RFQ Preparation Guide
RFQ Preparation Guide | How to Request an Accurate Injection Molding Quote
A practical checklist for submitting a complete injection molding RFQ — 3D file formats, material specs, tolerances, surface finish, and volume data needed for an accurate quote within 24 hours. Written for OEM engineers and procurement managers.
Most injection molding RFQs arrive incomplete. The buyer sends a 3D file — sometimes just a screenshot — and writes “please quote.” The supplier has two choices: make assumptions and quote a tool that may not match what the buyer needs, or reply with a list of questions that adds 2–3 days to the response time. Neither serves the buyer well.
A complete RFQ gets an accurate quote within 24 hours. An incomplete RFQ gets a conversation. This guide tells you exactly what to include so the quote you receive reflects the tool you actually need.
1. The RFQ Checklist
Six items are required for an accurate injection molding quote. Everything else is helpful context but optional.
| # | Item | Why It Matters |
|---|---|---|
| 1 | 3D part file (STEP) | Determines part geometry, mold complexity, side actions, undercuts, and gate location |
| 2 | 2D drawing with tolerances | Critical dimensions with tolerance bands — without these, the mold is machined to general tolerance (±0.05 mm) |
| 3 | Annual volume | Dictates mold steel grade, cavity count, and hot/cold runner decision — the largest cost driver after part geometry |
| 4 | Material specification | Determines mold steel, process parameters, shrinkage factor, and per-part material cost |
| 5 | Surface finish requirement | SPI grade or VDI number — affects mold polishing labour (SPI A-2 adds 8–16 hours per cavity) and texture method |
| 6 | Target cost or budget range | Optional but helpful — allows the DFM engineer to propose a tooling strategy that hits your target rather than over-engineering a solution |
Optional but Recommended
| # | Item | Why It Matters |
|---|---|---|
| 7 | Regulatory requirements | FDA Class I/II, ISO 13485, PPAP Level 3, EN71, UL — determines documentation, material certification, and process validation scope |
| 8 | Colour and texture | RAL or Pantone colour reference; Mold-Tech or equivalent texture specification. Affects material formulation (masterbatch) and mold surface treatment |
| 9 | Packaging requirements | Bulk, layer-pack, or retail-ready — affects per-part cost and secondary operations |
2. File Formats
The 3D file is the foundation of the quote. The format you send determines whether the mold designer can work with your geometry directly or must reverse-engineer from an approximation.
| Format | Suitability | Notes |
|---|---|---|
| STEP (.stp / .step) | Preferred | ISO 10303 standard. Preserves solid geometry, assembly structure, and dimensional accuracy. Accepted by all CAD/CAM systems |
| IGES (.igs) | Acceptable | Older standard. Works but loses some feature information. STEP is preferred |
| SolidWorks (.sldprt / .sldasm) | Direct import | Native format. Fastest turnaround for SolidWorks users |
| UG NX (.prt) | Direct import | Native format |
| Pro/E / Creo (.prt) | Direct import | Native format |
| STL (.stl) | Reference only | Triangle mesh — no solid geometry, no dimensional accuracy. Cannot be used for mold design. Acceptable for rough cost estimation only |
| Screenshot / PDF drawing only | Insufficient | Cannot produce a mold quote from a 2D image of a 3D part |
2D drawings should be in PDF or DWG format. Mark critical-to-function dimensions with tolerance bands (e.g., 45.00 ±0.05 mm). General tolerances apply to all undimensioned features; critical tolerances drive the machining strategy and inspection plan.
If you do not have a 2D drawing, provide a marked-up PDF or a list of critical dimensions with tolerances. A 3D file alone tells the mold maker what shape to produce, not how precisely to produce it.
3. Material Specification
You have three options for specifying material:
Option A: Exact grade. “PA66-GF30, heat-stabilized, UL94 V-0, black.” The molder quotes exactly what you specified. No ambiguity. Use this option if your material is locked into the BOM.
Option B: Performance requirements. “Operating temperature 120°C continuous, UL94 V-0, chemical resistance to automotive coolant, colour RAL 9005 black.” The DFM engineer recommends grades that meet the requirements with cost and processing trade-offs explained. Use this option if you know the functional requirements but are open to material alternatives.
Option C: “Recommend something.” The DFM engineer reviews the part geometry, functional requirements, and volume, then recommends a material with reasoning. Use this option for early-stage designs, prototypes, or when you are new to injection molding and want engineering guidance.
For a detailed technical guide to resin selection, see How to Choose the Right Plastic Resin for Injection Molding →
4. Surface Finish
Surface finish determines how much polishing and texturing labour goes into the mold — and directly affects mold cost and lead time.
| Standard | Grade | Appearance | Cost Impact |
|---|---|---|---|
| SPI A-1 | Diamond polish, mirror finish | Optical surfaces, lenses | +10–20 hours polishing per cavity |
| SPI A-2 | High polish, glossy | Cosmetic A-side surfaces | +8–16 hours |
| SPI A-3 | Medium polish, semi-gloss | General cosmetic surfaces | +4–8 hours |
| SPI B-1 | 600-grit paper finish | Low-gloss functional surfaces | Standard — no adder |
| SPI B-2 | 400-grit paper finish | Non-cosmetic internal parts | Standard |
| VDI 3400 12–18 | Fine texture (0.3–1.0 µm) | Matte finish, soft-touch | Chemical etch required |
| VDI 3400 24–30 | Medium texture (2.0–4.5 µm) | Textured grip surfaces | Chemical etch |
| VDI 3400 36–45 | Coarse texture (7.0–12.5 µm) | Heavy texture, hides sink | Faster, lower-cost etch |
If you do not specify a surface finish, the default is SPI B-2 on the cavity and core. Cosmetic surfaces should be called out on the 2D drawing with the required finish grade.
Full details: Surface Finish & Texture Standards — SPI, VDI 3400, and Mold-Tech Explained →
5. How to Compare Quotes Fairly
Three buyers send the same part file to three molders and receive three quotes. The mold costs are $6,500, $12,000, and $22,000. All three are correct — for different tools.
The single largest mistake buyers make when comparing quotes is comparing different molds as if they were the same product. Before evaluating price, confirm that all suppliers are quoting the same:
| Variable | Lower-Cost Quote | Higher-Cost Quote |
|---|---|---|
| Steel grade | P20 (50K–200K shot life) | H13 hardened (500K+ shot life) |
| Cavity count | 1 (one part per cycle) | 4 (four parts per cycle) |
| Runner system | Cold runner (runner scrap) | Hot runner (zero scrap, faster cycle) |
| Surface finish | SPI B-2 (standard) | SPI A-2 (high-gloss cosmetic) |
| Side actions | Assumed none (simpler design) | Quoted with 2 slides (as designed) |
The fix: send a specification sheet with your RFQ — steel grade, cavity count, surface finish, and estimated shot life. Every supplier quotes the same scope, and the price comparison becomes meaningful.
For a full breakdown of injection molding costs, see Injection Molding Cost Breakdown — Tooling, Material, and Per-Part Economics →
A complete RFQ takes 15 minutes to prepare and saves 2–3 days of back-and-forth during the quoting process. Send your part file, 2D drawing, volume projection, and material preference — and you will have an accurate, comparable quote within 24 hours, with a free DFM report that identifies potential issues before steel is cut.