What Drives Part Cost
The eight levers of part price: material, volume, tolerance, finish, quantity and more
Part cost is a product of eight levers: material choice, part volume, geometric complexity, tolerance, surface finish, quantity, lead time and tooling. Most cost reduction is design-led — a 30-minute geometry change beats weeks of supplier negotiation. This article ranks the levers by their typical impact and shows where to look first.
1. Material and volume
Material is volume × density × price/kg: aluminum ≈1 index, steel ≈1.2, stainless ≈3–4, titanium ≈8–12, PEEK ≈30–60. On machined parts, you pay for the stock removed too — design near-net and expect 2–5× finished volume in waste.
Part volume also sets machine time, print height and mold size: every cubic millimeter of unnecessary material adds cost across the whole process chain. Lightening cores, reducing envelope and cutting non-functional material is the highest-leverage move.
2. Complexity and tolerance
Feature count drives machining minutes: deep pockets, fine threads, tight GD&T, multiple setups. Complexity is multiplicative with quantity — a complex part at 500 units is very expensive. Simplify by consolidation, standard sizes and looser non-critical tolerances.
Tolerance bands: general ±0.127 mm is free; ±0.025 mm roughly doubles time; ±0.005 mm is 5–10× and usually unnecessary. Surface finish similarly: as-machined is free; fine polish is premium; anodize/powder is a modest area-based cost.
3. Quantity, lead time and tooling
Quantity tiers discount setup and amortize programming: 100 parts can cost 60–70% per unit of a 1-off. Lead time is a multiplier: expediting adds 20–40%. Tooling (molds/dies) is a separate line that pays off only above the crossover quantity.
Overhead and margin add 15–30% on top — the platform’s transparent lines show these; they are not negotiable but they are visible.
4. The 80/20 of cost reduction
Check in order: (1) material grade — can a cheaper alloy/plastic do it? (2) volume — lighten non-functional mass; (3) tolerance/finish — loosen what does not mate; (4) features — remove deep pockets and fine threads; (5) quantity — buy to the tier; (6) lead — plan standard, not expedite.
Every redesign that removes material or complexity compounds across all other levers; the quoting engine’s live calculator shows the price impact of each change instantly.
Quick reference
| Lever | Typical impact | Action |
|---|---|---|
| Material grade | 2–60× between families | Choose the minimum adequate |
| Part volume | Scales material + time | Lighten, core, reduce envelope |
| Complexity | Multiplies machine time | Consolidate, standardize |
| Tolerance | 1–10× on features | Loosen non-critical |
| Finish | +5–40% by spec | Match finish to function |
| Quantity | −30–50% per tier | Buy to the tier |
| Lead time | +20–40% expedite | Plan standard |
| Tooling | Amortized per part | Cross above crossover |
Sources & references
- Xometry Learning Center — Cost Drivers (public engineering reference)
- Protolabs — Design for Manufacturing Cost Guide (public engineering reference)
- ISO 9001:2015 — Quality management systems (prevention & appraisal cost context)