How To Send Accurate RFQ For Custom CNC & Die Cast Parts (Drawing Standard)
1. Introduction
Sending a complete, standardized RFQ is the fastest way to receive an accurate, fixed-price quotation from OEM CNC and die casting manufacturers. Incomplete drawings, missing tolerance requirements, unclear surface finish demands will lead to repeated back-and-forth communication, delayed quotes and even inconsistent finished products.
This guide covers the universal drawing standards and RFQ checklist for custom CNC machined parts and zinc/aluminum die cast components, helping global buyers streamline the procurement process.
2. Mandatory Drawing File Standards for RFQ
2.1 Acceptable 2D & 3D File Formats
Suppliers can only fully calculate costs and verify manufacturability with these standard files:
- 3D Drawing (Must-have for complex structures): STEP / IGES / STL / SolidWorks SLDPRT
- 2D Engineering Drawing (Must-have for dimension & tolerance): CAD DWG / DXF / PDF Annotated Drawing ⚠️ Warning: Simple JPG/PNG photos without labeled dimensions cannot support formal quotation.
2.2 Core Information Must Be Marked On Drawings
All below items must be clearly labeled on your 2D engineering drawing:
- Full overall dimension of the finished part
- Critical dimensional tolerance (key assembly positions, fit holes, shaft diameters)
- Wall thickness (especially for thin-wall die casting shells)
- Draft angle requirement (unique demand for die casting molds)
- Fillet & chamfer size
- Thread specification, depth and tolerance
- Positioning hole & assembly datum reference
- Weight limit requirement (if any)
2.3 Tolerance Standard Reference
List common tolerance rules to mark on drawings for RFQ:
- Standard CNC general tolerance: ±0.02mm
- High-precision CNC matching position: ±0.001~±0.01mm
- Aluminum/zinc die casting standard tolerance: ±0.05mm
- Thin-wall die casting appearance surface: ±0.1mm Write special tolerance demands separately if you need tighter standards than industry norms.
3. RFQ Information Checklist For CNC Machining Parts
Fill all items below in your RFQ email/form to avoid missing info:
- Attached complete 2D annotated drawing + 3D model file
- Raw material grade: 6061/7075 aluminum, 304/316 stainless steel, brass, POM, PEEK etc.
- Quantity: Sample order qty / Mass production MOQ / Monthly repeat demand
- Surface treatment: Anodizing, polishing, sandblasting, plating, passivation, powder coating
- Special processing: tapping, tapping depth, cross-hole, engraving, deburr requirement
- Packaging demand: Anti-scratch film, individual foam box, export carton
- Delivery term: EXW / FOB Shenzhen / DHL door-to-door sample delivery
- Target lead time for samples and bulk goods
- Special certification demand: RoHS, FDA for medical parts, ISO test report
4. RFQ Information Checklist For Die Casting Parts
Die casting RFQ needs extra mold-related specifications besides the above CNC items:
- Alloy material: ADC12 aluminum, Zamak 3#/5# zinc alloy, magnesium alloy
- Mold life expectation: 50k / 100k / 500k shots (affects mold cost)
- Appearance grade: A-class visible surface / B-class internal structural part
- Special die cast limits: No shrinkage cavity, no air bubble on outer surface
- Post-casting secondary processing: CNC trimming, tapping, drilling, assembly
- Logo engraving: Embossed / debossed logo position & size on mold
- Mold ownership: Buyer full ownership / supplier shared mold
5. Common Mistakes That Lead To Inaccurate RFQ Quotations
- Only send picture photos without dimensioned engineering drawings
- Missing critical tolerance requirements for assembly matching areas
- Not specify surface finish, resulting in different surface cost calculation
- Confuse die casting draft angle requirements, leading to rework cost
- No clear quantity separation between prototype samples and mass orders
- Omit special certification requests (RoHS, food-grade medical standard)
6. Standard RFQ Email Template (Direct Copy & Use)
Subject: RFQ - Custom CNC / Die Cast Parts Drawing No.XXX Dear Sales Engineer, We need quotation for custom mechanical components as attached drawings, details as below:
- Part No.: XXX
- Processing Type: CNC Milling/Turning / Aluminum Die Casting
- Material: XXX
- Order Quantity: 1 pcs sample, 5,000 pcs monthly mass order
- Tolerance Requirement: As marked on 2D drawing, critical hole ±0.01mm
- Surface Finish: Hard black anodizing
- Delivery: FOB Shenzhen, sample within 5 working days
- Certification: RoHS compliance required Please send detailed quotation including unit price, mold cost (for die cast), sample charge and lead time. If you have any DFM optimization suggestions for our drawing, kindly inform us. Looking forward to your accurate offer soon. Best regards, [Name] [Company]
7. Conclusion
A standardized drawing with full RFQ specs eliminates repeated communication between buyers and manufacturers. Clear dimension, tolerance, material and surface demands allow CNC and die cast factories to calculate raw material, labor and mold costs precisely, so you can receive an accurate, stable quotation in 24 hours without price revisions afterward.
If you cannot provide complete 3D drawings, you may send physical samples to our factory for reverse engineering and drawing creation service.
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