JPH0197610A - Manufacture of simple mold - Google Patents

Abstract

PURPOSE:To provide a simple mold for producing uniform products in dimensional accuracy by a structure in which an original mold is coated with thin rubber- like composition and then with a buffer layer, and it is further coated with a backup layer. CONSTITUTION:Liquid silicone rubber is applied to the surface of an original mold 1 using a brush and hardened to form a silicone rubber layer 2, 2'. A foamed silicone layer 3, 3' is provided as the second layer, and thereon a backup layer 4, 4' is formed of an FRP assembly of epoxy-glass fiber, on the periphery of which a frame 6, 7 is formed of an epoxy honeycomb. The foamed silicone 3, 3' serves as a buffer layer to absorb the difference in expansion coefficient between the silicone rubber layer 2, 2' and the backup layer 4, 4', so that it is possible to obtain a product with good dimensional accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a simple mold used for molding using a liquid reactive resin material. In order to perform molding using resin materials, metal molds manufactured by cutting, casting, thermal spraying, etc., and rubber molds made of silicone rubber, polysulfide rubber, etc., are used. In the era of small-volume production, the depreciation burden of molds obtained by metal cutting is a major problem, so many methods of using so-called simple molds, such as quick and inexpensive rubber molds, have been studied and put into practice. Since such a simple mold can be obtained by a direct transfer method from a master mold, a mold for molding can be obtained in a short time.

Problems to be Solved by the Invention However, conventional rubber molds: (1) If the entire mold is made of rubber, the molding cycle is long because the heat transfer coefficient is low and it takes time to raise the temperature.

■ When forming a thin layer of rubber and backing it up with other high-quality reinforcing materials, the difference in expansion coefficient causes deformation of the rubber layer, resulting in problems such as poor molded product accuracy and appearance. That's what I'm doing.

Means for Solving the Problems In order to solve these conventional problems, the present invention forms a thin rubbery composition layer on the surface of the original shape, and then coats the rubbery composition layer on top of the rubbery composition layer. The present invention is characterized by a simple manufacturing method characterized by forming a buffer layer that absorbs deformation of the composition layer, and further forming a backup layer that also serves as reinforcement on the buffer layer.

Function By making the rubbery composition layer thinner, the heating time can be shortened. In order to prevent the rubber from expanding due to temperature rise and deformation caused by the difference in expansion coefficient from the backup material, the rubber composition layer should be made of the same rubber composition as the first layer rubber and without air inclusion. The buffer layer interposed between the rubber composition layer and the backup layer can prevent deformation of the rubbery composition layer caused by the difference in expansion coefficients between the two.

This makes it possible to obtain a simple mold that can be heated in a short time and has stable dimensional accuracy.〇Example An example of the present invention will be explained based on Figs. 1 and 2〇Original form 1 A thin layer of liquid silicone rubber was applied to the surface of the substrate with a brush to form a silicone rubber layer &2' of about 2 to 3H and cured. After that, the second layer is closed and the foamed silicone layer 3
．． 3', a sheet wax of approximately 3M is pasted onto the silicone rubber layer 2.2', and then an epoxy/glass fiber F layer is applied as a buffer layer 4.4'.
An RP structure was formed and a frame was formed around it using epoxy honeycomb.

After curing the buffer tube layers 4, 4', the sheet wax was removed and foamed silicone was injected.

Note that 5 is a reinforcing material, 6 and 7 are formworks, and 8 is a parting line.

The cavity mold and core mold thus obtained were heated to about 60°C, and urethane resin was injected into the molds in a vacuum.Then they were taken out of the vacuum chamber and placed in a heating furnace at about 60°C for 2 hours. After heating for a period of time, the molded product was removed from the mold, cooled to room temperature, and then dimensions were measured at the locations shown in FIG. 2 using a tool microscope and compared with the original shape.

The results are shown in Table-1.

On the other hand, Comparative Examples 1 and 2 were molded for comparison with the simple molds of Examples. Comparative Example 1 consists of a thin silicone rubber layer and a backup layer, and does not have a buffer layer such as a foamed silicone layer. Also, Comparative Example 2 has a thin silicone rubber layer and a backup layer.
The dimensions of Comparative Examples 1 and 2 were also measured at the same measurement points as in the Examples.The results are shown in Table 1.

Table 1 As is clear from the above comparison results, the silicone rubber layer has a larger expansion coefficient than the buffer bubble layer, and the dimensions change by the difference at the same temperature. Changes in the difference in coefficients appear as changes in the molded product, resulting in a decrease in quality. Therefore, it is necessary to absorb the changes by forming a buffer layer such as a foamed silicone layer between the silicone rubber layer and the backup layer. In addition, by making the entire silicone rubber layer thinner, the temperature increase speed is far away and the volumetric expansion is reduced, so it is possible to manufacture a simple mold that can yield molded products with excellent dimensional accuracy. be.

Effects of the Invention Since the present invention has the above-described structure and operation, it is possible to manufacture a simple mold that can produce a molded product with excellent dimensional accuracy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold according to the present invention, and FIG. 2 is a longitudinal sectional side view showing the dimensional measurement points of the simple mold of the embodiment. 1... Original form % 2, 2'... Silicone rubber layer, 3°3'... Foamed silicone layer, 4
f 41...Buffer layer 0

Claims (1)

[Claims] After forming a thin rubbery composition layer on the surface of the original shape, a buffer layer is formed on top of the rubbery composition layer to absorb the deformation of this rubbery composition layer, and a backup layer that also serves as reinforcement is formed on top of the buffer layer. A simple manufacturing method characterized by forming layers.