JPH06182836A - Mold opening method - Google Patents

Abstract

PURPOSE:To eliminate a spring back sound without making a mold opening/ closing cycle time longer by a method wherein only in the vicinity of a mold touch position, a cross head speed at the time of mold opening is reduced to be as low as a spring back sound is eliminated. CONSTITUTION:Prior to the start of injection molding, a normal clamping condition is set from an MDI connected to an NC device. In addition, when a mold is opened after being locked up, only in the vicinity of a mold touch position, a cross head speed is reduced to be as low as a spring back sound is eliminated. Namely, a cross head speed is set to 800mm/sea from a lock-up position to a first mold opening speed change position A and to 70mm/sea from the first mold opening speed change position A to a second mold opening speed change position B, furthermore being set to 800mm/sea after a mold touch. In this manner, a spring back sound never occurs at the time of mold opening, and a clamping cycle is not made longer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a link type electric mold clamping device for an injection molding device.

[0002]

2. Description of the Related Art A link type electric mold clamping device of an injection molding machine drives a toggle mechanism or a crank mechanism by a servomotor for mold clamping to move (advance) a movable platen with respect to a fixed platen to move the fixed platen. Clamp the mold between the platens. The mold is clamped from the mold touch position where the fixed side mold attached to the fixed platen and the movable side mold attached to the movable platen first contact, and then the tie bar connecting the fixed platen and the rear platen for several mm ( (Depending on the size of the device) to the extended lockup position.

In mold opening, contrary to the above, the movable platen is retracted from the lock-up position to the position where the molded product can be taken out through the mold touch position. And there is a so-called springback sound called Don. Although the detailed reason why the sound is generated is not clear, it is a sound that makes a shock guess. Conventionally, the springback noise has no particular effect on molding, so it is left alone or only in special cases, at the mold release speed (lock-up position and shift position that is decelerated to protect the mold during mold clamping). (Between) has been extremely slow since the beginning of the lockup release.

However, the generation of the springback noise means that a shock is generated inside the mold clamping device every time the mold is opened, and it is mechanically removed, so that the fixed platen,
A shock absorbing mechanism is provided at the joint between the rear platen and the tie bar. Also, when the injection molding equipment of our company or another company competes as the product, the product image is better when the mold opening / closing cycle time is short and there is no springback noise.

[0005]

PROBLEM TO BE SOLVED BY THE INVENTION It is an object of the present invention to provide a mold opening method which eliminates springback noise without making the cycle time of mold opening and closing particularly long.

[0006]

[Means for Solving the Problems] The crosshead speed at the time of mold opening is set to a low speed at which the springback sound disappears only near the mold touch position.

[0007]

The means for reducing the crosshead speed eliminates the springback noise. The means in which the section for reducing the crosshead speed only in the vicinity of the mold touch position prevents the mold opening / closing cycle time from becoming long.

[0008]

[Examples] The springback noise disappears when the mold opening operation is performed without locking the mold or when the mold releasing speed until the mold touches the position is extremely slowed. 1 and 2 show the results of experiments on an electric mold clamping device equipped with a toggle mold clamping mechanism, where the vertical axis represents the crosshead speed (mm / sec) and the mold clamping force (tons). Is the position of the crosshead, graph line a is the change in crosshead speed, graph line b is the change in mold clamping force during mold clamping, and graph line c is the change in mold clamping force during mold opening.

Since these figures show three experiments at a time, the respective graph lines overlap. Further, in these drawings, a section where the crosshead position is 47 mm from the crosshead position 0 mm (lock-up position) is called a mold release speed section.

The mold clamping device used in the experiment has a horizontal three-plate structure having an electric toggle mechanism which employs a mold clamping servomotor controlled by an NC device (numerical controller), and a standard mold clamping force of 40 tons. , The reference block used for the test was used instead of the mold, and this was clamped. The die touch position is 41.2 mm at the crosshead position.

The detection of the mold clamping force is converted from the strain amount of the strain gauge attached to the tie bar, and the vibration measuring element is attached to the die attachment surface side of the movable platen. Also,
The crosshead position is a value known to the NC device,
The crosshead speed is a set value.

The grasping of the mold opening / closing state in this type of electric mold clamping device is performed on the basis of the position and speed of the crosshead which drives the toggle mechanism. The actual moving amount of the movable platen is extremely small with respect to the moving amount of the crosshead.

FIG. 1 shows a mold opening speed of 800 mm / sec.
In this case, a springback sound is generated at a position where the crosshead exceeds the mold touch position by 2 to 3 mm.

In FIG. 1, the change of the mold clamping force when the mold is opened (graph c) is the change of the mold clamping force when the mold is clamped (graph b).
As is clear from the comparison with the above, the mold clamping force of about 8 ton remains at the mold touch position which should be 0 ton without being released, and after passing the mold touch position, the cross head position 47 is reached.
It can be seen that it is opened between mm. Also, it can be seen that the change in speed of the crosshead (graph a) initially rises steadily, but rises slightly before and after the mold touch position, and normally resumes after passing through the mold release speed section.

In FIG. 2, 70 mm / sec (low speed) is initially set from the lockup to the crosshead position 42 mm slightly beyond the die touch position, and 800 m thereafter.
m / sec (high speed). In this case, the springback sound is almost inaudible. According to the graphs b and c in FIG. 2, the change in the mold clamping force is well matched between the mold clamping and the mold opening, and the residual mold clamping force is 1 ton at the mold touch position during the mold opening. It is less than enough.

During the mold clamping, the speed control of the crosshead is not performed as in the conventional case until the lock-up after touching the mold, and the mold clamping servomotor M performs the mold clamping at a constant high speed and maximum torque. Has been done.

From this, the springback sound is generated when the mold touch position reaches a mold touch position while a part of the mechanical strain inside the mold clamping device generated during mold clamping is preserved during mold opening, and the mold position is passed. It can be inferred that it occurs because it acts to inhibit the opening operation. Therefore, when the speed of the crosshead is as high as 800 mm / sec, the above-mentioned saved strain is released rapidly to generate a springback sound, and when the crosshead speed is low, the saved strain is It can be inferred that the springback noise does not occur because the opening is gentle. And
The slow speed increase observed near the die touch position when the crosshead is at high speed is considered to be due to the resistance when the strain is rapidly released.

To make this estimation more reliable, FIG.
The experimental results shown in FIG. 8 were obtained from the mold clamping device. First, FIG. 3 shows a case where a reference block is attached between the fixed platen and the movable platen to close the mold, and the mold is opened by setting the crosshead speed in the release speed section to a large value of 800 mm / sec. It is a speed rising curve of a crosshead. In this case, a springback sound is generated.
Then, similarly to the graph a in FIG. 1, a slow increase in speed is observed at the crosshead position 35 to 47 mm centering on the mold touch position.

On the other hand, in FIG. 4, after moving the crosshead to the lock-up position without attaching the reference block, that is, without applying actual force, the mold opening is performed at the same 800 mm / sec as described above. Is a rising curve of the crosshead speed when the crosshead speed is increased. In this case, no springback sound is generated. Moreover, the slowdown of speed increase as seen in FIGS. 1 and 3 is not observed. That is, it is almost clear that the cause of the springback noise is due to the distortion inside the mold clamping device during mold clamping.

FIGS. 5 to 8 show that the reference block is attached to the mold clamping device, the mold is clamped up to the lock-up, and then the mold is opened by variously changing the crosshead speed in the mold release speed section. It is a thing. according to this,
When the mold release speed is set to a high speed of 800 mm / sec as shown in FIG. 5, a large vibration, which is a springback sound, is detected near the crosshead position 47 mm, which slightly exceeds the mold touch position.

However, with this vibration, the crosshead speed (release speed) in the release speed section becomes small (FIG. 6).
Amplitude decreases almost proportionally as the mold release speed increases from 70 mm / sec to 50 mm / sec as shown in FIGS.
Then, almost no vibration is detected, and the springback sound disappears. That is, it is almost clear that the springback noise can be prevented by releasing the distortion inside the mold clamping device at the time of mold clamping at a low speed.

Therefore, in the present invention, when the mold is opened after lockup, the crosshead speed is set to a low speed at which the springback sound disappears only near the mold touch position. Figure 9
Shows a mold clamping device 1 in an injection molding machine and an NC device 2 provided in this injection molding device. The mold clamping device 1 is
Fixed platen 3, movable platen 4 and rear platen 5
The fixed platen 3 and the rear platen 5 are connected by four tie bars 6. A mold space is provided between the fixed platen 3 and the movable platen 4, and a fixed side mold 7 and a movable side mold 8 are provided.
Is installed. The movable platen 4 and the rear platen 5 are connected by a toggle type mold clamping mechanism 9. The toggle type mold clamping mechanism 9 is provided with a toggle link 10 and a cross head 11 connected by a rotary node, a ball screw 12 for moving the cross head 11, and a mold clamping servo motor M.

From the encoder P of the mold clamping servomotor M to the input / output circuit D / O of the NC device 2, the crosshead 11
The current position of is input. The NC device 2 includes a CPU (arithmetic device), a RAM, in addition to the input / output device I / O described above.
(Rewritable memory), ROM (fixed memory), MD
It is an ordinary one having an I (manual input device) and a servo circuit for driving the motor M.

Prior to the start of the injection molding, the MDI connected to the NC device 2 sets the mold opening speed in addition to the normal mold clamping condition in the mold release speed section. In this embodiment, the first position from the lockup position
800 mm / sec up to the mold opening shift position A (crosshead position 25 mm), the first mold opening shift position A to the second mold opening shift position B (die touch position 41.2 mm)
Is set to 70 mm / sec, and after the die touch is set to 800 mm / sec. The mold opening shift position after touching the mold is a deceleration start position that is normally set to avoid a shock due to the rapid stop of the movable platen 4.

At the speed thus set, the mold clamping device 1
When you drive, no springback noise is generated when opening the mold. Moreover, since the crosshead speed is set to a low speed in only a part of the mold clamping cycle and the other is high, the mold clamping cycle time does not become particularly long.

Regarding the reason why the springback noise is not generated, looking at the crosshead speed change (graph a) and the mold clamping force change (graph c) when the mold is opened by the above setting,
As shown in FIG. 10, the crosshead speed is 70 mm / sec near the die touch position. The reason why the graph a is connected by a smooth curve is due to the acceleration / deceleration processing characteristics of the NC device 2. Eventually, the crosshead speed near the die touch position is around 70 mm / sec, and it is considered that this speed is the speed at which the strain partially remaining inside the mold clamping device can be released without impact.

It should be noted that although FIG. 10 also shows the change in the mold clamping force (graph b) during mold clamping, it is in good agreement with the curve during mold opening, and the mold clamping force remaining at the mold touch position. It can be seen that the above-mentioned residual strain is released without impact.

In order to confirm this situation, the mold clamping device 1 was driven with the crosshead speed from the first mold opening shift position A to the second mold opening shift position B set to 50 mm / sec in the above setting. However, there was no springback sound when opening the mold.

Taking the crosshead speed (graph a), the mold clamping force change (graph c) and the mold clamping force change (graph b) during mold opening at this time (FIG. 11), The minimum crosshead speed at the die touch position is almost 5
Although it is 0 mm / sec, it is almost the same situation as described above, and if the crosshead 11 is set to a low speed such that the springback sound disappears only near the touch of the mold, the spring is irrelevant regardless of the crosshead speed in other sections. It is clear that the back sound can be eliminated. This means that the crosshead speed can be slowed only in the vicinity of the die touch position and the other can be moved at high speed, so that the springback noise can be eliminated without making the die opening / closing cycle time particularly long.

Although the present invention has been carried out for various mold clamping devices, the crosshead speed during mold opening is set to a low speed at which the springback noise disappears only near the mold touch position as described above. Then, it turns out that the springback sound can be eliminated. Furthermore, in any case, when the low speed value was set to 50 mm / sec to 70 mm / sec, the springback sound disappeared without fail.

The above is an embodiment. The set values of the first and second mold opening shift positions A and B in the mold release speed section are not limited to the above values, and are set in relation to the normal mold release speed. The technical idea of the present invention can be applied to a mold clamping device including a crank type mold clamping mechanism.

[0032]

EFFECTS OF THE INVENTION The springback noise can be eliminated without increasing the mold opening / closing cycle time. The conventional springback cushioning mechanism is not required, and the structure of the mold clamping device can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram (conventional / high speed) for showing changes in crosshead speed during mold opening, and mold clamping force changes during mold opening and mold clamping.

FIG. 2 is a diagram (at low speed) showing changes in crosshead speed during mold opening, and mold clamping force changes during mold opening and mold clamping.

FIG. 3 is a diagram showing a crosshead speed during mold opening (after lockup).

FIG. 4 is a diagram showing a crosshead speed when a mold is opened (without lockup).

FIG. 5 is a diagram showing the vibration of the movable platen when the mold is opened (release speed 800 mm / sec).

FIG. 6 is a diagram showing the vibration of the movable platen when the mold is opened (release speed 200 mm / sec).

FIG. 7 is a diagram showing the vibration of the movable platen when the mold is opened (release speed 70 mm / sec).

FIG. 8 is a diagram showing the vibration of the movable platen when the mold is opened (release speed 50 mm / sec).

FIG. 9 is a schematic mechanism diagram of a mold clamping device.

FIG. 10 is a diagram showing the crosshead speed during mold opening, and the mold clamping force changes during mold opening and mold clamping (the present invention, the first example).

FIG. 11 is a diagram (second embodiment of the present invention) showing changes in crosshead speed during mold opening and changes in mold clamping force during mold opening and mold clamping.

[Explanation of symbols]

 1 mold clamping device 2 NC device 3 fixed platen 4 movable platen 5 rear platen 6 tie bar 9 mold clamping mechanism 10 toggle link 11 crosshead

Claims (2)

[Claims] 1. A mold opening method characterized in that a crosshead speed during mold opening is set to a low speed at which a springback sound disappears only near a mold touch position. 2. The mold opening method according to claim 1, wherein the low speed of the crosshead in the vicinity of the die touch position is 50 to 70 mm / sec.