Why File Formats Matter More Than You Think

From a supplier’s perspective, quoting is not just pricing — it’s risk evaluation.

Every missing detail increases uncertainty:

• Unclear tolerances → risk in machining
• Missing dimensions → risk in inspection
• Undefined finishes → risk in final cost

To compensate, suppliers either:

• Add a safety margin (higher quote), or
• Quote aggressively and adjust later

Neither outcome helps the buyer.

The goal of a good RFQ is simple:

Remove guesswork before pricing starts

The Core Files Every CNC RFQ Should Include

3D CAD File (STEP Preferred)

This is the foundation of your RFQ.

Recommended formats:

• STEP (.step / .stp)
• IGES (.igs / .iges)
• Parasolid (.x_t / .x_b)

Why STEP is preferred:

• Universal compatibility
• High geometry accuracy
• Works across most CAD/CAM systems

What it’s used for:

• Toolpath generation
• Geometry interpretation
• Machining feasibility analysis

Without a 3D file, suppliers cannot accurately estimate machining time or complexity.

2D Drawing

This is where most RFQs fail.

A 3D model shows shape.
A 2D drawing defines requirements.

Include:

• Critical dimensions
• Tolerances
• GD&T (if applicable)
• Surface finish requirements
• Notes and special instructions

Common mistake:

Sending only a 3D file with “quote as per model.”

This forces suppliers to assume tolerances and inspection scope — which almost guarantees quote revisions later.

Tolerance Specification

Tolerances should not be left to interpretation.

Clearly define:

• General tolerances (e.g. ISO 2768)
• Critical feature tolerances
• Fit requirements

Why this matters:

Tighter tolerances increase:

• Machining time
• Inspection requirements
• Scrap risk

Over-tolerancing is one of the fastest ways to inflate cost — often without improving function.

Material Specification

Always go beyond “aluminum” or “steel.”

Specify:

• Exact grade (e.g. 6061-T6, 7075-T6, SUS304)
• Certification requirements
• Acceptable substitutes (if any)

Material choice affects:

• Machinability
• Tool wear
• Cost
• Lead time

Clear material definition reduces back-and-forth communication.

Surface Finish and Post-Processing

Finishing is often quoted separately — and misunderstood.

Include:

• Anodizing (type, color, thickness)
• Plating (type and standard)
• Powder coating
• Polishing level
• Heat treatment

Each process may involve:

• Minimum batch requirements
• Additional cost
• Extra lead time

If not specified upfront, finishing becomes a source of delay and cost increase.

File Formats That Are Not Enough

STL Files

STL files are common in 3D printing — but problematic for CNC.

Limitations:

• No dimensional data
• No tolerance definition
• Mesh-based geometry (not ideal for machining)

Most CNC shops will request a STEP file if you send STL.

Images or Screenshots

Some RFQs include only:

• PNG images
• PDF screenshots
• Marked-up visuals

These are useful for reference — but not for manufacturing.

They cannot be used for:

• CAM programming
• Accurate quoting
• Inspection planning

How File Quality Affects Your Quote

wo RFQs can describe the same part — but produce completely different quotes.

Why?

Because suppliers are pricing uncertainty, not just machining.

A clear RFQ:

• Reduces assumptions
• Improves quote accuracy
• Speeds up response time

An unclear RFQ:

• Increases cost buffer
• Delays quoting
• Leads to revisions during production

Better files don’t just improve communication — they directly impact cost and delivery.

What Experienced Buyers Do Differently

Professional sourcing teams treat RFQs as structured inputs — not casual requests.

They typically:

• Send both 3D and 2D files together
• Clearly define tolerances and materials
• Specify production stage (prototype vs production)
• Standardize RFQ templates across projects

This reduces variability and makes supplier performance more predictable.

How Kachi Precision Evaluates Your RFQ

At Kachi Precision Manufacturing, quoting is not handled as a simple pricing task.

It’s an engineering review process.

When we receive an RFQ, we:

• Cross-check 3D and 2D files
• Identify cost-driving features
• Flag unclear tolerances
• Evaluate machining feasibility
• Review finishing requirements

Any ambiguity that affects cost or quality is addressed before quoting, not after production starts.

This is how we help customers avoid:

• Quote changes
• Unexpected cost increases
• Redesign delays

RFQ File Checklist

Before sending your RFQ, confirm you have:

• 3D CAD file (STEP preferred)
• 2D drawing with dimensions and tolerances
• Material specification
• Surface finish requirements
• Quantity and production stage

If any of these are missing, expect delays or revisions.

Conclusion

Getting an accurate CNC machining quote doesn’t start with the supplier.

It starts with the files you send.

Clear, complete, and well-structured RFQs:

• Reduce cost uncertainty
• Improve supplier response
• Shorten lead time
• Prevent production issues

In 2026, where speed and precision both matter, better input leads to better outcomes.