How to make metal molds

High tolerance accuracy, no flash, super high surface quality, all these standards are some of the requirements that must be met in the manufacturing process of metal parts die-casting molds. There is no doubt that although there are a few metal mold manufacturers that can reach this level, there are very few. Quality is the key. First of all, the design of the mold must have a good plan. Because this is the basis and key to success or failure. It should include an excellent cooling water circuit layout and parting line locking device to prevent the dislocation of the mold during processing and production, a pair of mold frames that can well support the mold cavity and core side walls, and a mold frame suitable for specific parts. The method of the model. The detailed design includes the selection of mold parts materials, mold and cavity tolerances, surface quality and coating, gate and runner size, vent position and size, and pressure sensor position. In the successful manufacturing of MIM molds, demolding and cooling have become key issues.

1. Steel used for cavity/core:

The steel used in the cavity/core should be able to withstand the wear caused by the molding material. All steel materials (including gates and runners) in contact with molded composite materials should be made of high wear resistance, high chromium content and high hardness tool steel, such as D-2 or A-2 tool steel. H-13 steel is also available, because of its high hardness, it is also electroplated with a high-hardness coating. Any detailed parts that do not come into contact with the molded composite material can be made of more standard S-7 tool steel. (Guide: The advantages of high-speed milling mold CNC machining center are beginning to show)

2. Closing angle/slider:

In the MIM mold production process, flash is a serious problem, and it is a substantial problem for mold workers. In order to prevent this kind of problem, a good fit of all closing corners and sliding areas is very important. Only in this way can a high-quality MIM part be produced. The mold manufacturer must calculate the rolling size by using the triangulation method, and then use this knowledge to check the closing angle of the steel on the female and male surfaces to ensure that it is within the ±0.0001 tolerance range of his calculated size. The tolerances that people need to maintain are generally quite accurate for metal molds, because the feed parts of MIM molds are very sensitive to flash, which is easy to produce flash. If the plastic part has flash, it is easy to remove the flash, but if it is metal, the flash will cause problems like a blade. You must make a mold that will not produce flash.

3. Depth of vent:

In various molds, in order to release the internal gas generated by the molded material, it is very important to use a good vent. He pointed out that MIM molds are very different from injection molds in terms of vent depth. A typical plastic mold, depending on its molding resin, may have 0.0005~0.002in (1inu003d25.4mm) deep vents everywhere, and MIM molds will definitely produce flashes in the depths of these vents, MIM molds The depth of the vent is generally between 0.0001 and 0.0002in, but it may also vary with the selection of different molded composite metal materials. Good feed material has very low shrinkage during the subsequent solidification process. In order to strengthen the shape retention as much as possible, a large number of metal powder fillers are used, and the amount is often close to 70% of the volume. In order to obtain good fluidity of high-filled feedstock, low-molecular-weight molecules and binders are used to make MIM feedstock produce high flash sensitivity, similar to the characteristics shown by many filled nylon materials. Paraffin and polyethylene/glycerol-based feeds have better characteristics than acetyl feeds, but will affect their higher flash sensitivity.

4. Polishing:

Another key area of u200bu200bMIM parts is the surface quality of the compression molding area. Demolding 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 compression molding process. The shrinkage of the metal molded part does not actually occur unless the binder material is extracted through the post-compression molding process. Therefore, the polishing of the compression molding area is very critical. Generally speaking, the molded surface should reach a composite finish of 600, and diamond finish may be required in rare cases.

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