MIM Metal Injection Molding Process Chain and Material Systems

MIM metal injection molding combines the geometric freedom of plastic injection with the volume economics of powder metallurgy. A feedstock of fine metal powder and binder is molded into a green part, then debound and sintered at high temperature into a near net shape. Yujiaxin Tech runs MIM metal injection molding lines covering 316L, 17-4PH, 420 stainless, and iron nickel alloys, with stable batch volumes from tens of thousands to over a million pieces (see the process overview).

Feedstock and molding

The first step in MIM metal injection molding is feedstock preparation. Metal powder occupies 55% to 65% of the volume, the rest being wax and polypropylene binders. Median powder size sits between 5 and 20 microns, which sets the post sinter surface finish and strength. The molding stage reuses plastic tooling and can form side holes, helical teeth, and thin walls down to 0.3 mm, features that are hard to cut in one setup on CNC.

Debinding paths

Debinding removes the binder and opens pores for sintering. Three routes dominate: solvent debinding, catalytic debinding (nitric acid gas on a POM system), and thermal debinding. Catalytic cycles finish in 2 to 4 hours and suit thin walls; thermal debinding is more general but takes 10 to 30 hours. Uniformity in this stage drives later distortion and dimensional drift in MIM metal injection molding.

Sintering and shrinkage

Sintering in MIM metal injection molding runs at 1300 to 1450 degrees C in a protective atmosphere. The compact densifies through liquid or solid phase sintering, with linear shrink near 15% to 20%. Yujiaxin Tech controls final tolerance through cavity enlargement factors and sintering fixtures. Standard results reach ±0.3% to ±0.5%, and key features can tighten to about ±0.1 mm, comparable to ISO 2768 medium class (the quality system supplies the basis).

Material systems

MIM metal injection molding handles austenitic 316L (corrosion resistance, common in structural parts), martensitic 17-4PH (hardness adjustable from 28 to 42 HRC), 420 stainless (blades and valves), Fe-2Ni low carbon steel, and WC-Co hardmetal. Material choice follows strength, corrosion, and magnetic needs. MPIF Standard 35 defines MIM material properties (MPIF standard), and the full grade table is on the product page.

When to choose MIM

For parts weighing 0.1 to 200 grams, annual demand above 10,000 pieces, and complex geometry, MIM metal injection molding drives unit cost down steeply with volume. For lower volumes or very large parts, investment casting or CNC fits better, and the process selection guide explains the boundaries.

In short, MIM metal injection molding excels at complex small parts made in volume, because it folds several operations into one net shape step. If your part is in design validation or production ramp, contact Yujiaxin Tech for a feasibility check on materials and tolerances.

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