JPH0716896A - Method of controlling mold opening of injection molding machine - Google Patents

Abstract

PURPOSE:To avoid causing impacts even when mold opening is started immediately after cooling at high speed by conducting an auxiliary mold opening operation right before the stationary mold and movable mold are spaced apart at the time of detecting resin infected into the mold, and performing mold opening after the completion of cooling, in a mold of the type that is opened and closed by a serve motor. CONSTITUTION:When dwelling is complete to resin within a mold 40, a CPU 18 for a PMC causes a mold opening liner and a cooling liner to operate each for timing a lapse of time from the completion of dwelling and a cooling time, and arrival of the mold opening timer to a given lapse of time required to cure resin in within the mold 40 causes the CPU 18 to output a predetermined low speed mold opening command to a servo CPU 20 in order to drive-control a mold opening servo motor M1 for retracting the cross-head and conduct an auxiliary mold opening operation while absorbing mold clamping reaction forces so as not to produce impacts. Subsequently, as a set time of the cooling liner lapses and mold opening is started, impacts never occur even when mold opening is carried out at high speed because mold clamping forces of the mold 40 are released.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An injection molding operation using an injection molding machine is carried out in one cycle of mold closing → injection → holding pressure → measurement and cooling (measurement is completed during cooling) → mold opening → eject, which is generally mold closing. At the time from the completion of the mold clamping to the completion of cooling, the fixed side mold and the movable side mold are strongly crimped by the mold clamping mechanism so as to withstand a strong injection holding pressure. In order to reduce the cost of molded products, it is necessary to shorten the cycle time, and there is a desire to speed up mold closing and mold opening as much as possible unless the structure of the mold is special.

[0003]

However, in the conventional injection molding machine, the fixed side mold and the movable side mold were strongly pressure-bonded to each other until the completion of cooling, so that the mold was immediately and rapidly cooled. When it starts to open, there is a problem that a strong impact is generated due to the reaction of the mold clamping force. In particular, this tendency is strong in an injection molding machine that uses a toggle-type mold clamping mechanism, and when the molded product bites strongly on the core of the stationary mold due to conditions such as holding pressure and cooling, Such impact repeatedly causes problems such as core breakage,
A great deal of time may be wasted in mold repair work.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and even if the mold is opened at high speed immediately after the completion of cooling, the mold and the injection molding machine are not adversely affected, and the molding cycle is short. An object of the present invention is to provide a mold opening control method for an injection molding machine that can perform an injection molding operation.

[0005]

According to the mold opening control method of the present invention, when solidification of a molded product in a mold is detected after completion of holding pressure and before completion of cooling, a mold opening assisting operation is started at a low speed and fixed. The object is achieved by completing the auxiliary operation at a position immediately before the side mold and the movable mold are separated from each other, and starting the mold opening operation after the completion of cooling.

Further, in the mold opening control method according to the embodiment, the elapsed time from the completion of the holding pressure, the mold temperature after the holding pressure is completed, or the mold pressure after the holding pressure is completed is monitored. The solidification of the molded product was detected based on the fact that these variables reached preset values.

[0007]

[Operation] Elapsed time after holding pressure is completed, or mold temperature,
Alternatively, the pressure inside the mold is monitored and the solidification of the molded product inside the mold is detected. If solidification of the molded product in the mold is detected before cooling is completed, the mold opening assist operation is started at a low speed, and the mold clamping mechanism reaches the position just before the fixed side mold and the movable side mold are separated. To remove the strong mold clamping force acting between the molds, complete the mold opening assisting operation, and wait for the completion of cooling. After the cooling is completed, the normal mold opening operation is started.

Since the mold clamping force has already been released at the time of mold opening, even if the mold is rapidly opened upon completion of cooling, no accidental impact is caused, and high-speed mold opening operation becomes possible, and the cycle is completed. Time is shortened. Further, since problems such as core breakage due to impact are eliminated, the work of reworking the dies and the unloading work associated therewith are not required, and the production efficiency is further improved.

[0009]

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 30 of an embodiment to which the method of the present invention is applied.
Reference numeral 33 is a fixed platen, reference numeral 32 is a movable platen, reference numeral 34 is an injection cylinder, and reference numeral 35 is a screw.

The movable platen 32 is moved along the tie bar (not shown) of the injection molding machine 30 via the mold clamping mechanism 31 including a ball nut & screw and a toggle mechanism by the axial output of the mold clamping servomotor M1. Be moved. Figure 3
And FIG. 4 shows a schematic configuration of a toggle head and a toggle mechanism that constitute a part of the mold clamping mechanism 31.

Fixed platen 33 and movable platen 32
A large number of bolt holes are threaded in each of the molds, and the clamp member is bolted in accordance with the size of the mold 40 used for the injection molding work, so that the fixed mold of the mold 40 and the mold 40 are fixed. Each of the movable molds is connected to each platen 33 and 32.
It can be attached to.

The screw 35 is axially driven by the injection servomotor M2 via a drive conversion device 37 for converting the axial rotation of the drive source into a linear motion in the injection axial direction, and a gear mechanism 36. A screw rotation servomotor M3 is used to measure and rotate the screw. A pressure detector 38 is provided at the base of the screw 35 to detect the resin pressure acting in the axial direction of the screw 35, that is, the injection holding pressure in the injection holding process and the screw back pressure in the metering and kneading process. The injection servomotor M2 is provided with a pulse coder P2 for detecting the position and moving speed of the screw 35, and the mold clamping servomotor M1 is provided with a toggle head of a mold clamping mechanism 31 for driving the movable platen 32. A pulse coder P1 for detecting the position is provided.

A control device 1 for driving and controlling the injection molding machine 30.
0 is a CPU for CNC 25 which is a microprocessor for numerical control, a CPU for PMC 18 which is a microprocessor for a programmable machine controller, a servo CPU 20 which is a microprocessor for servo control, an A / D converter 16 and pressure detection. It has a pressure monitor CPU 17 for sampling injection holding pressure and screw back pressure via a device 38, and transfers information between each microprocessor by selecting mutual input / output via a bus 22. You can do it.

The PMC CPU 18 is connected to the ROM 13 storing a sequence program for controlling the sequence operation of the injection molding machine and the RAM 14 used for temporary storage of operation data, and 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 monitor 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 sampling processing of molding data. The ROM 11 and the RAM 12 used for temporary storage of data are connected. Further, the servo CPU 20 is connected with a servo amplifier 15 for driving a servo motor for each axis for ejector (not shown), mold clamping, injection, screw rotation, etc. based on a command from the CPU 20. Each of the outputs from the pulse coder P1 provided in the mold clamping servo motor M1 and the pulse coder P2 provided in the injection servo motor M2 is fed back to the servo CPU 20, and the pulse coder P
Servo CPU2 based on feedback pulse from 1
The current position of the toggle head of the mold clamping mechanism 31 calculated by 0, the moving speed of the screw 35 calculated by the servo CPU 20 based on the feedback pulse from the pulse coder P2, and its current position are stored in the current position storage register of the RAM 19 and The current speed storage registers are sequentially 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. A manual data input device 29 with a display is connected to the bus 22 via a CRT display circuit 26 so that a monitor display screen, a function menu can be selected and various data input operations can be performed. Also, various function keys and the like are provided.

The non-volatile memory 24 is a memory for storing molding data for storing molding conditions (injection pressure holding condition, metering and kneading condition, etc.) and various set values, parameters, macro variables and the like related to injection molding work.

With the above configuration, the CNC CPU 25 distributes pulses to the servo motors of the respective axes based on the control program of the ROM 27, and the servo CPU 20 distributes the pulses to the respective axes of the movement commands and the pulse coder P.
Based on the position feedback signal and the velocity feedback signal detected by the detectors such as 1, P2 and the like, servo control such as position loop control, velocity loop control and current loop control is performed as in the conventional case, so-called digital servo. Execute the process.

FIG. 2 shows the PMC CPU 18 of the controller 10.
It is a flow chart which shows the sequence control of 1 cycle performed by this, and below, with reference to this flow chart, the mold opening control method of this example is explained.

First, the PMC CPU 18, which has started the one-cycle sequence control, executes the processing of each process from mold closing → injection → pressure holding according to a sequence similar to the conventional one (steps S1 to S3). In the final process of mold closing, the toggle mechanism of the mold clamping mechanism 31 operates in order to withstand the injection holding pressure and maintain the mold clamping state from the completion of the mold clamping to the completion of injection and pressure holding. It is completely locked up in the state as shown in (3), and a strong mold clamping force acts between the fixed side mold and the movable side mold of the mold 40.

When the holding pressure is completed, the PMC CPU 18
First, the mold opening timer that measures the elapsed time from the completion of pressure holding and the cooling timer that measures the cooling time after completion of pressure holding are started (step S4). Next, CP for PMC
U18 outputs a predetermined back pressure command to the servo CPU 20, applies a predetermined back pressure to the screw 35 by driving and controlling the injection servo motor M2, and outputs a predetermined screw rotation command to the servo CPU 20. The screw rotation servomotor M3 is drive-controlled to rotate the screw 35 to start a predetermined measuring operation (step S5).

Next, the PMC CPU 18 determines that the elapsed time measured by the mold opening timer is a preset elapsed time according to conditions such as the mold temperature, the cavity shape and its volume, and the type of resin used. Then, it is determined whether or not the elapsed time required for the solidification of the resin in the mold 40 has been reached (step S6). If the elapsed time measured by the mold opening timer has not reached the set elapsed time, CP for PMC
U18 reads the current position of the screw 35 from the current position storage register of the RAM 19 (step S10),
It is determined whether or not the screw 35 is retracted to the measurement completion position preset as the molding condition (step S
11).

If the screw 35 has not retracted to the measurement completion position, the PMC CPU 18 will determine whether the elapsed time measured by the mold opening timer has reached the set elapsed time.
Alternatively, until the screw 35 retracts to the measurement completion position, in the same manner as described above, step S5 and step S
6, the processing of step S10 and step S11 is repeatedly executed, and the measuring operation by the rotation of the screw 35 is continued.

Before the screw 35 retracts to the measurement completion position, the elapsed time set by the mold opening timer elapses and the step S
When the determination result of 6 is true and the solidification of the resin in the mold 40 is detected, the PMC CPU 18 causes the RAM 19 to
Servo motor M for mold clamping from the current position storage register of
1, that is, the current position of the toggle head in the mold clamping mechanism 31 is read, and it is determined whether or not the toggle head is retracted from the lockup position by a predetermined amount (step S).
7). The predetermined amount here means that the mold clamping force applied to the mold 40 by the toggle mechanism of the mold clamping mechanism 31 is almost completely released, and moreover, the fixed side mold and the movable side mold in the mold 40 are brought into close contact with each other. The amount of retreat is such that the state is maintained (state of FIG. 3), and this value is preset and stored in the nonvolatile memory 24.

At the stage immediately after the set elapsed time of the mold opening timer has elapsed, the toggle mechanism of the mold clamping mechanism 31 is completely locked up in the state shown in FIG. Is also in the lockup position, the determination result of step S7 is false. Therefore,
The PMC CPU 18 outputs a predetermined low-speed mold opening command to the servo CPU 20 to drive and control the mold clamping servomotor M1, thereby causing the crosshead of the mold clamping mechanism 31 to retreat at a slight speed so that no impact occurs. The mold opening assist operation is started while absorbing the tightening reaction force (step S
9), similar to the above, steps S10 and S1
Process 1 is performed.

Thereafter, the PMC CPU 18 judges whether the toggle head is retracted from the lock-up position by a predetermined amount and the determination result of step S7 is true, or the screw 35 is retracted to the measurement completion position and the determination of step S11 is performed. Until the result becomes true, in the same manner as described above, step S
5 to step S7 and step S9 to step S11
The above process is repeatedly executed to rotate the screw for weighing, and to perform the mold opening assisting operation in which the crosshead of the mold clamping mechanism 31 is retracted at a slight speed.

Then, the toggle head retracts from the lock-up position by a predetermined amount before the screw 35 retracts to the measurement completion position, the determination result of step S7 becomes true, and the mold clamping force applied to the mold 40 is released. If it is confirmed, the PMC CPU 18 stops outputting the low speed mold opening command, and causes the crosshead of the mold clamping mechanism 31 to retreat at a slight speed.
That is, the mold opening assist operation is completed (step S8).

In this way, when the solidification of the resin in the mold 40 is detected after the pressure holding is completed and before the measurement is completed, and the mold opening assist operation is completed before the measurement is completed, the PMC CPU 18
Until the screw 35 moves backward to the measurement completion position and the determination result in step S11 becomes true,
The processing of step S8, step S10, and step S11 is repeatedly executed to rotate the screw for weighing.

Then, when the screw 35 moves backward to the measurement completion position and the determination result of step S11 becomes true and it is confirmed that the measurement is completed, the PMC CPU 18
The output of the screw rotation command is stopped, the screw rotation process related to the measurement is ended, and the processes of steps S6 to S8 and steps S10 to 13 are repeatedly executed until the set time of the cooling timer elapses (step S13). , Wait for cooling to complete.

On the other hand, when the solidification of the resin in the mold 40 is detected after the completion of the measurement and before the completion of the cooling, that is, the set time of the mold opening timer is longer than the time required for the measurement. If the determination result of step S11 becomes true earlier than the determination result of step S6, the processes of steps S7 to S9 required for the mold opening assist operation are performed while weighing is performed. All are canceled, and during this period, the mold opening assist operation is not performed.

In this case, after the screw 35 retracts to the measurement completion position and the determination result of step S11 becomes true,
The PMC CPU 18 performs steps S6 and S10.
~ The process of step S13 is repeatedly executed to wait for the resin to solidify.

When the determination result of step S6 is true and the solidification of the resin in the mold 40 is detected, the PMC CPU 18 determines that the determination process of step S7 is true and the retraction of the toggle head is completed. Until the confirmation, the processes of step S6, step S7, and step S9 to step S13 are repeatedly executed, and the crosshead of the mold clamping mechanism 31 is slightly retracted while absorbing the mold clamping reaction force in the same manner as described above. Performs the mold opening assist operation. Then, when the toggle head retracts by a predetermined amount and the determination result of step S7 becomes true, and it is confirmed that the mold clamping force applied to the mold 40 has been released, the PMC CPU 18 outputs the low speed mold opening command. The output is stopped, and the mold opening assist operation is completed by slightly moving the crosshead of the mold clamping mechanism 31 backward (step S
8) Hereinafter, similarly to the case where the mold opening assist operation is completed after the pressure holding is completed and before the metering is completed, the processes of steps S6 to S8 and steps S10 to 13 are repeated until the set time of the cooling timer elapses. It will be executed and it will wait for completion of cooling.

When it is confirmed by the determination processing in step S13 that the cooling has been completed after the elapse of the set time of the cooling timer, the PMC CPU 18 causes the injection molding machine 30 to perform the mold opening operation according to the same sequence as the conventional one. It is started (step S14), and the ejecting process for the protrusion of the molded product is performed in the same manner as the conventional method (step S15).
One cycle of sequence control is completed.

Since the mold clamping force acting on the mold 40 has already been released when the mold opening is started, an unexpected impact occurs even if the mold 40 is suddenly opened at a high mold opening speed upon completion of cooling. Instead, a high mold opening speed can be set. As a result of eliminating inadvertent impacts, problems such as core breakage of the fixed-side mold, which tends to occur when a molded product that bites into the fixed-side mold core remains in the cavity of the movable-side mold and is peeled off, is also eliminated It In addition, since the actual allowable range of resin shrinkage that causes biting increases, it is possible to forcibly cool the mold, which leads to a shorter cooling time, and thus a faster cycle time can be realized. It will be possible.

As described above, as one embodiment, the case where the presence or absence of solidification of the molded product is detected based on the elapsed time from the completion of the holding pressure has been described. The solidification of the resin is detected when the detected temperature and the detected pressure are lower than the set values (the processing corresponding to step S6 in FIG. 2) and the same processing operation as the above-described embodiment is performed. However, the same effect as the above can be obtained.

[0037]

The mold opening control method of the present invention detects the solidification of the molded product in the mold and performs the mold opening assisting operation at a low speed, so that the mold can be preliminarily used after the holding pressure is completed and before the cooling is completed. The mold clamping force that acts on the mold is released, and the completion of cooling is waited for while maintaining the close contact between the fixed side mold and the movable side mold.Therefore, start the high-speed mold opening operation immediately after cooling is completed. Even if the mold and the injection molding machine are not impacted by the mold clamping reaction force. Therefore, a high mold opening speed can be set to shorten the molding cycle time. In addition, as a result of eliminating inadvertent impact at the time of mold opening, problems such as core breakage of the fixed side mold that tends to occur when peeling off the molded product biting on the core of the fixed side mold by mold opening are solved, Eliminates the need to repair the mold due to careless core breakage, and the work of loading and unloading the mold associated with this, and efficient injection molding work can be performed continuously.

In the case of a thick molded product, in order to prevent the molded product from being distorted, the molded product is gradually cooled in the mold and then the mold is opened to take out the molded product. In the case of such molding, it may be sufficient if the mold is closed without applying a mold clamping force while the molded product is gradually cooled in the mold. When the present invention is applied to such molding, the mold can be closed without generating a mold clamping force while the molded product is gradually cooled in the mold. Therefore, the mold clamping force is generated only when necessary, so that the life of the mechanical portion of the molding machine can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an electric injection molding machine of an embodiment to which a method of the present invention is applied.

FIG. 2 is a flowchart showing an outline of sequence control by the control device of the embodiment.

FIG. 3 is a schematic view showing a mold clamping mechanism of the electric injection molding machine of the embodiment (a state in which the toggle head is retracted by a predetermined amount).

FIG. 4 is a schematic view showing a mold clamping mechanism of the electric injection molding machine of the embodiment (locked-up state).

[Explanation of symbols]

 10 Control Device 30 Electric Injection Molding Machine 31 Clamping Mechanism 32 Movable Platen 33 Fixed Platen 40 Mold M1 Servo Motor for Clamping P1 Pulse Coder

Claims (4)

[Claims] 1. In a mold opening control method for an electric injection molding machine in which a mold is opened and closed by a servomotor, when solidification of a molded product in the mold is detected after completion of holding pressure and before completion of cooling, the mold is operated at low speed. An opening auxiliary operation is started, the auxiliary operation is completed at a position immediately before the fixed side mold and the movable side mold are separated from each other, and the mold opening operation is started after cooling is completed. Mold opening control method. 2. The mold opening control of the injection molding machine according to claim 1, wherein the time elapsed from the completion of the holding pressure is measured, and when the preset time has elapsed, it is detected that the molded product in the mold has solidified. Method. 3. The injection molding according to claim 1, wherein the temperature inside the mold after the completion of the holding pressure is monitored, and when the detected temperature falls below a preset temperature, it is detected that the molded product inside the mold has solidified. Control method for machine mold opening. 4. The injection molding according to claim 1, wherein the pressure inside the mold after completion of the holding pressure is monitored, and when the detected pressure falls below a preset pressure, it is detected that the molded product inside the mold has solidified. Control method for machine mold opening.