If you want a sheet metal supplier to quote accurately without making assumptions, you should provide more than just a PDF drawing.
A complete RFQ package helps us evaluate:
- manufacturability
- tooling requirements
- material usage
- tolerance risks
- assembly fit
- surface finish expectations
- packaging and logistics
When information is missing, suppliers usually do one of two things:
- Add hidden risk cost into the quotation
- Quote incorrectly and later request engineering changes or price adjustments
For custom sheet metal and stamping projects, I recommend including the following files and information.
Quick Answer
The most important files in a sheet metal RFQ are:
| File Type | Purpose |
|---|---|
| 3D CAD file (STEP preferred) | Defines actual geometry for manufacturing |
| 2D drawing PDF | Defines dimensions, tolerances, finish, notes |
| BOM (Bill of Materials) | Clarifies quantities and assemblies |
| Surface finish specification | Prevents appearance and coating misunderstandings |
| Assembly drawings | Helps check fit and interference |
| Quantity forecast | Determines process selection and tooling |
| Packaging requirements | Avoids transport damage |
| Sample/reference photos | Clarifies cosmetic expectations |
Without these documents, suppliers must estimate critical details themselves.
1. 3D CAD File (STEP Format Preferred)
This is the most important file in modern sheet metal manufacturing.
Recommended formats:
- STEP (.step / .stp)
- Parasolid (.x_t)
- IGES (.igs)
- SolidWorks native files if agreed
A 3D model allows us to:
- unfold sheet metal correctly
- verify bend feasibility
- check tool access
- estimate laser cutting time
- identify collision risks
- evaluate welding accessibility
STEP files are preferred because they are universal and reduce software compatibility problems.
According to Siemens Digital Industries Software, using 3D model-based manufacturing workflows can reduce engineering interpretation errors by over 30%.
2. 2D PDF Drawings With Full Manufacturing Notes
A 3D model alone is not enough.
The 2D drawing defines manufacturing intent.
Your drawing should include:
Critical Dimensions
Especially:
- hole positions
- bend locations
- threaded features
- assembly interfaces
Tolerances
Do not use unnecessarily tight tolerances.
Example:
- General tolerance: ISO 2768-m
- Critical fit holes: ±0.05 mm
- Cosmetic gap control dimensions
Without tolerance information, suppliers must guess acceptable variation.
That creates assembly risks later.
Material Specification
Include:
- material grade
- thickness
- temper if required
Example:
- SPCC 1.5 mm
- SUS304 2B
- AL5052-H32
Surface Finish
Specify clearly:
- powder coating
- anodizing
- zinc plating
- brushing
- silk printing
- texture requirements
Include:
- color code
- gloss level
- salt spray requirement if needed
Example:
Powder coating RAL 9005 matte black, 70–90 μm thickness, 500-hour salt spray resistance.
3. Bill of Materials (BOM)
A BOM helps suppliers understand the complete project scope.
Include:
| Item | Description |
|---|---|
| Part number | Unique identification |
| Revision | Prevents version confusion |
| Material | Material grade |
| Qty per assembly | Assembly usage |
| Annual volume | Process planning |
| Remarks | Special instructions |
This is especially important for enclosure assemblies with:
- PEM fasteners
- hinges
- handles
- cable accessories
- gaskets
- PCB mounting hardware
4. Assembly Drawings
Many sheet metal issues only appear during assembly.
For example:
- tolerance stack-up
- interference between bends
- door alignment
- welding distortion
- cable routing conflicts
Assembly drawings help suppliers evaluate whether parts actually work together.
This is critical for:
- power distribution equipment
- server cabinets
- medical housings
- industrial control boxes
We often find problems during DFM review before production starts.
That can save weeks of redesign time.
5. Quantity Information and Forecast
Process selection depends heavily on volume.
For example:
| Volume | Recommended Process |
|---|---|
| 1–50 pcs | Laser cutting + bending |
| 500–5,000 pcs | Simple tooling optimization |
| 10,000+ pcs | Progressive stamping die |
If you do not provide volume information, suppliers cannot optimize pricing correctly.
A project quoted as prototype production may become unnecessarily expensive in mass production.
At Premium Rapid & Mold, we often help customers transition from low-volume sheet metal fabrication to stamping once annual demand justifies tooling investment.
6. Surface Finish Reference Photos or Standards
Cosmetic expectations vary significantly between customers.
A photo reference helps avoid misunderstandings such as:
- inconsistent texture
- gloss mismatch
- weld appearance issues
- brushing direction differences
This is especially important for:
- consumer electronics
- audio equipment
- lighting products
- visible enclosures
Powder coating alone has hundreds of texture and gloss combinations.
A visual sample is often faster than long explanations.
7. Packaging Requirements
Many RFQs ignore packaging until products arrive damaged.
For export projects, packaging should be defined early.
Include requirements such as:
- individual PE bag
- scratch protection film
- foam separators
- carton weight limits
- pallet standard
- barcode labels
According to Packaging Digest, transport vibration damage accounts for a large percentage of cosmetic metal part claims during international shipment.
Good packaging design also reduces shipping cost.
Nested packaging and stack optimization can significantly reduce carton volume.
8. Hardware Specifications
If your product uses hardware, specify:
- PEM nuts
- rivets
- studs
- screws
- inserts
- brand requirements
Include:
- thread specification
- material
- plating requirement
Example:
PEM CLS-M4-2 stainless self-clinching nut.
This avoids substitution risks.
9. Testing and Compliance Requirements
If applicable, specify:
- IP rating
- RoHS
- REACH
- UL requirements
- salt spray test standard
- grounding requirements
Especially for electrical enclosures and industrial equipment.
These requirements can affect:
- material selection
- coating process
- welding method
- gasket design
10. Revision Control Information
One of the biggest causes of manufacturing mistakes is revision confusion.
Always include:
- drawing revision
- ECO reference
- latest release date
Use consistent file naming such as:
PD-001_REV-B_STEP
PD-001_REV-B_DRAWING
This prevents suppliers from quoting outdated files.
Common RFQ Mistakes That Cause Re-Quotes
Sending Only a PDF
Suppliers must redraw the model manually.
This increases engineering time and risk.
Missing Tolerances
Without tolerance definition, every supplier assumes differently.
Quotes become impossible to compare fairly.
No Quantity Information
The supplier cannot recommend the best production process.
Undefined Surface Finish
This causes major cosmetic disputes later.
No Assembly Context
Individual parts may look correct but fail during final assembly.
My Recommended RFQ Package Structure
RFQ_Project_Name/
│
├── 3D/
│ ├── STEP files
│
├── 2D_Drawings/
│ ├── PDF drawings
│
├── BOM/
│ ├── BOM.xlsx
│
├── Assembly/
│ ├── Assembly PDF
│
├── Surface_Finish/
│ ├── Photos
│ ├── Color standards
│
├── Packaging/
│ ├── Packaging requirements
│
├── Compliance/
│ ├── RoHS
│ ├── Test requirements
│
└── RFQ_Info.xlsxFinal Thoughts
A good sheet metal RFQ does more than request pricing.
It helps the supplier:
- identify manufacturing risks early
- recommend cost-saving improvements
- prevent assembly issues
- improve lead time accuracy
- reduce quality disputes
The more complete your RFQ package is, the fewer assumptions the supplier needs to make.
That usually leads to:
- faster quotations
- more accurate pricing
- fewer engineering changes
- smoother production launch
For complex enclosures or assemblies, a strong RFQ package can easily save several weeks of project time and avoid expensive redesigns later.
