How to send CAD files to a China CNC factory is a packaging job: one STEP (or STP, IGES, X_T) solid, one PDF drawing with the same revision, and a short RFQ line for material, temper, quantity, and finish. Put datums, threads, Ra 3.2 or Ra 1.6, and Type II anodize notes on the PDF, not only in the model. Name files so a programmer can see part number and Rev C without opening them. Zip those files. Send through the channel the factory agreed (email, WhatsApp, or a portal), then get a written echo of the revision. If the shop quotes from an old STEP, you will pay for the wrong pocket. Units must be obvious. A 25.4 scale surprise is a bad pack, not a “communication issue.”
You are sending an RFQ across a time zone. The estimator will open what arrived, not what you meant to attach. US and EU teams lose days when the ZIP has five native files, two PDFs, and no statement of which one is live.
This is the pack a Dongguan programmer can run. It is also the pack you can reuse for custom CNC machining on the next revision. File control is the whole topic. Pretty CAD is not.
Key takeaways
- STEP plus PDF, same revision in both filenames, is the default pack.
- Native CAD is a backup for questions, not the only file.
- Units, material, finish, and quantity belong in the email body and on the drawing.
- Confirm the factory echoed the revision before you treat the quote as real.
- One zip per part family beats a dump of every export your CAD can make.
What the factory can actually program
A CNC programmer builds toolpaths from a solid and inspection from a 2D sheet. STEP AP214 or AP242 is the usual solid. PDF (or DWG) carries tolerances, Ra, threads, and finish. IGES and X_T are acceptable if STEP is not available. STL is for looking, not for milling metal.
If the part is mostly prismatic, CNC milling needs clean faces and a clampable datum. If it is a shaft, CNC turning needs the axis and the PDF for grooves and runout. More axes do not remove the need for a ballooned drawing.
ASME Y14.5-2018 is how many US PDFs state datums. Keep that language on the sheet; see ASME Y14.5. ISO 2768-1 (1989) can govern unmarked sizes if you name the class. See ISO 2768-1.
The solid must be the configuration you will buy. Suppressed bodies, leftover sketches as surfaces, and an assembly with fasteners still in it all waste the first hour in China. Export the machined piece only. If a bushing is purchased, do not include it as a cut body.
Units are a file-control item, not a later chat. The STEP and the PDF must agree: millimetres or inches, stated in the title block and in the email. A 25.4 error shows up as a part the size of a coin or a door. The mill that machines the scaled solid is not mind-reading. They opened your file.
Native SolidWorks, Creo, or NX can ride along when a face is broken. They are not the machining file. The receiving seat may be a different year. STEP is the interchange you can defend six months later when quality asks what was quoted.
How to send CAD files to a China CNC factory, step by step
How to send CAD files to a China CNC factory is a repeatable export, not a drag-and-drop from Downloads.
- Freeze the model (PDM or a dated folder). Done when nobody is still pushing fillets on the filename you are about to export.
- Export STEP from the released configuration (CAD export, mm or inch as on the drawing). Done when a second person can open the STEP and the overall size matches the PDF title block.
- Export a PDF of the 2D with revision, material, Ra, threads, and finish. Done when every critical is on the sheet, including “ISO 2768-m unless boxed.”
- Name both files with part number and revision (
PN-1234-REV-C.step,PN-1234-REV-C.pdf). Done when a search onREV-Creturns one pair. - Write a five-line RFQ (material/temper, quantity, finish, three criticals, Incoterm if freight matters). Done when those lines are in the email or form.
- Zip, send, and demand an echo (email, WhatsApp, or form). Done when the factory replies “quoting PN-1234 Rev C” in writing.
A common failure is attaching housing_final_FINAL2.sldprt and a PDF still titled Rev A. The mill will cut the wrong intent. The filenames were wrong.
If finishing is in scope, put the spec on the PDF. Anodizing finishing services should be visible as part of the route, not a later chat.
Zip hygiene is part of the procedure. One zip named PN-1234-REV-C-RFQ.zip. Inside: the STEP, the PDF, and nothing else unless you add a one-line FILELIST.txt that repeats the revision. Do not include Rev B “for reference.” Someone will import it. Do not include a full assembly STEP “so they understand.” They will mill a fastener.
Send through one channel the factory already uses, then archive that send. If you WhatsApp the zip at 21:00 and email a different PDF at 09:00, you created two live packs. Pick one. Follow the chat with the same zip on email so both sides can search.
Demand the echo before you shop the number internally. A quote that never names Rev C cannot be compared to a quote that does. If the shop replies with price only, write back: “Please confirm you are quoting PN-1234 Rev C from the zip dated 12 Mar.” Until that sentence exists, the quote is unattached.
Native CAD, STEP, and what not to send
Native SolidWorks, Creo, or NX files help when the factory asks about a broken face. They also lock the shop to your license year. STEP is the interchange. Send native only as a supplement.
Do not send STL as the machining file, a dozen STEP exports of the same part, a full assembly when you want a single piece, or a password-protected zip the shop cannot open at 22:00 China time.
| File | Use it for | Do not use it for | Best for | Watch-out |
|---|---|---|---|---|
| STEP / STP | Solid, toolpaths | Tolerances, Ra, threads | Almost every RFQ | Units and config |
| PDF / DWG | GD&T, finish, Rev | Replacing a broken solid | Inspection | Must match STEP rev |
| Native CAD | Repair, questions | Only file in the pack | Complex surfacing | License / version |
| IGES / X_T | Alternate solid | Preferred default | Older CAD chains | Surfaces can split |
| STL | Visual check | Metal cutting | 3D print cousins | No true CAD kernel |
Bottom line: if the zip is not STEP (or equal) plus PDF at one revision, you have not sent a machine-ready pack.
NIST manufacturing programs (2026 reference) treat versioned product data as part of making parts. You do not need a federal system. You need one live revision.
Other files that create re-quote loops: screenshots of a section view with a red arrow and no dimension, a spreadsheet of “updated holes” that never hit the PDF, and a cloud link that still lets your team overwrite the file after the shop downloaded it. If you use a link, freeze a dated copy. The mill should not be syncing to a live CAD folder you are still editing.
Password rules: if your IT requires a password, put the password in a second channel and make sure the night estimator can open the zip. An unreadable pack is a non-send. The clock did not start.
How to send CAD files to a China CNC factory after a revision
How to send CAD files to a China CNC factory after a hole change is a new pack, not an “updated STEP” email. Bump the revision on both files and say what changed in one sentence. “Rev D: Ø6.2 hole to Ø6.4, same datums” is a change note. “Updated STEP” is not.
Ask the factory to kill Rev C in their folder. If they quote overnight, your morning change needs a stop. Put “superseded” in the email subject when you pull a revision.
Keep a local folder: RFQ-2026-03-12-PN1234-REVC. When quality asks what was quoted, that folder is the answer.
Contact YXT CNC is the pattern: files, material, quantity, finish, criticals. Copy that structure even if you send to another mill.
Revision control on the machine side is your ask, not their hobby. Write: “Delete or archive PN-1234 Rev C. Do not cut or quote Rev C after this email. First article will be Rev D.” If they already programmed Rev C, they should say so. You then decide whether to pay for the reprogram. That is cheaper than discovering mixed holes in one carton.
Do not increment by filename tricks (PN-1234-REV-C-new.step). That is still Rev C to a tired programmer. Change the letter on the title block, the STEP, the PDF, the zip, and the subject.
If only the PDF notes changed (mask added, ISO class named) and the solid is identical, you still bump the drawing revision. The mill inspects from the PDF. A new note is a new contract. Send both files anyway so nobody wonders whether the solid moved.
For small-batch CNC repeats, pull the released pack from the dated folder. Do not re-export from a CAD file that designers kept editing. Production file control is “same zip as the approved sample,” not “latest from the server.”
Worked RFQ: one zip, one echo, no re-quote
This example is how to send CAD files to a China CNC factory so the quote sticks.
Folder on your side:
“`
RFQ-2026-04-02-BRKT-18-REVC/
BRKT-18-REV-C.step
BRKT-18-REV-C.pdf
FILELIST.txt
“`
FILELIST.txt contents:
- Part: BRKT-18 Rev C
- Units: mm
- Material: 6061-T6
- Qty: 10, breaks 30 / 100
- Finish: as machined Ra 3.2, no anodize
- Criticals: Ø6 H9 slot width 8.00±0.05, datum A flatness 0.05
- Open sizes: ISO 2768-m
- Inspection: CMM on slot and flatness; caliper elsewhere
- Zip date: 2026-04-02
Email subject: RFQ BRKT-18 Rev C STEP+PDF (mm) qty 10
Email body repeats FILELIST, then: “Please echo the revision before quoting. Quote only this zip.”
Factory echo you require: “Received BRKT-18 Rev C, mm, 6061-T6, qty 10, as machined. Quoting this pack.”
That echo is the gate. If they echo “aluminum bracket” with no revision, you have not sent successfully, even if the zip is perfect. Write back once. Do not start a second zip until they attach the quote to Rev C.
Second table for send failures:
| What you sent | What the mill quoted | Re-quote trigger | Fix before send |
|---|---|---|---|
| STEP only | Ra 3.2, no threads | PDF arrives later | PDF in first zip |
| Rev B PDF + Rev C STEP | Mixed hole | Incoming inspection fail | One letter on both |
| Native only | Delay or guess | They cannot open 2026 CAD | STEP export |
| Assembly STEP | Extra bodies | “Which part?” email | Single body |
| Cloud live folder | Moving geometry | Hole change mid-quote | Dated zip |
| Two zips, two chats | Two prices | Purchasing picks the cheap one | One channel |
Bottom line: a successful send is a dated zip plus a written revision echo. Anything else is a draft.
If you add Type II later, that is Rev D, a new zip, and a new echo. Do not patch finish into a chat and keep the old quote number.
A pack checklist you can paste
A complete send is done when the email body repeats the zip. Paste this under the attachment:
- Part number / revision
- STEP plus PDF (same rev)
- Units
- Material and temper
- Quantity (prototype vs batch)
- Finish spec
- Three critical features
- Inspection expectation (caliper vs CMM)
If a line is “TBD,” write TBD. Do not leave a blank the estimator will fill with ISO 2768-m and Ra 3.2.
Add three file-control lines to the same paste:
- Supersedes: none / Rev B killed
- Do not forward to unnamed mills
- Echo sentence required before we treat the quote as live
Those lines cost nothing. They prevent the mill from quoting a partner shop off a forwarded WeChat image. If a trader is in the loop, the zip still needs the same names. The mill programmer should see BRKT-18-REV-C, not image(3).jpg.
When the quote returns, archive it next to the zip: QUOTE-BRKT-18-REVC.pdf. If the quote PDF does not mention Rev C, it does not belong in that folder. Ask for a corrected quote header. That is still file control. It is how you send CAD files to a China CNC factory in a way purchasing can audit.
FAQ
How to send CAD files to a China CNC factory if I only have a STEP?
Send the STEP and a one-sheet PDF you export from the same model, even if tolerances are ISO 2768-m. Then add threads and Ra on that sheet before you approve the quote. A STEP-only send trains the shop to guess finish and inspection. Name both files with the same revision letter. Put units in the email. Ask for a written echo of that revision. Treat any price that arrives before the echo as a study number, not a PO basis. If you cannot make a PDF today, say that the pack is incomplete so nobody pretends it is frozen.
Is IGES OK for a China CNC RFQ?
Yes if STEP is not available and the solid opens clean. Ask the shop to confirm they imported a solid, not a surface quilt with gaps. IGES from old CAD chains often splits faces. A mill that has to stitch surfaces will either delay or quote extra CAM time. If they report gaps, export STEP AP214 or AP242 from the native file and resend as a new revision of the pack (same drawing letter if geometry did not change, but a new zip date and a new echo). Do not keep both IGES and STEP in one zip without saying which is live.
Should I send the assembly or the single part?
Send the single machined part plus any mating PDF notes that explain a fit. Full assemblies hide the piece the mill will fixture. Fasteners, PCBs, and purchased bearings in the STEP become bodies someone might try to mill. If the fit needs a mating dimension, put that dimension on the 2D as a reference or a note (“mates to Ø12 h6 shaft, not supplied”). You can attach a screenshot of the assembly for context. Do not make the screenshot the master.
Can I send files on WeChat or WhatsApp?
Yes if the factory agrees and you still get a written revision echo. Follow with email so both sides have the same zip in a searchable place. Chat compression can wreck a PDF or strip a zip. If the factory asks you to send “just pictures,” that is not a CAD send. Use the agreed channel for the zip, then paste the FILELIST in the chat so the night shift sees quantity and temper without opening CAD. One zip, one echo, two places to find it.
What if my drawing is in inches and the factory works in mm?
State units in the title block and the email. A good shop converts with a locked scale. A bad shop guesses. Do not mix units across STEP and PDF. If you export STEP in inches and PDF in mm, you will get a 25.4 problem or a dual-dimension fight. Pick one system for the pack. If the factory prefers mm, you can hard-convert the drawing and bump the revision, or you can require them to confirm the inch title block in the echo sentence. Confirmation belongs in writing.
How do I stop the factory from quoting an old STEP?
Kill the old revision in the subject line, send a new zip with new filenames, and require an echo that names the new letter. Ask them to archive the old toolpath. Do not send “final2.step” with the same Rev C title block. If they already quoted Rev C, say the quote is void. File control fails when purchasing keeps the old quote number because it was cheaper. Tie quote numbers to revision letters in your own folder names so that mistake is visible.
If you want a factory to show how to send CAD files to a China CNC factory in one cycle, attach STEP plus PDF at one revision, list material, quantity, and finish, and use the YXT CNC inquiry form. Wait for the revision echo, then treat the quote as belonging to that pack only.
