A first CNC project should not reach the start button until the released file, tool, stock, clamps, work zero, boundaries, dry run, and stop conditions all pass. Use this preflight as a go/no-go gate, not as a general beginner tutorial.
Release the File Before Approaching the Machine
Confirm that the current revision is the approved source and that the CAM project opens without missing geometry, fonts, tools, or external references. Check final dimensions, units, operation order, stock definition, and the target post-processor. A drawing that looks correct is not yet a released CNC job.
Preview Toolpaths and Machine Boundaries
Use CAM simulation and a boundary preview to confirm cut side, depth, entry moves, retracts, rapid travel, clamps, and stock limits. Inspect the first plunge and the final separation move. Resolve warnings in the source or CAM project instead of editing posted machine code blindly.
Match the Tool, Collet, and Stock
Verify the actual cutter identity, shank, cutting diameter, flute length, usable cutting length, projection, and collet compatibility against the tool record. Confirm stock material, thickness, flatness, and allowance. Stop if the physical tool or stock does not match the released setup.
Prove Workholding and Clearance
Secure the stock against sliding, lifting, and rotation without distorting it. Check that clamps, screws, fixtures, dust collection, cables, and the spindle body remain clear through cutting and rapid motion. Small offcuts also need a retention plan before surrounding material is removed.
This step sits within How to Choose a CNC Router Around Your Real Projects; continue with A CNC File Handoff Checklist for Units, Origin, Geometry, and Post-Processors and What to Verify After Assembling a CNC Router when the project reaches the neighboring decision.
Set and Verify Work Zero
Place the work coordinate at the datum named in the setup sheet. Verify X, Y, and Z separately, then move to a second known point or safe height to catch a mirrored origin, wrong corner, or surface-versus-bed Z assumption. Re-establish zero after any tool, stock, or fixture change that invalidates it.
Run a Dry Test Above the Work
With the spindle off and the tool safely above the stock, run or step through the boundary and initial moves using the supported machine workflow. Keep the stop control accessible. Confirm direction, travel, clearance, origin, and operation order before returning to the approved cutting height.
Use Explicit Go/Stop Criteria
Proceed only when the file revision, tool, stock, fixture, origin, clearances, spindle state, and first motion all pass. Stop for unexpected direction, missing clearance, loose stock, abnormal sound, controller alarms, or any mismatch with the setup record. Record the failed checkpoint rather than improvising around it.
Questions About Before Your First CNC Project, Check the File, Zero, Clamps, and Dry Run
What should I check before running my first CNC file?
Confirm the released file, units, dimensions, tool, stock, workholding, work zero, clearances, post-processor, and first motion. Do not start cutting while any item differs from the setup record.
Is CAM simulation enough to prove a CNC job is safe?
No. Simulation can reveal toolpath problems, but it cannot prove the physical stock, clamps, tool, zero, cables, dust collection, or machine envelope match the project.
How high should the tool be for a CNC dry run?
Use a safe height defined by the machine and setup that clears the stock, clamps, fixture, and rapid moves while keeping behavior observable. Follow the supported controller workflow rather than guessing a universal distance.
When must I repeat the CNC preflight?
Repeat affected checks after changing the file, CAM, post, tool, collet, stock, fixture, origin, controller profile, or machine configuration. A previous pass does not cover a changed upstream condition.
