Wendelspanswick
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Would you need an override switch in the circuit to bypass the voltage monitor relay until the saw is up to speed? Otherwise the circuit would never start!
- Thread starter bigtip
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I thought that as soon as I saw it, probably still on his first cup of coffee?
daleyd
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no, the trip is on the saw traverse motor (I think). It would just prevent the saw from being driven (i.e moved on it's rails as the OP put it, not the chain drive) unless the chain is spinning - you would start the chain, which would then engage the voltage monitor and allow you to traverse the saw. I hope that's what the OP was talking about anyway!
daleyd
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no way, I have a 2 year old, I've been up for hours!!I thought that as soon as I saw it, probably still on his first cup of coffee?
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I think it would be better incorporated into the chain drive circuit as it would cover any problems with the chain?
daleyd
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you could be right but that's not what he asked for. He wanted something to stop the saw mangling itself up (I.e mashing itself against the stone rather than cutting it) if the chain stops. The tacho would be attached to the chain drive (Perhaps that bit wasn't clear) which monitors the chain speed. If the chain stops, the saw cannot move (Traverse).
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OK, we'll wait for feedback from the OP, I just thought stopping everything, chaindrive, traverse, etc. would be safer?.
daleyd
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Yes, the same arrangement could be put into the estop circuit, but the general idea would be the same.
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Just had a thought, any modifications the OP makes would become his responsibility (should comply with EN 60204 etc) and he should be made aware of the consequences if anything nasty happens 
daleyd
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Good point, I did advise a while back that if he wasn't electrically minded he should think about getting someone in to do it.
I did a course at Sick about 10 years ago and the one thing I learned is that doing things like this opens up a can of worms when modifying old machinery.
I did a course at Sick about 10 years ago and the one thing I learned is that doing things like this opens up a can of worms when modifying old machinery.
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Sounds similar to one I did at Pilz, covering machinery directive, CE marking etc., my boss wasn't too happy to find he couldn't stick CE markings on machines without any supporting paperwork!
daleyd
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I cringe at having to make on the fly software changes to things (I don't get involved so much in the hardware side of things now since I changed jobs last year) without having some sort of authorisation - the way I understood it was that the machine as a whole was CE certified, and any change to anything (electrical, mechanical or software)could potentially affect that. I could have got the wrong end of the stick but that seemed to be the gist of what the guy running the course told us.Sounds similar to one I did at Pilz, covering machinery directive, CE marking etc., my boss wasn't too happy to find he couldn't stick CE markings on machines without any supporting paperwork!
Back in the real world, you just get on with what you need to and make the machine/process work. (But I like things in writing if the customer asks me to change something!!)
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Yes, it has to be re-certified. In some cases even moving a machine can affect it!.
Thanks daleyd for the circuit diagram. as you can probably see it's an old beast. It has a winch which pulls it through the cut, a motor which runs the chain and a motor that raises and lowers the guide bar plus a fan to blow away the dust. It would be fine if it killed everything when the chain stops as the winch (or traverse function) and the chain drive are both running and need to be stopped and the fan doesn't matter either way. The picture above is us starting a plunge this morning. we slowly lower the bar until it's almost vertical then reverse up the track a bit then off she goes at the lightning speed of about 1 metre per hour. only problem is when it hits a hard bit or doesn't cut as quickly as the winch speed is pulling it. then (so i'm told) it gets into an awful mess. i think it could be left alone if it was relatively failsafe with perhaps a siren and flashing light so you know when it's stopped even from across the quarry and can come back and restart and adjust speed or whatever.
Pete, my boss is away til monday so can't discuss it with him and it;s probably better to discuss it with him than the owner so when i can i will get a budget that he's willing to spend to (hopefully) semi autonomise the saw. then i might buy your tacho off you!
daleyd
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That looks like it would have your fingers off in a jiffy!
Hope the circuit diagram explained it ok, you can put the relay contacts in the estop circuit to stop everything if thats what you want, but the general idea would stay the same. Good luck!
Hope the circuit diagram explained it ok, you can put the relay contacts in the estop circuit to stop everything if thats what you want, but the general idea would stay the same. Good luck!
Pete.
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That looks like it would have your fingers off in a jiffy!
The teeth aren't sharp at all but they do move pretty fast and could do you some serious damage. Compare it to catching your hand in a lathe chuck.
Bigtip: no stress at all, take your time. I was resigned to having it as an ornament unless I could find some way of using it myself.
daleyd
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You can, but it needs to be done right. If you add a cutout which then inadvertently restarts you have in effect made it "less safe".
I'm only an engineer, not a legal expert but having done (probably)the same course as robostar certainly opens your eyes as to the hoops that need to be jumped through, and also the pitfalls of modifying safety circuits and machine controls.
Having said that, there are probably thousands of mods every year that go by absolutely fine, but it only takes one oversight and an accident and the lawyers would have no hesitation in pointing the finger of blame at someone.
