So I just bought a Ruhla FUW 250/IV

[Farrismek]

Just bought a nice looking Deckel style mill. a WMW Ruhla FUW 250/IV. Mechanically it looks very good, but it has faulty electronics. The dealer suggested to change out the old DC drives with AC motors and VFD. The mill has infinite variable speed DC motos on both the feed and spindle.
Very interested if someone else has done a similar conversion or know someone who has. Just got it in today, and havent sorted out whats the problem yet

 

[AlfaGTA]

I would look into repairing the original setup. Most likely some issues with the power supply for the DC motors.
Staying original has advantage that the motors are integrated and already fit.
DC motors also provide better stall power than AC. Likely will have better power than a conversion, plus its all there, If going VFD You would need a separate VFD for every driven motor($$$$)

Likely long shot to acquire a wiring or electronics print, but stranger things have happened. Might be able to change just the power supply once you determine the output requirements (voltage and total current)with a commercial unit. Nice looking machine.
Cheers Ross

 

[zephyrous]

15 years ago, I went through a similar problem with my F315/III. It used to have an external cabinet with 70's electronics (bulb transistors etc) that went bad.An electronics technician at the time, suggested (as Ross above) to keep the 2 old robust motors and interchange the whole setup with an AC/DC converter to drive the motors, a PLC to guide the movements/mechanical switches and some relays.
Unfortunatelly I sold the machine some years ago with all documentation and schematics that could help...

 

[Farrismek]

Spindle motor burnt out. rewinding necessary to get it working. The electronics are worse. blown parts here too, and parts are super hard to find as they are from the 70's. So I decided to gut it. Tore everything out. Spindle and feed motor, several transformers (5 in total) and all the prehistoric thyristor speed controlling gear.
Ordered new motors. The spindle motor will be upgraded from DC 270V 4,8kw to 5,5kw 3⁓. the feed motor are upgraded from DC DC 270V 0,6kw to 3⁓ 0,75kw. both motors will be controlled by separate Siemens vfd's and the spindle motor will also get braking from DC injecting. vfd's are controlled by Siemens S7-1200, and the control panel will most likely be changed out with Siemens Simatic hmi display. the 9" version fits exactly in the control panel housing.
As AlfaGTA mentioned, this will be a costly refurbishment of an old mill. motors are already on order, and set me back about 11.000,- NOK/1100$. Luckily I have access to used plc's and vfd's through my work, so I might save big money here. If not, the vfd's are about the same price as the motors, and the plc is around 600$. Fuses, cables, terminals+++ are all over the place at home, as I have hoarded parts through many years as an electrical engineer.
The only motor I will keep is the lubrication pump.

 

[AlfaGTA]

Interested to see your finished product, keep us in the loop.
Good that this repair is right in your professional wheel house.
Cheers Ross

 

[DeadMahoDude]

Electronic nightmare from German Democratic Republic, I suppose ;-D

 

[Farrismek]

You bet!

 

[Farrismek]

Recieved new motors today, and although I ordered with the correct flange size, the new motor flange has internal threads. No way to get bolts through the gearbox casing, so a new flange or some kind of adapter plate is needed. Anyone with some suggestions here? The flange is named B14 large. The plc and vfd are on backorder. 90 days for the vfd

 

[AlfaGTA]

Not sure what the issue is, but think you could use studs in the motor flange, or
Drill out the threads of the motor flange and use the gearbox studs with nuts or bolts with nuts.
Cheers Ross

 

[AlfaGTA]

Iooking further, is it possible to just mill a clearance pocket into the motor flange at each hole to provide a space for a nut from the original gearbox studs. (drill out flange threads)
Can’t tell from the photo
Cheers Ross

 

[Farrismek]

I understand what you are saying, but I haven't figured that out yet.Might be possible, but i think the motor casting is hollow, and only about 10-15mm thick.
I've contacted the seller that i bought the motors from, and he says I should have ordered a special B5 flange for my application. He will give me a price tomorrow. I think the solution is a new flange.
With a adapter plate I might have to extend the axle. I dont know. the stickout is 65mm now, but I dont know if it needs to be fully inserted or not. it doesn't bottom out in the female shaft from the gearbox.

 

[rklopp]

I ran into a similar problem with the feed motor swap on my Aciera F4. I ended up transplanting the old motor end bell with flange onto the new motor. It was a relatively simple lathe job, fortunately.

 

[rimcanyon]

Another approach to consider: disassemble the motor and attach the end bell to the mill using bolts, then re-assemble the motor.

 

[Farrismek]

Another approach to consider: disassemble the motor and attach the end bell to the mill using bolts, then re-assemble the motor.

I'm afraid that's not possible here. New motor flange already on its way from supplier.

 

[Poloris]

I have a earlier 250 X 210 Ruhla. Recently I had to replace the spindle motor with a single speed unit. I lost 6 out of 18 spindle speeds including 720 900 and 1120 rpm,
Those are the speeds I prefer to use for my end mills, so I want to convert to VFD and PLC feed control.
There is not a lot of information on Ruhla's on the internet.
This guy has done a conversion but he did not post any details. There is a video https://www.youtube.com/@mrdiyrepairs
Mark

 

[Farrismek]

I ran into a similar problem with the feed motor swap on my Aciera F4. I ended up transplanting the old motor end bell with flange onto the new motor. It was a relatively simple lathe job, fortunately.

I too have a small problem with my new feed motor. the motor shaft is 19mm, and the receiving hole in the gearbox is 17,5mm. Either I'll have to take out the rotor and turn it down in the lathe, or clamping the entire feed motor to the milling table, and mill it to correct diameter with the motor running

 

[Farrismek]

By the way: New motor installed. Ordred the special mounting flange. It was NOT fun to install due to some weir bolt placement on the side facing the y axis. wish i got an extra elbow joint and backwards bending fingers when installing. Might regretting not to paint it in RAL6011 beforehand. It might be black forever now, or maybe some spray paint on visible areas