What Files Does a Mold Maker Need?

Last updated: 2026-09-01 · Reading time: about 4 min

The quality of a mold quote is capped by the quality of the files behind it — a vague package buys a vague number.
The working core is four items: a 3D model that defines the geometry, a 2D drawing that defines acceptance, a material and color specification, and the production figures that size the tool — plus the duty environment the part will live in. Each one answers a question the shop would otherwise answer by guessing, and guessing compounds through DFM, steel selection and price.

Key facts

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  • The 3D model says what the part is; the 2D drawing says what counts as good. A quote built on the model alone prices geometry, not acceptance — and acceptance is where disputes live.
  • Material is a grade, not a family: “ABS” spans dozens of grades whose shrink, flow and drying differ enough to change steel, gates and cooling — the datasheet decides, not the abbreviation.
  • The annual volume and expected mold life set cavity count and tool construction; give them late and the quote gets rebuilt, give them early and every option is priced on the same page.

    • Process parameter — A controllable variable in the injection molding process: melt temperature, injection speed, holding pressure, cooling time, mold temperature. Each parameter affects part quality — deviations cause defects. Parameters are set during T1 and locked for production. See also related guide.

    Flash — Thin excess material that escapes between the mold parting line or around ejector pins. Cause: insufficient clamp force, worn parting line, excessive injection pressure, or contaminated mold surface. Flash thickness: 0.02–0.1mm. Requires secondary trimming to remove. See also related guide.

    Which files drive the quote — and which drive the steel?

    The 3D model drives everything: exported as STEP from the native CAD, watertight, at the revision you actually intend to build. A translated file with broken surfaces costs the shop a repair bill before design even starts, and the repair bill lands in your lead time. The 2D drawing drives acceptance: critical dimensions with tolerances, datum scheme, the finish callouts per face, notes on where appearance matters.
    Tolerances you leave off the drawing get assumed at default — convenient until a mating part does not fit, which is why the RFQ checklist puts the drawing next to the model, not instead of it. The material specification drives steel and cooling: grade and filler decide shrinkage, corrosion risk and processing temperature; the steel conversation follows from it.
    Together the three turn a quote from a guess with a letterhead into a line-itemed number — the kind the breakdown page teaches you to read.

    What specifications stop surprises in steel?

    Color: state the resin’s coloring method — pre-colored natural, masterbatch percentage, or a supplier’s matched chip — because colorants change shrink and sometimes flow. Surface: name the finish per face, glossy or textured, with a reference plate where appearance is critical; finish decides polishing hours and, with texture, draft.
    Production: annual volume, expected tool life, and whether a second tool is planned — these set cavity count, and cavity count reshapes the whole quote, as the cavity-count page walks through. Environment: the duty the part survives — outdoor exposure points the design toward UV-stable grades, chemical washdown changes the resin, sustained heat changes both.
    And the honest extras that cost nothing to state: which faces are cosmetic, where the part mounts, what it must not do. None of this is paperwork for its own sake — each line removes one place where the shop would otherwise assume, and assumptions are where budget overruns begin.

    Which file checks belong in the RFQ?

  • 3D model exported as STEP — from the native CAD, watertight, revision number stated in the file name.
  • 2D drawing with tolerances and datums — critical dimensions, realistic ranges, finish callouts per face.
  • Material named by grade — with filler content, matching the datasheet you expect the mold to be built around.
  • Color method and masterbatch share — or the matched chip reference, stated before the first trial.
  • Volume and tool life figures — annual quantity and expected shots, so cavity count and construction are designed, not defaulted.
  • Duty environment noted — temperature, exposure, chemicals — the conditions that quietly veto material and steel choices.

    • Frequently asked questions

    Can we start from a sample part instead of files?

    Yes — the sample gets scanned and the geometry rebuilt, and reputable shops do it routinely.
    What the scan cannot give you is intent: tolerances, critical dimensions, cosmetic faces. Those still need a 2D drawing, so the practical answer is sample plus drawing; sample alone reproduces the part as it is, including whatever was wrong with it.

    What if our 3D model and 2D drawing disagree?

    They will occasionally, and finding the conflict is part of DFM — that is what the review is for. What helps is stating which document rules when they do: most programs make the drawing the authority for acceptance and the model the authority for geometry. Saying it up front costs one line; discovering it after steel costs a revision.

    Do we need to specify the mold steel ourselves?

    Usually not — the shop selects steel from your material, volume and life figures, and shows the choice in the quote where you can check it. What you should bring is the constraint, not the part number: expected shots, abrasiveness of the resin, corrosive additives if any. You can note a preference for standard component systems so spare parts stay obtainable; the steel grade itself follows from the duty.

    Key takeaways

    1. Four items anchor the RFQ: STEP model, dimensioned 2D drawing, grade-level material spec, and production figures with duty environment.
    2. The model defines geometry, the drawing defines acceptance — a quote built on one alone prices half the program.
    3. Color method, finish per face and annual volume are specification decisions, not details to sort out after the quote.

    If you are assembling an RFQ, send what you have — even a partial package gets a structured gap list back. You will get the file checklist reviewed item by item by a named tooling engineer, before any steel is ordered.

    Sources
    LKM — mold steel supplier, reference for steel grades and selection practice
    ISO 20457:2018 — Plastics moulded parts: Tolerances and acceptance conditions, International Organization for Standardization
    Plastics Industry Association — industry resources on part and tooling specification

    Sources: Plastics Technology · Plastics Technology Online · Society of Plastics Engineers (SPE) · ThomasNet