JPH07119030B2 - Injection molding machine purging method - 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 terminate the purge after detecting this.

Conventionally, as a method of terminating the purge,
A method 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, starting from the above-mentioned conventional method, generally, the screw is set to the most advanced position at the end of purging. The reason for this is that the resin (material) in the heating cylinder (heating cylinder) is advanced by advancing the screw to the most advanced position in the final stage of the purging process.
And then, as disclosed in the above-mentioned publication,
This is because the screw is rotated to detect the presence or absence of the residual resin, and when there is no residual resin, the purging ends and the screw is set to the most advanced position as it is.

However, even after the purging is completed, the inner surface 71i of the heating cylinder 71 and the screw 7 are actually, as shown in FIG.
A slight amount of material W remains between the two screw heads 72s. Therefore, when the screw 72 is set to the most advanced position, the residual material W is cooled and solidified as it is,
It is fixed to the inner surface 71i and the screw head 72s. As a result, at the next molding, the injection molding machine is operated and the screw 7
When 2 is rotated, there is a problem that the screw head 72s is fixed and the screw head 72s is damaged. That is, since the temperature near the tip of the heating cylinder 2 is relatively low, the melting speed of the solidified material W is slower than that of other portions, and the screw head 72s is usually provided with a backflow prevention ring. Since the screw 72 has the weakest mechanical strength, the screw head 72s is particularly likely to be damaged.

The present invention solves the problems existing in the prior art as described above, and effectively prevents the screw head from being damaged by the residual material, increases the melting rate of the residual material, and improves the working efficiency. An object of the present invention is to provide a purging method for an injection molding machine that can be achieved.

[0007]

A method for purging an injection molding machine according to the present invention detects the presence or absence of a material W in a heating cylinder 2 after executing a predetermined purging process, and detects the absence of the material W. Then, the screw 3 is retracted to a predetermined standby position Po to perform a purge end process of ending the purge. In this case, the standby position P
o is at least the inner surface 2i of the heating cylinder 2 and the screw head 3
preset settings for the presence of a predetermined gap S between s
Select a fixed position . The following method can be used as a method for detecting the presence or absence of the material W. First, the screw 3 is rotated for a preset time Ts to detect the retracted position Pd of the screw 3, and when the retracted position Pd is equal to or less than the preset set position Ps, the absence of the material W is detected. In addition, a drive motor 4 that rotates the screw 3
Of the load current is detected, the current detection value Id becomes equal to or less than the preset current setting value Is, and the current setting value Is
The absence of the material W is detected when the following time continues for a preset time Tt or more.

[0008]

According to the purging method of the injection molding machine according to the present invention, the presence or absence of the material W in the heating cylinder 2 is detected after the predetermined purging process is executed.

As an example, the detection of the material W is performed as follows. First, the set time Ts in which the screw 3 is preset
Just rotate. 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 compared with the preset set position Ps to determine the retracted position Pd.
If d is equal to or less than the set position Ps, it is determined that the material has run out. The set time Ts is set to a time sufficient for the rotation speed to stabilize from the start of rotation of the screw 3, and the set position Ps is set to a position farther than the most advanced position of the screw 3.
You can select a slightly rear position.

When the absence of the material W is detected, the screw 3 is retracted to the predetermined standby position Po. As a result, as shown in FIG. 4, the inner surface 2i of the heating cylinder 2 and the screw head 3s are axially separated from each other by the distance Lb, and a predetermined gap S is provided.

As a result, even if the remaining material W is solidified,
Almost no fixed area to the screw head 3s
Even if the material W is not sufficiently melted, screw 3
Even if rotated, the screw head 3s is prevented from being damaged.
Be done. Also, at the start of the next operation, the screw 3 will be the heating cylinder.
Of the solidified material W because it is located at the high temperature part in 2
The melting rate is increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. 3, M indicates an injection molding machine, and 1
Reference numeral 1 is 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 (driving motor 4) equipped with a pulse encoder 17, and a transmission mechanism 18 for transmitting the rotation of the motor 16 to the screw 3 is arranged to provide a screw rotation driving unit 19. Make up. Furthermore, the machine base 10 has a pulse encoder 21
While installing the injection servo motor 20 equipped with
The output shaft 20s is connected to the rear end of the slider 15 via a ball screw mechanism 22, and thereby a screw advancing / retreating drive unit 23 is configured.

On the other hand, the measuring servomotor 16 and the pulse encoder 17 are connected to the servomotor control unit 31, and the injection servomotor 20 and the pulse encoder 21 are connected to the servomotor control unit 32. Further, the servo motor control units 31 and 32 are 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 the rotation amount of the measuring servomotor 16, and the pulse encoder 21 detects the speed or the 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 3.

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 to execute the automatic purge process. The purging process itself is executed by repeating the rotation of the screw 3 and idle driving a predetermined number of times. Then, after the purging process, the automatic purging end process is executed. The screw 3 is set to the most advanced position by the purging process.

First, at the same time when the timer function section of the control device 33 starts timing, the measuring servomotor 16 operates,
The screw 3 starts rotating (steps 51 and 52).
The timer function unit counts up a preset set time Ts and then time-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.

At this time, when the retracted position Pd exceeds the set position Ps, that is, when Pd> Ps, the screw 3
Is advanced to the most advanced position, the material is discharged based on the purging process, and the processes from step 51 are executed again (steps 56, 57, 58, 59). In this state, the material is still present, and the purging process will be continued.

On the other hand, the retracted position Pd is less than or equal to the set position Ps,
That is, if the condition of Pd ≦ Ps is satisfied, it is determined that there is no material in the heating cylinder 2, and the screw 3 is retracted (step 60). The retracted position is up to the preset standby position Po, and the retracted amount at this time is set by the timer function unit. That is, the timer function unit starts timing at the same time when the screw 3 starts to move backward, and counts up a preset set time Tt, and then time is up (step 61,
62). Servo motor 16 for measurement due to time up
Is stopped, and the backward movement of the screw 3 is stopped (step 63). In this case, the standby position Po is set by the set time Tt and the backward speed of the screw 3. The standby position Po may be set as an absolute position and the retreat of the screw 3 may be controlled by the position information obtained by processing the output signal of the pulse encoder 21.
Then, the screw 3 is set to the standby position Po, the purge end command is output, and the purge is completed. This state is shown in FIG.

On the other hand, in step 60, the screw 3
The it is also possible Rukoto is retracted to the rearmost position. This place
In that case, it is executed according to the flowchart shown in FIG. In FIG. 2, the same steps as those shown in FIG. 1 are designated by the same reference numerals, and other steps that are the same as those in FIG. 1 are omitted. Screw 3
Is moved to the final retracted position, the metering servomotor 16 is operated to retract the screw 3, and when the final retracted position is reached, the operation of the motor 16 is stopped to stop the backward movement of the screw 3. (Steps 64, 65). Then, the screw 3 is set to the most retracted position, a purge end command is output, and the purge is completed. In this case, the heating cylinder
In addition to the provision of a predetermined space S inside the screw 2,
The rotation of 3 is locked by the interlock function. This
Therefore, it is necessary to unlock the
It is necessary to move the screw 3 forward without moving in front of the screw 3.
It becomes possible to scrape off the material W solidified by the progress
More effectively prevent damage to the screw head 3s
Be done.

As a method for detecting the presence / absence of the material W, the magnitude of the load current of the measuring servomotor 16 for rotating the screw 3 is detected by, for example, a current transformer attached to the power feed line, and the detected current value is detected. The absence of the material W may be detected when Id becomes equal to or less than the preset current setting value Is and the time equal to or less than the preset current value Is continues for the preset setting time Tt or more. In addition, as such a detection method, any detection method can be applied.

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.

[0026]

As described above, according to the purging method of the injection molding machine of the present invention, after performing the predetermined purging process, the presence or absence of the material in the heating cylinder is detected, and if the absence of the material is detected, Screw at least the inner surface of the heating cylinder and the screw.
Preset to ensure that there is a predetermined gap between
Since the purge end process is performed to retract the purge by retracting to the preset standby position, which is the set position, the screw head is effectively prevented from being damaged by the residual material, and the melting rate of the residual material is increased to improve work efficiency. There is a remarkable effect that can be improved.

[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 flowchart in which some steps of another embodiment related to the purging method according to the present invention are omitted.

FIG. 3 is a schematic configuration diagram of an injection molding machine capable of carrying out a purging method according to the present invention,

FIG. 4 is a vertical cross-sectional view showing a screw position by the purging method according to the present invention,

FIG. 5 is a vertical cross-sectional view showing a screw position according to a conventional purging method,

[Explanation of symbols]

 2 heating cylinder 2i inner surface 3 screw 3s screw head 4 drive motor Po standby position S gap W material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hisashi Matsuzaki Hisashi Matsuzaki 2110 Nanjo, Nanjo, Osaka, Hanashina-gun, Hanashina-gun, Nissei Plastic Industry Co., Ltd. (56) Reference JP-A-2-252517 (JP, A) JP 2-169225 (JP, A) Japanese Patent Publication Sho 52-9701 (JP, B2)

Claims (3)

[Claims] 1. In a purging method of an injection molding machine for discharging a material in a heating cylinder, the presence or absence of the material in the heating cylinder is detected after a predetermined purging process is performed, and if the absence of the material is detected. , Screw at least in the heating barrel
For creating a specified gap between the surface and the screw head
A purging method for an injection molding machine, comprising performing a purging end process in which the purging is completed by retracting the purging to a predetermined standby position which is a preset setting position . 2. A screw for detecting the presence or absence of a material.
Is rotated for a preset time, and the screw is retracted.
The position is detected and the retract position is set in advance.
The method for purging an injection molding machine according to claim 1 , wherein the absence of material is detected when the position is below the position . 3. A screw for detecting the presence or absence of a material.
Detects the magnitude of the load current of the drive motor that rotates the
The current detection value is less than or equal to the preset current setting value, and
Time below current set value continues for more than preset time
The method for purging an injection molding machine according to claim 1 , wherein the absence of the material is detected when the process is performed.