Is this machine safe? rotary indexing assembly table

Good morning

this may not be the ideal place to ask this question but any help is appreciated. It is machine controls related.

I'm currently working for a company that uses rotary indexing tables to make parts. Its about 4 ft dia with 12 nests running at around 60 parts/min.

The way this company operates the machines is that operator hand loads the parts into the nests while the indexing table is on the dwell portion. The table runs automatically and if you dont get your part into the next in time, the table will index.

Is this safe? I've worked on machines like this before but it was always vibratory feeder bowl fed. These parts in particular would not work with a feeder bowl very well.

Is safety usually a judgement call? or are there guidelines you need to follow? Thanks

Are there pinch points?
Are there places where an operator has to place his hands INTO something?
Have operators been hurt at this machine in the past?
Etc., etc., etc.

Without being able to see the machine, it's hard to tell. The best kind of question to ask when evaluating machine safety is "What would happen if.......?"

My rule of thumb is "Would I feel safe doing it, especially at the end of a long, monotonous shift/ or having my kids do it/ or first thing in the morning after a long night". If any flags come up, how can you make it better (i.e safer/ idiot proof)?

Just from the description, is it possible to be attempting to load a part and the table begins indexing? Would this occurrence lead to harm?

If the process could accept it - delayed indexing - then a light screen just above the level of the properly inserted part could detect a 'still being placed part' or a hand and prevent the next index.

Is safety usually a judgement call? or are there guidelines you need to follow?
If you don't know the answer to this, then seek help...Quickly.

Insist to have light curtains where hands are put in, which monitor when the hands must be out, else no index

could you post a photo of the operator area please

As Badger suggests you should seek advice from a functional safety expert, but you should understand it as well, because you should know the machine and operation the best. None of us are really in a position to look at your machine and your process. So, to educate yourself read up on NFPA 79, ISO 13849-1, and IEC 62061.

The first thing you and the functional safety expert will want to do is a hazard analysis. What can possibly go wrong with hand loading? Typically this involves looking at several criteria: severity, exposure, and avoidance.

When the table indexes without warning could the operator lose their life, their arm, their hand, a finger, or get a boo-boo? How often does the operator have to load this thing once a day, once an hour, once a minute, or even faster? How fast does this move, lightning quick or at a snail's pace?

Based on risk you can make an informed choice of the right mitigation. For example if the worst that can happen is you get a boo-boo, you only need to load it once a day, and your 86-year old grandmother moves faster you probably don't need a fancy function safety system. If it's a widow-maker, that you need to load 1000 times a day, and moves faster than the human eye can see you better get a high-integrity functional safety system using photocells and/or two-hand controls.

Remember the first choice is always to engineer the hazard out but it doesn't sound like this is an option.

The various standards usually deal with the minimum requirements you're always free to make it safer. Accidents can be very expensive, functional safety is relatively cheap.

If I was the equipment designer on this thing I know I would sleep better at night if there was a light curtain to make sure the operator wasn't still poking around when the table indexed.

I've always seen index tables require a two hands Push Button station to allow the machine to index. Basiaclly the table stop in position, the operator load the machines, then has to depress one PB with the right hand and one PB with the left. We programmed them so they needed to see a transition to work...ie you could not tie one down. If it took 10 sec to load a part or ten minutes the index table did not care, we also programmed some horns and light to let management know if the production rate was not being met.

Timbert said:

Based on risk you can make an informed choice of the right mitigation. For example if the worst that can happen is you get a boo-boo, you only need to load it once a day, and your 86-year old grandmother moves faster you probably don't need a fancy function safety system. If it's a widow-maker, that you need to load 1000 times a day, and moves faster than the human eye can see you better get a high-integrity functional safety system using photocells and/or two-hand controls.

Click to expand...

In my experience this is the weak point of the typical risk analysis. We recently developed a procedure at our facility for assessing risk of new machinery and implementing appropriate safeties. So far it has worked great for getting the right people involved and documenting all the hazards. But how do we make an "informed choice of the right mitigation"? Why does an air cylinder that exerts 5 pounds only need a warning label, while one that exerts 500 pounds warrant a light curtain? Just because five people agree on it instead of only one? And what about the wiring for that light curtain? Single channel if only a finger is at risk, but dual channel if a whole hand could get lopped off?

The topic of "risk assessment" always seems to come up when people raise safety questions on the forum, and the discussion often ends there with someone scolding the OP for not doing one. But either I'm missing something or the procedure is severely lacking. At some point a decision has to be made: A risk level of 'X' warrants a safety system of 'Y' complexity. Except for a few certain types of machinery, like punch presses, I can find no standards that specifically address these issues. It often seems that these decisions are made (by myself included) on the basis of questions like "would I let my children run it?" or "will I sleep at night?"

I agree with you Keith. When the OP first said, "Is safety usually a judgement call?", I had to bite my tongue because, yes, it actually is a judgement call at some level, even if you have an outstanding procedure for analyzing the safety of your equipment.

In my opinion the purpose (and a very useful one I might add) of risk assessment is to improve that "judgement call" by trying to clearly define as much as possible and get more people involved.

Of course, if you do it like China, it just aint safe.

http://www.youtube.com/watch?v=qd3OuWrvQz0

At least they're wearing their protective gloves.

During training at Toyota the Japanese told us that if the counterballance air cylinder seals fail the die will drop.

those presses were fully guarded.
But we had a Night shift that allowed this type of action once.
(smaller press) luckly no injury.

Note:
all of these machines are now mechanically loaded and unloaded.
have been for 20 years now

kolyur said:

At some point a decision has to be made: A risk level of 'X' warrants a safety system of 'Y' complexity. Except for a few certain types of machinery, like punch presses, I can find no standards that specifically address these issues. It often seems that these decisions are made (by myself included) on the basis of questions like "would I let my children run it?" or "will I sleep at night?"

Click to expand...

Take a look at IEC 62061 and/or ISO 13849-1. Both have charts for determining what level of safeguarding is required for a certain level of risk. These newer standards don't typically deal with complexity of the safeguard but rather how likely it is to fail dangerously. The standards are much more quantitative rather than qualitative.