Tooling is where most consumer-product schedules slip. Not because the mould machining is slow, but because design decisions that should have been settled before steel was cut get revisited after T1 samples arrive. This guide lays out the sequence we use to move from a CAD file to an approved first article, and the checks that actually prevent rework.
Freeze the DFM before cutting steel
Design for Manufacture (DFM) is not a formality. A proper DFM report should come back with:
- Wall thickness map with nominal values and thick sections flagged. Uneven walls cause sink marks, warpage and long cooling cycles. A common target for ABS/PP housings is 1.5–3.0 mm, kept as uniform as possible.
- Draft angles on every face perpendicular to the parting line. Textured surfaces need more draft than polished ones — often 1.5–3° versus 0.5–1°.
- Parting line and gate locations, with an explanation of where weld lines and visible gate marks will land.
- Undercut list with the proposed slider or lifter solution, since each one adds cost and maintenance.
If a supplier sends back a DFM with no gate locations, that is a signal to slow down.
Choose mould steel and cavity count from volume
| Annual volume | Typical approach |
|---|---|
| < 10,000 pcs | Aluminium or soft steel prototype tool, single cavity |
| 10,000–100,000 | P20 / 718H pre-hardened steel, 1–2 cavities |
| 100,000–500,000 | H13 hardened steel, 2–4 cavities |
| > 500,000 | Hardened multi-cavity tool with hot runner |
Cavity count is a trade-off: more cavities raise tool cost and require tighter process control, but lower unit price. Ask for the assumed cycle time and cavity count in the quote — without them, a unit price is not comparable between suppliers.
Resin selection changes the part geometry
Shrinkage is not a single number. Semi-crystalline materials (PP, PA, POM) shrink more and shrink differentially with flow direction, which makes warpage harder to control than with amorphous resins (ABS, PC, PS). Glass-filled grades reduce shrinkage but introduce anisotropy and visible fibre lines on cosmetic surfaces.
Lock in the exact grade — including manufacturer, additive package and colour masterbatch — before finalising tool dimensions. Changing from unfilled PA6 to PA6-GF30 after the tool is built usually means re-cutting cavities.
T0, T1, T2: what each trial should prove
- T0 (first shot): confirms the tool fills, ejects and resets. Cosmetic defects are expected. The output is a short-shot study and a filling balance check across cavities.
- T1: parts made with the intended resin and near-final process parameters. This is where dimensions are measured against the drawing across a full cavity layout, typically 5–10 shots per cavity.
- T2 / pilot run: process capability, assembly fit with mating parts, packaging drop tests, and a small production run under real cycle times.
Ask for a dimensional report per cavity, not just one "representative" part. Cavity-to-cavity variation is a classic cause of intermittent assembly failures.
First Article Inspection: what to require
A useful FAI package includes the dimensional report with ballooned drawing references, material certificate with lot number, a process parameter sheet (temperatures, pressures, cooling time), cosmetic approval samples defining acceptable sink/flow marks, and a signed limit sample for colour and texture.
Keep the limit sample physically. "Same as last batch" is not a specification; a sealed, dated sample is.
FAQ: how long does tooling take?
For a moderately complex single-cavity consumer housing, 25–40 days from DFM sign-off to T1 is realistic; multi-cavity or slider-heavy tools run longer. The biggest variable is engineering-change turnaround, not machining. Every change after steel is cut costs both time and tool life.
Wrapping up
The five decisions that matter most are exposure-free DFM, resin grade frozen early, steel and cavity count matched to volume, per-cavity dimensional data at T1, and a signed limit sample. Get those right and the first article is a formality instead of a negotiation.
For OEM/ODM injection moulding, tooling and assembly support, see DAYIN. Service details are also at madeindayin.com.
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