Mold Trial Stages

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Three injection molded samples from T0, T1 and T2 mold trials showing a short shot, a flashed part and an approved part.

Definition of Mold Trial Stages

Mold trial stages are the numbered rounds of sampling a new injection mold passes through between first shot and production approval, normally written as T0, T1, T2 and occasionally T3. T0 is the builder's own first shot, run to confirm that the tool fills, ejects and closes safely, and the parts are often incomplete and stay in the toolroom. T1 is the first formal trial, producing parts you receive and measure against the drawing, with a dimensional report attached. T2 follows the corrections made after T1 and should be close to production condition, with cosmetic and functional checks completed.

Each round takes time, since the tool must come off the machine, be reworked and be refitted between trials.

Taiwanese and Southeast Asian builders generally quote two or three rounds within the tooling price and charge for any beyond that, particularly where the change came from your side, so agree the allowance and the engineering change terms in the purchase order.

Why Mold Trial Stages Matter for Your Business

Tooling schedules slip at the trial stage more often than anywhere else, and the reason is usually arithmetic rather than incompetence. A builder quoting eight weeks is generally quoting to T1, and the four to six weeks that T1 rework can take are left out of the conversation entirely. Build the rounds into your launch plan rather than treating them as contingency.

Who pays for each round is the second question, and it is better asked before the first trial than after the third. Corrections arising from the builder's workmanship are his to make good, while changes to your part design after the steel is cut are normally chargeable, and the boundary between the two is where most disputes begin.

Trials give you your only sight of the tool before you commit to production. Ask for parts from every round, including T0 where the builder will release them, along with short-shot samples and the dimensional report, since these tell you far more about the tool than one approved part does.

Related Terms

Mold Flow AnalysisInjection Mold CostMold Ownership
Mold trial stages follow a set order, and each round answers a different question. T0 asks whether the tool works at all, meaning whether it fills, whether the part ejects and whether anything collides; parts from T0 are frequently short or flashed and stay with the builder. T1 asks whether the part meets the drawing, so you receive samples with a dimensional report and record what needs correcting. T2 asks whether those corrections held and whether the tool runs at a sensible cycle with acceptable cosmetics. A T3 appears when something material changed after T2. Approval normally comes at T2 or T3, against signed samples you keep.
Mold trial stages are separated by rework, and the rework is what sets the calendar. Allow one to two weeks between T0 and T1 for minor corrections and machine scheduling. Between T1 and T2, three to six weeks is more realistic, since dimensional corrections may involve welding and remachining a cavity, altering cooling or moving a gate. Shipping samples to you and waiting for your measurement and approval adds a further week or two at each round, and that time is regularly missing from the supplier's quoted lead time. Ask for the schedule broken down by trial rather than given as a single figure, and confirm who ships the samples.
Mold trial stages beyond the number quoted are chargeable under most agreements, and the charge is fair enough where the cause sits with the buyer. A tool that fails to fill because the builder machined an undersized runner is his to correct at his own expense. A tool needing a cavity reworked because you changed a wall thickness after the steel was cut is yours. Cases that fall between the two, such as warp on a part the builder cautioned you about but molded anyway, are best settled in writing before they arise. State the included trial count, the rate for further rounds and the engineering change procedure in the purchase order.