Dal prototipo alla serie: la transizione senza riqualifica
Cosa cambia tra un prototipo lavorato singolo e una serie da 5.000 pezzi, quando cambiare processo e come mantenere intatta la catena documentale perché il primo lotto sia approvato al primo colpo.
Scritto da Engineering Team
La documentazione tecnica è mantenuta in inglese per preservare la precisione dei termini ingegneristici.
The awkward moment in most hardware programmes is the one where a design that has been validated on three machined prototypes has to become five thousand parts. Handled badly, it means a new supplier, a new audit, a new first article and three months of schedule. Handled well, it is a process change on an existing part number.
What actually changes at volume
Fixturing. A prototype is held in a vice with soft jaws. A production part gets a dedicated fixture, often holding four or eight parts, designed so the operator cannot load it wrong.
Programme optimisation. A prototype programme is written to be safe. A production programme is written to be fast: optimised approach moves, tool life tracked per edge, in-process probing rather than off-machine checks.
Stock form. Prototypes come from whatever is on the shelf. Production buys near-net stock — the right bar diameter, tube instead of solid, or a small casting or forging if the volume justifies the tooling.
Inspection strategy. A prototype gets a full dimensional report. Production gets a first article, then SPC on nominated characteristics with a defined sampling frequency.
Deburring and finishing. Hand deburring at 10 pieces becomes vibratory finishing or a dedicated deburring operation at 1,000.
When a different process becomes cheaper
Machining is the most flexible way to make a part and rarely the cheapest at volume. Crossover points, as a rough guide:
| Alternative | Typical crossover | Tooling cost | Lead time to first part |
|---|---|---|---|
| Swiss turning (from milling) | 300 – 500 pcs | low | 2 – 3 weeks |
| Investment casting + machining | 500 – 1,000 pcs | €3k – €12k | 6 – 10 weeks |
| Die casting + machining | 3,000 – 5,000 pcs | €8k – €40k | 8 – 14 weeks |
| Injection moulding (plastics) | 1,000 – 3,000 pcs | €3k – €25k | 3 – 6 weeks |
| Stamping (sheet parts) | 5,000 – 20,000 pcs | €5k – €30k | 6 – 10 weeks |
| Cold forming + machining | 10,000+ pcs | €10k – €30k | 10 – 16 weeks |
These are indicative. The real crossover depends on part complexity, material cost and how much machining remains after the near-net process. A cast housing still needs its sealing faces and bores machined; the casting saves the roughing, not the finishing.
Note the lead time column. A crossover that saves 40 % per part but adds ten weeks before first delivery may be the wrong decision for a programme whose launch date is fixed.
Keeping the documentation chain intact
This is where the time is actually lost, and it is avoidable.
Keep the same part number and revision discipline. If the design does not change, the part number does not change. A process change is recorded as a process change, not a new part.
Carry the first article forward. If the prototype was inspected against a full dimensional report, that report is the baseline. The production first article is compared against it, and only the deltas need review.
Record the process, not just the result. The programme revision, tool list, fixture number, cutting data and inspection plan used for the approved prototype become the production routing. Two years later, a repeat order runs the same process.
Use one supplier across the transition. This is the single largest time saving. A new supplier means a supplier audit, a new quality agreement, a new first article, and — in regulated sectors — a change notification to your notified body or customer. Staying with the same supplier means a documented process change and nothing else.
What we do differently at each stage
Prototype (1 – 10 pieces). Machined from stock material in our prototype cell, 3 to 7 working days, full dimensional report, DFM feedback attached.
Pilot (10 – 100 pieces). Soft jaws or a simple fixture, the same programme refined, first-article inspection formalised, process notes written.
Low volume (100 – 1,000). Dedicated fixturing, optimised cycle time, control plan written, SPC started on nominated characteristics.
Series (1,000+). Automation where it pays — bar feeders, pallet changers, lights-out shifts. Kanban or call-off stock held at our facility. Annual process capability review.
At every stage the part number, the drawing revision and the quality system are the same. Nothing is re-qualified because nothing has changed that requires it.
The conversation to have early
If you already know the programme volume, tell us at the quotation stage even if you are only ordering three parts today. It changes how we quote:
- We will tell you whether machining remains the right process at your target volume
- We will design the prototype fixture so it can grow into the production one
- We will flag any design feature that will become expensive at scale while the design can still be changed
That conversation costs nothing and routinely saves months.