JP2529624B2 - Purging method of 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 of purging an injection molding machine for discharging a material in a heating cylinder at the time of completion of molding or material change.

[0002]

2. Description of the Related Art Generally, an injection molding machine performs a purge process to discharge all the residual material in a heating cylinder to empty it at the time of completion of molding or material change. The molding machine performs automatic purge processing. When performing the automatic purging process, the purging process itself can be automatically performed by repeating the rotation of the screw and the blanking a predetermined number of times, but when the purging is automatically terminated, the material in the heating cylinder is completely exhausted. It is necessary to detect this accurately.

Conventionally, as a method for detecting the end of purge, a method for detecting the end of purge disclosed in Japanese Patent Laid-Open No. 2-169225 is known. In this method, the screw is advanced from the retracted position to the tip of the cylinder, the purge process for discharging the residual resin (material) is performed, the screw is rotated for a predetermined time, and the melting pressure of the resin is detected. This operation is repeated until the value becomes equal to or lower than the value, and the purge is completed when the detected melting pressure becomes equal to or lower than the predetermined value.

[0004]

By the way, normally, various different resin materials are used in molding, but the fluidity of each resin material greatly differs depending on the type. For this reason,
In the above-mentioned conventional detection method, the melting pressure to be detected varies greatly depending on the type of the resin material, and accurate and stable detection cannot be performed when the purge is completed. In the case of a resin material, there is a problem that the melting pressure becomes considerably small and detection itself becomes difficult.

The present invention solves the problems existing in the prior art as described above, and it is possible to improve the reliability by accurately and stably detecting the end of the purge. The purpose is to provide a method.

[0006]

In the purging method for an injection molding machine according to the present invention, when the material in the heating cylinder 2 is discharged, after the purging process is performed, the screw 3 is moved to the most advanced position.
Then, rotate the screw 3 for a preset time Ts
The reverse position Pd is detected, and the reverse position Pd is
When the preset position Ps behind the most forward position is equal to or less than the preset position Ps , the screw 3 is stopped at the retracted position Pd to end the purge, and if it exceeds the preset position Ps, the purge process is performed. It is characterized in that it is done.

[0007]

According to the purging method of the injection molding machine according to the present invention, first, after performing a predetermined purging process, the screw 3 is rotated for a preset time Ts. At this time, if there is a material in the heating cylinder 2, the screw 3 moves backward due to the back pressure of the material accumulated in the front, while if there is no material, the screw 3 does not move backward but idles.

Therefore, after the set time Ts has elapsed, the retracted position Pd of the screw 3 is detected and the retracted position Pd is detected.
d and the preset position Ps are compared, and the backward position Pd
If is less than or equal to the set position Ps, it is determined that the material is exhausted, and the automatic end process is executed. Thus, the present invention
Is allowed to retreat to the retracted position Pd immediately,
Since some residual material is allowed, purge time
Can be shortened. On the other hand, at the end of the purge, the screen
2 is stopped at the retracted position Pd.
Therefore, the residual material after the completion of purging flows backward behind the screw 3.
The problem to be solved is solved. That is, the screw 3 was advanced
In this case, the material accumulated in front of the screw 3 is the injection nozzle.
At the same time as it is discharged from the
And flows backward behind the screw 3. Therefore, the last
Of the screw 3 after advancing the screw 3 by
The material remains attached inside the groove and solidifies in this state.
Will end up. Normally, the screw 3 does not have a heating unit.
Therefore, the material adhering to the groove, etc., will be
It is gradually melted and mixed into the changed material.
As long as the molding operation is not repeated several times, there is no residual material.
The problem arises of not becoming. However, in the present invention, the
Stop the clutch 3 at the retracted position Pd to end the purge.
Therefore, no backflow of material occurs. In this case, screw 3
Most of the material that remains in the front is heated with a heating section.
Since it adheres to the inner surface of the cylinder, it is ejected at the next first injection operation.
Will be issued. On the other hand, if the retracted position Pd exceeds the set position Ps, it is determined that the material remains, and the purging process is continued. It is desirable that the set time Ts be selected so that the rotation speed of the screw 3 becomes stable after the start of rotation. Further, the set position Ps can be experimentally selected at a position slightly rearward of the most advanced position of the screw 3.

[0009]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, a schematic structure of an injection molding machine capable of executing the purging method according to the present invention will be described with reference to FIG.

In FIG. 2, M indicates an injection molding machine, and 1
Reference numeral 1 denotes an injection device attached to the machine base 10. Injection device 11
Has a heating cylinder 2, has an injection nozzle 12 at the tip, and has a hopper 13 for supplying a material into the inside of the heating cylinder 2 at the rear. A screw 3 is inserted into the heating cylinder 2, and a rear end of the screw 3 is rotatably coupled to a front end of a slider 15 which is horizontally movable along a guide bar 14.
The slider 15 is provided with a metering servomotor 16 having a pulse encoder 17, and a transmission mechanism 18 for transmitting the rotation of the motor 16 to the screw 3 is arranged to form a screw rotation drive unit 19. Furthermore, the injection servomotor 20 having the pulse encoder 21 is mounted on the machine base 10, and the output shaft 2
0 s is connected to the rear end of the slider 15 via a ball screw mechanism 22.
Is configured.

On the other hand, the measuring servomotor 16 and the pulse encoder 17 are connected to a servomotor control unit 31, and the injection servomotor 20 and the pulse encoder 21 are connected to a servomotor control unit 32. Each of the servomotor controllers 31 and 32 is connected to a molding machine control device 33 having a built-in computer function for controlling the entire injection molding machine.

In this case, the pulse encoder 17 detects the speed or rotation amount of the measuring servomotor 16, and the pulse encoder 21 detects the speed or rotation amount of the injection servomotor 20. In addition, the control device 33 gives a control command to the servo motor control unit 31, and the servo motor 1 for measurement is controlled.
By controlling 6 to rotate the screw 3 and giving a control command to the servo motor control unit 32 to control the rotation speed and the rotation torque of the injection servo motor 20,
The position of the screw 3 is detected by controlling the back pressure during forward movement and rotation of the screw 3 and by processing the output signal of the pulse encoder 21 of the injection servomotor 20.

Next, the purging method of the injection molding machine according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a flow chart of the purging method according to the present invention, in particular, the automatic purging end process when the purging process is completed.

First, in the controller 33, the automatic purge program is called and the automatic purge process is executed. The purging process itself is executed by repeating the rotation of the screw 3 and idle driving a predetermined number of times. Then, when the predetermined purging process is completed, the automatic purging ending process is executed.

First, the screw 3 is set to the most advanced position, the measuring servomotor 16 is activated at the same time when the timer function section of the control device 33 starts counting, and the screw 3 starts rotating (steps 51 and 52). A preset time Ts is set in advance in the timer function unit, and after the preset time Ts is measured, the time is up (step 53). The operation of the metering servomotor 16 is stopped due to time-up, and thereby the rotation of the screw 3 is stopped (step 5).
4). The stop position at this time, that is, the retracted position P
The output signal of the pulse encoder 21 is processed to detect d (step 55). Then, the obtained retracted position Pd is given to the control device 33 and compared with the preset position Ps set in the control device 33.

[0018] At this time, the retracted position Pd is set position Ps or less, i.e., if they meet the conditions of Pd ≦ Ps, it is determined that the material in the heating cylinder 2 is exhausted, and outputs a path over di end command To complete all purging ( step 56).
In this case , the screw 3 is stopped at the retracted position Pd without being advanced.

On the other hand, when the retracted position Pd exceeds the set position Ps, that is, when Pd> Ps, the screw 3 is advanced to discharge the material based on the purge process, and the process from step 51 is performed again. Is executed (steps 56 and 58). In this state, the material is present, and the purging process will be continued.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the processing of each unit may be performed by a hardware configuration or software. The servo motor may be replaced with a general-purpose motor or a hydraulic drive mechanism. Furthermore, the position detection of the screw may be performed by a position detector attached to the screw. In addition, the detailed configuration and method can be arbitrarily changed without departing from the scope of the present invention.

[0021]

As described above, the purging method for the injection molding machine according to the present invention, when the material in the heating cylinder is discharged,
After performing the purging process, rotate the screw from the most forward position for the preset time, detect the backward position of the screw, and set the backward position behind the most forward position.
The screw is retracted when it is below the preset position
By stopping at the position to end the purge, and if the retracted position exceeds the set position, the purge process is performed, so by detecting the end of the purge accurately and stably,
The reliability can be increased . Moreover, the purge time is short
It is possible to reduce the volume and the residual material flows back after the purge is completed.
Eliminates the harmful effects of remaining stuck in the screw groove, etc.
It has a remarkable effect that it can be done .

[Brief description of drawings]

FIG. 1 is a flow chart showing a purging method of an injection molding machine according to the present invention,

FIG. 2 is a schematic configuration diagram of an injection molding machine that can perform the purging method,

[Explanation of symbols]

 2 Heating cylinder 3 Screw Pd retracted position Ps set position

Claims (1)

(57) [Claims] 1. A method of purging an injection molding machine for discharging material in a heating cylinder, wherein after the purging process, the screw is rotated from the most forward position for a preset time to detect the backward position of the screw. as well as the retracted position, the when fully forward the following set position previously set to the rear than the position, to stop the screw at the retracted position
The method for purging an injection molding machine is characterized in that the purging process is terminated when the set position is exceeded.