- Define the part with controlled drawings and scope with a list.
- Separate critical-to-quality features (CTQs) from ordinary dimensions.
- State prototype, batch and annual quantities.
- Require the supplier to list assumptions, deviations and one-time costs.
Values in this guide are practical starting points for RFQ, DFM and prototype validation. They do not replace load calculations, regulations, material certificates, qualified procedures or approved production drawings.
Build a Traceable RFQ Package
Give every part a unique part number and revision, for example KF-1024 Rev.B. PDF, STEP, DXF and BOM files must carry the same revision. Add a cover sheet listing filenames, quantities, target date, contact and open questions. Name the package by project, date and revision; remove obsolete files instead of mixing them with the current release.
Make the Drawing Answer Eight Questions
The drawing should answer: what is made; material and grade; stock thickness or tube size; critical dimensions and datums; default tolerances; welding/threading/insertion requirements; finish and masking; inspection, marking and packing. If 2D and 3D conflict, state which controls. Phrases such as “standard practice” or “good appearance” are not measurable acceptance criteria.
Identify CTQs Instead of Tightening Everything
Mark features affecting assembly, safety, sealing, movement or customer-visible appearance as CTQs and define how they are measured—for example, hole-pattern position from datums A|B|C, post-weld mounting-face flatness, hole diameter after coating, or cosmetic AQL. Do not apply ±0.1 mm across an ordinary laser-cut and formed part without functional need; tight tolerances can force machining, fixtures and 100% inspection.
Quote Against Real Quantity Breaks
State prototype, first-order and annual quantities—for example, five prototypes, 500 for the first lot and 6,000 per year over four releases. These figures affect generic versus dedicated tooling, stamping versus laser cutting, material MOQ, coating batch efficiency and packaging. If demand is uncertain, request price breaks such as 100/500/2,000 pieces and separate tooling, gauges and prototype charges.
Ask for a Closed-loop Quotation
A complete quotation states material, process, finish, packing, lead time, MOQ, commercial terms, validity and tooling ownership. The supplier should list assumptions and deviations, such as a proposed grade substitution or a tolerance change from ±0.1 to ±0.2 mm. Close these items before purchase order release, not at first-article inspection.
BEFORE SENDING
- Part number, revision, units and scale are consistent
- No revision conflict across 2D, 3D, BOM and photos
- CTQs, datums, post-finish dimensions and measurement methods are marked
- Prototype, batch, annual volume and supply scope are clear
- Packing, labeling, certificates and inspection records are defined
- Supplier must reply with assumptions, deviations, MOQ, lead time and one-time charges
REFERENCES
Dimensioning and geometrical specification may reference ISO 129-1, ISO 1101, ISO 2768-1 or project-specified ASME Y14.5. The contractually specified edition controls.