The Craftmans Shop > New from Old

Re-Birth of an EPCO 60 Ton Garage Press

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awemawson:
Thanks Rob for those kind words.

I've finally got round to doing what I'd planned back in 2010 when I first got this press - to fit upper and lower limit switches on the platen. Without them, if you go too high the screws jam in the nuts, and if you go too low the platen falls off the screws  :bugeye:

I'd bought the limit switches back then but hadn't fitted them for several reasons. Firstly I knew I still had things to fix on the hydraulic side, but mainly I was a bit stumped how to use a single pole limit switch to stop a three phase motor without introducing the complication of extra contactors and relays.

Then I hit on a plan - it's blindingly obvious once I'd thought about it. Put them in series with the 'stop / start / overload' unit.

The circuit below shows what I ended up doing - I'd initially thought that once the limit had been reached, I'd need another button to over ride it to reverse off the limit, I even mounted one and made a nice label. Then I realised that pressing the start button would pull the contactor in (but not hold in), and while still pressed the motor could be run off the limit

So I substituted a grommet for my button  :clap:

awemawson:
Now I wanted to mount the limits to the rear of the machine out of harms way, but the platten doesn't project far enough backwards to strike the switches, so I had to mount a protruding block.

Now I always have great difficulty free hand drilling and tapping holes for things like this - they always end up squiffy. So I first made the block with tapping size holes and used it clamped on as a jig to ensure that the holes in the platten were drilled perpendicular and in the right place. Then I drilled out and counterbored the block for final fixing

awemawson:
Then we needed a junction box to connect everything up

awemawson:
And to fit the limit switches themselves - I left about 1/2" of extra travel to be on the safe side

awemawson:
Then it was just a case of wiring it all up.

Perhaps I should explain, the platen motor which is 3 phase, has an overload contactor that doubles as a start stop swich. But when pressed 'On' although the contactor latches 'on' the motor doesn't run until you press the 'Dewhurst' reversing switch either 'Up' of 'Down' - it is spring biased centrally.

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