Advantages of MIM
Metal Injection Molding (MIM) is a net shape process for manufacturing complex metal parts at high volumes. The MIM process competes with cutting processes, press sintering as well as investment casting. Compared to cutting or press sintering of simple, rotational symmetric geometries MIM shows clear disadvantages in terms of cost aspects. In contrast, the innovative process is clearly advantageous when high volumes are combined with complex geometries, special requirements regarding material properties and high precision. Furthermore, this technique reduces post-processing to a Minimum.
Large freedom in design
The MIM process offers a freedom in design known from the plastics industry. Drill holes, threads or labeling, like logos can be easily integrated into the MIM tool and enable net shape parts directly out of the tool. Entire assemblies that were previously only producible by mounting multiple components can be made in one shot with MIM.
Excellent material properties
Sintered MIM parts have a homogeneous microstructure with densities > 96% and are free of internal stresses. The density of the parts is homogeneous and free of gradients in contrast to sintered parts from the often mixed up press sintering process. Mechanical properties are well comparable to that of sheet material.
High surface quality
Surface roughness of MIM parts is better than that of investment cast parts. A roughness of Ra = 4 µm is well achievable without additional grinding or polishing steps. Post-processes like tumbling, grinding and polishing can be applied if higher surfaces qualities are required. Even mirror finish can be realized on the pore free surface of MIM parts.
Tolerances of sintered MIM parts are narrow, very reproducible in the process but are geometry dependent. Minimum tolerances are as low as ± 0.05 mm for geometries < 3 mm. For larger parts (> 60 mm) a thumb rule for the tolerance is 0.5 % of the nominal length.
A broad range of materials is available for the metal injection molding process. Nearly every alloy that can be atomized as a powder can be processed. MIM is especially interesting for materials that are not easy to machine or that are expensive. Standard materials for serial production in the portfolio of MIMplus Technologies are stainless steels, low-alloyed steels, tool steels, soft magnetic alloys and also lightweight metals like titanium. Furthermore we offer Nickel based alloys, hard metals as well as copper. Our research and development department is focused on developing of innovative and new MIM materials that are not available so far. This includes permanent magnetic alloys (e.g. NdFeB) or complex composite materials.
As shown in the upper graph MIM is especially relevant for complex high volume parts. This is because the process is a tool-bound process and costs for the mold need to amortize over number of parts. This may vary between several thousand up to millions of parts, depending on the complexity of the mold.
For cost intensive materials this net shape process is economically very attractive, since no waste material is produced during shaping. Green parts that were produced during starting cycles or the gate of molded green parts can be regranulated and reused without any loss of material quality. This makes MIM to a “green” process.