Computer numerical control (CNC) machines are essentially routers controlled by a computer that guide machine tools. The equipment has two or more direction of motions, called axes that can be automatically and precisely positioned along their lengths of ravel. Instead of turning wheels and crankshafts as is the case with manual machines, the CNC moves through a series of pre- programmed commands that can be slow, rapid, linear or circular and produce very elaborate shapes. The machines usually have a feedback device that allows the controller to confirm the positions.
The processes of tolling, shaping and milling metals, plastics, wood or stone can be a dangerous activity. However, CNC machines, especially small mills, are safe compared with standard power tools. The routers on shaping devices are enclosed behind protective barriers. This prevents accidental contact with sharp parts of the machine and halts any sparks or other debris from flying out and injuring operators.
Nevertheless, a number of safety procedures should be followed when using CNC machines:
• It’s wise to wear eye protection at all times as well as steel-tipped or closed toe shoes or boots. Sometimes, it is also a good idea to wear ear plugs or headphones as milling of some materials can be extremely noisy. Never wear baggy clothes, gloves or jewellery that could become snagged inside the machine.
• Before turning on the CNC machine and starting work, always check that the locks, guards and other safety devices are fully in place, secured and operational. When loading material into the machine, make sure that it is centred correctly on the router’s vice. Activate the dust fan or other exhaust system as soon as you turn on the machine. Make sure that you never interfere with the guard until the milling process is complete.
Never make any assumptions that some materials are safer than others if you don’t find it described in the CNC guide from RS. Silica dust from sand products is well recognised as causing severe lung problems. However, just because the evidence that milled glass or glass fibres producing a similar disease is not as compelling, it’s still not a good idea to breathe in that type of dust. Similarly, although many people believe that platinum cure silicones are harmless and siloxane resins are non-reactive and non-toxic, it’s important to read the data sheet for any material you may be using. At the very least you may find out that it is extremely sticky and difficult to work with.
Maintenance is important, both for the machine functions, its operating lifetime and operator safety. The following tips are useful:
• The machine should be turned off completely before any cleaning or maintenance.
• Give the machine time to cool down before cleaning if you have been milling metal.
• Always clean the inside of the machine of old debris before milling a new product.
• Check inside and outside of the machine for any damage.
• Store the CNC machine in a place as free as possible from airborne dust and the danger of any liquid spillages.