This is one of those MUST READ studies for all safety professionals who deal with machine gaurding and interlocks, and/or have a behavior based safety process! Although the study was done on Computer Numerical Control (CNC) machines in the UK, we can certainly see how the results can be expected on ANY machinery and by ANY worker in any country. Defeating interlocks has been a problem for as long as interlocks have been on this earth; for us to ignore this fact is dangerous! This study, done in the UK on CNC machines, is something we can hang our hat on and begin to understand the mindset so many have when it comes to “acceptable practice”. The current research sought to identify reasons why operatives defeat interlocks on CNC machines, and to obtain an understanding of the extent of this behavior across the UK engineering industry. The findings from this research provided a number of valuable insights about the frequency of defeating interlocks and the influences upon this behavior.
HSL were commissioned by HSE to carry out research which sought to identify reasons why operatives defeat interlocks on CNC machines, and to obtain an understanding of the extent of this behaviour across the UK engineering industry. The findings from this research provided a number of valuable insights about the frequency of defeating interlocks and the influences upon this behaviour.
With regard to frequency of defeating, semi-CNC machines were identified as being commonly defeated in the sample used in this research. Common activities associated with defeating were setting, proving, swarf removal and deburring. Managers, and operatives / supervisors felt defeating was commonplace (the ‘norm’).
With regard to influences, three sets of influences on operative behaviour (Predisposing, Enabling and Reinforcing) were identified as influencing behaviour in relation to defeating interlocks.
Interventions that take into account these influences could be developed to promote behaviour change.
Suggestions for such interventions are provided within this report.
EXTENT OF THE PROBLEM
Current research findings imply that defeating safety devices is widespread within the UK engineering industry, involving a variety of machine types and techniques. However there is a lack of robust evidence in general and specifically in relation to CNC machines. Common activities associated with defeating were:
- setting1
- proving2
- swarf removal3 and
- deburring4
Semi-CNC machines5 were identified as being commonly defeated in the sample used in this research. Managers and operatives/supervisors perceived this practice to be the ‘norm’. It must be acknowledged however that this finding is drawn from small-scale qualitative research and may not generalise to the larger population of CNC machine users in the UK.
FACTORS INFLUENCING OPERATIVE BEHAVIOR
Characteristics of the individual (e.g. risk perception, knowledge of risks), and the environment (e.g. machine design and procurement), as well as the nature of rewards and/or punishment (e.g. lack of disciplinary action) following defeat of safety interlocks appear to exert an important influence on operatives’ behaviors. The current research explored the following three sets of influences upon operative behavior in the context of defeating interlocks.
- Predisposing: characteristics of the individual that motivate behavior. Key predisposing factors identified were beliefs about personal susceptibility and negative attitudes about the need for interlocks/guarding.
- Enabling: features of the environment that block or promote uptake of controls. Key enabling factors identified were poor machine design and procurement, lack of refresher/specific interlock use training and confusion regarding legislation/regulations.
- Reinforcing: rewards or punishments that follow as a consequence of behavior. Key reinforcing factors identified were lack of visible management commitment, production benefits (e.g. ensure the job is run correctly) and lack of consistent enforcement/disciplinary action.
ISSUES FOR CONSIDERATION
Issues for consideration have been drawn from the current research with regard to how to improve health and safety performance and worker involvement (in general and specifically regarding CNC machines/interlocks) within the engineering industry. It is suggested that stakeholders6 should develop pragmatic and cost-effective strategies to help implement such improvements.
CLICK HERE for the full study.
1 Setting up a machine to run e.g. selecting the correct programme, ensuring materials are in the right place on the machine. Source: http://en.wikipedia.org/wiki/setting
2 Checking that a programme is running as it should. Source: http://en.wikipedia.org/wiki/proving
3 The removal of swarf (debris e.g. turnings, chips, shavings of meta)l. Source: http://en.wikipedia.org/wiki/swarf
4 Removal of burr – (raised edge or small pieces of material remaining attached to a workpiece after machining. Source: http://en.wikipedia.org/wiki/burr
5 This is not a term recognised in the current EN ISO standard Machine tools – Safety – Turning machines 23125:2010. However
it does appear to be used by industry (also known as hybrid machines). It is understood that this term refers to manually
controlled machines with limited numerically controlled capability.