For CNC machining you need a STEP or IGES 3D model and a 2D drawing with GD&T callouts, tolerance specifications, surface finish callouts, and thread and hole specifications. The 3D model tells the machinist the geometry; the 2D drawing tells them what matters and what to hold. Without a dimensioned drawing, the supplier uses shop defaults—which may not be appropriate for your application.
Why this becomes hard
STEP files do not encode tolerance. A ±0.1mm clearance fit and a ±0.01mm precision bearing seat look identical in a 3D model. Without a 2D drawing with explicit callouts, the supplier cannot know which features are critical and which are cosmetic. This results in either over-inspection of non-critical features or under-inspection of critical ones—both of which cost you time and money.
What teams usually miss
The most commonly missing callouts are datum references, tolerance specifications for threaded inserts and press-fit bores, and critical mating surface finishes. Teams also frequently omit material temper—6061-T6 versus 7075-T651 versus raw stock—and surface finish specification: anodize type and class, hardcoat, bead blast, passivation, or none. All of these affect cost and lead time and become revision cycles if left to the supplier to guess.
What KnowYi does
KnowYi reviews your STEP and 2D drawing package, flags missing callouts or underdefined features before sending to any supplier, and routes to CNC suppliers matched to your batch size, material requirements, and tolerance range. We return dimensional inspection reports for each lot against your drawing—not against shop defaults.
What to send us
Send STEP or IGES file, 2D drawing (PDF or DXF) with GD&T callouts, material specification and temper, surface finish specification, batch quantity, and any critical delivery dates. If you have multiple parts that share a BOM, send the full BOM so we can review for assembly fit.
If you already have CAD, drawings, BOM, Gerbers, or even an incomplete file package, send it to KnowYi. We can turn it into a clear manufacturing path with missing inputs identified, quote blockers flagged, supplier routing handled, production records maintained, and delivery evidence returned.