CAM toolpaths don't fail randomly.
They fail because something in the geometry breaks reliability.
And most of the time, the issue wasn't visible during design.
It was introduced during export.
The illusion of "clean CAD"
Models can look valid in CAD but export introduces topology issues. Translation to STEP or IGES can create or expose faults that weren't visible in the native session.
Common export-introduced issues:
- Open shells (non-watertight) — gaps in the boundary so the body is not watertight (see open shells (non-watertight) in CAD)
- Surface stitching gaps — edges that should be shared are not properly connected
- Zero-thickness edges — knife edges where two faces meet with no material (see knife edges in CAD)
- Non-manifold conditions — edges or vertices shared by more than two faces, or other invalid topology
Why CAM is less forgiving
CAM needs watertight geometry and clear boundaries to compute toolpaths. It assumes closed solids, finite thickness, and consistent face adjacency. Small issues—gaps, zero-thickness edges, non-manifold topology—cause toolpath generation to fail or produce invalid results.
What looks like a minor export artifact in a viewer becomes a hard stop in CAM.
The real cost isn't the error
The cost is the loop: CAM fails, the job is sent back, someone investigates, re-exports or repairs, then re-runs. That loop adds days—to prototype cycles, to vendor quoting, to delivery.
The geometry error is fixable; the calendar impact is what extends your timeline.
Why these issues survive
Export is often treated as "final"—the file is sent and the handoff is done. But export is translation. Most workflows validate design intent and DFM rules in-CAD; fewer validate post-export geometry integrity. So topology issues introduced or exposed by STEP/IGES translation slip through until CAM or a vendor catches them.
The gap isn't in design quality; it's in the missing check after the format change.
The missing layer: DFM pre-flight
DFM pre-flight is a set of checks run on the geometry you actually hand off—the exported file—before it reaches CAM or a vendor. It answers: does this file have the integrity required for manufacturing?
Typical checks include:
- Geometry integrity — closed shells, no open boundaries, no invalid topology
- Surface continuity — stitching and adjacency as expected
- Structural risks — e.g. wall thickness below manufacturable minimum
- Sharp edges that violate constraints (e.g. zero-thickness edges that break toolpaths)
Manufacturing reliability is a speed multiplier
The fastest hardware teams don't design faster. They remove preventable rework.
Manufacturing reliability isn't established at the machine. It's established before handoff.
Check geometry before handoff with the Geometry Error Checker.