Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.
John Hasler wrote: ↑Mon Dec 21, 2020 3:23 pm
Since it sat for many years I'd go through and clean and burnish every contact pair and then check with an ohmmeter that they made and broke when operated manually.
Heh!
The induction furnace power supply I recently got operational has seven relays in the control system. Your comments have merit, as I had experienced intermittent operation due to the poor condition of the relays. The way they were built it was virtually impossible to access the contacts to clean them, and they are no longer available, so I eventually replaced all of them with different relays, using the base of the originals to make it easy.
A full electrical rebuild like that would be a huge undertaking; the wires would all have to be removed, and they're unmarked, and there are hundreds.
That diabolical relay I found with an NC switch in the middle of 3 NO ones gave me pause.
Still it might be what I do in the end. This machine has been mucked with, and whoever was in the mechanical part had no business being there.
I hope a different person, with more between the ears, did the electrical repairs.
The diagram comes with a explanations. I'm working on repairing the scans [they're made from a faded + yellowed book], then I'll run them through OCR, then translate the text.
Hopefully that will do the bulk of the work.
I cannot imagine tackling a project like your East German milling machine without a wiring diagram!
'Glad you got one, and hopefully it is for your specific machine!
RussN
I got it for free, someone from another forum shared it with me.
It does appear to be specifically for this machine, although I'm only starting to get into it.
it will take time, and at this moment 2 weeks of rain [rain is good] has stopped so I need to get to the landscaping chores, laundry, etc.
I've been looking for relays online; I'm thinking to change the 10 mind boggling variable architecture ones that are in there for plug in standard no/nc cubes. But those have fewer contacts so there would have to be more of them.
The 10 control relays [excluding the motor contactors] would become about 30.
The original ones are 6A, if I can go down to 3A then I can use 4 pole relays, which will mean fewer of them.
That would be a function of coil power vs. the return spring; the published specs where I shop [ebay] rarely include coil current. But I assume the larger current rating power contacts are a partially a function of contact pressure which will equate to higher coil / spring power.
This machine is a real dinosaur, without a single transistor.
The rectifier for the clutches is selenium; I had to look that up, they were phased out in the mid 60's in the west. it still works but output voltage is fading. I may swap that out for a modern one.
The mercury switches I mentioned earlier do indeed function as delay relays. Crazy intricate mechanical gizmos with glass vials of toxic metal instead of $0.50 worth of silicone.
And after 45 years, they still work!
Liveaboard writes:
The rectifier for the clutches is selenium; I had to look that up, they were phased out in the mid 60's in the west. it still works but
output voltage is fading. I may swap that out for a modern one.
Be careful about that. You'll get significantly higher output voltage.
I'm aware.
The transformer has lower taps; if it won't go low enough, a big diode or two inline will burn off a bit.
At the moment it's on the highest tap, but I don't know if it left the factory that way. It could be that the higher taps are intended for compensating when the selenium rectifier ages and output voltage drops.