Investment casting vs MIM: a complete guide

If you're looking to create high-quality metal components and can't decide between metal injection moulding (MIM) and investment casting, you aren't alone. Many businesses struggle to choose the best metal manufacturing process, knowing it will ultimately affect their profitability.

What is metal injection moulding?

MIM is a unique hybrid technology combining the processes of powder metallurgy and plastic injection moulding. It begins when ultra-fine metal powders are mixed with a primary paraffin wax material and a secondary thermoplastic polymer. The final mixture is extruded and chopped into tiny pellets called "feedstock", which are then heated before being injected into a mould cavity under high pressure. It is a technique that delivers tighter net-shape tolerances over high production runs, making it possible to produce extremely complex components with enhanced surface finishes.

What is investment casting?

Investment casting, also known as lost-wax casting, begins with the creation of a wax injection die. Wax patterns are grouped and assembled onto a sprue to form a complete mould. The mould is then coated with layers of ceramic slurry and rapidly dried to harden the shell. Once dry, the mould is put into an autoclave to remove the wax from the mould. Molten metal is then added to the mould and allowed to cool. Finally, the shell is removed with high-pressure water jets to reveal the final precision part.

Material options – which process is best for certain alloys?

Both investment casting and metal injection moulding produce strong, durable parts using a wide variety of alloys. For MIM, OptiMIM's distinguishing factor is custom feedstock and the ability to specify metal particle size distribution and develop unique binder compositions. This makes the process fully customisable to deliver the final mechanical performance and properties your application requires. This also ensures that parts are more structurally sound, more reliable and less prone to embrittlement (cracking).

OptiMIM specialises in various ferrous and non-ferrous alloys, including several stainless steel grades, copper and low-alloy steel components, which make up about 70% of our business. Specialty alloys, such as Cobalt-Chromium (F-75) and other high-alloy materials, are also available.

Investment casting is such a versatile manufacturing solution in part because the material options are nearly endless. At Signicast, we pour everything from 400-series stainless steel and plain carbon steel to nickel and aluminium. This wide array of materials helps deliver corrosion resistance, increased tensile strength and ductility.  The availability of material options means that you do not necessarily have to sacrifice one element of a design in favour of lowering cost, and the versatility means we can more easily resolve traditional casting challenges in design, production, cost control and delivery. 

Part size and quantity – what is achievable?

MIM is ideal for producing large batches of small parts, roughly a half pound or smaller. In fact, most MIM parts fit in the palm of your hand down to a single grain of rice. Investment casting, on the other hand, is best suited for smaller lot sizes of large parts that are half a pound to 250 pounds, making it a cost-saving alternative to machining from solid. When it comes to IC, think larger parts and smaller lot sizes. Both processes scale very well; however, MIM is the clear winner in terms of achieving high volumes - typically 10,000 parts or more - as this technology is a batch-driven process.

IC weight capability: 3g - 250 lbs

MIM weight capability: .05g - 35lbs

Common applications and designs – which industries are served?

The MIM process is known for producing incredibly dense, precise parts with high strength and wear resistance, making it ideal for medical and dental manufacturers looking to meet strict regulatory requirements. In addition, scalability and heat resistance make MIM an excellent solution for automotive applications. Our ability to create parts from custom-formulated alloys means we can deliver precisely the required performance characteristics.

Signicast's complex casting capabilities, rapid prototyping and secure supply chains make it the perfect solution for a variety of industries. Stainless steel is especially effective for industries requiring high strength and temperature resistance, such as  aerospace and defence applications. Our specialised processes allow us to address specific needs – such as thin-wall casting for a lightweight, streamlined design in medical and dental instruments or part consolidation in locks, hardware and recreational vehicles.

To learn more about the capabilities of investment casting and metal injection moulding, download our free, on-demand webinar on IC vs. MIM by completing the form below.