JP2002307502A - Method for automatically regulating mold clamping force of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for automatically regulating a mold clamping force so that a crosshead may not overrun an origin when the mold clamping force is feedback controlled. SOLUTION: The method for automatically regulating the mold clamping force comprises the steps of previously setting the maximum mold clamping force and a criterion of the maximum mold clamping force, moving a mold clamping housing by a driving stroke amount in response to the maximum mold clamping force from the origin of the crosshead to regulate the clamping force, clamping the mold, measuring the real mold clamping force, again regulating the clamping force when the real mold clamping force is out of the criterion of the maximum mold clamping force, and changing the driving stroke amount until the real mold clamping force falls within the criterion of the maximum mold clamping force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic mold clamping force adjusting method for an injection molding machine having a mold clamping force feedback mechanism.

[0002]

2. Description of the Related Art Conventionally, this type of automatic mold clamping force adjusting method has
First, the mold clamping housing is retracted in the mold closed state, and the position of the crosshead when the toggle is extended to some extent is set as the crosshead origin. Next, the effective length of the tie bar is adjusted by reducing the distance between the fixed platen and the mold clamping housing by the necessary additional stroke by the mold thickness adjusting device. The necessary additional stroke is calculated from a mold clamping force table (the relationship between the additional stroke from the crosshead origin and the generated mold clamping force) stored in the control device based on a preset normal maximum clamping force. .

[0003]

According to the above-mentioned conventional adjusting method, when the actual adjusted clamping force is slightly lower than the set clamping force during the automatic mold clamping adjustment,
Even if the maximum mold clamping force is set by the mold clamping force feedback control during automatic mold clamping operation, the desired clamping force will not be achieved with the amount of additional stroke for the automatic clamping adjustment. Try to take control. There is no problem if the overrun amount is very small, but if it becomes impossible to adjust to the maximum mold clamping force due to machine differences or for some reason, the overrun amount increases and the ball screw that moves the movable plate back and forth collides with the stroke end. For example, there is a possibility that mechanical parts may interfere with each other and be damaged. Measures should be taken to increase the set clamping force during automatic clamping force adjustment to a value larger than the maximum so that the maximum clamping force can be reliably obtained with the prescribed additional stroke even if there is variation due to machine differences. However, when performing automatic operation with open control that does not perform mold clamping force feedback, the mold clamping force that is greater than the maximum mold clamping force of the machine itself is applied each time the mold is clamped, and the life of machine parts is reduced. Has a negative effect. Further, in this case, there is a possibility that a large difference occurs in the mold clamping force between the mold clamping force feedback control and the open control, and the search for the molding conditions when switching between the two becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an automatic mold clamping force adjusting method in which a crosshead does not overrun the origin during mold clamping force feedback control. With the goal.

[0005]

According to the present invention, a criterion for determining the maximum mold clamping force (allowable range of the actual mold clamping force) is determined, and the mold clamping is automatically performed once the mold clamping force is adjusted. Then, the actual mold clamping force calculated from the detection values sent from the sensors and the amplifier is compared with the above-mentioned judgment criterion. If the actual mold clamping force is deviated downward (or upward), the additional stroke is slightly reduced. Increase (or decrease) by a small amount and adjust the mold clamping force again.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.

A mold clamping device of a toggle type injection molding machine having a feedback mechanism using the automatic mold clamping force adjusting method of the present invention will be described.

As shown in FIG. 1, the fixed platen 1 and the mold clamping housing 3 are fastened with a tie bar 4 at an interval, and a movable platen 2 is provided between the fixed platen 1 and the mold clamping housing 3 on the tie bar 4. It is movably provided. Note that a mold 15 is attached to the fixed platen 1 and the movable platen 2. The movable platen 2 and the mold clamping housing 3 are connected via a toggle link 11. A ball nut 9 is connected to the crosshead 10 of the toggle link 11, and a ball screw 8 that moves the movable platen 2 back and forth through the toggle link 11 is connected to the ball nut 9.
Is screwed.

The control device 14 is connected to the tie bar extension sensor 12 attached to the tie bar 4 via the amplifier 13, and is connected to the servo motor 5 via the motor drive circuit 6. The servo motor 5 is connected to the ball nut 9 via a timing belt pulley 7.

Next, feedback control of the mold clamping force using the mold clamping device will be described.

The servo motor 5 is driven by the control device 14, the ball screw 8 is rotated, the cross head 10 is advanced, the toggle link 11 is moved, and the mold is closed to perform a mold clamping operation.

During the mold clamping operation, the value detected by the tie bar elongation sensor 12 is converted by the amplifier 13 and fed back to the control device 14, compared with a preset mold clamping force and issues a command to the motor drive circuit 6. , The servo motor 5 is driven, the ball screw 8 is rotated via the timing belt pulley 7, and the crosshead 10 connected to the ball nut 9 is rotated.
Control the position of. Thereby, a predetermined mold clamping force is obtained.

Next, the automatic mold clamping force adjusting method of the present invention will be described with reference to the flowchart shown in FIG. It should be noted that the automatic mold clamping force adjustment is performed after the mold is replaced, prior to the feedback control of the mold clamping force.

The criteria for determining the maximum clamping force in advance, that is, the allowable range of the actual clamping force corresponding to the set maximum clamping force,
It is determined as follows.

F1 <Fm <F2, where F1 is the lower limit,
F2 is the upper limit and Fm is the actual clamping force.

Once the mold clamping force is adjusted (step S1), the mold clamping is automatically performed (step S2), and the actual mold clamping force Fm is calculated from the detected values sent from the sensor and the amplifier (step S1). Step S3). The calculated actual mold clamping force Fm is compared with the lower limit value F1 and the upper limit value F2 of the criterion (step S4). If the actual mold clamping force Fm is smaller than the lower limit value F1 (step S4), the stroke S The increment ΔS is added (step S5), and the process returns to step S1 to automatically perform the mold clamping force adjustment. If the actual mold clamping force Fm is larger than the upper limit value F2 (step S6), the decrease ΔS is subtracted from the follow-up stroke S (step S7), and the process returns to step S1 to automatically perform the mold clamping force adjustment. This is repeated until the judgment criteria are satisfied, thereby adjusting the actual mold clamping force within the reference value (step S8).

At this time, if the lower limit value F1 is set to the same value as the maximum mold clamping force, the actual mold clamping force is always greater than or equal to the maximum mold clamping force when the additional stroke is added. Therefore, the mold clamping force feedback control is performed. In this case, the crosshead does not overrun the origin.

If the upper limit value F2 is set to a value slightly larger than the maximum mold clamping force, the excessive mold clamping force does not adversely affect the life of the machine and parts.

Here, ΔS is an upper limit value F2 and a lower limit value F
The crosshead stroke may be fixed to a value sufficiently smaller than the crosshead stroke corresponding to the difference of 1, for example, about 1/5, or the crosshead corresponding to the difference between the actual clamping force Fm and the set maximum clamping force. The stroke amount may be a value calculated from the mold clamping force table.

[0020]

Since the present invention is configured as described above, the following effects can be obtained. (A) The danger of interference between mechanical parts, such as overrunning the origin of the crosshead during mold clamping force feedback control and the ball screw crashing at the stroke end, can be avoided. (B) When performing the mold clamping force open control, even if only one type of clamping force table is provided, due to mechanical differences and aging,
Excessive clamping force greater than the maximum clamping force is not adversely affected on the life of machine parts. (C) Since the mold clamping force does not greatly differ between the mold clamping force feedback control and the mold clamping force open control, molding conditions are easily set when switching between the two during injection compression molding or the like. (D) When the set mold clamping force cannot be obtained due to a failure of the mold thickness adjusting device or the like, molding can be performed without noticing that, and the danger of causing damage to mechanical parts and the mold can be avoided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a mold clamping device of a toggle-type injection molding machine having a feedback mechanism in which the automatic mold clamping force adjusting method of the present invention is used.

FIG. 2 is a flowchart illustrating an automatic mold clamping force adjusting method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed board 2 Movable board 3 Mold clamping housing 4 Tie bar 5 Servo motor 6 Motor drive circuit 7 Timing belt pulley 8 Ball screw 9 Ball nut 10 Cross head 11 Toggle link 12 Tie bar extension sensor 13 Amplifier 14 Control device 15 Mold

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[Procedure amendment]

[Submission date] May 2, 2001 (2001.5.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Once the mold clamping force is adjusted (step S1), the mold clamping is automatically performed (step S2), and the actual mold clamping force Fm is calculated from the detected values sent from the sensor and the amplifier (step S1). Step S3). The calculated actual mold clamping force Fm is compared with the lower limit value F1 and the upper limit value F2 of the criterion (step S4). If the actual mold clamping force Fm is smaller than the lower limit value F1 (step S4), the stroke S The increment ΔS is added (step S5), and the process returns to step S1 to automatically adjust the mold clamping force. If the actual mold clamping force Fm is larger than the upper limit value F2 (step S6), the decrease ΔS is subtracted from the follow-up stroke S (step S7), and the process returns to step S1 to automatically perform the mold clamping force adjustment. By repeating this until the criteria are satisfied, the actual mold clamping force is adjusted to within the standard value
I do.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

Continued on the front page F term (reference) 4F202 AP01 AR01 AR20 CA11 CB01 CL02 CL22 CL32 CL42 4F206 AP01 AR01 AR20 JA07 JL02 JM02 JP17 JQ83 JT05 JT32

Claims (1)

[Claims] 1. A maximum clamping force and a criterion for determining the maximum clamping force are set in advance, and the clamping housing is moved from the crosshead origin by an additional stroke amount corresponding to the maximum clamping force to adjust the clamping force. The actual mold clamping force is measured by clamping, and if the actual mold clamping force is out of the judgment criteria of the maximum mold clamping force, the mold clamping force is adjusted again and the actual mold clamping force is An automatic mold clamping force adjusting method for an injection molding machine having a mold clamping force feedback mechanism, characterized in that the additional stroke amount is changed until the force judgment criterion is satisfied.