Designing enclosure for safety

This is a machine you are going to be selling presumably...

You need to work with the production engineering guys...The trick is to acknowledge their concerns, but say,
' It's no good just saying what you don't want, lets have your suggestions'

You don't have to actually do what they want, but do be open to other ideas.
I think your basic aim is right...it must be 'fool proof' safety wise, and added sound/heat insulation for the operator is great brilliant and should pay dividends eventually in product acceptance.
You just need to be smart about how this is achieved, design for ease of manufacture, minimum cost, maximum effectiveness. Don't just limit yourself to the 'slap a box around it' mentality.

I will get pilloried for my next comment....
Forget 'standards' you know what is safe! Don't compromise on safety, but try to make it intrinsically safe rather than adding umpteen bolt on over-rides and interlocks as an after thought.

As a designer one of your greatest free resources is the people who use the equipment and those who have to build it....talk to them, it will pay huge dividends in loads of ways.

Del

Good comments indeed.

However, we are not selling these machines. They are for deployment in our own factories in the 3rd world (where a worker costs less than a FESTO cylinder). Obviously, if we were to sell the machines, my life would be easier securing industrialisation buy-in. The market does demand safety.

I am facing a de-facto override of the design right now (prototype is in final assembly stage). It's going to be either that, a modification therof (that's what prototypes are for), or the old way: hence no safety. I'd rather avoid the latter for the sake of some poor brazilian operator, who might be tempted to cut corners or just loose concentration while on the job.

So, I am thinking along the line: safety standards for bech presses. Feedback?

I'm out of the office right now, but if you google OSHA power press rule 29 CFR 1910.217 you should get plenty of info on how we have institutionalized the safeguards for workers in US. They are working on modifications to the regs, but should be wealth of information.

ALso we have double switches, so that the press will not actuate unless both of workers hands are on buttons out of harms way.

milo

Make sure those switches need to be activated simultaneously (i.e. one cannot "jam" one and activate the other using one hand). The ones on our press (optical) need to be activated within half a second of each other. I'm not sure if this can be done pneumatically only...

good luck,

R.

Thanks for making it perfectly clear!

milo

Cheers!

I read it; it will do fine.

Thank you.

Glad to hear that, hopefully you'll be able to convince the powers-that-wannabe the OSHA Standards are applicable. Safety should NEVER be compromised, even where workers are cheaper than components; after all they are PEOPLE, not parts of the machine! Please consider registering as a member here, I think your input would be valued!!!

I agree with Milo on the double switches. I just built a pnuematic press for use in our plant to install a plastic ring inside a plastic tube to hold in the product. I purchased a double palm button anti-tie down kit from "Grainger", complete with logic block and all except the selonoid valve, which the info describing the kit will recommend. The operator places the part and must use both hands to activate. It has worked great so far. I was asked to build a second one for a similar process. We just had a visit from OSHA and the press was sitting in plan view but was never mentioned by the OSHA reps. as being unsafe, yet they pointed out a spray bottle with water in it that was not labled as such.

I applaud your consideration of safety especially considering the equipment is going to an area where this kind of thing may be little regulated or enforced.

US OSHA is a good set of rules to apply. Also the suggestion to include others and be practical is first rate. One other thing I might throw out is, when designing the safety into the equipment (not an afterthought) you may also try to make the safeguards hard to bypass and as unobtrusive to operation as possible. This will encourage the users to keep them in place in the long term. Down the road when an interlock switch fails it will likely be bypassed depending on the work attitudes. Having said that I understand the double palm buttons is sometimes the best way to go.

Physical guarding I have found works the best when it is very durable, easy to remove AND easy to install. That way when the guards are removed (after lock out) to remove a jam they will be easily put back on.

Having designed similar machines in the past I can tell you you need to have two hand operated switches to actuate the machine cycle. They must both be pressed simultaneously to start the machine cycle, and must be far enough apart to prevent the operator from actuating with one hand. Also, if you are going to enclose the machine (Hard guarding) then access to the die head to change dies, foil, clearing jams, etc. must not be too difficult or time consuming or the machine operators or plant maintenance personnel will remove it.

I retired from a company in 2003 that designed and built machines for textile industry. They were attaching machines. I have a joint patent for a safety device using mechanical switches and a solenoid operated rotating clutch. The rotating clutch has 2 levers. The first lever releases as soon as the operator presses the foot pedal or hand switch. The second lever releases only when and if the safety guard passes through the area where an operators hand might be thus activating the second switch. The timing is such that as long as the operator is not in the way, the second lever never touches the rotating clutch catch area. I say all this to qualify my expertise on safety devices and indeed your design may be overly costly and need to be simplified. Rethink your objectives and come up with a viable solution that uses cheaper parts but is still workable and safe. mechanical switches, air cylinders and movable guards come to mind.

Regards,

Keywalker