Collision checking must include the cutter, shank, collet nut, holder, spindle body, clamps, fixtures, stock, machine travel, and rapid moves. Simulation is useful only when its stock, origin, tool assembly, and machine assumptions match the setup on the floor.
Model More Than the Finished Part
Model the complete moving envelope: cutting edge, flute, shank, collet nut, holder, spindle or router body, dust shoe, hose behavior, and any mounted accessories. Deep pockets and tall clamps often clear the tip while another component occupies a much larger diameter above it.
Review the First Approach and Every Retract
Fixture geometry must be current. Include clamps, screws, fences, vises, vacuum pods, stock tabs, and the support beneath the part. A clamp moved after simulation invalidates the relevant check; its new position should be treated as a setup revision, not an operator detail.
Check Holder Clearance, Not Only the Cutter
Review more than cutting moves. First approach, entry, links, retracts, between-operation travel, tool changes, and final return can cross uncut stock or hardware at a different height. Inspect the deepest engagement and the lowest non-cutting move separately.
Verify Machine and Work Coordinate Context
Account for stock that changes shape. Bowed sheet, released cutouts, a flexible skeleton, and chips beneath a part can raise material above the model. Simulation cannot see those conditions. Combine the digital check with a supported boundary or dry-run method on the assembled real setup. A clearance simulation is trustworthy only after the machine-specific output has passed Test a CNC Post-Processor Before It Reaches Valuable Stock.
Investigate Warnings and Near Misses
Define clearance margin from uncertainty and consequence. Model accuracy, tool projection, fixture tolerance, machine repeatability, and stock movement all consume margin. A zero-interference result in software is not permission to run with zero physical clearance.
Use Simulation as One Release Gate
Release the setup with screenshots or reports showing verified envelopes, actual tool projection, fixture revision, work offset, stock state, and real-machine verification. If the tool, holder, dust shoe, fixture, or offset changes, rerun the affected collision review before continuing.
