A computer numeric control (CNC) machine is a computer-controlled router that moves freely along multiple axes to carve complex designs with precision. While the milling, tooling and shaping of metal, plastic and wood are inherently dangerous activities, CNC machines are among the safest tools for this work. The router assembly, and the materials being shaped, are often enclosed in a protective barrier, preventing flying debris and accidental contact with fast-moving machine parts. Still, accidents do happen, especially when the machines are used inappropriately or safety features are disabled or malfunctioning.
When working with a CNC mill of any size, always wear personal protection equipment to reduce the chance of injury. Always wear gloves, eye protection and closed-toed boots or shoes, especially when working on large-capacity CNC machines or milling metals. Wear hearing protection such as soundproof buds or headphones to prevent cumulative hearing damage from loud noises. Avoid baggy clothing and jewelery and keep long hair tied back. Never attempt to use a CNC unsupervised or without receiving proper training for the specific tool you are using.
CNC machines are controlled by computers that the operator must program. The machine will do what it is told to do, even if the command is a dangerous one, so the programmer must be careful when designing and programming the machine. Setting a maximum depth no less than .1 inch will prevent overdrilling on most machines. If you are cutting a part out of a piece of material, design your part with sprues connecting the frame of material around the perimeter to the piece that you are cutting out.
Before turning on the milling machine, make sure your materials are centred in the vice and the correct router bit is securely fitted into the router's chuck. Lock the guard in place before turning on the machine. Turn on the machine and activate the exhaust system or dust fan. Load the design you wish to mill into the CNC's computer and initiate the milling. Do not remove the guard or interfere with the machine until the milling finishes.
All CNC machines have an emergency shutoff switch, usually located on the control panel, that can stop the milling in the event of a malfunction. Locate this switch (some machines have more than one) before operating the mill. Industrial-sized CNC mills also have pressure mats that automatically stop the machine if an operator comes too close to the moving machine. They also have soundproof casings, special curtains to block flying debris and a cutout valve to remove pressure from pneumatic systems. Familiarise yourself with all failsafes and safety features before operating a CNC mill.
Removal and Storage
When the piece is finished milling, turn the CNC mill off and open the guards. If you are milling metal or another thermally conductive material, give the piece time to cool before removing it from the vice. Always clean debris from inside the machine before milling a new piece and store your CNC machine somewhere free of airborne sawdust and liquids to prevent damage to electrical components and safety features.