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| Slippy clutch material? |
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| AdeV:
As you may recall, I recently bought an EDM spark eroder. It's quite an old machine, and I'm guessing it hasn't been stored in a heated workshop of late; but for whatever reason, it's destroyed its friction clutch. The idea is, the head descends under motor power, then moves up & down (under motor power); but one can manually wind the electrode back off the work piece (or wind it down into the work piece when you first switch it on). That's where the slippy clutch comes in, it allows you to wind the electrode up or down without affecting the motor. The clutch appears to have been some kind of fibre disc, maybe some kind of bakelite material, with a fairly shiny side which is obviously designed to slip under higher torques. The other side has a pin, obviously to hold it in place, but as a result now that the disc has disintegrated, the pin engages in a hole in the driven side, so it can't be wound up or down by hand (because you're trying to drive a motor through a 100s:1 reduction gearbox. The manufacturer (Wickman) have acted exactly like I would expect any British company to react (that machine is obsolete, we deny all knowledge it ever existed). So..... after that ramble.... what material should I make the clutch out of? It's compressed by quite a sturdy looking spring, so it shouldn't need too much sticktion, but it does need to survive being wound backwards against a metal plate turning in the opposite direction... |
| awemawson:
How thick, what diameter? Several possible materials on that link posted in Rob Wilson's insulation thread this morning. |
| micktoon:
Hi Ade, sorry I can't help with the clutch , but your comment of the companys response made me laugh, you would think they would pride themselves in helping owners of there old machines out rather than deny it had anything to do with them, ..................ln a ' not me mate , I think you have the wrong bloke ' type way :palm: Cheers Mick |
| AdeV:
Andrew- diameter is about 2", the pin is maybe 1/8" and offset from the centre. I can't remember how it holds itself in position radially, I assume there's either 2 pins, or a central hole as well. Thickness - I don't know, but at least 1/8", more like 1/4" at a guess. All I found was one face and some powder in the machine, it had completely disintegrated. Mick - yeah, it's pretty common these days :( Mind you, I can sort of see why - we have an old product which we no longer develop or actively support, which is kind of tough on people who already have it & don't want to upgrade to the new version. Our problem is the team is too small to actively support the old product AND develop the new product; and since the old product no longer earns any money.... So I can sort of understand it, but it's still frustrating as someone who can't afford (or justify) buying new kit. |
| PekkaNF:
Does it looks like a pertinax washer? http://uk.rs-online.com/web/p/bonded-washers/1360842/ http://uk.rs-online.com/web/c/fasteners-fixings/nuts-washers/bonded-washers/ That is a bad picture but in real life it looks a lot like old printed circuit board material. I have seen some clutch designs and there seems to be least two approaches: * Use bearing materials like POM or Teflon (usually solid) * Use friction pad material (usually has a backing or support disk/structure) All depends how much load you are transmitting, how much slip and how much you must disipate energy. Probably original maker used whatever they had in inventory and was reasonable enough. Pekka |
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