Powder Metallurgy
Powder metallurgy (PM) is a manufacturing process that forms metal parts from fine metal powder by compacting it in a rigid die and then sintering it below the melting point to bond particles into a solid component. It is a near-net-shape process with high material utilization, often above 95%, suited for repeatable medium-to-high volume production.
On a CNC or manufacturing floor, PM is selected when part geometry is stable, quantities are high, and material waste must be minimized. The typical sequence is powder blending, die compaction, sintering, then secondary finishing such as sizing, heat treating, or plating when tighter dimensions or surface properties are needed. Compaction occurs in a rigid die at roughly 400–800 MPa, producing a green compact that is sintered in a controlled furnace at about 70–90% of the metal's melting temperature. Compared with CNC machining, PM eliminates most chip waste and gives higher throughput, but tooling costs are justified only by volume. As-sintered tolerances commonly fall around IT8–IT9, improving to IT6–IT7 after sizing, with surface finishes around Ra 1.6–3.2 µm. Critical functional faces often still require secondary machining, so process engineers treat PM as a near-net-shape production method rather than a complete finish-machining replacement.
Is powder metallurgy additive manufacturing?
In common manufacturing practice, PM is usually classified as a forming and sintering process, not powder-bed additive manufacturing; it compacts powder in a die rather than selectively fusing powder layer by layer.
Why is PM economical at volume?
Because the part is produced close to final shape with minimal machining, so material utilization is high and per-part labor drops sharply after the die cost is amortized.
When is CNC machining still the better choice?
CNC is usually better for low-to-medium volumes, prototypes, frequent design changes, tight tolerance features, and parts that need full cutter access or complex re-entrant geometry.