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#1 Posted : 07 February 2024 16:21:44(UTC)
Rank: New forum user

I typically deal with construction but have been asked to look into a tool ejection on a portal frame CNC router. The router is used on composites (frp), but the machines are typically designed to be used on wood (they have been adapted with more robust motors and cutting heads designed for frp).

I have read through WIS22(rev1) Routers and Machining Centres Safe working practice,

L114 Safe use of woodworking,

BS EN 847-1&2 and BS EN ISO 19085-3 (instead of the withdrawn BS EN 848-3).

Regarding safeguarding, I concluded that the machine should be guarded to keep people from moving parts and, secondly, protect people from ejections of tools and workpieces.

Our machines have AOPD fitted to protect people from making contact with a moving frame or tool head. 

None of our machines have any guarding against ejection or disintegration. I checked these findings with our external consultant, who agreed with my findings as presented. Then I presented these them to our directors, who asked me to dig a little deeper into the guards that protect from ejection as they had not seen them used in their previous experience, That it's not been raised by our consultants in audit or found much evidence of examples of them fitted on or near machines on the web, the little we did see was typically steel mesh fences, that would give limited protection from a tool disintegration. They are not against the guards in principle; they just want me to ensure that the fixed guards are practicable as they will impact our machine loading strategies, workflow, etc.   Does anyone who uses portal frame CNC routers use guarding against ejections? If so, is it only workpiece, or do you factor in disintegrated tooling? If not, are there  other mitigations that can be considered? Does anyone mount guards that enclose the tool heads? If so, how do you tackle this if there is a carousel? Do you use brushes on the bottom of the guard, or do you mount them to the z-axis?

Has anyone seen the 6-ply overlapped curtains from BS EN ISO 19085-3, used to protect gaps in guarding? I have yet to find a supplier that has heard of them. I am also looking for a trainer/consultant who can help perform a PUWER assessment and enhance our house safety training; that's not trying to sell me a new machine.

peter gotch  
#2 Posted : 15 February 2024 17:35:51(UTC)
Rank: Super forum user
peter gotch

Hi Ron

A little surprised that nobody has responded to your thread as yet.

It is a very long time since I was regularly dealing with machinery guarding in the factory setting and CNC was a bit new fangled in those days.

I am not surprised that your "consultants" haven't said anything about the set up on your specialised equipment. Remember that few consultants know everything there is to know about machinery guarding.

To put this in perspective, if you imagine one major source of trained and experienced consultants is the Health and Safety Executive - but HSE has traditionally deliberately rotated its Inspectors so that they didn't get stale and remained inquisitive.

The result is that an HSE Inspector with say 10 years experience before heading off to work as a Consultant might know quite a lot about several sectors, but not be an EXPERT in any of them.

Times have changed somewhat since I joined HSE, but at the time it was Departmental policy that a new Inspector wasn't allowed anywhere near the sector they had previously worked in until all their preconceptions as to acceptable "custom and practice" had been firmly put to bed. For me that meant that I didn't get to inspect any large engineering factories until I had been with HSE for about 10 years.

So each move meant being new to some industry and being forced to admit to ignorance when some manager said "What do you know about our industry and its processes?" Easy answer - "Nothing, please explain the processes, what you see as the risks, and how you mitigate those risks."

Part of the rationale was that an Inspector could transfer knowledge from one sector to another and, of course, part of the routine was to ask "stupid questions" where with greater experience the Inspector should become better at recognising which of the answers they might expect - and if those were given, that provided a bit more confidence in the answers given to the other questions being asked where the Inspector did NOT know what answer to expect.

.....but so it came to pass that I went to an engineering factory to investigate a fairly basic accident on a bench grinder, but decided to do a routine "General Inspection" at the same time.

MD said "I don't suppose you know much about tube bending machinery?" and my reply was "Well, I am probably the only one of about 650 front line Inspectors who has worked on a hand operated tube bending machine like that one over there........." followed by "...and I see that you have a Cincinatti CNC tube bending machine over there in the corner. I served a Prohibition Notice on the last one of those I came across."

Said MD went into very quiet mode and I didn't need to tell him that I had only ever seen one CNC tube bending machine previously which just happened to have been made by Cincinatti and I didn't bother to explain why I had served the Notice - the factory had changed its lay out and had moved the CNC tube bending machine but not all its safeguarding!

So, unless your "consultants" specialise in machine guarding and little else, it is more than probable that their experience of the type of equipment you are dealing with is nil or minimal. 

However, it seems to me that you are applying the right approach. 

OK so its not wood being processed but you have referenced appropriate standards and guidance.

I don't have the competence to judge whether the risk of tool ejection is greater or less when processing frp instead of wood but if you can assess the likelihood then that gives you somewhere to start in terms of what guards would be practicable and/or reasonably practicable depending on which bit of PUWER comes into play in the evaluation of what mitigations to put in place.

I suppose you probably need some form of localised fixed guards to contain ejection but you probably need a guarding specialist to advise you on what would be appropriate - the market leaders when I worked for HSE were Procter and they are still in business. https://www.machinesafety.co.uk/ 

NOTE - I don't know what Procter's current reputation is, so you would need to ask the right questions.

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