Preparation method of negative pressure mold for mobile phone middle frame forming in metal injection molding (MIM) process

Abstract

The invention relates to a preparation method of a negative pressure mold for mobile phone middle frame forming in a metal injection molding (MIM) process. The preparation method comprises the following steps of (1) analyzing a final filling area of a cavity of a mobile phone middle frame mold; and (2) processing at least one exhaust hole communicating with the outside and a filling area cavity atthe mold part corresponding to the filling area cavity in the step (1), wherein an air outlet of each exhaust hole is connected with an air inlet of a pneumatic needle valve, an air outlet of the pneumatic needle valve is connected with a vacuum pump through an air pipe, and each exhaust hole is controlled by the pneumatic needle valve so as to open and close. The preparation method of the negative pressure mold for mobile phone middle frame forming in the MIM process provided by the invention has the advantages that large-size mobile phone middle frame stainless steel products are injected and produced through the negative pressure cavity mold, so that the product quality is high, the injection demand pressure is low, the machine table loss is less, and the equipment life is long.

Description

technical field [0001] The invention relates to a method for preparing a middle frame of a MIM mobile phone. Background technique [0002] With the continuous advancement of social science and technology and the vigorous development of global industrialization, the powder metallurgy injection molding process has developed rapidly due to its many advantages, and its technology has been widely used in military, transportation, machinery, electronics, aviation, aerospace and other fields. [0003] Stainless steel is one of the most widely used raw materials in the powder metallurgy industry. Due to its many advantages such as corrosion resistance and high strength, it is widely used in the mobile phone industry. Among them, the stainless steel mobile phone middle frame has invested a lot of money in the development of domestic MIM factories. , has been gradually replaced by the traditional machining process to the MIM process. It is the current highlight product in the MIM indu...

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Problems solved by technology

[0003] Stainless steel is one of the most widely used raw materials in the powder metallurgy industry. Due to its many advantages such as corrosion resistance and high strength, it is widely used in the mobile phone industry. Among them, the stainless steel mobile phone middle frame has invested a lot of money in the development of domestic MIM factories. , has been gradually replaced by the traditional machining process to the MIM process. It is the current highlight product in the MIM industry. Because the advantage of the MIM process is the production of smaller product parts, for larger products such as mobile phone frames, There are still certain difficulties, especially the injection molding of the product, because the product is large in size, and a variety of molding agents (polyoxymethylene, paraffin, polyethylene, etc.) with different melting points are evenly mixed in the feeding material. Under the high-temperature, high-pressure, high-speed injection screw propulsion of the injection machine, and the pressure difference shearing between the hot nozzle flow channel and the plastic inlet channel of the injection nozzle, a large amount of gas is easily generated during feeding, and the ordinary exhaust groove of the product cavity cannot meet the large amount. The gas is discharged, the pressure of the cavity is getting higher and higher, and the feed material is not well fused in the cavity, and finally the product has various defects such as material shortage, melting lines, flow lines, black lines, and uneven density in the area, which seriously affects The quality of the product after sintering hinders the development of the industry