Initial samples are often made under special conditions. For series production, you need evidence on measurement, production trials, scrap, traceability and revision status. This lets you assess whether the supplier can meet volume, cycle time and consistent quality requirements.
Why good samples say little about series production
An experienced setter makes a few initial samples without time pressure. The material comes from a selected batch, and the supplier removes faulty parts before dispatch. Those conditions often differ from series production. Good samples therefore say little about what happens with 5,000 parts across three shifts.
Series production adds tool wear, shift changes, changing material batches and sub-suppliers. That is why every set of samples raises the question of the conditions under which it was made.
- Who made the samples – series staff or the sample shop?
- With which tool – series tool or pre-series tool?
- From which material batch and with which sub-suppliers?
- How many parts were made, and how many of them were sorted out?
Five pieces of evidence before series approval
Request this evidence before approving series production or making the final payment for a series tool. If evidence is missing, make an explicit decision about how to handle the open question.
| Evidence | What you want to see | Typical warning sign |
|---|---|---|
| Measurement basis | A gauge that suits the tolerance and a repeat measurement on the same part | A dimension with a tolerance in hundredths of a millimetre is checked with a calliper |
| Production trial | Series tool, series staff, agreed quantity and real cycle time | “We made 30 parts in the sample shop.” |
| Scrap and rework | Counted, documented and with causes | No figures, just “very little” |
| Traceability | Batch, material and sub-supplier traceable per lot | Heat treatment is outsourced and not approved |
| Revision status | Drawing, tool and inspection plan at the same revision | The inspection plan is still at revision A, the drawing at revision C |
What a meaningful production trial looks like
Agree the conditions of the later series production for the trial. Check on site whether the supplier follows them. You can then relate the results to the planned production run.
- Agree beforehand: quantity, cycle time, staff, tool, material batch and inspection scope
- Observe during the trial: set-up, first-part approval, in-process checks, recording of scrap and rework
- Evaluate afterwards: measurement report for the agreed characteristics, scrap rate with causes, open actions with dates
An illustrative example
A zinc die-cast housing at revision B is due to enter series production at a supplier in Changzhou. The initial samples meet the dimensions. On site, the supplier has checked the critical bore with a tolerance of ±0.02 mm using a calliper. Its process data come from 30 parts made in the sample shop. An unapproved sub-supplier carries out the coating.
The subsequent production trial uses the series tool and series staff to make 300 parts. A limit plug gauge confirms the bore dimension. However, 4% of parts need rework for a burr at the parting line. We therefore recommend approval with a condition. Each lot should undergo a burr check until the toolmaker has reworked the parting line.
Illustrative example – not a client case; figures and names are invented.
What you decide afterwards
You can approve, approve with conditions, or withhold approval and require rework. Base the decision on the position supported by evidence. An on-site review supplies the basis; you grant approval.
We can support a planned production trial with a Production Readiness Review. First resolve any missing prerequisites, such as an approved drawing or named critical characteristics.