JPS5872424A - Manufacture of synthetic resin gear - Google Patents

Abstract

PURPOSE:To manufacture the titled gear having high strength and mechanical accuracy by cutting a cavity through an electric discharge machining by means of an electrode master, applying lapping machining and molding reinforcing material mixed synthetic resin by using a molding die grinding-finished for a cut end. CONSTITUTION:The machining-finished surface 3 of the cavity electrically discharge machined by using the electrode master 2 is lapping-machined, and the molding die to which a grinding-machined surface 4 is formed is obtained. Synthetic resin into which approximately 20% carbon fibers of potassium titanate, etc. are mixed as a reinforcing material is injected into the molding die, and the synthetic resin gear 1, a module thereof is 0.3% or lower and an outside diameter thereof is 10mm. or lower, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a synthetic resin gear having a module of 0.3 or less and an outer diameter of 10111 or less.

The ultra-small gears made of the synthetic resin described above are required to have greater mechanical strength and mechanical precision such as finishing dimensions of 9 dimensions than ordinary gears. To improve this mechanical strength,
When carbon fibers such as potassium titanate are mixed in as a reinforcing material, the desired strength can be obtained, but on the other hand, the shrinkage rate during molding changes, which poses a problem in the accuracy of finished dimensions.

The present invention provides a method for manufacturing synthetic resin gears that solves this problem. The present invention will be explained based on an embodiment shown in the figure below. The figure is an enlarged view of one tooth for explaining a gear mold, and the dimensions of each part are not proportional to the actual dimensions, but for the time being. The size relationship is shown as a guide. In the same figure, (1) shows the tooth profile of the gear to be manufactured, and in order to mold the tooth profile (1), it is necessary to process a metal block to manufacture the required female mold. Electrical discharge machining is usually used as a means for precisely machining this metal block. To perform electrical discharge machining, first a male mold is manufactured by precision machining the conductive material that will become the electrode. Same figure (2
) is this electrode master as a male mold, and when processing this electrode master (2), it is manufactured in a shape that is expanded to a certain size in anticipation of the shrinkage rate during molding. In this case, as a shrinkage rate during molding, as a result of many tests, when carbon fiber such as potassium titanate is mixed as a reinforcing material, the required mechanical strength can be obtained by setting the mixing ratio to about 20-. At the same time, when the mixing ratio of the carbon fibers was set to 0, which was required to have a constant shrinkage rate, the molding shrinkage was 3.5/1000. In other words, the electrode master (2) is 3
．． It is made larger than the molded tooth profile (1) with a ratio of 5/1000. (3) is the finished surface of the cavity, that is, the female mold, which was electrically discharge machined using this electrode master (2), and it can be seen that it is actually finished to have almost the same dimensions as the electrode master (2). This finished surface (3) is microscopically rough because it is melted and cut by electric discharge. It may be molded as is in a normal mold, but by mixing the above-mentioned carbon fibers, the shrinkage rate can be made relatively small, and if this is done, release from the mold will be extremely difficult. Therefore, the above finished surface (3)
The cut end is then lapped to obtain a desired mold (4) with a so-called polished surface (4).

As explained above, the desired mechanical strength is obtained by mixing 20% carbon fiber such as potassium titanate as a reinforcing material into the synthetic resin material during molding, while the shrinkage rate during molding, i.e. 3.5/1000
Electric discharge machining is performed using an electrode master (2) in anticipation of the molding process, and the finished surface (3) is lapped to create a polished mold (4), which improves mold release during molding. As a result, it is possible to obtain an ultra-small gear having sufficient mechanical strength and high mechanical precision.

[Brief explanation of the drawing]

The figure is an enlarged explanatory diagram of a main part showing the relationship between a gear and a mold according to a synthetic resin manufacturing method according to an embodiment of the present invention. In the same figure

Claims (1)

[Claims] In synthetic resin gears with a module of 0.3 or less and an outer diameter of 108 or less, carbon fiber such as potassium titanate is mixed as a reinforcing material, and the ratio of the reinforcing material is about 29 to obtain a constant shrinkage rate. , a synthetic resin gear characterized in that it is made using a molding die in which the edge of a cavity is cut by electrical discharge machining using an electrode master corresponding to the above-mentioned shrinkage ratio, and the cut end is polished. Production method.