MIM part cost is mostly decided before the first shot: uniform walls in the practical 0.5–6 mm band, solid sections cored out, side actions counted and justified, and tolerances held only where function demands them — these four design moves typically move price more than any negotiation that follows. Process economics do the rest: tooling amortization dominates at low volume, so at a few thousand units the design choices that simplify the mold are the ones that cut the quote. The levers below are ranked roughly by how often they appear in real cost-reduction reviews.
This page walks each lever with the reasoning and the numbers behind it — what it saves, what it risks, and how it interacts with the tooling economics covered in the MIM tooling cost guide.
Lever 1: Uniform Walls and Honest Thickness
Thickness is the master variable. Walls in the practical band (about 0.5–6 mm for common parts, with the economical sweet spot in the lower-middle of that range) fill cleanly, debind and sinter predictably, and hold tolerance without intervention. Thick sections do the opposite on every axis: more feedstock, longer debind, longer sinter, and a distortion and void risk that turns into scrap — which is why practical upper guidance commonly sits around 12–15 mm before a design is better off redesigned. The mechanics are detailed in the uniform wall and coring guide.
When thickness change is unavoidable, make it gradual — published rules of thumb cluster around a taper of about 1:3 and a thick-to-thin ratio kept at or below 2:1. Abrupt steps concentrate sintering stress exactly where the section changes, and that is where distortion begins.
Lever 2: Core Out Solid Sections
A solid boss is the most expensive way to buy height: you pay for the powder in it, the furnace time through it, and the distortion risk inside it. Coring the same envelope to a uniform wall keeps stiffness in the outer geometry, cuts mass, shortens cycle time, and improves dimensional stability — usually at zero tooling penalty, because the core is a simple steel pin. Ribs restore stiffness where coring removes too much, at a fraction of the mass they replace.
- Cored geometry is usually cheaper than solid sections of the same envelope — material, debind and sinter time all scale with mass.
- Ribs and bosses tie back to the same uniform-wall rule: their thickness should relate to the adjacent wall, not stand alone.
- Every gram removed from a high-volume part is paid back thousands of times — mass reduction is the quiet compounding lever.
Lever 3: Count Your Side Actions
Undercuts, holes perpendicular to the mold opening, and internal threads need mechanisms — side cores, lifters, unscrewing devices — and those mechanisms are where simple molds become expensive ones. Published guidance puts side-action additions at roughly 15–30% of tooling cost, per mechanism. Sometimes the feature is worth it; often the same function is available with a redesign (a slot instead of a cross-hole, a two-part assembly logic, a secondary drilling operation on a non-critical hole). The undercut design space is mapped in the undercut guide — the cost question is answered here: each mechanism avoided is tooling money returned, every shot.
Lever 4: Tolerance Only Where Function Lives
As-sintered MIM holds roughly ±0.3–0.5% of dimension; sizing or repressing tightens critical features toward about ±0.1%; machining after that for the few dimensions that truly need it. The cost ladder is steep, so the discipline is: let the sintered tolerance carry every dimension it can, reserve secondary operations for the interfaces that function names (seats, bores, alignment features), and never scatter tight tolerances across a drawing as a habit. The framework is in the tolerances guide; the cost point is that tolerance is bought per feature, not per part.
Lever 5: Batch Thinking and Material Honesty
| Lever | Typical saving mechanism | Risk if overdone |
|---|---|---|
| Uniform walls (0.5–6 mm band) | Cycle time, scrap, distortion all improve | Very thin walls need special feedstock — yield risk |
| Coring solid sections | Mass, debind and sinter time scale down | Wall stiffness must be checked after coring |
| Fewer side actions | ≈15–30% tooling cost per mechanism avoided | Feature may move to a secondary operation |
| Tolerance discipline | Secondary ops only on functional features | Underspecifying a real interface |
| Right alloy, right volume | Feedstock and amortization matched to demand | False economy at marginal volumes |
Two structural notes close the list. First, volume: at low thousands of units, tooling can represent a large share of part cost — published molding guidance puts it around half or more in the 1,000–10,000 range — which is exactly when simpler molds and multi-cavity thinking pay fastest; the tooling cost page carries the amortization logic. Second, material honesty: specify the alloy the function needs (see the material selection guide), not the one that sounds premium — feedstock price scales directly with alloy content, and over-specification is a permanent per-part tax.
Frequently Asked Questions
Q: What is the single biggest cost lever in MIM design?
Wall thickness discipline. Uniform walls in the practical band control cycle time, scrap and distortion simultaneously — and every downstream cost (material, debind, sinter, rework) scales with it. If only one DFM pass is done, make it the wall-thickness pass.
Q: How much does an undercut really add to tooling cost?
Commonly around 15–30% per side-action mechanism, on top of the base mold. The honest question is whether the undercut is function or habit — cross-holes, slots and assembly features can often be redesigned or moved to a secondary operation for less.
Q: Is a thinner part always a cheaper part?
No. Below the comfortable band, very thin walls need specialized feedstock and tighter process control, and yield can drop enough to erase the material saving. The economical zone is thin-but-not-heroic — and above all, uniform.
Q: Should I tolerance the whole drawing tight, just to be safe?
That is the most common self-inflicted cost in MIM quoting. Sintered tolerance (about ±0.3–0.5%) already covers most features; buy sizing or machining only on the interfaces that function names. Blanket tight tolerances price secondary operations into every part.
Q: When is it worth consolidating multiple parts into one MIM part?
When the assembly being replaced has handling, fastener or alignment cost that exceeds the MIM part's own cost — and when the consolidated geometry still respects uniform walls and minimal undercuts. Consolidation is the one lever that can raise unit price while lowering product cost.
Cost reduction in MIM is mostly geometry decisions made early, and the least expensive time to make them is before the mold exists. Send the part or assembly through the contact page — the 24-hour quotation comes back with a DFM view that names which levers apply and what each is worth.
Precision Metal Parts from Emitech
Nanjing Emitech delivers MIM, CNC machining, and custom metal parts. MIM services · Request a quote