Last updated: 2026-09-02 · 5 min read

What Does a Mold Trial Cost — and Who Pays for T2 and T3?

A trial’s cost is machine hours, mold handling, material, labor and verification time — and who pays for the second and third trial depends on one word the quotation must define: cause. Tooling-caused corrections belong to the mold maker, buyer-caused changes belong to the buyer, and everything else is a scope question. Contracts that skip that definition buy their disputes in advance.

Shrinkage — The dimensional reduction from mold cavity to cooled part. Amorphous resins: 0.4–0.7% (uniform). Semi-crystalline: 1.0–2.5% (directional). Mold makers apply shrinkage factor when machining cavity. Actual shrinkage varies with wall thickness, gate location and packing pressure. See also related guide.

Key Facts

  • What a trial consumes: press time at an hourly rate that scales with tonnage, setup and handling hours, resin for the shots, operator and technician time, and the reporting work afterward — dimensional measurements, photos or video, and the trial report. The visible invoice is only part of the cost; the calendar time a trial occupies is often the bigger number on your project plan.
  • The standard baseline: T1 is included in the tooling price almost everywhere. From T2 onward, responsibility follows cause — if the mold maker’s correction fixes their steel, they carry the trial; if your design change drives the trial, you carry it. Ambiguity appears exactly where nobody wrote the rule down.
  • The most expensive trials are the ones a better DFM would have prevented: missing material data, undecided cosmetic criteria, or acceptance rules invented after T1. Each undecided question at the quotation stage becomes a trial on the calendar later.

    • Shrinkage — The dimensional reduction from mold cavity to cooled part. Amorphous resins: 0.4–0.7% (uniform). Semi-crystalline: 1.0–2.5% (directional). Mold makers apply shrinkage factor when machining cavity. Actual shrinkage varies with wall thickness, gate location and packing pressure. The related guide covers adjacent topics.

    What Gets Billed at Each Stage

    Trial Typical Inclusion Who Pays, and Why
    T1 Included in tooling price Mold maker — the tool must at least run
    T2 after tooling correction Usually seller-carried Mold maker — the correction was theirs
    T2 after buyer design change Buyer-carried Buyer — the geometry changed, not the tool
    Process-only re-runs Often included up to a defined limit Split by contract — define the cap
    T3 and beyond Contract-dependent Follows cause, with escalation defined up front

    How to Structure Trials in the Quotation

    1

    Define the included trials

    Ask the quote to state, in one line each: how many trials are included, what each includes (hours, material, report scope), and what a trial actually is — a defined shot count with measurements, not “some parts shipped.” Two suppliers can both write “T1 included” and mean different invoices.

    2

    Define the cause categories

    Three categories cover reality: tooling-caused (steel, mechanism, workmanship), buyer-caused (design or specification changes), and process-caused (settings, drying, molding environment). Write which side carries the cost in each case, and what evidence decides the category when it is disputed.

    3

    Define what a failed trial means

    A failed trial is a documented miss against the acceptance criteria — not a feeling. Name the criteria before T1: dimensional report on named dimensions, cosmetic boundary sample, function checks. With criteria in place, “who pays for T2” is a records question instead of a negotiation.

    4

    Cap and escalate

    Define the maximum included re-trials per cause category and what happens beyond it — priced per trial, per hour, or by a fixed schedule. A cap protects both sides: the buyer from open-ended exposure, the maker from unlimited free corrections when the root cause turns out to be the drawing.

    5

    Record each trial’s cause in writing

    Every trial report ends with the cause statement and who carries it, signed before the next trial is scheduled. The habit costs minutes; the ledger it builds decides the argument at T3.

    Cost Drivers That Turn One Trial Into Three

  • Undecided cosmetic criteria — “looks fine” at T1 and “not acceptable” at your desk is a re-trial with a cause dispute attached.
    Sign a boundary sample instead.
  • Incomplete material data at the RFQ — the tool cuts for the wrong shrinkage, and the correction lands after T1 where it costs the most.
  • Design changes after steel start — each one moves cost from the drawing to the tool room, and the trial calendar grows with it.
  • Missing acceptance criteria — without named deliverables, every trial’s success is negotiable, and negotiation is another trial.
  • Skipping mold flow on a known-hard part — weld lines and fill problems found on the press are found one trial later than they should have been.

    • Frequently Asked Questions

    Can I accept the tool straight from T1?

    Sometimes, on simple tools with a clean T1 — full dimensional report to drawing, cosmetic samples signed, weights stable.
    What you cannot do is skip the criteria: accepting from T1 without the report is not skipping a trial, it is skipping the evidence. For precision or cosmetic-critical parts, plan on T2 regardless; it is where the corrections get verified.

    Why was I billed for a T2 I thought was included?

    Almost always a scope gap: the quote said “T1 included” and said nothing about T2, so the supplier priced it as a new event. This is why the cause categories and the re-trial cap belong in the quotation — not because suppliers act in bad faith, but because unpriced events get priced when they arrive.

    What does a typical trial actually cost?

    It scales with press tonnage, shot weight, and report depth, so the honest answer is a structure rather than a number: press hours times the shop’s rate, plus setup and handling, plus material, plus reporting. Ask your supplier to price a trial day explicitly — you need that unit price in hand before the contract defines who pays, because a cap in vague currency is not a cap.

    Key Takeaways

    1. T1 included is the baseline; from T2 on, cost follows cause — tooling-caused to the maker, buyer-caused to you, process-caused by contract with a defined cap.
    2. Write the trial definition, the cause categories, and the failure criteria into the quotation; a trial without criteria is a re-trial waiting to be scheduled.
    3. Cut the trial count at the source: complete material data, signed cosmetic boundary samples, and acceptance criteria agreed before steel — every undecided question becomes machine hours later.

    Trial costs are not an accident of the process; they are the price of questions left open at the quotation stage. aCatMould prices trials explicitly — what is included, what a trial day costs, and how cause moves the bill — so the third trial, if it ever happens, is an invoice you expected against a rule you signed.

    Sources
    MoldMaking Technology — trial planning and acceptance
    Plastics Technology — mold trial practice
    Plastics News — tooling contract practice

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