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Woodworking Sheet No 22
This information sheet is one of a series prepared by HSE's Woodworking National Interest Group in agreement with the Woodworking Machinery Suppliers Association.
Computer numerical control (CNC) routers and machining centres can be hand loaded or automatically fed. They are designed to work on wood and may also work on plastics and light alloy metals.
The standard of safeguarding outlined in this Information Sheet is also applicable to point-to-point boring machines which are capable of being fitted with routing cutters and which are used for profiling operations.
Each machine has its own characteristics and configuration which should be considered when identifying the hazards and assessing the risks, but all of the following hazards will need to be considered:
As the control systems on routers have developed from manual control to CNC, so the degree of operator intervention during the machining process has decreased. The addition of automatic loading and unloading facilities and automatic tool changing further reduce the need for close approach to the cutting area. This enables the manufacturer to adopt safeguarding methods that differ from those used for manually operated machines.
Access to the cutting area during the machining process should be prevented by enclosure or other effective means. Where access into an enclosure is necessary for loading/unloading the workpiece, for cleaning, setting or adjustment, or for tool changing, then access should be via a door which is interlocked so that it is not possible to gain access while the cutters and other dangerous parts are moving. The interlocking system should be at least of the single control system type2.
In situations where infrequent access is required, for example, for maintenance operations, then a fixed guard should be used2.
Dust and chippings should be effectively delivered to an extraction outlet which is integral with the machine.
On machines capable of producing noise levels greater than 85 dB(A) during the machining process, the enclosure should be designed to reduce noise emission.
Enclosures should be made of impact resistant materials capable of containing ejected workpieces, machine components or parts of either2.
Where tandem loading is used, the machine operator must not be at risk from the machining heads operating at the adjacent workstation while loading or unloading the workpiece. The following two examples illustrate ways in which this may be achieved:
Figure 1: Example layout for tandem loading
Figure 2a: Example layout for tandem loading
Figure 2b: Example layout for tandem loading Where the machine design allows the heads to overhang the work table into the loading enclosure, for example while machining at the edge of the tables at the centre of the machine, then either:
As an alternative to enclosure, effective close guarding of the cutters may be used. Guarding should be within eight millimetres of the workpiece surface. Plastic skirts or brush borders may be fitted to these guards in order to improve extraction, but these will not be considered to be part of the guarding for the cutters.
Where effective close guarding of the cutters is used, other hazards such as those created by noise, dust, ejection from the machine or crushing or trapping points must also be addressed.
In some cases the enclosure for the cutting area will prevent contact with the tool changer. In other cases there may be a separate access door or access from the tool magazine. Such access doors should be interlocked with the tool changer and if there is access to the cutters, also interlocked with the cutters. During manual tool changing, there should be no risk of rotation of the tool holder while tools are being inserted or removed. 'Hold to run' or single step pendant controls may be used to index the toolholder.
Safety devices etc should be checked by a suitably trained and competent person at regular intervals, taking into account the use of the machine and the supplier's/manufacturer's recommendations. Records should be kept detailing maintenance and inspection checks which have been carried out.
Additional advice and information can be obtained from local HSE offices, which are listed in the telephone directory.
Further copies of this Information Sheet may be obtained from the Woodworking National Interest Group, Health and Safety Executive, 14 Cardiff Road, Luton LU1 1PP (Tel: 0582 34121) or from the HSE Infoline, Caerphilly Business Park, Caerphilly, CF83 3GG (Tel: 0742 892345 or Fax: 0742 892333).
This publication may be freely reproduced, except for advertising, endorsement or sale purposes. The information it contains is current at 3/93. Please acknowledge the source as HSE.
Printed and published by HSE NIS/08/22 C50 3/93