CAD Units and Scale That Break a Quote
Wrong Units or Wrong Scale = A Different Part
The quote engine reads the solid you uploaded. A mm/inch mix or a scaled export makes volume and shutoff wrong, so the first number is a different part. Re-export the molded solid at 1:1 in the drawing's units, prefer STEP, and upload a new record. Notes cannot resize the geometry.
Read STEP vs STL for a quote for format. This page only covers units and scale.
Engine reads the file, not the title block
The engine does not guess units. It reads them. A wrong unit is a new part, not a typo. Asking the title block to override the solid does not work. The solid wins until you replace the solid.
mm saved as inch = giant envelope; inch as mm = tiny
A millimeter part saved as inches looks huge. An inch part saved as millimeters looks tiny. Either way the engine is not guessing. It reads the units in the file. Review then sees an envelope that does not match the drawing.
Scaled mesh or screenshot derivative breaks volume
A screenshot path, a presentation model, or a mesh pulled from a visualizer can be the wrong size even when the units string looks right. Export the molded solid at 1:1 from the CAD system that owns the design. STL already lost the curve. A scaled STL lost the size too.
A worked example: a handheld housing is exported with inch units. The envelope looks like a crate. Review flags a file change. The buyer writes please scale. The fix is a new export at true size, then a new upload. The old record stays as history.
What to tell sourcing: if the envelope looks wrong versus the print, stop the comparison and re-export. Upload the corrected solid through the instant quote platform.
How the Break Shows Up on the Quote
Envelope looks wrong vs drawing
The first symptom is visual. The preview looks like furniture or like a coin. The drawing says a handheld housing. That mismatch is enough to stop. Do not accept the number and hope someone will scale it later.
Review flags file change, not a DFM change
Units and scale are a file class, not an RFQ class and not a DFM class. Read why an instant quote changes after CAD review. Write units or scale in the note so the next record is not compared as if resin changed. Design for manufacturing notes are a different class.
Old quote stays as history; new upload gets new ID
The old quote is not wrong. It is just for a different envelope. Volume and shutoff move when the solid is the wrong size. Steel scope follows the solid. Keep the old quote ID. The corrected file needs its own record. Read compare two quote revisions only after the cause is named.
A worked flag: quote Q-5502, envelope far larger than drawing Rev C. Review: file change, units. Buyer exports STEP in mm at 1:1. New quote Q-5510. Q-5502 stays.
What to tell sourcing: if the preview looks the wrong size, it is. Re-export. Do not negotiate a factor. Do not change quantity to compensate for a giant envelope.
What to Export Instead
Units match drawing (mm with mm, inch with inch)
Open the CAD units before you export. If the drawing is inches, do not export a millimeter solid and write see print. If the drawing is millimeters, do not export inches and write scale in notes. Align the system, then export STEP.
1:1 from the design CAD, not presentation scale
Export the molded solid at 1:1 from the design CAD. No presentation scale. Do not upload a scaled screenshot derivative, a visualizer mesh, or a presentation assembly built for a slide.
STEP over STL; molded solid only, no assembly junk
Prefer STEP if you still have a solid. Read what to upload for a molding quote for one molded solid and no assembly junk. A fastener at inch units can pollute a mm housing if you export the assembly.
Note the unit system, but the solid still must be correct
A note that says multiply by 25.4 resizes nothing. Only a correct solid does. If the file is still ambiguous, write the unit system in notes and still export 1:1. Notes help review. They do not replace a correct solid.
A worked export: CAD units mm, drawing Rev C mm, molded solid only, STEP, 1:1, note: units mm. That package can be quoted. Mesh at presentation scale with see drawing cannot.
What to tell sourcing: the export settings are part of the RFQ. If they cannot confirm units, they are not ready to compare numbers. If the solid moved, follow how to re-quote after a CAD change.
CAD Unit and Scale Checklist
Use this list before anyone treats the first click as the part.
- Confirm CAD units match the drawing units.
- Export the molded solid at 1:1, not a scaled screenshot path.
- Prefer STEP over a mesh if you still have a solid.
- Write the unit system in notes if the file is ambiguous.
- Upload the new file. Keep the old quote ID as history.
Step 1 is the pair. mm with mm. Inch with inch. Mixed is a new part.
Step 2 is scale. 1:1 from the design CAD. No presentation scale.
Step 3 is format. STEP if you have it. The format article explains why.
Step 4 is the note. Units mm or units inch. Useful. Not a substitute for step 1.
Step 5 is the new record. The old quote is history. Do not ask review to edit it in place.
A worked submit block: drawing Rev C mm, CAD mm, STEP 1:1, note units mm, old quote Q-5502 kept as history, new upload Q-5510. That block ends the scale argument.
Common mistakes at submit:
- Writing multiply by 25.4.
- Attaching only the PDF.
- Uploading the same wrong file with a longer note.
- Sending both a wrong-unit STEP and a correct STL.
- Treating the file-change flag as a DFM insult.
What to tell sourcing: send this checklist with the new STEP. Hold the first number as void for comparison until the envelope matches the print.
What to tell purchasing: the first number is a different part if the envelope is wrong. Re-export. Keep the old quote as history. A factor in notes is not a requote. A new STEP at 1:1 is.
What to tell review: name the cause as file, units or scale. Do not mix it with resin or quantity. The next record is comparable only after that class is written.