Injection Mold Trial and T1/FAI Acceptance Guide

A mold trial is not a video showing the machine opening and closing. It is a controlled test that links the mold, machine, material, process settings and measured samples.

TL;DR

Define the acceptance standard before the trial. Record the process, identify samples by cavity, measure critical dimensions and retain part of the payment until agreed T1 or FAI results are approved.

Five trial red flags

1. The supplier changes material or settings without recording them.
2. Samples are mixed and cannot be traced to individual cavities.
3. Only one attractive sample is submitted from a multi-cavity mold.
4. The mold runs briefly but no stable production window is demonstrated.
5. Final payment is requested before dimensional results are available.

Define acceptance before T1

Agree in writing:

• product drawing revision;
• material and grade;
• critical dimensions and tolerances;
• appearance and texture standard;
• cavity count;
• cycle target;
• allowed defects;
• sample quantity;
• machine and auxiliary equipment;
• report format and approval authority.

Record the setup

The trial record should include:

• machine manufacturer, model and screw diameter;
• mold number;
• material, batch and drying;
• barrel-zone and mold temperatures;
• injection speed and pressure;
• transfer position;
• hold pressure and time;
• cooling and total cycle time;
• hot-runner temperatures and valve timing;
• observations and changes.

Stabilize before sampling

Do not measure startup parts as if they represent stable production. Allow the mold and process to reach agreed stability, then collect consecutive shots. If parameters are changed, identify which samples correspond to each condition.

Identify samples by cavity

For each cavity, check:

• part weight;
• critical dimensions;
• visual defects;
• gate and ejection quality;
• assembly or leak performance where applicable.

Cavity identification reveals imbalance and local cooling, venting or ejection problems that pooled samples hide.

T1 versus FAI

T1 is the first formal trial after the mold is completed or modified. It identifies tooling and process corrections.

First Article Inspection (FAI) compares measured parts with the approved drawing or inspection plan. The project may require additional trials—T2, T3 and beyond—until acceptance criteria are met.

Common defects to document

• flash;
• short shots;
• sink marks;
• burns;
• weld lines;
• warpage;
• drag or scratches;
• ejector marks;
• gate vestige;
• color or contamination;
• dimensional variation.

Use the English Xometry guide to injection molding defects as background, but judge the project against its own specification.

Corrective-action loop

1. List each non-conformance.
2. Identify tooling, process or material cause.
3. Assign action and responsibility.
4. Approve modifications before cutting steel.
5. Repeat the trial under documented conditions.
6. Close findings with samples and measurements.

Payment retention

For used, refurbished or modified molds, consider retaining 10–20% until the agreed China trial and T1/FAI approval are complete. The percentage and release conditions should be contractual and appropriate to supplier leverage and project value.

FAQ

Does T1 need to meet every final tolerance?

Not always, but the contract should define expectations. T1 normally identifies corrections; no mold should be accepted merely because it produced a complete part.

Can video replace an inspection report?

No. Video demonstrates operation but not dimensional compliance or cavity consistency.

Who should approve samples?

The buyer’s authorized engineering or quality representative, based on the agreed drawing and report.

Request a trial plan

Provide the product drawing, inspection plan, machine information, material and acceptance requirements. The trial plan should be approved before the mold is mounted.