JPS6082318A - Method of injection molding - Google Patents

Abstract

PURPOSE:To make easy molding possible without being charged with a high mold expense, by mounting a resilient body to a nonmolding surface of an undercut working section of a mold, and removing the undercut working section from the inside of the product by physical treatment or chemical treatment after the injection molding. CONSTITUTION:A resilient body sheet 60 is stuck to a nonmolding surface 31 of a core 30 that will be oppositely fitted to a nonmolding surface 53 of an undercut working section 50. A resilient body sheet 61 is stuck to a nonmolding surface 41 of a slide core 40 that is opposite to a nonmolding surface 54 of the undercut working section 50. The undercut working section 50 is made of a sinter produced from a brittle material and the shape of the undercut working section 50 can be lost or collapsed physical or chemically. Thus when molding of a product is effected, the undercut working section is molded, and it is mounted in a mold to form a cavity corresponding to the shape of the product, so that a product with an undercut having a complicated shape can be easily injection molded. Further since resilient body is stuck to a part where an undercut working section is required thereby absorbing the molding error at the undercut working section, high accuracy of molding at the undercut working section is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of injection molding a synthetic resin product having an undercut portion.

Figure 1 (al is a cross-sectional view of the floor trap;
1 is a main body, 2 is an opening, 3 is a flow path opening, 4 is a side hole 5 is a fluid guide, and 6 is a connecting portion.

In the case of this floor trap, the trap part X surrounded by the fluid guide 5 and the flow path opening 3 becomes an undercut in injection molding, and since the undercut part is complicated, there is no one made of synthetic resin made by injection molding. .

An object of the present invention is to provide an injection molding method that can easily mold products with complex undercuts as described above without incurring high mold costs. The above-mentioned undercut of the mold is used to form a product-shaped cavity in the mold by pre-molding the part into a mold so that its shape can be broken down chemically or physically, and attaching it to the mold in a removable manner. An elastic body is attached to part or all of the non-molded surface that is in contact with the non-molded surface of the treated area to absorb molding errors in the undercut treated area, and the undercut treated area is physically or chemically removed after injection molding. It is characterized by being removed from the product through processing.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In Fig. 2, 10 is a stationary template, 20 is a movable template, 30 is a core, 40 is a slide core, and 50 is an adder cut processing section. A cavity with the shape of a floor trap) is formed. The undercut processing section 50 has a molding surface 51 that forms a cavity for molding the fluid guide 5 between the molding surface of the core 30 and the molding surfaces of the fixed mold plate 10 and the movable mold plate 20. The shape of the undercut portion X shown in FIG. A complex shape with (
This corresponds to the shaded area in FIG. 1(a)).

The undercut processing portion 50 is removably locked to a locking pin 70 that is implanted in the movable mold plate 20 and extends in the mold opening direction. In addition to using a locking pin as a means for locking the undercut processing portion 50 to the movable template 20, it may also be temporarily bonded with an adhesive so that this temporary bonded surface is separated when the mold is opened after molding. .

Reference numeral 60 and 61 are elastic sheets for preventing paris, and the elastic sheet 60 is the non-forming surface 5 of the undercut processing portion 50.
It is attached to the non-molded surface 31 of the core 30 that fits and contacts the core 30. Since the undercut portion 50 is strongly pressed by the resin pressure and comes into pressure contact with the non-molded surface portion 32 of the core 3 that is continuous with the non-molded surface 31, an elastic sheet is not necessary. The elastic sheet 61 is attached to the non-molding surface 54 of the undercut treatment section 50.
It is attached to the non-molding surface 41 of the slide core 40 that is in contact with the slide core 40 . Note that the elastic sheets 60 and 61 may be fixed by pinning or the like other than adhesion.

Undercut processing section 5 comprising the above-mentioned molding surfaces 51 and 52
For example, materials that easily lose or collapse their shape physically or chemically, such as heat-resistant brittle materials such as ceramics or sand, hardened with phenol resin and sintered;
Alternatively, sand is hardened with a water-soluble adhesive, and the third
As shown in the figure, it is preformed using a simple mold 100. In FIG. 3, a bottle hole 55 is formed in a portion corresponding to the side hole 4 of the floor trap.

80 is a product ejection bin, and 81 is a sprue.

In injection molding the floor trap shown in FIG. 1+a), the undercut treatment section 50 is pin-locked to the movable mold plate 20, attached to the mold, and the mold is closed. As a result, a cavity having the shape of a floor I/lap is formed in the mold.

Next, molten resin is injected into the cavity through the sprue 81, the mold is opened after a predetermined period of time, and the ejecting pin 8
0 and take out the molded floor I/wrap from the mold. At this time, the locking pin 70 is oriented in the product ejection direction, and the floor trap, which is a molded product, is removed from the mold without being caught, with the under force/throat processing section 50 built-in. After being removed from the mold, the undercut portion 50 remaining in the floor trap is removed using a screwdriver, etc. if the undercut portion 50 is made of a heat-resistant brittle material such as ceramics or sand hardened with phenol resin and sintered. If the sand is hardened with a water-soluble adhesive, soak it in water and remove it from the floor trap.

Since the undercut processing portion 50 is made by a simple method as described above, there is a molding error, and if left as it is, the non-molded surfaces 53, 54 and the non-molded surfaces of the core 30, slide core 40, etc. However, in this embodiment, elastic sheets 60 and 61 are attached to the non-molding surfaces 53 and 54 of the mold to absorb the above-mentioned molding errors. Therefore, the occurrence of Paris is sufficiently prevented.

FIG. 4 shows an example of molding the pipe joint shown in FIG. 1(b) according to the present invention. In this pipe joint, the three water stopper grooves 6, 7, and 8 and the branch portion 9 serve as undercut portions. In this example, the water stop material groove 6.7
．． 8 are nests 106, 107, . . . having these groove shapes.
108 is molded so as to easily collapse its shape as in the case of the insert 50 shown in FIG. 2, and is fitted and molded into the core 300 and the slide core 400 and 400, respectively, as an undercut portion. In addition, the base side of each core 300 and slide core 400.400 is stepped 1061.107.
1.1081, and an elastic sheet 65, 66, 67 is attached to that part. Further, the branch part 9 is molded with a nest 109 having a molding surface along its inner surface so that its shape can be collapsed, and this is easily inserted into and removed from the core 300 as an undercut part. On the side of the nest 109 not indicated by reference numeral A, there are provided pin holes into which pins 56 protruding from the core 300 are loosely fitted, and the pins 56 and 56 are inserted into the pin holes to attach the pins 56 and 56. .

In this case, the elastic sheets 63 and 64 are attached to the A side and B side of the core 300 and slide core 400. If the elastic sheet 6-3 is attached in this way, the elastic sheet 63
Due to the zero elasticity, the contact surfaces of the core 300 and the nest 109 (noted by reference numeral A) are pressed into contact with each other, so that the occurrence of cracks is prevented. Moreover, if the elastic sheet 1-64 is attached to the fitting surface of the insert 109 of the slide core 400, it is possible to prevent the part indicated by the symbol B from breaking.

As described above, according to the present invention, when molding a product,
The undercut processing part is molded with a substance whose shape easily collapses through physical or chemical processing, and this is attached to the mold by means such as gluing or locking with pins to form a cavity in the shape of the product inside the mold. This makes injection molding of undercut products with complicated shapes easier, and elastic bodies are attached to necessary parts of the undercut treatment area to absorb molding errors in the undercut treatment area. As a result, high precision is not required for forming the undercut portion, and a simple method is sufficient, so that the above effects can be obtained without incurring large costs.

[Brief explanation of the drawing]

FIG. 1(B), (bl is an example of a product molded by the method of the present invention, (a) is a vertical cross-sectional view of a synthetic resin floor trap, (bl is a vertical cross-sectional view of a synthetic resin pipe joint, FIG. 2 is a cross-sectional view of a mold for carrying out the injection molding method of the present invention, FIG. 3 is a cross-sectional view of a mold for forming an undercut portion in the mold, and FIG. 4 is a cross-sectional view of a mold according to the present invention. It is a cross-sectional view of a molding die for explaining another example. 10-fixed side template, 20 movable side template, 30.300--
・Core, 40.400. -'-Slide core, 50.1
09-undercut processing part, 51.52--molding surface, 53.54-non-molding surface, 55-bottle hole, 60-67-
Elastic sheet. Patent applicant Tobu Sekisui Co., Ltd.

Claims (1)

[Claims] 1. When injection molding a product with an undercut, the undercut treated part of the molding die is molded in advance so that its shape can be collapsed chemically or physically, and the molded undercut treated part is molded into the molded part. When removably attached to the mold, an elastic body is attached to a part or all of the non-molding surface of the mold that is in contact with the non-molding surface of the undercut treated portion to prevent molding errors in the undercut treated portion. An injection molding method, which comprises: absorbing the above-mentioned product, and after injection molding and cooling of the product, removing the above-mentioned molded undercut portion from the product by chemical or physical treatment.