JPS6155457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stepped molding method in which, when forming characters, figures, or other appropriate patterns on a resin molded product such as a molding area or a bumper, the part is recessed.

Conventionally, this type of construction has been carried out using the high-frequency welding method, but when working on thick resin molded products, the volume depressed by the steps will bulge out in the form of burrs on the edges of the steps. There's a problem. If the wall thickness is thin as shown in FIG. 1A, the step a can be easily formed, and no burr-like protuberances will occur. However, in the case of a thick wall as shown in FIG. 1B, the volume c of the shaped recess b is pushed out, and the more the depth increases, the more it overflows, reducing the commercial value. Therefore, if the wall thickness is thick, a deep stepped pattern cannot be formed, and only a shallow stepped pattern d as shown in FIG. 1C can be formed.

An object of the present invention is to provide a stepped molding method for a resin molded product that eliminates such drawbacks and enables beautiful stepped molding.

That is, in the stepped molding method according to the present invention, a resin molded product is formed into a shell shape using a thermoplastic synthetic resin, and the thick portion can be invaginated into the shell by heating and pressing.

This will be explained below based on the second to fourth illustrated embodiments.

The resin molded products 1 and 2 are made of a suitable resin such as non-foamable polyvinyl chloride and are formed into a shell shape with outer shell portions 1a and 2a. It is desirable that the wall thickness of these outer shell parts be made thin enough not to impair the strength of the product. In the second illustrated embodiment, their interiors are made solid with a foamed resin layer 1b made of foamed polyvinyl chloride or the like. In addition, in the third illustrated embodiment, the hollow space is made hollow, and in order to reinforce the hollow space, a vertical rib 2 is used to separate the stepped width, which will be described later.
b, 2b are integrally molded with the main body 2a.

These resin molded products 1 and 2 are subjected to heat softening treatment at least at the stepped portions, and at the same time are subjected to pressure pressing treatment using a rod-shaped body (not shown). The tip of the rod-like body is formed in a shape opposite to the desired shaping shape, and is used to press the outer portions 1a, 2a of the resin molded products 1, 2 so as to make a depression. In addition, heat treatment can conduct heat to the rod-shaped body itself, thereby making it possible to soften the rod-shaped body at the same time as pressing it. Furthermore, when a resin molded article is formed from non-foamed polyvinyl chloride, a high frequency welding method can be employed, and the resin molded article can be softened by self-heating due to high frequency.

When performing construction in this manner, the thickness of the wall recessed by the step will invade into the inside of the shell. In the second illustrated embodiment, when the foamed resin layer 1b is compressed, a wall thickness 1c protrudes into the shell. Further, in the third illustrated embodiment, the wall thickness 2c protrudes within the hollows of the vertical ribs 2b, 2b, and can be prevented from protruding outward from the respective recesses 1d, 2d. Therefore, no burr-like protuberances are formed on the edges of the recesses 1d and 2d, and these edges can be beautifully finished.

This stepped molding method can be applied to form the model name 3rd class letters and symbol 4 on the bumper as shown in Figure 3, and the bottom surface of the recessed part of the letters etc. can be colored with paint, ink, or a resin sheet. It can also be applied to cases.

As described above, according to the stepped molding method for a resin molded product according to the present invention, even if the formed stepped portion is deep, the edges can be finished beautifully, and the product value can be increased.

[Brief explanation of the drawing]

Figures 1 a to c are explanatory diagrams of the conventional stepped forming method;
FIGS. 2a and 2b and 3a and 3b are explanatory diagrams of the stepped forming method according to the present invention, and FIG. 4 is an explanatory diagram showing a specific embodiment according to the present invention. 1, 2: Resin molded product, 1a, 2a: Shell-shaped outer part, 1b: Foamed resin layer, 2b, 2b: Vertical rib, 1c, 2c:

Claims (1)

[Scope of Claims] 1. A resin molded product is formed into a shell shape using a non-foamable thermoplastic synthetic resin, and a desired region including at least the outer surface portion to be stepped molded is heated and softened,
A stepped forming method for a resin molded product, characterized in that the softened portion is pressed by a rod-shaped body with a given stepped shape engraved at the tip, thereby causing the thick portion to invade into the shell. . 2. The stepped molding method according to claim 1, wherein the resin molded product is molded into a hollow shell shape. 3. The stepped molding method according to claim 1, wherein the resin molded product is molded into a solid shell shape using a foamed resin layer. 4. The stepped forming method according to claim 2, wherein the hollow space is reinforced with vertical ribs formed integrally with the main body to separate the recessed width intervals. 5. The stepped molding method according to claim 1, wherein the resin molded product is made of polyvinyl chloride. 6. The stepped forming method according to claim 5, wherein the pattern engraving is performed using a high-frequency welder.