How MIM is revolutionizing traditional manufacturing?

Metal Injection Molding (MIM) has both similarities and differences to traditional Powder Metallurgy (PM). Comparatively Metal Injection Molding has a competitive advantage for manufacturing small precision components which would be costly to produce by alternative methods. Metal Injection Molding holds a higher ground when it comes to perfection, delivery time, efficiency, and operation. It is effective in both small and large volumes, creating complex shapes from all types of materials including metals, ceramics, intermetallic compounds, and composites is much easier.

The base step involved is similar in both processes, when it comes to pulverizing metal into powder, the only difference is the irregular shape and size of the powder and this is due to the water atomization process. In the Metal Injection Molding process the powder is equally distributed and spherical in shape due to the requirements of flowability, and this is achieved through a gas atomization process.

MIM is a development of the traditional PM process, thereby rightly constituted as the branch of that technology. The standard PM process involves compacting lubricated powder mix in a rigid die by applying pressure on it, the mold is then ejected from the die. There is a limitation to this process, after the compaction process, the part must be ejected by pushing it out of the cavity. It is obvious that parts with undercuts or projections might not be made at right angles to the pressing direction.

Although the technique is derived from traditional plastic injection molding which has been known and applicable for many years, most of us come into contact with them in some or the other way every day. However, despite its low cost of production, the engineering dynamics of thermo-plastic have inadequate mechanical properties. Therefore, innovations and improvements were made by using solid fillers such as ceramic and metal powders.

The real breakthrough happened when it was found possible to incorporate a very high volume fraction of metal powder so that instead of a filled plastic part, a plastic-bonded metal or ceramic part is produced. The removal of plastic binders leaves a skeleton of metal/ceramic which, although fragile, can be handled safely and sintered in a much similar way as the traditional die-compacted parts. Post-sintering the density reaches up to 95% or more, making Metal Injection Molding superior to traditional techniques.

MIM has an advantage over conventional PM as far as density is concerned. The ‘green part’ formed during the process has a high density of binders, this eliminates the possibility of shrinkage, non-uniform density, and porous components. The viscosity of the mix at the molding temperature should be constant and flow smoothly for even distribution of materials without any segregation. The mix will be more rigid after cooling down.

Feasibility- Metal Injection Molding does not generate material waste and scrap like traditional machining techniques. This is beneficial in using high-quality and expensive raw materials like titanium alloys, super alloys, and speciality metals. The process helps in converting the majority of the material into usable metal parts.

Surface Finish- The surface finish with MIM is far better than traditional techniques. It provides significantly smoother surfaces for the end product. The method, requirements, and standards of surface finish should be decided by vendors and customers. If needed, the surface can be enhanced even more with the additional process.

Size and cost- Theoretically, there is no limit to the maximum and minimum size of components with Metal Injection Molding. The cost can differ with the requirements, larger and thicker parts require more raw materials which might require more cost. The important benefit here is the volume of components to be manufactured, if the production amount crosses a certain number depending on the thickness and size, then it is more feasible to adopt Metal Injection Molding.

Dr Ravi Bollina is an authority in Semiconductor Technologies, Additive manufacturing, Metal Injection Molding (MIM), and Material Sciences. He also works in the areas of Diamond based abrasives, micron diamond powders, diamond paste and diamond slurry, and custom diamond-based grinding wheels.His areas of expertise include Diamond powders, Diamond slurries, Semiconductor fabrication, Power Electronics, Thermal Management, Aerospace, Lighting industry, LED, Micro-Electronics, Opto-Electronics, Defense Technologies & Manufacturing.

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