opinion; old German milling machine

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

Moderators: GlennW, Harold_V

User avatar
Harold_V
Posts: 20231
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: opinion; old German milling machine

Post by Harold_V »

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.

https://www.chaski.org/homemachinist/vi ... 4&start=60 post #66, with pictures.

The power supply now operates reliably. It was definitely worth the effort.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
User avatar
liveaboard
Posts: 1970
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: opinion; old German milling machine

Post by liveaboard »

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.
User avatar
NP317
Posts: 4557
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon, USA

Re: opinion; old German milling machine

Post by NP317 »

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
User avatar
Bill Shields
Posts: 10459
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: opinion; old German milling machine

Post by Bill Shields »

Best $50 you will invest in this project
Too many things going on to bother listing them.
User avatar
liveaboard
Posts: 1970
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: opinion; old German milling machine

Post by liveaboard »

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.

First I'll try to find the problem[s] and fix it.
User avatar
Bill Shields
Posts: 10459
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: opinion; old German milling machine

Post by Bill Shields »

Beware of Ice cubes in machine enviroments.

There is something to be said for big heavy relay coils that are not subject to transients.
Too many things going on to bother listing them.
User avatar
liveaboard
Posts: 1970
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: opinion; old German milling machine

Post by liveaboard »

Ice cubes!

Have you had trouble with that sort of thing? even small relays have coils that are quite robust.
User avatar
Bill Shields
Posts: 10459
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: opinion; old German milling machine

Post by Bill Shields »

Yes

It is not a case of the coil failing it is a case of the relay stuttering in the presence of transients.

It is a safety thing more than anything else. I have seen ice cube relays stutter when the machine next to it cycles.

You want relays that are not going to a activate unless they get a good SOLID power shot.
Too many things going on to bother listing them.
User avatar
liveaboard
Posts: 1970
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: opinion; old German milling machine

Post by liveaboard »

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!
John Hasler
Posts: 1852
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: opinion; old German milling machine

Post by John Hasler »

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.
User avatar
liveaboard
Posts: 1970
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: opinion; old German milling machine

Post by liveaboard »

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.
Post Reply