The Craftmans Shop > New from Old
Resurrection of a CFEI 100 KVA Induction Furnace
awemawson:
OK a bit more dismantling - the contactor is in pieces all over my bench :bugeye:
Essentially there is a plate that slides that has three sets of contact pieces on both sides arranged so one way up it gives a 'normally closed' contactor, and in my use the other way up gives a normally 'open contactor'. These contacts on their plate slide impaling themselves on the 'bridge piece' thus making a circuit. There is an over centre spring loaded toggle arrangement keeping them slide to the operating side, but when the no volt coil or the manual lever hits the release they spring apart.
There is a spring loaded 'hook interlock' preventing the slider returning to the operating position which when the contactor goes to 'reset' should be lifted out of the way. At the moment I cannot see what is supposed to lift this hook, and indeed it isn't lifting.
The toggle has two springs, and the one on the right sits in a die cast cup with guide lugs and travel limiting lugs. The travel limiting lugs have broken off :bang:
More work to fully understand this device but I'm nearly there.
If I really have to I can either machine from solid, or 3D print and lost wax cast a replacement cup but I will probably work out how I can try the furnace without this contactor before c omitting the time and effort to what might be a lost cause.
Remember - all this started mid melt so the contactor was closed anyway so there may well be more serious problems once this one is over come.
awemawson:
This morning I lashed the 'trip coil' back into the circuit as relay K1 needs it's continuity, and made temporary links round where the failed big contactor had been.
I powered it up via the 30mA RCD protected 16 amp three phase supply that normally feeds my guillotine as it's close enough to see & hear what's happening but far enough away for safety.
This was just for testing to see what faults are being displayed - and very sadly it's LOTS :bang:
Much more head scratching needed - sadly it's possible that this will be the end of this journey, as I have no circuit diagrams of the main microprocessor equipped logic board, nor have I ever seen another one after years of watching.
. . .early days yet, I need to retreat, lick my wounds, and cogitate!
russ57:
In general, sudden onset of lots of faults is unlikely, although 1 fault could cause lots of damage.
I'd be looking for a power supply issue.
A missing rail, etc.
Or a loose / faulty connector. Is there any other components /modules near that corroded solenoid?
Otherwise a possible sad end to an epic journey...
-russ
awemawson:
Yes I agree Russ.
Well out I went after lunch armed with circuit (just block diagram sadly) to test voltages and try and locate all the fuses. Poked and prodded before applying power and - guess what - it went ready once I'd given it water flow and pressure and pressed the reset button.
I'd been lead astray earlier by all the lights on for the power supplies and microprocessor on the front panel thinking we were awash with errors - but actually being 'green' they are showing 'OK' - the red ones show errors when on :bang:
Nothing had measured wrong - all supplies were there - no idea what has changed, and of course this may only be a temporary respite but at least it gives me hope. Obviously the program and basic microprocessor are still able to function.
I pinged the resonant frequency of the crucible, and did a very brief 'heat' (16 amp supply remember)
Having typed this out, I've just been back and repeated the process and amazingly it's still working. Again a very brief 'heat' as 70 amps from a 16 amp supply cable is not good :bugeye:
Still need to sort the contactor out, but at least this makes it worth doing.
Now faults don't just go away - something is lurking - but at least the fundamental electronics seems OK (ish)
awemawson:
So now the priority is to mend or replace the contactor.
Were it not for it's remote tripping facility it seems that there are quite a few just as 'manual isolators' - but the tripping is the only thing that the eStop button acts on and I'd like to retain that !
World wide searches haven't turned up any used ones, and although new compatible ones seem to be available their price rules them out at several hundreds of pounds.
The bit that is broken is a zinc or maybe aluminium based die casting - boxing it up is occupies about 50 x 50 x 65 mm. The hole for the big spring is 40 mm o/d by 36 mm deep.
Options:
A/ Machine one from the solid - time consuming but many of the features are there to minimise material use so wouldn't need to be incorporated.
B/ 3D model it, print in PLA and get it lost PLA cast in bronze.
I'm leaning towards option B - it worked well when I needed that drive dog for the Beaver lathe live tooling. I'm not even sure my copy of Fusion 360 is still operable - not used it for over a year and they have a habit of chucking you out !
As always comments and suggestions would be very much welcomed.
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