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How do I make sure my supplier builds the right revision?

Larry Wu, CEO, Kyumi · Last updated October 12, 2026

Name the exact drawing revision on the purchase order, send one current PDF and STEP pair per part, and ask the supplier to confirm the revision in writing before cutting metal. Most wrong-revision parts happen because the PO, the drawing and the latest email disagree, and the supplier picks one.

Why suppliers build the wrong revision

A supplier rarely builds an old revision on purpose. It usually traces back to one of these:

  • The change never reached them. Machine Design notes that changes are often made while solving a problem, and either the print is never updated or the new revision is never sent to the supplier (Machine Design).
  • The documents disagree. On the Elsmar quality forum, one commenter describes a case where the PO named Rev A, the CAD file was at A and the drawing at B. Another reports that the drawing attached to the purchase order was the one that governed the contract (Elsmar).
  • The new drawing is buried. Rev C sits in a thread with eight replies, and the shop's buyer forwards Rev B to the floor.
  • Changes travel in side channels. After production starts, changes often go out as a slide, a chat message or a marked-up photo instead of a revised drawing.

In an Eng-Tips thread about a supplier dispute, one reply puts it plainly: it is up to the buyer to pass down configuration control and to state the correct revision on the purchase order (Eng-Tips).

Six checks that keep a supplier on the current rev

1. Put the revision on the PO line

Write the part number and the drawing revision on every PO line, for example 100-0234 Rev C. If the PO says Rev C, a part built to Rev B is usually the supplier's nonconformance.

2. Send a matched pair, named by revision

Send the PDF drawing and the STEP model together, both with the revision in the file name: 100-0234_RevC.pdf, 100-0234_RevC.step. Check that the revision in the title block matches the file name before you hit send.

3. Release before you send

Only send files from a released revision. One Eng-Tips poster describes their rule: files are reviewed before they go out for quote, and when a change happens the fabricator is told only after it is approved, then the PDF and DXF are resent (Eng-Tips). Sending a working copy "just to get a quote started" is how a draft becomes the build revision.

4. Tell them what changed, not just that it changed

A new drawing with no explanation makes the supplier diff two PDFs by eye. Fill in the revision block with a short description of each change and, where it helps, balloon the changed features. ASME Y14.35 covers how revisions are identified and recorded on drawings (ASME Y14.35 overview, NDIA).

5. Get a written acknowledgment

Ask the supplier to reply with the part number and revision they will build. It takes one email and catches the case where their buyer and their floor are on different files.

6. Pull the old revision back

Ask the supplier to mark or discard superseded prints. Inside your team, move old files to an _obsolete folder so nobody forwards them again.

Which channel to send changes through

Channel Revision is clear? History kept? Risk
Email with PDF + STEP attached If named well In inboxes only Gets buried in long threads
Chat apps (Slack, WeChat, WhatsApp) Rarely Scattered Photos and screenshots, no revision
Slides with screenshots No No Supplier works from an image, not a drawing
Shared folder or portal link Yes, if one file per rev Yes Folder gets cluttered with old revs
PDM web access for vendors Yes Yes Usually needs PDM Professional and setup

An Eng-Tips user notes that with SolidWorks PDM Professional, the web client can let a vendor pull the current PDF from the vault after an email notice (Eng-Tips).

What it costs when it goes wrong

A wrong-revision part costs the scrapped material and machine time, the rework or remake lead time, and often a slipped build. Machine Design lists wrong parts, costly returns and liability among the results of out-of-date prints (Machine Design).

When the part matches the print but still doesn't fit

A new supplier can build exactly to an old print and still ship a part that doesn't work, because a mating part changed, or a fix was made on the floor, and the drawing was never updated. When you revise one part, check the drawings of the parts it touches.

FAQ

Who is responsible if a supplier builds an old revision?

It usually comes down to what the purchase order named. If the PO stated the revision and the supplier built another, that is their nonconformance; if the PO was silent, expect a dispute.

Should the PO reference a drawing revision?

Yes. Put the part number and drawing revision on every PO line so there is one written answer to which revision governs.

How do I send a change to a supplier after production has started?

Release a new drawing revision with the change described in the revision block, send the matched PDF and STEP, and get a written acknowledgment. Avoid sending changes as screenshots or chat messages, which carry no revision.

What does "use latest revision" mean on a drawing note?

It tells the manufacturer to build to the most current version of a referenced specification. It can be ambiguous, so name the revision when a specific one matters.

Related questions

Sources

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