For long, investment casting has been a widespread metalworking technique. Investment casting is the process by which molten metal is poured into a mold made of a wax pattern, which is then melted. However, it has many disadvantages. For one, it is an expensive process. As a result, the profit margin is low. Also, it is a wasteful process, and its quality of precision and volume of production leaves a lot to be desired. This is where metal injection molding comes into the picture. Metal injection molding, or MIM, has set itself as a worthy successor to the traditional form of casting.
Metal Injection Molding is used in building net-shape metal parts. The process involves combining ultra-fine metal powders and a polymer binder system to create a feedstock suitable for injection molding. These binders are later removed, and the remaining powders sintered to acquire the final product. MIM is best used for parts with complex shapes, low mass and moderate to large production volumes. The materials available from this process include low alloy, stainless and tool steels, and soft magnetic and superalloys. MIM is widely is practice for part of all major sectors, including aerospace, automotive, electronics, and the rest.
There are a few factors which make Metal Injection Molding indispensable: While the investment casting process delivers superior or comparable results in a variety of materials, tensile strength, density, hardness, and elongation, etc., Injection Molding can offer added advantages in a few other areas.
Surface Finish & Precision
MIM allows for more complex designs and greater precision. It is also better suited to making parts that are lighter than 20g, and smaller than 100mm. MIM can achieve a surface finish of 1 (µm), compared to 3.2 (µm) by investment casting.
Complexity & Part Size
MIM allows for more complexity in design a product such as thinner wall sections, sharper cutting points and tighter tolerances of up to +0.005″ per linear inch – as compared to the investment casting process.
Low Wastage
In MIM, almost 95% to 98% of raw material or feedstock is turned into the finished product so as a result, the generation of scrap or wastage is MIM is very low, which is one major advantage of MIM.
Lesser Manufacturing Processes
MIM produces products of complex geometries yet with lesser processes, which is a great advantage of MIM. With MIM one can avoid machining processes like threading, grooving, gripping patterns, insignias, emblems and pores or lubrication channels. MIM also extends an additional advantage of minimum finishing time in secondary operations like plating and heat treating.
Low Cost of Production
With the elimination of multiple manufacturing setups and processes for small and intricate components, MIM reduces the cost per component. Also with the low wastage rate, MIM is a cost-effective process as compared to investment casting.
Process of Mass Production
MIM provides high equipment productivity compared to conventional tools. MIM supports the mass production of tiny materials with unlimited shape and micro geometric nature without compromising high production volume. It is considered an ‘economy of scale’ technology, ideal for large scale production of to the scale of 1,50,000 to 2,00,000 parts per day using a multi-cavity system which is relatively a big number by deserving high accuracy and ultra-precision as its key driving factors.
So, overall there is momentum in the use of MIM as compared to investment casting processes as it is the process of choice to produce large volumes of small, highly intricate parts made of high melt alloys, where finish and tolerance are critical.