Debinding and Sintering: The Critical Steps Behind MIM Part Density
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A MIM part straight out of the injection mold is only about 60% metal. The rest — roughly 40% by volume — is polymer binder, the temporary scaffold that makes the feedstock flowable at around 190 °C. Turning that green part into solid metal happens in two steps: debinding and sintering, and both decide the final quality.
Debinding removes the binder without disturbing the powder skeleton. In catalytic debinding, a gaseous catalyst rapidly dissolves the binder backbone at relatively low temperature; in thermal debinding, the binder is gradually decomposed by heat. Either way, the result is a fragile brown part — pure metal powder held together only by particle contact.
Sintering is where the part becomes metal. In vacuum furnaces or atmosphere-protected push-plate furnaces, the brown part is heated close to — but below — its melting point. Diffusion bonds the particles, pores shrink and close, and the part densifies. The volume shrinks substantially during this step, but the geometry is preserved, which is why MIM shrinkage can be engineered into the mold from the start.
The density target tells the story: relative density of at least 95%, and in production typically 98% or higher. In absolute terms, our iron-base parts reach 7.5–7.7 g/cm³, stainless steel 7.6–7.8 g/cm³, and pure copper above 8.4 g/cm³ — with mechanical properties comparable to wrought material.
This is also why debinding and sintering discipline matters more than any single machine. Incomplete debinding leaves carbon residue and blistering; poor sintering atmosphere control costs density, strength and surface quality. With more than 20 sintering furnaces across vacuum and atmosphere-protected types, we match each material platform to the furnace and profile it needs.