Metal Injection Molding vs Machining

In similarities, Metal Injection Molding is able to produce finished components with same mechanical properties as machined parts. Typically, MIM parts can be applied in the same area as machined parts, such as medical, electronic, industrial and automotive. In special cases, MIM parts has similar surface appearance as machined parts.

In the following table, we summarize the main properties of Metal Injection Molding (MIM) vs Machining:

There are a few key differences between MIM vs Machining, all these elements will assist you to figure out the most suitable methods for your specific project requirements.

MIM can satisfy unique geometry and complexity capability requirement in any MIM parts. In addition, parts consolidation is widely used in MIM design process to produce one single part with desired features. By contrast, machining only can provide limited intricacy, design freedom and flexibility. It is difficult to produce complex structure, the cutting tools need sufficient working space for interior features. As we know, complex parts structures will need more machining time, which will no doubt increase total cost. While MIM is the most cost-effective way, its cost will never affect by parts geometries.

Although MIM and machining both can produce high strength metal parts with excellent mechanical properties. We should notice that MIM parts never need to endure induced stress or internal pressure in manufacturing process. For special design parts, these stresses and pressure in machining process will result in part deformation and failure. MIM parts are injection molded by conventional ways, then sintered in furnace, finally create a solid strong metal components. Therefore, MIM process will never create any stress or pressure to final parts.

Metal injection molding applies metal feedstock for injection molding process. Powdered metal feedstock is molded at high temperature and pressure to create small precision parts in large quantities. Therefore, it is suitable for small size metal components with sophisticated shapes and high precision. In addition, this technology provides high mechanical properties, strength, ductility, and magnetic response.

In reason of the flexibility of MIM technology, we also can customize MIM materials’ composition by customers specific attributes. Our common metal injection molding materials are stainless steels, low alloy steel, copper alloy, titanium alloy, nickel alloy, and tungsten alloys.

MIM is ideal for high volume production of small and complex geometric metal parts. It can achieve 96% to 99% density, or 100% density after Hot Isostatic Press (HIP) treatment. Furthermore, it also has a significant lower cost than machined metal components.

In MIM production process, the part complexity are always determining the final mold investment. Complex parts design requires indeed molds with complex insider cavities, in order to satisfy parts formation in injection molding process. Therefore, molding cost is an upfront cost before manufacturing process. Otherwise, with machining method, the main factor affect cost is process time, any complexity of parts will increase process time, and finally increase extra cost.

In machining way, the removal of metal material from the block is obvious material scrap, and this is inevitable because of its manufacture way. However, MIM will never create any material scrap in process, so you can save cost in total.

Machining needs long time to produce complex parts. Once you need high volume capacity, the only way is buying more CNC machines for more production. Otherwise, we have the most effective way to increase MIM capacity without any new machines purchase. Just need to plan our MIM parts production process in high volume production schedule.

Therefore, metal injection molding is suitable for automated production in large quantities with consistent quality. But machining is typically well-suited for lower production volumes with complex shapes and tighter tolerances. In normally, there are quite minimal finishing operations with MIM as less critical tolerances’ requirement in final applications. Although the initial investment of MIM molding is tremendous high, this cost is recovered quickly in high-volume production.

Metal injection molding has expected tolerances from ± 2 % to ± 0.4 %, all the final tolerances depend on detail feature size. In reason of shrinkage error in debinding and sintering, the larger features will result in the larger tolerances. As we know, the typical shrinkage in sintering process are from 15 % to 18 %. Non-isotropic is another factor affects the expected tolerance. Furthermore, gravity will cause more shrinkage on the vertical direction, while drag forces will result in less shrinkage on the lengthwise direction.

However, as machining has precise control on milling and turning tools, there are higher tolerances of final machined parts.