JPH0661800B2 - Metering control device for injection molding machine - Google Patents

Description

The present invention relates to a metering control device for an injection molding machine.

[Problems to be Solved by Prior Art and Invention]

The molding process by the injection molding machine is a metering process in which the material (resin) is sent to the cylinder tip by rotating the screw to determine the injection amount, and the material at the cylinder tip is injected from the nozzle into the mold. Including steps. Here, the injection amount is one of the important parameters for obtaining a high-quality molded product. Therefore, the injection amount must always be a predetermined optimum value.

As the measuring process of the injection molding machine, during the measuring process, the number of rotations of the screw is always constant and the number of rotations of the screw is not changed, and the number of rotations of the screw is switched by the program control. Multi-tiered ones are known.

Conventionally, in the case of a single-stage weighing process, reaching a preset weighing completion position is detected by, for example, a position detector such as a limit switch, and the screw is rotationally driven when the weighing completion position is detected. The rotation drive signal to the device is stopped. However, even if the rotation drive signal is stopped, the screw does not stop immediately due to inertia, but stops after a certain delay time elapses. This delay time becomes longer as the screw rotation speed increases. Therefore, the conventional one-step weighing process is
Inevitable screw overruns occur. Since the overrun amount of this screw is not constant and varies, the molded product also varies accordingly.

On the other hand, in order to eliminate this defect, if the injection process has multiple stages, the type of resin and the screw rotation speed of the stage immediately before the final stage (hereinafter referred to as the front stage) are adjusted so that there is no overrun of the screw. The position of the start of the final stage and the rotation speed of the screw of the final stage are preset according to the above. However, this method has a drawback in that when the screw rotation speed of the preceding stage or the measurement completion position (injection amount) is changed, the final stage start position and the final stage screw rotation speed must be reset.

Therefore, an object of the present invention is to provide an injection molding machine capable of accurately stopping the screw at the measurement completion position without overrun by changing the settings even if the measurement completion position or the screw rotation speed is changed. It is to provide the measurement control device.

Another object of the present invention is, even when the type of resin is changed,
It is an object of the present invention to provide a metering control device for an injection molding machine that can decelerate and stop at a set measurement completion position without overrunning the screw.

[Means for solving problems]

A metering control device for an injection molding machine according to the present invention comprises a screw position detecting means for detecting a screw position, a screw speed detecting means for detecting a backward speed of the screw, and a screw rotation driving means for rotationally driving the screw in accordance with a rotational drive command. And a screw rotation that stops the screw at a preset measurement completion position according to a predetermined arithmetic expression in response to the screw position detected by the screw position detection means and the screw retreat speed detected by the screw speed detection means. And a calculation control means for calculating the number and transmitting the calculated screw rotation number as a rotation drive command.

[Action]

Since the screw deceleration start position is automatically calculated from the calculation formula and the screw is decelerated, the final stage start position and the final stage screw rotation speed are set to prevent overrun, as in the case of conventional program control. No need. or,
Since the screw retreat speed and screw position are detected and the deceleration start position and screw rotation speed are calculated based on these, it is possible to decelerate and stop without overruning the screw even if the resin type changes. You can

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a molding process using an injection molding machine includes a weighing process and an injection process.

In the weighing process, the material from the hopper 1 falls into the heating cylinder 2 due to its own weight. The screw 4 is rotated by the hydraulic motor 3, and the material dropped by this is kneaded and sent to the tip of the cylinder along the groove. At this time, the material is heated by a heater (not shown) on the outer periphery of the heating cylinder 2, and the frictional heat generated by the kneading action is added to increase the temperature from the inside to the molten state. As the molten material is stored at the tip of the heating cylinder 2, the back pressure of the material pushes the screw 4 backward. By adjusting the retreat amount, it is possible to measure the injection amount for one injection.

On the other hand, in the injection process, the injection force is applied to the screw 4 by the injection cylinder 5 at the rear of the injection molding machine, and the screw 4 serves as an injection plunger, and the material at the tip of the screw 4 is transferred from the nozzle part under high pressure to the mold. It is injected into (not shown).

Here, the hydraulic motor 3 and the piston 5a in the injection cylinder 5 are drive-controlled by a screw rotation flow control valve 6 and an injection flow control valve 7, respectively. Further, the flow rate control valves 6 and 7 operate in accordance with a rotation drive command and an injection drive command from the control device 10 described later, respectively.

Further, as shown in the drawing, the screw 4 and the piston 5a in the injection cylinder 5 are fixed so as to be rotatable with respect to each other and not to move in the axial direction. Therefore, the position and the retreat speed of the screw 4 are detected by the screw position detector 8 and the screw speed detector 9 attached to the piston 5a of the injection cylinder 5, respectively. The screw position and screw retreat speed detected by these detectors 8 and 9 are sent to the controller 10.

The control device 10 includes a main processing unit 11 and a storage unit 12.
The main processing unit 11 performs processing according to a program stored in the storage unit 12. The processing flow of this program will be described later in detail with reference to FIG. Main processing unit 11
Receives the screw position S _A and the screw retreat speed V _N detected by the detectors 8 and 9 via the interfaces 13 and 14, respectively, and receives the rotation drive command N _X via the interface 15 for screw rotation in the weighing process. It is sent to the flow control valve 6. In the injection process, an injection drive command is sent to the injection flow control valve 7 via the interface 16.

Next, the principle of the control method of the weighing process according to the present invention will be described.

In the present invention, the screw rotation speed and the measurement completion position are set in advance and set to N (rpm) and S ₉ (mm), respectively. If screw 4 was rotating at N, screw 4
Time t _{a (in} seconds) required for stopping the is represented by the following equation.

^{Here, GD 2 (kg · m 2} ) is flywheel effect of the hydraulic motor 3 and the mechanism, _{T M} (kg · m) represents the braking torque of the hydraulic motor 3. At this time, set the screw retreat speed to V _N (mm
/ Sec), the distance S _N (mm) that the screw 4 travels before stopping is as shown in FIG. Becomes Therefore, metering completion position since it is _{S 9 (mm),} may start a deceleration from the position of the S 9 -S _N.

Distance S _X (mm) to go from deceleration start to t _X (seconds)
Is, as shown in FIG. Becomes In addition, the screw rotation speed at this time is N _X (rp
m) _Therefore , S _X is Is represented.

Further, if the screw position at this time is S _A (mm), S ₉ −S _A = S _N −S _X , so the screw rotation speed N _X is Is represented.

From the above, the screw rotation speed N _X is determined by the position detector 5
From the screw position S _A detected in step S6, it can be seen that it can be obtained by the equation (6).

Next, referring also to FIG. 2, the control device 1 shown in FIG.
The operation of the weighing process of 0 will be described.

First, the main processing unit 11 sends the preset screw rotation speed N as a rotation drive command to the screw rotation flow control valve 6 via the interface 15. By this,
The screw rotation flow control valve 6 drives the hydraulic motor 3 so that the rotation speed of the screw 4 becomes N.

Next, the main processing unit 11, the rotational speed of the screw 4 through the interface 14 reads the screw retracting speed V _N when N from the screw speed detector 9 (step 101).
Next, the main processing unit 11, the time t _a the (1) to the rotational speed of the screw 4 is screw 4 is stopped when N is calculated from equation (step 102). The main processing unit 11, calculated from the time t _a to the stop calculated by screw retracting speed V _N and step 102 read in step 101, the distance S _N which screw 4 is advanced until it stops according to Equation (2) (Step 103).

Next, the main processing unit 11 reads the screw position S _A from the screw position detector 8 via the interface 13 (step 104). The main processing unit 11 calculates a value (S ₉ −) obtained by subtracting the screw position S _A detected in step 104 from the preset measurement completion position S _{9 for the} distance _SN to advance to the stop calculated in step 103. It is determined whether or not S _A ) or more (step 105). _If, S 9 -S
_{If A} > S _N , return to step 101. On the other _hand, S 9 -S _A
If ≦ S _N , proceed to step 106.

In step 106, the main processing unit 11 determines in step 104
The screw rotational speed N _X is calculated according to the equation (6) from the screw position S _A detected in. The main processing unit 11 sends the screw rotation speed N _X calculated in step 106 to the screw rotation flow control valve 6 via the interface 15 as a rotation drive command (step 107). As a result, the screw rotation flow control valve 6 drives the hydraulic motor 3 so that the rotation speed (rotation speed) of the screw 4 becomes N _X.

Next, the main processing unit 11 determines whether the screw position S _A detected in step 104 has reached the measurement completion position S ₉ (108). If S ₉ > S _A, step 104
Return to. On the other hand, if S ₉ ≦ S _{A, the} process proceeds to step 109.
In step 109, the main processing unit 11 sends a rotation drive command for the screw rotation speed control valve 6 to the screw rotation flow control valve 6. As a result, the screw rotation flow control valve 6 is
The rotation drive of the hydraulic motor 3 is stopped, and the rotation of the screw 4 is stopped.

In this way, the screw 4 can be stopped at the measurement completion position S ₉ without overrunning.

In the above-mentioned embodiment, the case where the measuring process is applied to one stage has been described, but it is needless to say that the present invention can also be applied to a plurality of devices in which the rotation speed of the screw is switched by program control. However, even in this case, in the present invention, since the deceleration start position is automatically calculated and obtained, the setting of the final stage for preventing overrun as in the past is unnecessary.

Further, in the above-described embodiment, the hydraulic system drive device including the hydraulic motor 3 and the screw rotation flow control valve 6 is used as the device for rotating the screw 4, but the electrical system drive including the servo motor and the servo amplifier is used. Of course, the device may be used.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the deceleration start position of the screw is automatically obtained by calculation and the screw is decelerated, so that the final stage start position for preventing overrun as in the conventional case. Also, there is an effect that setting of the screw rotation speed becomes unnecessary. Also, since the screw retreat speed and screw position are detected and the deceleration start position and screw rotation speed of the screw are calculated based on these values, even if the type of material (resin) changes ，
There is also an advantage that the screw can be decelerated and stopped without overrunning to the set measurement completion position.

[Brief description of drawings]

FIG. 1 is a sectional view and a block diagram showing the construction of an injection molding machine and its measuring control apparatus according to an embodiment of the present invention, and FIG. 2 is for explaining the operation executed by the control apparatus in FIG. FIG. 3 is a diagram for explaining how to determine the traveling distance depending on the screw reverse speed V _N and the time from the start of deceleration. 1 ... Hopper, 2 ... Heating cylinder, 3 ... Hydraulic motor, 4 ... Screw, 5 ... Injection cylinder, 5a ... Piston, 6 ... Screw rotation flow control valve, 7 ... Injection flow control Valve, 8 ... Screw position detector, 9 ... Screw speed detector, 10 ... Control device, 11 ... Main processing unit, 12 ... Storage unit, 13-16 ... Interface.

Claims (1)

[Claims] 1. The position of the screw is detected in a metering control device of an injection molding machine, which retracts while rotating the screw at a preset screw rotation number and stops the screw at a preset measurement completion position. Screw position detecting means, screw speed detecting means for detecting the backward speed of the screw, screw rotation driving means for rotationally driving the screw in accordance with a rotation driving command, screw position detected by the screw position detecting means, and the screw. In response to the screw retreat speed detected by the speed detecting means, a screw rotational speed for stopping the screw at the measurement completion position is calculated by a predetermined arithmetic expression,
A metering control device for an injection molding machine, comprising: an arithmetic control unit that sends out the calculated screw rotational speed as the rotational drive command.