Key takeaways
- Specify every profile the machine must run — not just the first one. Future profiles cost nothing to include in the specification but a lot to retrofit later.
- Output requirements in concrete numbers (metres/shift at specified gauge) prevent incomparable quotations based on 'high speed'.
- Define cut length tolerance explicitly — ±2 mm (standard) and ±0.5 mm (precision) require different measurement systems.
- Factory acceptance test (FAT) with witnessed sign-off before shipment is the last practical chance to correct problems.
- Scope of supply must list every item — decoiler, stacker, coil cart — because suppliers routinely exclude these from headline prices.
What a specification needs to cover
Specifying a roll forming machine means writing down, in unambiguous terms, what the machine must produce and how it must do it. A complete specification covers four areas: the product (what profile, what dimensions, what material), the output requirement (how fast, how many shifts per day, how many product changes), the quality requirements (dimensional tolerances, surface quality, cut precision), and the scope of supply (what is included — decoiler, stacker, installation, training, commissioning, spare parts).
An incomplete specification produces quotations that are incomparable. One supplier quotes a stop-cut machine at a low price; another quotes a flying-cut machine at a higher price. Both meet the specification as written because the cut type was not specified. The buyer compares prices and buys the cheaper machine — then finds it cannot meet the production target.
Product specification
List every profile the machine must produce — not just the one you are planning to run first. A machine that cannot run your second and third profiles has no flex for business development. For each profile, specify: the cross-section drawing or a reference to a standard, the cover width in millimetres, the rib height and pitch, and whether punching, embossing or other inline operations are required.
Material specification: the steel grade, yield strength range and surface coating for each product in your range. A machine specified only for G300 pre-painted will be inadequate if you later need to run G550 structural steel. Specifying the heaviest material you might ever run costs little in the specification phase but avoids a major capital cost later.
| Item to specify | Why it matters | What to include |
|---|---|---|
| Profile cross-section | Defines tooling geometry | Drawing or standard reference, all critical dimensions |
| Cover width | Sets coil width requirement | Finished width, not coil width |
| Material grade range | Sets roll material and drive power | Min and max yield strength |
| Material thickness range | Sets gap adjustment, shaft size | Min and max BMT |
| Surface coating | Affects roll material choice | Bare, GI, PPGI, stainless, etc. |
| Inline operations | Adds tooling and press requirements | Punching, embossing, notching, hole patterns |
Output and production requirements
State the required output in concrete terms: metres per shift, or pieces per shift, at your specified gauge and profile. Do not just ask for 'high speed' — give the number. A required output of 2000 m/shift at 8 hours implies a sustained throughput of about 4.2 m/min, well within most standard lines. A required output of 15,000 m/shift implies sustained throughput of 31 m/min, which is a flying-cut machine with automatic stacking.
State the number of operating shifts per day and the planned profile change frequency. If you change profiles daily, a cassette-change system is necessary. If you run one profile for weeks at a time, simple roll replacement is adequate. The changeover frequency drives a significant portion of the machine cost.
Quality and tolerance requirements
Dimensional tolerances: state the allowable deviation on the critical dimensions — cover width, rib height, flange length. Industry norms for roll-formed structural sections under EN 10162 are typically ±0.2 mm on critical dimensions, ±0.3 mm on non-critical. For roofing sheet, cover width tolerance of ±1.0 mm is common; for structural purlins used in prefabricated buildings, ±0.5 mm or tighter may be required.
Cut length tolerance: state the required tolerance in millimetres. A standard PLC with measurement wheel gives ±2 mm over 6 m (typically ±1 mm). For precision structural members, ±0.5 mm requires a higher-spec encoder and a stop-to-cut system with a precision shear.
Surface quality: state whether surface marking, scratch depth limits or coating damage limits apply. For pre-painted material, zero visible marks is the typical requirement — this affects roll surface selection and lubrication system design.
Scope of supply and acceptance criteria
Define what is included: is the decoiler part of the scope? The run-out conveyor? The stacker? The coil cart? These accessories add 15–40% to the machine cost and are frequently excluded from headline quotations.
Define the acceptance criteria: what measurements will be taken at factory acceptance test (FAT) and what the pass limits are. A FAT witnessed at the manufacturer's factory before shipment is the last chance to correct problems without the cost of returning a machine. State that the FAT must be witnessed by the buyer's representative and that payment of the final instalment is conditional on FAT sign-off.
Spare parts: require a commissioning spare parts kit (blades, key belts, sensor spares) and a recommended spare parts list with part numbers and prices. A machine in production that stops for a spare part with a 6-week lead time costs far more than the part itself.