JPH04244823A - Gate cutting method in mold in thermoplastic material injection molding - Google Patents

Abstract

PURPOSE:To provide a gate cutting method in which a gate can be cut automatically and a plastic material solidified in the gate is removed automatically in gate cutting operation, in which a thermoplastic material is injection-molded into a cavity through a runner and the gate and the thermoplastic material solidified in the gate is cut and removed. CONSTITUTION:A gate cutting pin 11 is moved forward when a thermoplastic material injected is brought to the state in which cooling and solidified are not completed, and the plastic material approximately solidified in a gate 16 is cut off from a molded form 17 as it is left as it is connected to a runner 5'. When said plastic material is cooled and solidified and a mold is opened, a sprue 4 and the runner 5' are projected from a core clock 2 by a piston 14 energized by a spring 15, and plastics 18 solidified in the gate are extracted and removed from the inside of the gate 16.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for obtaining a molded product by injection molding a thermoplastic material into a mold, in which a molten thermoplastic material is injected from a runner into a cavity through a gate. When solidified,
This relates to a method of obtaining a molded product by cutting the plastic material solidified in the sprue and the plastic material (molded product) solidified in the cavity, which are connected by the plastic material solidified in the runner and gate. .

0002

2. Description of the Related Art FIG. 4 is a schematic cross-sectional view showing a conventional plastic injection mold. The mold in this example is
A cavity 3 is formed between a cavity block 1 and a core block 2 by combining them.

Molten thermoplastic material is press-fitted from a sprue 4 and is injected into the cavity 3 from a gate 6 via a runner 5.

[0004] When the molten plastic is cooled, it solidifies,
A molded product is formed in the cavity 3, and this molded product is taken out from the mold in a state in which the plastic solidified in the gate 6, the plastic solidified in the runner 5, and the plastic solidified in the sprue 4 are connected.

[0005] Therefore, the portion corresponding to the gate 6 must be cut using nippers or a hot knife, which requires a great deal of labor.

Furthermore, if a precise shape is required, the cut portions must be manually finished, which further increases the number of man-hours required.

[0007] Cutting using a robot, applying vibration, cutting using a laser beam, etc. are theoretically possible, but the equipment costs are high and daily maintenance is not easy. Because it is not, it is not practical.

[0008]

A method shown in FIG. 5 can be considered as a method for automatically or semi-automatically cutting the gate portion in a mold.

A gate cut pin 7 is provided opposite the gate 6 and can be driven vertically in the figure.

[0010] thermoplastic in cavity 3;
When the thermoplastic in the gate 6 is solidified, the gate cut pin 7 is driven upward in the figure to cut the gate. Reference numeral 8 in the figure is a sprue ejector pin for discharging the solidified sprue 4, which is fixed to the ejector plate 9 together with the gate cut pin 7, and is driven in the vertical direction in the figure via the ejector plate 9. Ru.

However, the conventional gate cutting method shown in FIG. 5 described above has the following difficulties.

As can be easily understood from FIG. 5, in this conventional example, the forward and backward strokes of the gate cut pin 7 and the forward and backward strokes of the sprue ejector pin 8 are equal and are caused to move forward and backward at the same time.

For this reason, the stroke of the sprue ejector pin 8 cannot be made larger than the stroke of the gate cut pin 7, and the sprue ejector pin 8 closes the sprue 4 before the gate cut pin 7 finishes its gate cut operation. Start pressing . As a result, gate cut pin 7
At the time when the sprue ejector pin 8 has performed its gate cutting action, only a small amount of the forward stroke of the sprue ejector pin 8 remains.

Therefore, in the gate cutting method described with reference to FIG. 5, the plastic material solidified within the gate 6 is caught within the gate 6 and is not removed.

The present invention was made in view of the above-mentioned circumstances, and it is possible to automatically cut the plastic material solidified within the gate, and furthermore, when the mold is opened, the plastic material solidified within the gate is automatically cut. The purpose of the present invention is to provide a gate cutting method that allows for efficient discharge.

[0016]

[Means for Solving the Problems] In order to achieve the above object, an in-mold gate cutting method for thermoplastic injection molding according to the present invention provides a method for cutting a cavity formed between a cavity block and a core block. In the method of cutting the gate portion after injection molding a molten thermoplastic material through a runner and a gate, when the plastic material injected into the cavity has not yet completely cooled and solidified, the gate Advance the gate cut pin placed facing the
The plastic material in the cavity is separated from the plastic material in the gate, and when the injected plastic material cools and solidifies and then opens the mold, the piston, which is biased by the extension force of the spring, solidifies the material in the runner. The method is characterized in that the plastic material is protruded from the core block, and the plastic material solidified in the gate, which is integrally connected with the plastic material solidified in the runner, is pulled out from inside the gate and removed.

[0017]

[Operation] According to the above method, the gate cut pin is advanced before the injected plastic material has finished cooling and solidifying, and the plastic material in the cavity and the plastic material in the gate are separated. The plastic material of the gate part can be cut with a small amount of force.

Further, when the plastic material is cooled and solidified and the mold is opened, a piston biased by a spring pushes out the plastic material solidified within the runner from the core block. This ejecting action is performed automatically because it is based on the biasing force of the spring.

The plastic material solidified within the gate is
Since it is integrally connected to the plastic material solidified in the runner, when the plastic material solidified in the runner is ejected from the core block as described above, the plastic material solidified in the gate accompanies this. is automatically pulled out from inside the gate and removed.

[0020] As described above, gate cutting is easily and automatically performed in the mold, and the plastic material solidified in the gate is automatically pulled out and removed from the gate as the mold is opened. be done.

[0021]

Embodiment FIGS. 1 to 3 are process explanatory diagrams schematically depicting one embodiment of the method of the present invention.

FIG. 2 shows the state before the injection process, in which a cavity 3 is formed between the cavity block 1 and the core block 2.

The molten thermoplastic material is injected from the sprue 4 through the runner 5 into the cavity 3.

A gate cut pin 11 is disposed between the runner 5 and the cavity 3, and is driven forward and backward in the vertical direction in the figure. This gate cut pin 11 is provided with a gate 16 that communicates the runner 5 and the cavity 3. The gate 16 is formed into a tapered hole having a large diameter on the runner side and a small diameter on the cavity side.

The gate cut pin 11 and sprue ejector pin 10 described above are fixed to the plate 12,
It is driven forward and backward in the vertical direction in the figure by a drive source (not shown).

A cylinder 13 is provided in the core block 2 concentrically with the sprue ejector pin 10, into which a piston 14 for pushing out the sprue is slidably fitted, and a spring 15 is used to push the sprue upward (in the figure). 4 from the core block 2).

When the gate cut pin 11 is driven upward in the figure, it becomes as shown in FIG. 3, and the small diameter side (left side in the figure) of the tapered hole-shaped gate 16 is cut off from the cavity 3. The large diameter side (right side in the figure) of the gate 16 remains in communication with the runner 5. This cutting operation is performed before the injected plastic material has yet to completely cool and solidify. With this operation, gate 1
The almost solidified plastic material in the runner 6 is separated from the molded part formed in the cavity 3 and still remains connected to the solidified plastic material in the runner 5. Since the plastic material has not yet completely solidified,
The gate cutting operation described above can be performed with relatively little force.

When the mold is opened from this state (FIG. 3), the mold becomes as shown in FIG. 1, and the piston 14 is urged by the spring 15 to project the sprue 4 and the runner 5' from the core block 2.

The plastic 18 solidified inside the gate is molded to be integrally connected with the runner 5', so when the runner 5' is pushed out as described above, it is pulled out from inside the gate 16. removed.

[0030]

Effects of the Invention As explained above, the gate cutting method according to the present invention allows cutting of molten thermoplastic plastic material into the cavity formed between the cavity block and the core block via the runner and the gate. In the method of cutting the gate part after injection molding, when the plastic material injected into the cavity has not yet completely cooled and solidified, the gate cut pin placed opposite the gate is advanced to cut the cavity. The plastic material inside the runner is separated from the plastic material inside the gate, and when the injected plastic material cools and solidifies, when the mold is opened, the piston, which is biased by the extension force of the spring, removes the solidified plastic inside the runner. The material is ejected from the core block, and the plastic material solidified in the gate, which is connected integrally with the plastic material solidified in the runner, is pulled out from inside the gate and removed, so the thermoplastic material solidified in the gate is removed. The plastic material can be cut automatically, and the plastic material solidified within the gate is automatically removed when the mold is opened, which is an excellent practical effect.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the method of the invention, depicting the solidified plastic material and the opened mold.

FIG. 2 similarly depicts the state before molten plastic is injected into the cavity 3 from the gate 6.

[Fig. 3] Similarly, by advancing the gate cut pin 11,
A state in which the gate 16 and the cavity 3 are blocked is depicted.

FIG. 4 is a schematic cross-sectional view of a mold shown to explain a gate cutting method according to the prior art.

FIG. 5 is a sectional view for explaining a conventional mold having a structure including a gate cut pin and its problems.

[Explanation of symbols]

1 Cavity block 2 Core block 3 Cavity 4 Sprue 5 Runner 6 Gate 7 Gate cut pin 8 Sprue ejector pin 9 Ejector plate 10 Sprue ejector pin 11 Gate cut pin 12 Plate 13 Cylinder 14 Piston 15 Spring 16 Gate 17 Molded products

Claims (1)

[Claims] Claim 1: A method of injection molding a molten thermoplastic material into a cavity formed between a cavity block and a core block via a runner and a gate, and then cutting the gate portion. When the plastic material injected into the cavity has not completely cooled and solidified, the gate cut pin placed opposite the gate is advanced to separate the plastic material in the cavity from the plastic material in the gate. When the mold is opened after the injected plastic material has cooled and solidified, the piston, which is biased by the extension force of the spring, ejects the plastic material that has solidified inside the runner from the core block. It is integrated with the plastic material,
An in-mold gate cutting method for thermoplastic plastic injection molding, characterized by pulling out and removing plastic material solidified within the gate from within the gate.