JPS6099626A - Mold for injection molding - Google Patents

Abstract

PURPOSE:To exhaust fully the inner part of a cavity to mold a good molded piece and to prevent flashes from occurring by a method wherein an inner pin for molding the inner surface of a molded piece is supported by a specified means so that a communication port (exhaust port) to a cavity can be opened or closed by the inner pin. CONSTITUTION:When a molded piece with a cavity is molded, the inner pin 11e to mold the cavity is supported by the pressure of a spring, a rubbery elastic material, an air cylinder or an oil cylinder. Before plasticized material (molding material) is injected into the cavity 18, this inner pin 11e is pushed into the cavity 18 to make the communication ports 16, 36 open state so that sufficient air discharge can be conducted. When the molding material is injected into the cavity 18 after air discharge, the inner pin 11e is returned and the communication ports 16, 36 are closed by the inner pin 11e to prevent flashes from being formed.

Description

[Detailed description of the invention] The present invention relates to improvements in injection molds.

The entrance shown in FIG. 1 is a perspective view of an example molded product, and FIG. B is a sectional view taken along line K-K'. The conventional injection mold for molding this is as shown in the cross-sectional view of Figure 2.
It is composed of divided molds 1a, lb, and lc, and a plasticized material is injected into the mold cavity through an injection hole 2 by an injection machine, and is cooled and solidified to become a molded product 3. When the plasticized material is injected, the air in the mold cavity flows out through the gap between the grooves LJ provided on the dividing surfaces 4a and 4b of the split mold, or A method was adopted in which the inside of the cavity was maintained in a vacuum state by drawing suction from the small grooves formed by the iJ using a vacuum pump.

These conventional methods have the following problems.

If the groove dimensions are set to a very small depth of 0.1 to 0.2 fins,
Although the amount of injection material protruding from the gap is small and it is easy to finish the molded product, the degree of vacuum inside the mold cavity only decreases by about 30 to 60 m/m11g,
Therefore, articles molded in this cavity often have weld lines and cracks on their surfaces.

In addition, the depth of the groove was increased to 0.4 to 0.6 +n, and the degree of vacuum in the mold cavity was increased to 70 m/m I.
If the weight is about 1g, weld lines and cracks in the molded product can be eliminated, but the molded product has a large part that protrudes into the mold groove, which not only takes time for post-finishing, but also causes the molded product to have a large protrusion into the mold groove. Because the material had a lot of adhesion resistance, disassembling and cleaning it was time-consuming and reduced efficiency.

The present invention has been made to solve the above-mentioned problems, and its gist is to use an inner bottle for forming all or part of the inner surface of a molded product in an injection mold. The mold is supported by the pressure of a spring spring, rubber-like elastic body, air cylinder, or oil cylinder, and a gap is provided between it and the outer mold, and a vacuum pump is used to draw air through the communication hole installed through the gap. The cavity is made into a vacuum state, and then the material is injected, and at the same time the inner pin is pushed down by the injection force to close the communication hole.

With this type of mold configuration, the plastic material does not leak into the vacuum suction hole, so the suction hole can be set to the desired size, and the degree of vacuum in the cavity can be easily increased to 70 m in a short time.
/m11g or more. As a result, there is no air entrapment in the injected plastic material, and there are no weld lines or cracks, making it possible to produce good molded products at a high yield. In addition, since there is no protrusion of T and 1 into the vacuum suction hole, there is no need to disassemble and clean the mold by removing material adhering to it, improving operating efficiency, and there is almost no need to finish the protruding parts of the molded product. This greatly contributed to cost reduction.

EMBODIMENT OF THE INVENTION Hereinafter, the mold of this invention is demonstrated with reference to the drawing of an Example.

The mold shown in FIG. 3 was used to manufacture the molded product shown in FIG. 1, and the figure shows a cross section thereof.

The split mold is composed of an outer mold, lla, 11b, and 11c, and an inner mold, commonly known as a medium bottle lid. The outer mold 11a has an injection hole 12 for the plastic material, and the outer mold 11C has an insertion hole 13 for the middle pin lid located at the center. Holes 15 into which spring springs or rubber-like elastic bodies 14 are inserted are provided at three equally spaced locations around the hole in the portion covered by the hole. In addition, a vacuum suction hole I6 was installed at one location in the middle between the holes 15 so as to communicate with the outer surface of the outer mold 11C.

Spring springs or rubber-like elastic bodies 14 were inserted into the three holes, the middle bottle lid of the inner mold was inserted, and the split mold was assembled and attached to a mold clamping mechanism (not shown). A partial plan view of the mold is shown in Figure A of Figure 4. That is, this shows the state before the material is injected, and the elastic body 14 causes the bottom surface of the head lie of the middle pin lid to be 11 degrees lower than the top surface of the outer mold 11C.
．． It is set so that the gap S is between 0 and 2.01. The spring constant or elastic force of the spring spring or rubber-like elastic body used at this time and its dimensions are determined by the size and shape of the molded product.

Next, when the plasticized material produced by gJIil is put into the inlet of the injection machine, it is heated to a constant temperature within the cylinder, and further kneaded with a screw to further plasticize it. During this time, the mold cavity 18 is sucked by a vacuum pump (not shown) through the communication hole 16 installed through the gap S, and the mold cavity 18 is vacuumed for 70 m.
/ml Create a vacuum state of 1g or more. At this time, the mold is maintained at a constant temperature, and the plasticized material is injected into the cavity at a constant injection pressure, and the injection pressure lowers the inner bottle lid, closing the gap S. Plasticized material is filled into the cavity. A partial cross-sectional view at this time is shown in Figure B of Figure 4, and the molded product 17 is cooled and solidified.
And so.

Next, another embodiment will be explained with reference to FIG. 5.

Figure A in Figure 5 is a cross-sectional view of a molded product of a circular deep-bottomed container.
Figure B is a partial sectional view of the molding die, and Figure 0 is a partially enlarged sectional view of the center pin and hole portion of the mold.

The split mold is composed of mold parts 32a and 32t) and a middle bottle 34a that forms part of the inner surface of the molded product. Mold 3
2a has a plastic material injection hole 33, and the mold 32b has an insertion hole larger in diameter than the middle pin 34a installed at the center position. The middle pin is nail-shaped and consists of a bottle head 34b forming part of the inner surface of the molded product and a cylindrical portion.

The enlarged view of FIG. 0 shows the state before the plasticized material is injected, and the head 34b of the middle pin 34a is supported by the spring 2.35, forming a gap between it and the upper surface of the mold. 3b
is a gap that also serves as a vacuum suction hole.

The operations and operations of the method of charging the plasticized material into an injection machine and molding it are the same as in the previous embodiment.

Examples will be described in detail below.

Example 1 Please refer to FIGS. 1, 3, and 4.

The molded product has dimensions of 70mm outer diameter x 4omm inner diameter x 40m height. The dimensions of the three holes 15 into which the spring springs 14 of the outer mold 11c are inserted are 7.0φ in diameter and 10 in depth.
．． The spring spring 14 installed at 0 ++++ and inserted therein has a spring constant of 0.5 Kgf/mA and an outer diameter of 6.0.
Use a crane with a wire diameter of 0.8 fins, and a vacuum suction hole of 1G.
was provided with a fin with a hole diameter of 2.0φ.

The plasticized materials used for this molding were 100 parts by weight of ceramic powder, borisdylene resin, low-molecular polyethylene resin, ester wax, dibutyl phthalate-1,
It is obtained by kneading 48% by weight of a fatty acid ester.

The material plasticized in the cylinder of the injection machine is heated to 180°C, further kneaded and plasticized by a screw, and then injected into the vacuum cavity of the mold at a temperature of 45°C under an injection pressure of 1. to
It was injected at n/cJ, cooled and solidified, and molded.

This molded product has almost no weld lines or cracks.
The desired product could be obtained with a good yield. In addition, since there is no material protruding from the separation surface of the mold, there is no need to disassemble and clean it, resulting in a high operating rate and greatly improved efficiency.

Example 2 Please refer to figures A, B, and C of FIG.

The molded product 31 has dimensions of outer diameter 606 x inner diameter 45''' x height 351 and a wall thickness of 3 twag.

A 9.0 φ fin hole was provided in the center of the mold 32b into which a middle pin 34a and a spring spring 35 loosely inserted around its outer periphery were inserted. The head 34b of the middle pin is 16.0φ in diameter at its maximum, and the diameter of the cylindrical part is 6.0φ.
5 has a spring constant of 0.4 kgf 7 mm and an outer diameter of 8.5
φTsuru, wire diameter Q, (3 mm) was used.

The same plasticized material as in Example 1 was used, and the injection molding conditions were also the same as in Example I.

This thin-walled molded product also has no weld lines or cracks.
The desired product was obtained with good yield. Replacement processing is not necessary as there is no protrusion, and the mold can be easily disassembled and cleaned, resulting in a significant TIJ improvement in cost reduction.

[Brief explanation of the drawings] Figure 1 shows the molded product, Figure A is a perspective view, and Figure B is line K -
A sectional view taken from K', Fig. 2 is a sectional view of the conventional type, Fig. 3 is a sectional view of the mold of the embodiment, Fig. 4 A is a partial view of a part of the mold before material injection, and Fig. B is a molding. Figure 5 shows another embodiment, Figure A is a cross-sectional view of the molded product, Figure B is a partial cross-sectional view of the mold, Figure C is a partially enlarged view of the center pin and hole. Show the diagram. 11a, Ilb, llc, 32a, 32b・----
Outer mold, 11d, 34a...Inner pin, lie, 3
4b...Pin head, 12.33...Injection hole, 13...Insertion hole, 14.35...
・Elastic body, 15...Elastic body insertion hole, 16.36
...Suction hole, 17.31... Molded object Fig. 1 (A) (B) Fig. 2 Fig. 4 (A) (B)

Claims (1)

[Claims] In a mold for creative molding in which plasticized material is injected and molded, the inner bottle for forming all or part of the inner surface of the molded product is used with a spring spring, a rubber-like elastic body, or an air cylinder or oil cylinder. The material is supported under pressure, a gap is created between it and the outer mold, and a vacuum pump is used to draw air through the communication hole installed through the gap to create a vacuum in the mold cavity, and then the plasticized material is removed. An injection mold characterized in that, at the same time as injection is performed, a central pin is pushed down by the injection force to form a communicating hole in a cold configuration.