Blog Post #108 – CNC Machine Tools – Follow Safe Principles

Ensure that the operator is properly trained in the operation of the CNC machine. If the operator has little experience with CNC machine operation, ensure a competent supervisor oversees the operation.

Below are a set of safety instructions and recommendations involved with the setup and running of most CNC machines.

CNC mean Computer Numerical Control

– Ensure that the CNC machine is attached firmly on a workbench or other rigid frame.
– Verify the location of the off switch and/or emergency power disconnect.
– Wear safety glasses and hearing protection at all times.
– Do not wear gloves while operating the CNC machine.
– Do not wear loose long sleeves, ties, dangling jewelry or any other loose fitting clothing while operating a CNC machine.
– Ensure that long hair is tied back and secured from falling into the path of the saw blade.
– Wear non-slip footwear or ensure that taped or painted non-slip surface is in place.
– Ensure the dust collection system is connected, and operational.
– Keep the floor clean around the machine.
– Ensure that a taped or painted safety zone of at least 1 metre is in place around the CNC machine.
– Inspect tools to ensure they are sharp and set correctly.
– Ensure that the correct tool data is entered into the CNC program.
– Ensure that guards are available for the CNC machine and that they are in position while the machine is in
operation. An interlocking guard which shuts the machine off if opened is preferable.
– Always ensure that all materials and fixtures are securely clamped before starting the CNC machine.
– Ensure that the spindle direction is correct for right-hand or left-hand operation.
– Always conduct a dry run to ensure the program is correct.
– Never overload the machine table; follow the manufacturer’s recommendations regarding load limit.

Whenever simple and conventional production equipment, such as machine tools, is automated, the result is complex technical systems as well as new hazards. This automation is achieved through the use of computer numeric control (CNC) systems on machine tools, called CNC machine tools (e.g., milling machines, machining centres, drills and grinders). In order to be able to identify the potential hazards inherent in automatic tools, the various operating modes of each system should be analysed. Previously conducted analyses indicate that a differentiation should be made between two types of operation: normal operation and special operation.

It is often impossible to prescribe the safety requirements for CNC machine tools in the shape of specific measures. This may be because there are too few regulations and standards specific to the equipment which provide concrete solutions. Safety requirements can be determined only if the possible hazards are identified systematically by conducting a hazard analysis, particularly if these complex technical systems are fitted with freely programmable control systems (as with CNC machine tools).

In the case of newly developed CNC machine tools, the manufacturer is obliged to carry out a hazard analysis on the equipment in order to identify whatever dangers may be present and to show by means of constructive solutions that all dangers to persons, in all of the different operating modes, are eliminated. All the hazards identified must be subjected to a risk assessment wherein each risk of an event is dependent on the scope of damage and the frequency with which it may occur. The hazard to be assessed is also given a risk category (minimized, normal, increased). Wherever the risk cannot be accepted on the basis of the risk assessment, solutions (safety measures) must be found. The purpose of these solutions is to reduce the frequency of occurrence and the scope of damage of an unplanned and potentially hazardous incident (an “event”).

Always remember to read the manufacturer’s manual as it will almost always have the safe operating procedures and principles designed into their machine. As a designer and manufacturer, it is their job to make suggestions on safe application. An old time worker may know the machine in and out but a new employee/operator would need special safety orientation and the best way to do this is to review the safety tips that are provided in the manufacturer’s manual.

The MOL will always revert back to the manual’s safe handling suggestions when an accident has occurred. Remember section 25, 2(a) of the OHSA which states,

“The employer shall provide information, instruction and supervision to a worker to protect the health and safety of the worker.”

Remember — In Ontario, “ALL Accidents are Preventable”

‘Work’ and ‘Play’ safe.

Daniel L. Beal
CHSEP – Foundation Level
VP & Senior Trainer
HRS Group Inc.