---
title: "What CAD Files to Send for a Manufacturing Quote"
description: "STEP, STL, native CAD, DXF or a PDF drawing? What each file format carries and loses, what to send for each process, and the file mistakes that stall quotes."
canonical: https://openspindle.com/blog/cad-files-for-quoting
author: "Tom"
datePublished: 2026-09-16T00:00:00.000Z
dateModified: 2026-09-16T00:00:00.000Z
category: "Process & DFM"
---

# What CAD Files to Send for a Manufacturing Quote

For most machined, molded and bent sheet metal parts, send a STEP file per part plus a PDF drawing with tolerances, threads, finish and notes. The STEP gives exact geometry, and the drawing carries what a typical STEP export leaves out. Flat cut parts can be quoted from a clean DXF, and 3D printed parts from STL or 3MF. In an OpenSpindle RFQ, upload one CAD file per part, attach each drawing under Reference Files & Technical Drawings, and check that each part's Process matches how it will be made.

## The short answer: a 3D model plus a drawing

A quote is a prediction of how long a part will take to make, what it will be made from, and how much risk comes with it. The shop builds that prediction from your files. Geometry drives the machine time, and the requirements on the drawing drive setup, inspection and finishing.

No single file format carries both well. A neutral 3D format such as STEP describes the shape precisely but, in the way most people export it, says nothing about which dimensions are critical, which holes are threaded, or what the surface should look like. A PDF drawing says all of that but is slow and error prone to rebuild a model from.

That is why the standard package for most custom parts is a STEP file for the geometry and a PDF drawing for the requirements, one of each per part. Everything else in this guide is a variation on that rule for a particular process, or a way to avoid the file problems that turn a two day quote into a two week email thread.

If all you have is a paper or PDF drawing, that is still enough to start. We can have the CAD model created from it for an additional cost, covered in the RFQ section below.

## What each CAD format carries and what it loses

CAD formats fall into four groups. Solid model formats (STEP, IGES, Parasolid and native files) describe exact surfaces and edges, known as a boundary representation or B-rep. Mesh formats (STL, OBJ, 3MF) approximate the surface with small triangles. 2D formats (DXF, DWG) describe flat lines and arcs. A PDF drawing is a document for people to read.

STEP is the default neutral format for a reason: almost every CAD and CAM package reads it, and it carries an exact solid with units. The common AP203 and AP214 exports do not include product manufacturing information (PMI) such as tolerances and GD&T. The newer AP242 can, but support varies between programs, so a shop cannot count on it arriving.

IGES is older and describes surfaces rather than a closed solid, so imports more often arrive with small gaps between faces that have to be repaired before programming. Send STEP when you have the choice. Parasolid (X_T, X_B) is the modeling kernel behind several major CAD programs and usually translates very cleanly, which makes it a good second file.

Native files (SolidWorks, Inventor, Fusion, Creo, NX, CATIA and others) keep the full feature history, but the shop needs the same software, often a version at least as new as yours, to open them. They are fine to include, and some shops prefer them. Send a STEP alongside so any shop can open the part.

| Format | What it is | Best for | What it loses |
| --- | --- | --- | --- |
| STEP (.step, .stp) | Neutral exact solid (B-rep) with units | CNC machining, sheet metal, molding, casting, and a safe default for everything | Usually no tolerances, thread callouts, finish or notes; no feature history |
| IGES (.iges, .igs) | Older neutral surface format | Legacy systems that cannot export STEP | Often arrives as loose surfaces with gaps; same missing requirements as STEP |
| Parasolid (.x_t, .x_b) | Exact solid in the kernel format many CAD programs use | A clean second file next to STEP | Tolerances, threads, finish and notes |
| Native (.sldprt, .ipt, .f3d, .prt, .catpart and others) | The original CAD file with feature history | Shops running the same CAD package | Anything, if the shop's software or version cannot open it |
| STL, OBJ, 3MF | Faceted triangle mesh | 3D printing | True arcs, cylinders and flat faces; STL also has no units |
| DXF, DWG | 2D lines, arcs and layers | Flat laser, waterjet, plasma and router cut parts | Thickness, bends and any 3D shape; units are often unset or ignored |
| PDF drawing | Dimensioned drawing for people to read | Tolerances, GD&T, threads, material, finish, notes and revision | Machine-readable geometry |

## Why the drawing still matters

A 3D model is a single nominal shape. Every dimension on it is perfect, so it cannot tell a shop that one bore must be within ±0.0005 in while the outside profile can move ±0.010 in. Without that, the shop either quotes everything to its standard tolerance and your critical feature may come back out of spec, or quotes everything tight to be safe and the price goes up.

The same goes for threads, which most CAD programs model as cosmetic features that disappear in a STEP export, and for surface finish, coatings, hardware, marking and inspection requirements. See the tapped holes guide for why a threaded hole in a STEP file often looks like a plain drilled hole.

The drawing does not have to be a full production print for a quote. A simple PDF that dimensions only the critical features, lists the tolerances that differ from general, calls out threads and finish, and shows a revision letter does most of the work. If you have no drawing yet, a screenshot of the model with the important features marked up is far better than nothing.

## Which files to send for each process

The best package depends on how the part will be made. The rules below are what most shops in a network like ours expect, and they overlap on purpose: when in doubt, a STEP file plus a PDF drawing is almost never the wrong answer.

Sheet metal with bends deserves a special mention. Send the 3D model of the formed part rather than your own flat pattern. The shop develops the flat pattern using the bend allowance for its own tooling, material and press brake, and a flat pattern calculated with different assumptions can put holes and bends in the wrong place. State the material and thickness, and the inside bend radius if it matters.

| Process | Send this | Also helpful | Avoid relying on |
| --- | --- | --- | --- |
| CNC machining and turning | STEP per part plus a PDF drawing | Parasolid or native file | STL or other mesh, which most shops cannot program from |
| Flat laser, waterjet or plasma cutting | DXF or DWG at 1:1 scale, cut geometry only | PDF with material, thickness and quantity; STEP is also fine | A DXF exported with the title block and dimensions on it |
| Sheet metal with bends | STEP of the formed 3D part plus a PDF drawing | Native sheet metal file | A flat DXF alone, since bends and bend direction are lost |
| 3D printing | STL or 3MF at adequate resolution, or STEP | Note on which faces are cosmetic or mating | A coarse mesh with visible facets on curved faces |
| Injection molding and casting | STEP of the part plus a PDF drawing | Native file; notes on cosmetic faces, draft and parting line if known | Mesh files, which a mold designer has to rebuild |

## Common file mistakes that slow a quote

Most file problems are invisible to the person who exported them, because the part looks correct on their own screen. These are the ones shops see over and over.

Unit errors are the classic. A part drawn in millimeters and read as inches arrives 25.4 times too large, and the reverse makes it 25.4 times too small. STL files store no units at all, and many DXF files leave the units field unset, so the receiving software guesses. STEP files do record units, but a model built at the wrong scale exports the wrong size just as faithfully. The fix is to say the units in writing and to give one overall dimension the shop can check against.

| Mistake | What happens | Fix |
| --- | --- | --- |
| Wrong or missing units in STL, DXF or STEP | Part imports 25.4x too large or too small | State units in a note and give one overall size to check |
| DXF with title block, dimensions or construction lines | The cutting software treats every line as a cut path | Export only the cut profiles, on one layer, at 1:1 |
| Open profiles or duplicate lines in a DXF | Shapes will not close, or the machine cuts the same edge twice | Join contours into closed polylines and delete overlapping entities |
| Whole assembly exported when one part was meant | The shop quotes, or asks about, parts you already have | Export each part to its own file and list what is being made |
| Drawing revision does not match the model | Conflicting dimensions stop the quote until someone decides which is right | Put the same revision in both file names and on the drawing |
| Very large files | Uploads fail or time out, and some viewers will not open them | Export single parts, lower the mesh resolution, and remove embedded images from PDFs |
| Splines and tiny segments in a DXF | Jerky, slow cuts and a higher quote for cut time | Convert splines to arcs and lines before export where your CAD allows |

## Exporting clean files

A few export habits prevent most of the problems above.

For STEP, export one part per file for anything you want quoted as a separate part, check that the file opens at the right size in a free viewer, and use an AP214 or AP242 export if your software gives a choice. Name the file with the part number and revision, for example BRKT-104_revB.step.

For DXF, export from a flat view or a sketch of the part rather than from a drawing sheet, keep only closed cut profiles, set the units explicitly, and draw at full scale. If a part has etched or marked lines, put them on a separately named layer and say so.

For STL and 3MF, choose a fine enough export resolution that curved surfaces look smooth, without going so fine that the file becomes enormous. 3MF has the advantage of storing units. For PDF drawings, include the part number, revision, units, material and general tolerance block, even on a simple one page quote drawing.

## Sending files with your OpenSpindle RFQ

The quote form is built around the file package described above, so a little care on upload saves questions later.

**Step 1: Upload one CAD file per part.** On the Upload step, each CAD file you add becomes its own part card. PDFs and images become reference files rather than parts, so a drawing uploaded here will not turn into an extra part. The form accepts STEP, IGES, Parasolid, DXF, DWG, STL, OBJ, 3MF and common native formats, up to 10 files at 25MB each.

**Step 2: Keep each file under 25MB.** Each file needs to stay under the 25MB limit. If a file is too large, split an assembly into individual parts, reduce the resolution of a mesh export, or simplify cosmetic detail such as knurling and text.

**Step 3: Check the Process on every part.** On the Parts & specs step, the form suggests a process from the file type, so check Process on every part card before moving on. For a flat part cut from sheet, set Process to Sheet Cutting. For a part that is cut and then bent, choose Sheet Metal.

**Step 4: Attach the drawing to its part.** On each part card, use Reference Files & Technical Drawings (optional) and the Add drawing, photo, sketch, or PDF button to attach that part's PDF drawing, so the shop sees the requirements next to the right model.

**Step 5: State units and revision in the Note.** Use the part Note to say what units the file is in, the revision, and one overall dimension to check against. Add anything the file does not carry, such as threads or which faces are cosmetic.

**Step 6: Replace STL with a solid model for CNC.** If a part set to CNC only has an STL, the form shows this message: "Most shops don't cut parts from STL mesh files. If you can, upload another CAD file (STEP, STP, IGES, DXF, or DWG) to speed up the quoting process." A STEP export is usually the answer.

If you have no CAD files yet, use the No files yet? Describe your project instead link on the upload screen. You can describe the part in words and add files once they exist.

**Only have a drawing?** We can have a CAD model created from it, at an additional cost quoted separately from the parts. Because a PDF on its own does not create a part, start with Describe your project instead, attach the drawing under Add photos or files (optional), and say in the description that you need a CAD model made. A drawing with complete dimensions and a stated revision is the fastest to model.

## A complete example package

Here is a package that lets a shop quote a small order the first time, for a machined aluminum bracket and a laser cut stainless cover plate.

Files uploaded: BRKT-104_revB.step, BRKT-104_revB.pdf, PLATE-210_revA.dxf, PLATE-210_revA.pdf. That produces two parts, with the two PDFs attached to their parts under Reference Files & Technical Drawings (optional). The bracket is set to CNC, and the plate is set to Sheet Cutting.

Note on the bracket: STEP in millimeters, revision B, overall size 120 x 45 x 30 mm. Drawing rev B attached, critical bore tolerance and 4X M5x0.8 threads called out on page 1. Faces marked A on the drawing are cosmetic.

Note on the plate: DXF in millimeters at 1:1, revision A, overall size 200 x 150 mm, 1.5 mm 304 stainless. Only cut geometry is in the file. Etch lines for the logo are on the layer named ETCH. Drawing rev A attached.

Nothing in that package asks the shop to guess about size, revision, process or which requirements matter. If you are unsure of a format or a requirement, say so in the note. A shop can tell you what it needs, which beats a quote built on an assumption.

## Related reading

- [How to write an RFQ](https://openspindle.com/blog/how-to-write-an-rfq.md)
- [Tapped holes: design, callouts and quoting](https://openspindle.com/blog/tapped-holes.md)
- [What is DFM?](https://openspindle.com/blog/what-is-dfm.md)
- [GD&T symbols reference](https://openspindle.com/reference/gdt-symbols-reference.md)
- [Sheet metal bend radius chart](https://openspindle.com/reference/sheet-metal-bend-radius-chart.md)
- [Laser cutting capabilities](https://openspindle.com/capabilities/laser-cutting.md)
- [CNC machining capabilities](https://openspindle.com/capabilities/cnc-machining.md)

## Frequently asked questions

### What is the best file format to send for a CNC machining quote?

A STEP file of each part plus a PDF drawing. STEP carries exact geometry that nearly every CAM system can read, and the drawing carries the tolerances, threads, finish and notes that a typical STEP export does not include. A Parasolid or native file is a useful extra, not a replacement.

### Can a machine shop use an STL file?

Most CNC shops prefer not to. An STL approximates curved surfaces with flat triangles, so holes and bores are no longer true cylinders and the part has to be remodeled before it can be programmed. STL and 3MF are standard for 3D printing. For machining, export a STEP from the original CAD model if you can.

### Should I send a DXF or a STEP file for laser cutting?

For flat parts, a clean DXF at 1:1 with only the cut profiles is the usual choice, along with the material and thickness in writing. A STEP works too, and it is the better file when the part is bent, because the shop needs the formed shape to develop its own flat pattern.

### Is it OK to send native SolidWorks or Fusion files?

Yes, and some shops prefer them, but only a shop with the same software, and often the same or a newer version, can open them. Include a STEP export as well so any shop can quote the part.

### What if I only have a drawing and no CAD file?

You can still request a quote. We can have a CAD model created from your drawing at an additional cost, quoted separately from the parts. Choose Describe your project instead on the upload screen, attach the PDF or a clear photo of the drawing, and say that you need a model made. A fully dimensioned drawing with a revision is quickest to model.

### Why did my part import at the wrong size?

Usually a unit mismatch. STL files carry no units and many DXF files leave units unset, so software assumes millimeters or inches and a part ends up 25.4 times too large or too small. State the units and one overall dimension in your note so the shop can confirm the scale.

### How do I add a drawing to an OpenSpindle quote request?

Upload the CAD files first, since each becomes a part. Then on each part card, use Reference Files & Technical Drawings (optional) to attach that part's PDF drawing. PDFs added on the Upload step become reference files, not extra parts.