MIM Parts

MIM parts are metal components molded from a metal-powder feedstock and then sintered to full density, so complex geometry such as gear teeth, cross-holes and undercuts forms in one cycle instead of several machining setups. Ningbo Precision Tech produces custom MIM parts from 0.1 to 150 g in stainless, low-alloy, titanium, tungsten and soft magnetic alloys.

What kinds of parts MIM makes well

MIM pays off where a small metal part is complex, runs in volume, and would otherwise be machined feature by feature or assembled from several pieces. Five families cover most of what we ship:

• Drive and motion parts — gears, sprockets, pawls, ratchets, cams, bearing cages.
• Lock and mechanism parts — cylinders, deadbolts, slide tongues, hinge components.
• Medical and instrument parts — forceps jaws, surgical clamps, device housings, small implant components in titanium.
• Magnetic and thermal parts — soft magnetic cores, pole pieces, copper heat-sink components, Kovar parts.
• Wear parts — cemented carbide nozzles, thread guides, tungsten-heavy inserts.

Complexity is nearly free in the mold: a part with four machining setups on a bar stock usually becomes one molding cycle plus one finishing operation. What MIM does not do well is very large parts, thick sections, or single-piece prototypes — those stay with casting or CNC.

Typical MIM parts by industry

Industry	Typical parts we mold	Where to look
Automotive & bicycle	Oil-pump gears, brake components, derailleur pawls, positioning ratchets, slider parts	Automotive & bicycle parts
Precision machinery	Toggle forks, needle-threading inserts, linear bearing cages, drive gears	Precision machinery parts
Medical equipment	Forceps jaws, hemostatic clamp parts, diagnostic device components, aesthetic device parts	Medical device parts
Consumer electronics	Smart-lock cylinders, deadbolt mechanisms, bevel gears, slide tongue holders	Consumer electronics parts
Aerospace & military	Triggers, locating pins, power-tool gears and pawls, air-gun valve parts	Aerospace & defence parts
Outdoor sports	Bow release triggers, arrow inserts and nocks, fishing reel components	Outdoor sports parts
Carbide	WC-Co nozzles, threaded carbide connectors, wear inserts	Cemented carbide parts

Materials for MIM parts

Stainless steels (316L, 17-4PH, 420, 440C, 304/SUS304), low-alloy steels (Fe-2Ni, Fe-8Ni, 4140, 4340, case-hardened 8620), tool steels (M2, D2), nickel and cobalt alloys (Inconel 718, Hastelloy X, Co-Cr F75), titanium (CP Ti, Ti-6Al-4V), cemented carbide (WC-Co), tungsten heavy alloys (W-Ni-Fe, W-Ni-Cu), soft magnetic alloys (Fe50Ni, Fe-Si) and copper or Kovar for thermal and electrical parts.

Grade-by-grade tensile data is on MIM material properties; the application matrix is on MIM materials and applications.

What a MIM part can hold

Parameter	Capability
Part weight	0.1–150 g typical; up to 250 g demonstrated
As-sintered tolerance	±0.3% of dimension; ±0.5% on complex net-shape features
With secondary machining	±0.1% on selected features; bores to H7
Minimum wall	0.3 mm; under 6 mm recommended
Sintered density	>97% typical
Surface, as-sintered	Ra 0.8–1.6 µm; below Ra 0.4 µm after electropolishing
Finishing	Heat treatment, hardening, plating, passivation, tumbling, CNC touch-up, assembly
Batch	Prototypes 500–1,000 pcs; production 10,000+ pcs/year
Lead time	5–8 weeks from design release to tooling and samples

From drawing to serial part

1. Send a drawing or STEP file. Include tolerances, material, surface and annual volume. A photo of the current machined part is often enough to start.
2. DFM review, 2–3 days. We flag walls that are too thin, features that need secondary machining, gate positions and where the design costs money for no function.
3. Quotation. Piece price at your volume plus tooling by cavity count, with the volume where MIM beats your current routing.
4. Tooling and first articles, 4–6 weeks. Mold build, trial shots, dimensional report and samples for your inspection.
5. Serial production. SPC on critical dimensions, material certificates per lot and change control.

Ready to price a part? Send the drawing — DFM feedback and an indicative piece price come back together.

Frequently asked questions

What is the smallest and largest part you can mold?

From 0.1 g micro parts up to 150 g typical; 250 g has been demonstrated. Above roughly 250 g, casting or machining is usually the better route.

How many MIM parts do I need to order?

Prototypes from 500–1,000 pieces. Production economics turn at 10,000+ pieces per year; below that we still quote and will say if CNC is cheaper.

Can you match the material of our current machined part?

In most cases yes. 316L, 17-4PH, 420, 440C, low-alloy steels, titanium and soft magnetic alloys are standard for us; send the spec and we confirm the sintered equivalent.

Do you do the finishing and assembly as well?

Yes — heat treatment, hardening, plating, passivation, tumbling, CNC touch-up and assembly are handled or managed in one place.

How do you guarantee the tolerance on a MIM part?

As-sintered ±0.3% is standard, ±0.1% on selected features after machining. First articles come with a dimensional report, and serial parts run under SPC on the critical dimensions.

What do you need to quote a MIM part?

A 2D drawing with tolerances or a STEP file, the material, surface requirement and annual volume. If you have a target price, include it — it tells us where to focus the DFM work.