3D Models Show Geometry
STEP, STP, X_T, IGS, and similar 3D files help the supplier understand the full part shape, tool access, complex surfaces, pockets, ribs, holes, and assembly geometry.
For custom CNC machined parts, the supplier cannot quote accurately from a part name alone. The best RFQ includes drawings, material, quantity, tolerance, surface finish, inspection needs, and the part application.
2D Drawings Confirm Requirements
PDF, DWG, or DXF drawings confirm tolerances, threads, surface finish, material, datum references, heat treatment, notes, and critical dimensions that may not be obvious from the 3D model.
Files to Send for a CNC Machining Quote
- 3D model: STEP, STP, X_T, IGS, SLDPRT, or other export format.
- 2D drawing: PDF, DWG, or DXF with dimensions, tolerance, and notes.
- Material grade and acceptable alternatives when possible.
- Quantity for prototype, first batch, and expected repeat orders.
- Surface finish, coating, anodizing, passivation, polishing, or deburring requirements.
- Critical dimensions, mating surfaces, datum references, and inspection requirements.
What to Mark Clearly on 2D Drawings
A good 2D drawing tells the supplier what matters most. It prevents quoting based only on appearance and helps avoid expensive rework after machining.
Critical Tolerances
Mark bearing seats, locating holes, sealing faces, sliding fits, datum features, and assembly-critical dimensions separately from general tolerance.
Thread Details
Show thread type, pitch, depth, class, direction, and whether thread gauges or special checking are required.
Surface Finish
State roughness, polishing, brushing, bead blasting, anodizing, plating, passivation, black oxide, or cosmetic surface requirements.
Post-Process Dimensions
If dimensions matter after coating or anodizing, mark that clearly. Surface treatment can change final dimensions on precision parts.
Information That Helps Suppliers Quote Faster
The more practical information you provide, the easier it is to choose the right process, inspection method, and delivery plan.
Part Function
Tell the supplier whether the part is a fixture, bracket, shaft, housing, medical equipment component, automation part, prototype, or production component.
Assembly Context
Explain mating parts, movement, alignment, load, temperature, corrosion exposure, or cosmetic requirements when they affect manufacturing choices.
Quality Documents
State whether you need material certificates, first article inspection, dimensional reports, CMM reports, photos, or special packing confirmation.
Delivery Target
Tell the supplier your target date and whether partial shipment, prototype first, or batch delivery is acceptable.
Common RFQ Mistakes That Delay Quotation
- Sending only a screenshot instead of a real drawing or 3D model.
- Not specifying material grade or acceptable substitute materials.
- Applying tight tolerance to every dimension without marking critical features.
- Forgetting surface finish, deburring, or coating requirements.
- Not stating quantity, which makes unit price and setup cost difficult to estimate.
- Requesting urgent delivery without confirming material availability and inspection needs.
RFQ Checklist Before You Send Drawings
- 2D drawing and 3D model are attached.
- Material grade, quantity, finish, and delivery target are included.
- Critical dimensions and datum references are marked.
- Threads, fits, sealing surfaces, and mating faces are clear.
- Inspection report or certificate requirements are stated.
- Application notes are included if the part has assembly risk.
What XHR Reviews Before Quoting a CNC Machined Part
After receiving your drawings, XHR reviews more than the outside shape. The quotation depends on manufacturability, material, tolerance, surface finish, inspection scope, and whether the part can be produced consistently.
Manufacturing Route
We check whether the part is better suited for CNC milling, CNC turning, 4-axis machining, 5-axis machining, grinding, EDM, or a combination of processes.
Tool Access and Fixturing
Deep pockets, narrow slots, angled holes, thin walls, and several critical faces may require special tools or fixtures. These details affect cost and delivery.
Risk Features
Sharp internal corners, very thin walls, long slender parts, tight threads, sealing surfaces, and cosmetic faces should be reviewed before quoting to avoid later changes.
Inspection Plan
For critical parts, XHR reviews whether calipers, micrometers, thread gauges, height gauges, CMM inspection, or functional checks are needed before shipment.
Good RFQ Email Example
A short but complete RFQ email helps the supplier reply faster. Buyers do not need a perfect technical report, but the basic information should be clear.
- We need CNC machined parts according to the attached STEP model and PDF drawing.
- Material: Aluminum 6061-T6. Please advise if 7075 is better for strength.
- Quantity: 5 pcs prototype first, then possible 100 pcs repeat order.
- Surface finish: black anodizing. Please confirm whether critical dimensions apply after anodizing.
- Critical dimensions: hole position and mating face flatness marked on drawing.
- Please quote unit price, lead time, shipping option, and whether inspection report can be provided.
What Happens If RFQ Information Is Missing?
Missing information does not always stop quotation, but it can make the quotation less accurate. The supplier may need assumptions, and those assumptions can change cost or delivery later.
No Material Grade
The supplier cannot confirm machining difficulty, material cost, surface treatment compatibility, or certificate needs.
No Quantity
Prototype pricing and batch pricing can be very different because setup, programming, and fixture cost are spread across different quantities.
No Tolerance Notes
The supplier may quote general machining, but the part may later require slower cutting, CMM inspection, grinding, or extra process control.
No Surface Finish
Anodizing, plating, polishing, passivation, or coating can affect dimensions, appearance, packing, and lead time.
Related CNC Machining Pages
Use these pages when you are ready to review machining capability, tolerance, or inspection requirements.
Guide FAQ
Can XHR quote from incomplete drawings?
Yes. Send the available model, drawing, material, quantity, and notes. XHR can review the part and ask follow-up questions before quoting.
Should I send both PDF and STEP files?
Yes, when possible. The 3D file helps geometry review, while the PDF drawing confirms tolerances, threads, surface finish, and critical features.