Many tools need four or five trials before approval, each costing weeks. How to plan trials with clear objectives, use data instead of trial and error, and separate tool corrections from design changes to approve tools faster.
A housing tool reached approval at T6, almost four months after T1. Looking back over the trial reports, the pattern was clear. T1 had no defined objectives, so it produced parts and opinions. T2 tried to fix cosmetic issues before the dimensional problems were understood. T3 introduced two design changes at once, so nobody knew which one helped. And at each trial, a different setter started the process from scratch.
Every trial costs time: travel, machine time, material, measurement and a toolmaker's correction cycle, typically one to three weeks. Halving the number of trials is one of the most effective ways to shorten a tooling program.
Before the first trial
- Agree trial objectives and acceptance criteria in advance: dimensions, cosmetics, function and process capability.
- Prepare the measurement plan: which dimensions, which method, which equipment.
- Check the tool before it goes into the press: cooling circuits flow-tested, hot runner zones checked, ejection and actions working.
- Have the right material, properly dried, and the right machine.
- Review mould flow predictions so you know where to look first.
A structured T1
Treat T1 as an engineering exercise, not a sample run:
- Establish fill: short-shot the part progressively to see the fill pattern and check for imbalance, air traps and hesitation.
- Run the basic scientific moulding studies: viscosity, gate freeze, and a quick process window.
- Produce samples at a stable, documented process, not at whatever settings happened to make a good-looking part.
- Measure dimensions fully and record every issue with photos and part numbers.
Separate the issues
After each trial, sort the issue list into three groups:
- Tool corrections: the tool does not match the agreed design, such as dimensions, finish or function. The toolmaker's responsibility.
- Process issues: can be solved within the process window. Solve them at the trial if possible.
- Design changes: the part design itself needs to change. These need engineering decisions, and usually affect cost and timing.
Mixing these is the main reason trials multiply. Fix tool and process issues first, and treat design changes formally, with someone responsible for approving each one.
Make corrections steel-safe
Where dimensions need adjusting, agree whether corrections are made by removing steel, which is quick and cheap, or adding it, which means welding and is slow and risky. Toolmakers usually build critical dimensions steel-safe so the first correction only removes material. Plan this with them before T1.
Keep the process consistent
Run each trial with the same documented process, adjusted only deliberately and recorded. If the process changes from trial to trial, you cannot tell whether a dimension moved because of the tool correction or the process.
Close out efficiently
- Issue a short trial report within days: issues, owners, dates and next trial objectives.
- Agree the corrections and the next trial date with the toolmaker before leaving the trial.
- Track issues across trials until every one is closed.
- Plan the approval trial, with capability runs and PPAP or first article samples, as soon as dimensions are stable.
The goal is not just fewer trials. It is reaching an approved, robust, documented process, the evidence that the launch checklist needs.
