P of the ejector rod 31 when the mold is opened in the molding cycle executed at that time is actually retracted. In other words, even if the set return position of the ejector rod 31 is set ahead of the correct position, as long as the ejector rod 31 can be returned to the correct position by the force of the return spring 35, basically, the setting error occurs. Is not detected as. However, in the present embodiment, the detection timing of the return position R at the end of the product release operation in the immediately preceding molding cycle is such that the pulse distribution to the ejector servomotor M for returning the ejector rod 31 is completed and the excitation is released. Since it is set as the previous time point (see step S14), the return position R before the ejector rod 31 is retracted by the return spring 35 is detected, and as a result, the set return position R and the current position are set. As in the case of the first molding cycle in which the determination process is performed based on the position P, the set return position of the ejector rod 31 (= the position of the ejector rod 31 at the time of completion of pulse distribution) is set ahead of the correct position. If so, this setting abnormality will always be detected by the determination processing in step S7. Of course,
In the mold structure that does not include the return spring 35, the position of the ejector rod 31 at the time of completion of pulse distribution is maintained as it is, so there is no particular restriction on the detection timing of R for detecting abnormality in the set return position ( In short, it may be any time after step S13 until the completion of one molding cycle). Further, if the set return position of the ejector rod 31 is set to the retracted side with respect to the correct position, the ejector rod 31 will not be forcibly retracted under any circumstances, and thus the R-P = 0 <ε is always established. Therefore, it is impossible to detect a setting error by the process of step S7 when the set return position of the ejector rod 31 is set to the retracted side from the correct position, but as described above,
There is no particular problem with the ejector rod 31 retracting more than necessary.

As described above, when R−P> ε and the determination result in step S7 is true, it means that there is a setting error regarding the set return position of the ejector rod 31 in any case. To do. Therefore, if the determination result in step S7 is true, the PMC CPU 18 displays a warning message such as "the setting of the ejector return position is abnormal" on the display of the manual data input device with display 29, and the setting is abnormal. This is notified to the operator (step S8).

As described above, in the present embodiment, when the determination result of step S7 becomes true, the molding operation is immediately stopped and the warning display is not automatically stopped. Ejector rod 31 as far as possible
This is because there is still room for molding a normal product even if the return position is set to the front by mistake. It is ultimately up to the operator to judge whether the product is good or bad and whether the setting abnormality of the setting return position actually causes a big problem such as damage of the injection molding die.

The value of R-P may be displayed numerically when the warning message is displayed in the process of step S8. When performing an injection molding operation by mounting an injection molding die having no return spring 35 having elasticity sufficient to return the ejector pin 37 to the original position, R-
If the value of P becomes extremely large, it means that the fixed side mold a2 and the tip of the ejector pin 37 interfere with each other during the mold closing operation, and such an injection molding operation is performed. Repeatedly, the cavity 40 of the fixed side mold a2 is scratched, and this scratch is transferred to the outside of the product to give an unfavorable result. Therefore, the operator immediately stops the injection molding work and resets the set return position. Should be set. This is not limited to the mold configuration in which the ejector pin 37 is arranged only on the runner portion and the runner and the product are released from the movable mold a1 at the same time (the product is not scratched), but the ejector pin 37 collides. Since there is a risk that the runner will bite on the scratches on the fixed side runner block and the fixed side will remain, or the runner will bite on the ejector pin 37 itself with a deformed tip and prevent normal mold release work. The molding operation should be stopped. Further, if the value of R-P is relatively small, there is no direct interference between the ejector pin 37 and the fixed side mold a2,
This means that the ejector pin 37 is pushed back by the resin pressure, so continuous operation is possible as long as there is no abnormality in the product itself.

The PMC CPU 18, which has completed the determination processing in step S7 or the display processing in step S8, then excites the ejector servomotor M for the first time after the start of the molding cycle (step S9), and the CNC CPU2.
5, the eject command is output to the servo CPU 20, and the servo CPU 20 is directed toward the projection target position set and stored in the non-volatile memory 24.
Under the drive control of (1), pulse distribution is performed to the ejector servomotor M to start the ejection of the ejector rod 31 (step S10). In the case where the ejector rod 31 is forcibly pushed rearward from the set return position, the ejector servomotor M is strongly driven at the initial stage of the drive start due to the position deviation accumulated in the position control loop. However, since the mold opening has already been completed and the ejecting force required for releasing the product is small if the molding state is normal, the ejector pin 37 is buckled or deformed. Does not occur, and the position deviation accumulated at the start of drive control is immediately eliminated. When the pulse distribution to the ejector servo motor M is completed, the PMC CPU 18 causes the servo C
A value C of the drive current flowing through the ejector servomotor M at this point through the PU 20 and the servo amplifier 15.
Is immediately detected (step S11), and it is determined whether or not the value is within a preset allowable value A range, that is, whether or not an excessive load acts on the ejector servomotor M (step S11). Step S12). If the projection of the ejector pin 37 is prevented from moving until reaching the projection target position, the value of the position deviation at the time of completion of pulse distribution increases and the drive current increases. Load acting on the ejector servomotor M, that is, the ejector rod 3
The magnitude of the load acting on 1 can be confirmed.

Therefore, if the load acting on the ejector rod 31 becomes excessive and the determination result of step S12 becomes true, the PMC CPU 18 releases the excitation of the ejector servomotor M (step S16). ),
Stop the drive control of the injection molding machine. As described above, since the mold opening operation has already been completed at this point, the tip of the ejector pin 37 does not interfere with the fixed-side mold a2 to prevent the ejector rod 31 from protruding. If the ejecting action of the ejector rod 31 is hindered at this point, the cause is that the large diameter portion of the stepped ejector pin 37 is trying to forcefully enter the small diameter portion of the hole of the core plate 38, or , Before that, the ejector plate 33 is in contact with the core plate 38. In any case, there is an error in the setting of the projection target position, and this problem arises because the ejector rod 31 is made to project more than necessary, and in particular, the large diameter portion of the ejector pin 37 has the core plate 38 In the case where the small-diameter portion of the hole is plunged into the hole, the biting is extremely severe, and it is difficult to return the ejector plate 33 to the original position by the force of the return spring 35. Further, even if the ejector plate 33 is fixed to the ejector rod 31 with bolts or the like and the original position can be returned, the ejector pin 37 will buckle if such an operation is repeated, so the operation must be stopped. Generally, the injection molding die A is not damaged by the extent that the ejector plate 33 is in contact with the core plate 38. However, if such an operation is repeated, the clamp loosens due to the vibration at the time of protrusion and the movable platen is not supported. There is a possibility that the movable side mold a1 may be attached with a gap,
As a result, it may lead to damage such as galling of the core block and the cavity block, so the operation must be stopped.

On the other hand, when the result of the determination in step S12 is false and it is confirmed that the load acting on the ejector rod 31 is slight, there is no such problem and the molding operation can be continued. . In this case, the PMC CPU 18 outputs an ejector original position return command to the CNC CPU 25, toward the set return position set and stored in the non-volatile memory 24, and under the drive control of the servo CPU 20, the ejector servomotor M. Pulse distribution is performed to start the degeneration of the ejector rod 31 (step S13). When the pulse distribution to the ejector servo motor M is completed, the PMC CPU 18
The current position R of the ejector rod 31, that is, the value R used as the return position at the end of the product releasing operation in the immediately preceding molding cycle in the next molding cycle is read and stored from the current position storage register of the RAM 19 (step S1).
4) The excitation of the ejector servomotor M is released (step S15), and the sequence control for one molding cycle is completed. When the number of ejector projections is set to two or more, steps S10 to S14 are performed.
The above process is repeated according to the set number of times.

In this embodiment, the value of the drive current flowing through the ejector servomotor M is detected as the load acting on the ejector rod 31, but an observer is attached to this servomotor M for ejector. The load acting on the ejector rod 31 may be detected by detecting the output from the. Note that the structure of the observer has already been disclosed by the method of measuring the mold internal pressure proposed by the present applicants in Japanese Patent Application No. 6-113449, and therefore the description thereof will be omitted. Further, the timing of detecting the load is not limited to the above-described example, and for example, the drive current and the observer output are detected at every predetermined period during the ejecting operation of the ejector rod 31, and the maximum value, the average value, or the like is obtained. It may be used as a detection load.

[0042]

According to the ejector control method of the present invention, since the motor for driving the ejector rod is placed in the non-excited state in the steps other than the mold releasing work of the product, the ejector rod is not closed during mold closing, mold clamping and injection operations. Free to move. As a result, even if the ejector rod return position is mistakenly set to the projecting side and the tip of the ejector pin interferes with the fixed side mold when the mold is closed, the ejector rod is forced by the pressing force from the fixed side mold. The pin can be easily retracted, and damage to the ejector pin and the injection mold is prevented. Also, since the ejector pin can be easily retracted, the position specified by the structure of the injection mold itself, that is, the position where the tip of the ejector pin is flush with the product surface, is provided if sufficient injection holding pressure is applied. Even if the ejector pin can be forcibly retracted and the ejector rod return position is mistakenly set to the protruding side, there is room for molding a normal product.

The return position of the ejector rod at the time of completion of the product release operation in the immediately preceding molding cycle,
In other words, if the difference between the set return position of the ejector rod and the return position of the ejector rod pushed back by the collision with the fixed mold or the injection holding pressure exceeds a predetermined value, the setting abnormality detection signal is output. It is possible to easily know the setting abnormality regarding the return position of the ejector rod.

Further, when the load acting on the ejector rod during the projecting operation exceeds the allowable value, a setting abnormality detection signal is output, so that even if the projecting target position of the ejector rod is set largely erroneously, It is possible to prevent buckling of the ejector pin and damage to the injection-molding die due to interference with the core plate of the movable-side die caused by excessive protrusion of the ejector pin.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an injection molding machine to which an ejector control method of the present invention is applied and a main part of a product release mechanism of a general injection molding die.

FIG. 2 is a flowchart showing an outline of sequence control in the injection molding machine of the embodiment.

FIG. 3 is a continuation of a flowchart showing an outline of sequence control.

[Explanation of symbols]

 10 Numerical Control Device 15 Servo Amplifier 18 CPU for PMC 20 Servo CPU 31 Ejector Rod 33 Ejector Plate 35 Return Spring 37 Ejector Pin 40 Cavity A Injection Mold a1 Movable Side Mold a2 Fixed Side Mold

Claims (3)

[Claims] 1. In an ejector control method for an injection molding machine in which an ejector rod is projected by a motor during product release work to perform product release work, the motor is excited only during product release work. An ejector control method for an injection molding machine, comprising: 2. The ejector rod return position at the time of completion of product release work in the immediately preceding molding cycle is stored, and the ejector rod is set at a set timing after completion of mold closing in the next molding cycle and before start of product release work. 2. The ejector control method for an injection molding machine according to claim 1, wherein the position abnormality detection signal is output, and a setting abnormality detection signal is output when the difference between the detection position and the return position exceeds a predetermined value. 3. The injection molding machine according to claim 1, wherein a load acting on the ejector rod during the projecting operation is detected, and a setting abnormality detection signal is output when the load exceeds an allowable value. Ejector control method.