JPH0156150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention is directed] This invention relates to an electroforming mother mold and a method for manufacturing the same.

[Prior art and its problems]

The surface of an electroformed mold generally has a complex shape, which makes machining difficult and requires precision. Therefore, an electroformed mother mold is obtained by plating the surface of the mother core.
Due to its nature, plating the uneven portions formed on the surface requires a considerable amount of time and time. In other words, the uneven parts are plated at a low current density and over a long period of time, and when the surface of this plating layer becomes smooth, the current density is increased again.
It is normal to form a plating layer for reinforcement at high speed, but the plating layer for reinforcement generally reaches a thickness of more than ten millimeters, and it takes from several days to more than ten days to perform plating for that thickness. There are some drawbacks.

In order to improve this drawback, a reinforcing method has been adopted in which the base core is melted and sprayed with a low-melting point alloy, but the melting point is as low as 150 [℃], which has the disadvantage of low mechanical strength. .

In addition, reinforcing methods using ordinary cement have been appropriately adopted, but these have not always been satisfactory in terms of heat resistance, pressure resistance, mechanical strength, and workability.

[Purpose of the invention]

In view of these conventional problems, it is an object of the present invention to form an electroforming mold having sufficient mechanical strength, heat resistance, and pressure resistance in a short time.

[Summary of the invention]

This invention involves plating the surface of a base core so as to cover its uneven parts, inserting the base core into an injection mold having an inner diameter larger than the outer diameter of the base core, and A molten tin and zinc alloy is injected between the mold and the core under normal pressure or vacuum, and then the core is melted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

That is, in FIGS. 1 and 2, a mother core 1 serving as a core material is formed, for example, by machining an aluminum material, and a large number of recesses 2 and protrusions 3 are provided on its outer peripheral surface. For example, if the core 1 is a pinion gear, an uneven portion consisting of peaks and valleys is formed on its outer periphery.

First of all, on the surface of this core, there are especially uneven parts 2,
Apply plating to a predetermined thickness so as to cover 3. This plating is performed slowly with a low current density and over a sufficient period of time. As a result, a plating layer 5 is formed, and the uneven portions 2 and 3 are smoothly covered with this plating layer.

On the other hand, an injection mold 7 having an inner diameter larger by a predetermined dimension than the outer diameter of the mother core 1 on which the plating layer 5 has been applied is prepared, and the mother core 1 is inserted approximately into the center of the injection mold. In this state, a space having a predetermined dimension is formed between the base core 1 and the injection mold 7.

Next, add 5 to 40% zinc by weight to this space.
% of tin and zinc and melted at a temperature of 250 to 400 [°C] is injected under normal pressure or vacuum. Particularly in the case of a narrow core with fine irregularities 2 and 3, degassing can be achieved very well by injecting in a vacuum state. As a result, a reinforcing layer 11 is formed, and this reinforcing layer connects the base core 1 and the injection mold 7.
are strongly connected and integrated.

Thereafter, both end surfaces of the thus obtained molded body intersecting the axis are uniformly ground using a lathe to expose the mother core 1 itself, that is, the aluminum core material.

Further, when the molded body is immersed in a caustic soda solution, only the base core 1, that is, the aluminum core material, melts, and a female shape having the same shape as the base core 1 is formed in the center of the molded body. The electroformed mother mold is completed.

〔Effect of the invention〕

As described above, the present invention is to apply plating to a predetermined thickness of a base core having an uneven surface on its surface so as to cover the irregularities, and then compare the base core with the outer diameter of the base core to a predetermined size. By inserting the mold into the center of the injection mold, which has a larger inner diameter, and then injecting the molten tin and zinc alloy into the space formed between the injection mold and the plated base core. Since the metal reinforcing layer is formed and then the mother core is melted, an electroformed mother mold having sufficient strength and heat resistance can be obtained in a short time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the manufacturing process of an electroforming mold according to the present invention, and FIG. 2 is a front sectional view. 1... Mother core, 2... Concave portion, 3... Convex portion, 5...
Plating layer, 7... Injection mold, 11... Metal reinforcing layer.

Claims (1)

[Scope of Claims] 1. After applying plating to a predetermined thickness to cover the uneven portions of a core having an uneven surface, the core is compared with the outer diameter of the core to a predetermined value. It is inserted approximately into the center of an injection mold that has an inner diameter that is larger than the above dimension, and then a molten tin and zinc alloy is poured into the space formed between the injection mold and the plated mother core at normal pressure. A method for manufacturing an electroforming mother mold, characterized in that the mother core is injected in a vacuum state, and then the mother core is melted. 2. The method of manufacturing an electroforming mother mold according to claim 1, wherein the mother core is made of aluminum. 3. The method of manufacturing an electroforming mother mold according to claim 1, wherein the alloy has a zinc content of 5 to 40% by weight. 4. The method for manufacturing an electroforming mother mold according to claim 3, wherein the alloy is melted at a temperature of 250 to 400 [°C]. 5 A plating layer applied to a base core having an uneven surface and covering the irregularity with a predetermined thickness, and an inner diameter that is larger by a predetermined dimension than the outer diameter of the base core to which this plating layer is applied. and a reinforcing layer made of an alloy of tin and zinc formed by injection under normal pressure or vacuum between the injection mold and the base core. Equipped with an electroforming mother mold. 6. The electroforming mother mold according to claim 5, wherein the mother core is made of aluminum. 7. The electroforming mother mold according to claim 5, wherein the tin and zinc alloy constituting the metal reinforcing layer has a weight ratio of 5 to 40% zinc. 8. The electroforming mother mold according to claim 5, wherein the tin and zinc alloy constituting the metal reinforcing layer has a weight ratio of 5 to 40% zinc.