An RFQ is not a request for a price. It is the engineering brief that decides whether the price you receive is comparable to the next supplier's price — and whether the parts you receive match the ones you designed.
Incomplete RFQs are the single largest source of re-quotes, schedule slips and disputes in custom insulation part sourcing. This guide lists the 12 items every RFQ should carry, how to specify tolerances realistically, and the mistakes that cost the most.
1. What an Incomplete RFQ Actually Costs
- Non-comparable quotes. If material grade or thickness tolerance is left open, each supplier quotes a different product.
- Two rounds instead of one. Every clarification cycle adds days to the lead time before production even starts.
- A hidden price increase later. Suppliers protect themselves against unclear specs by adding contingency to the unit price.
- Disputes at goods-in. "Within tolerance" is impossible to argue without a written tolerance on the drawing.
2. The 12-Item RFQ Checklist
| # | Item | What to send |
|---|---|---|
| 1 | 2D drawing | PDF with dimensions, datum scheme and title block |
| 2 | 3D model | STEP (.stp) or IGES — far cheaper than re-modelling from a PDF |
| 3 | Material grade | Specific grade and, where it matters, brand: e.g. FR4 epoxy glass fiber 1.6 mm, UL94 V-0 |
| 4 | Sheet thickness & tolerance | Nominal plus whether it is stock thickness or machined to size |
| 5 | Critical dimensions | Mark them. Not every dimension needs ±0.05 mm |
| 6 | Edge & hole finish | Chamfer, radius, deburr, tap type and thread class |
| 7 | Surface finish / appearance class | Functional, visible cosmetic surface, or optical (light guide, display) |
| 8 | Colour & transparency | Clear / tinted / opaque, and the reference for colour matching |
| 9 | Compliance requirements | RoHS, REACH, UL, halogen-free, food-contact, flame rating |
| 10 | Quantities | Prototype, pilot, and expected annual volume — separately |
| 11 | Packaging & labelling | Bulk, tray, individual bag, ESD, moisture barrier, label content |
| 12 | Delivery & documents | Incoterm, target date, required CoC / inspection report / material certificate |
3. How to Specify Tolerances Realistically
Tightening a tolerance from ±0.20 mm to ±0.05 mm can multiply the process cost with no functional benefit. Give tolerances only where the assembly needs them.
| Feature | Typical achievable (standard) | Precision option | Where it is actually needed |
|---|---|---|---|
| Sheet thickness (as supplied) | ±10% of nominal | Machined to size ±0.05 mm | Sealing faces, shims |
| Hole diameter (CNC) | ±0.10 mm | ±0.05 mm | Press-fit pins, bearings |
| Hole position | ±0.15 mm | ±0.05 mm | Multi-part stack assembly |
| Outline / profile | ±0.20 mm | ±0.10 mm | Panel fits, bezels |
| Flatness (per 100 mm) | 0.4 mm | 0.15 mm | Vacuum chucks, sealing |
| Edge chamfer | ±0.2 mm | ±0.1 mm | Handling safety, cosmetic |
Practical rule: mark only the dimensions that affect fit or function as controlled, and add a general tolerance note for everything else (e.g. "general tolerance ISO 2768-m"). This usually saves 10–25% of the unit price on machined plastic and composite parts.
4. Copy-Ready Material Callout Examples
Vague callouts are the main reason a supplier substitutes material. Write them like this instead:
FR4 epoxy glass fiber sheet, 1.6 mm nominal, UL94 V-0, RoHS compliant, natural green, thickness machined to 1.60 ±0.05 mm
Polycarbonate (PC) sheet, clear, UV-stabilised, 3.0 mm, flame rating V-0, both faces with protective film until assembly
Carbon fiber composite panel, 2.0 mm, 3K twill weave, epoxy matrix, fibre volume fraction ≈60%, matte finish
Phenolic (bakelite) sheet, grade 3240, 5 mm, electrical insulation grade per GB/T 1303, high-voltage application
5. Five RFQ Mistakes That Cost the Most
- No 3D model. The supplier re-models the part from a PDF, and the first article comes back subtly different.
- A single global tolerance block. Either everything is over-specified (expensive) or key features are under-specified (scrap).
- No quantity breakdown. A quote built on 100 pcs cannot be extrapolated to 100,000 pcs — and vice versa.
- Appearance left undefined. On PC and acrylic parts, "as machined" can mean anything from polished to visibly tool-marked.
- Certificates requested after the order. Compliance must be a requirement at RFQ stage, not a favour at shipping.
6. What a Good Supplier Returns
You should expect more than a number:
- A DFM note flagging features that are difficult, thin or likely to warp
- A cost breakdown — material, machining, finishing, packaging — so you can see what changes drive the price
- Lead time by stage: material, machining, inspection, packing
- Explicit confirmation of grade, tolerance and documentation quoted
7. FAQ
Q: How detailed does a drawing need to be for a first quote?
A: Enough to define geometry, material and fit-critical tolerances. For an indicative price, a 2D PDF plus material and quantity is workable — but always send the STEP file before production.
Q: Should I send my drawing or ask the supplier to design it?
A: If you have a design, send it and ask for DFM feedback — it is faster and protects your IP position. Use supplier design only for simple brackets and spacers.
Q: How do I compare quotes from different countries fairly?
A: Normalise everything: same grade, same tolerance, same packaging, same Incoterm, same documentation. Compare landed cost, not FOB price.
Q: Do you sign NDAs?
A: Yes — we routinely sign mutual NDAs for custom drawings and will not share customer data.
Q: How fast can Chaorong quote a custom part?
A: Typically within 1–2 working days for a complete RFQ with a STEP file; prototypes in about a week depending on material and finishing.
8. Send a Complete RFQ
Chaorong Electronics (潮荣电子, Dongguan, China) machines FR4/epoxy, phenolic, PC, acrylic and carbon fiber to drawing — panels, insulation sheets, spacers, guards, brackets and precision components, from prototype to scheduled production.
→ Send your RFQ with STEP file · Product overview
Related reading: Acrylic (PMMA) Machining Guide · Carbon Fiber vs FR4 vs Phenolic