The MIM mold is composed of three parts: gating system, forming parts and structural parts. The gating system and forming parts are the parts that directly contact with the feed of the mold filling.

1、 Gating system: refers to the runner part before molten materials enter the mold cavity from the nozzle, including the main runner, cold material cavity, splitter channel and gate. The main channel refers to a section of channel from the nozzle to the split flow or cavity, which is generally conical and concave at the top to connect with the nozzle; The cold charge cavity is a cavity at the end of the main runner, which is used to cover the cold charge generated between two injections at the nozzle end to prevent blocking the runner and gate; The splitter channel is the channel between the sprue and the gate, which is generally used in the mold with multiple cavities; The gate is the connection point between the runner and the mold cavity. The molten material enters the mold cavity through the gate for forming.

2、 Formed parts: refer to various parts forming the shape of products, including moving die, fixed die, cavity, core, forming rod, exhaust port, etc. The moving mold is installed on the moving template of the injection machine, while the fixed mold is installed on the fixed template of the injection machine. When working, the moving mold and the fixed mold are closed, and the core and parting cavity form the cavity of the mold. The air outlet is a grooved air outlet opened in the mold, which is used to discharge the gas brought in by the melt.

3、 Structural parts include guide, demoulding, core pulling and parting parts, such as front and rear buckle templates, pressure bearing plates, guide columns, demoulding templates, demoulding rods, etc. The guide part is to ensure that the moving die and the fixed die can be accurately aligned when they are closed. The guide part must be set in the die for positioning; The demoulding part is used for pushing out formed parts and resetting; Some products with complex shapes usually need to design the core, which can be demoulded smoothly after the core is drawn out.

With the rapid development of MIM technology in China, many traditional plastic mold manufacturers have started to make MIM molds, and more manufacturers are concentrated in Kunshan, Suzhou. In a sense, MIM mold has been developed by leaps and bounds. But the application scope of products is becoming wider and wider, and the requirements are getting higher and higher. The manufacturing and design process of MIM mold must also be constantly improved to meet the needs of product development.

At the same time, the MIM mold extremely tests the processing ability of the equipment. Most of the molds made by domestic equipment are about 5 wires. Recently, I visited a dust-free mold workshop with an accuracy of 0.2-0.5 wires, which is an advanced mold workshop in China. The mold has a very high requirement on the equipment, and the designer should pay attention to the selected materials and mold details to make a qualified mold.

1. Steel used for cavity/core

The steel used for the cavity/core shall be able to withstand the pressure caused by the wear of the formed material. All steel (including gate and runner) in contact with formed composite materials shall be tool steel with high wear resistance, high chromium and high hardness, such as D-2 or A-2 tool steel.

2. Closing angle/slider

In the process of MIM mold production, flash is a serious substantive problem. In order to prevent such problems, it is important that all closure angles and sliding areas are well matched. Only in this way can high-quality MIM parts be produced. In the manufacturing of MIM dies, the rolling dimension must be calculated by trigonometry, and then the closed angle of the steel on the male and female surfaces shall be checked with this knowledge to ensure that it is within ± 0.0001 tolerance.

3. Exhaust port depth

In various molds, it is very important to use a good exhaust port in order to release the gas generated inside the molding material.

4. Polishing

Another key area of MIM parts is the surface quality of the molding area. Demoulding from the mold cavity area largely depends on the surface quality of the mold cavity and core tool steel, because the shrinkage rate is extremely low during the molding process, and the shrinkage of the metal molding part will not really occur unless the adhesive material is extracted through the post molding process. Therefore, the polishing of the formed area is very important.

5. Electroplating

High hardness coatings such as chromium plating or nickel plating will improve the efficiency of the demoulding process of formed metal parts, combined with high polished surfaces, so that they can have a better impact. Some types of chromium and nickel are added mold release agents to improve their mold release.