Send STEP, STL, or both
Keep STEP as the solid CAD source and STL as the print mesh when both exist, then explain what the plastic prototype proved.
Model + process preference + functional context
The human step sits where file fidelity, geometry, process, price, and risk meet. That is more useful than pretending every mesh or solid can be priced the same way.
Keep STEP as the solid CAD source and STL as the print mesh when both exist, then explain what the plastic prototype proved.
Model + process preference + functional context
A person checks file quality, geometry, interfaces, precision needs, support/tool access, and likely post-processing before pricing.
Process route + questions + DFM notes
STEP can remain the source for either route. STL-to-CNC reconstruction may change geometry, so the converted model must be reviewed and approved.
Approved source or reconstructed manufacturing model
Process, material, quantity, finish, timing, inspection, post-processing, and documentation are confirmed before work begins.
A quote based on explicit requirements