[barchdesigns]

Hi, I have a 3 Axis Mitsui Seiki VMC from the early 1980's with a Fanuc 6M control system on it. I feel the Fanuc 6M system is nearing the end of it's life expectancy and would like to retrofit the machine with a newer system. It's getting too costly to keep repairing the Fanuc system. I am going to start with replacing just the servo drives, however, the motors and encoders will remain on the machine.

What is a good replacement for Fanuc's 6M servo drive?

The motors are DC 151V 9A and labeled as a Fanuc 5M Motor part# A06B-0642-B005

I can't seem to find many people who have done this kind of retrofit and would like to know if this setup seems like a good match or if there would be a better approach. The machine itself is solid, but the control system is getting too costly to keep repairing. I'd like to retrofit it all eventually.

So far I have come across a Viper 200 Drive which seems to do what I want. Viper Servo Motor control products

The price seems right, but where would I get the power supply from? Am I on the right track?

Thanks,
Benjamin

[Al_The_Man]

It sounds like you intend keeping the motors? hopefully they have life in them as after the age of that machine the brushes and com. should be inspected or maybe an overhaul would be a good idea.
You could look at Camsoft with Galil Motion and A-M-C drives, or use Dynomotion with Kanalog and use A-M-C analogue drives for an alternative closed loop system.
Power supplies can be had from Antek or as he lists on ebay Jonango.
The reason the 6 did not have a power supply, per-se, is it used full wave SCR drives.
Al.

[barchdesigns]

Is it better to replace the motors and drives at the same time then?

The intention of the retrofit is to keep this machine going for 10-20 more years which I believe would be cheaper than buying a newer machine.

Is there a major price difference between having the brushes and commutator inspected/overhauled and just replacing the motors? Would A/C motors and drives be cheaper than trying to keep it DC as it is now?

[Al_The_Man]

The cost difference could be quite a bit for those size motors, if you have a decent local motor outfit, it may be worth the cost of getting them just to do an assessment?
You can still be them up as NOS on ebay occasionally.
Al.

[barchdesigns]

Moving forward with replacing the Fanuc drives, for now I am going to keep the motors. The Fanuc motors are 151VDC 9A. From what I have read it looks as if I want to supply about a 10%-20% higher voltage to the Viper drive board than what the motor needs for it's max. With the Viper 200 being able to handle up to 170V it seems like a good fit to run 151V motors.

I have two 2KVA transformers on the machine to supply power to the original drives. These are 185V secondary with a 200V or 220V primary taps. My incoming line voltage is already a bit high with some days reaching as much as 250V. When I measured the 185V output of the transformer I am getting 210VAC.

See attached page of the viper manual. It shows that "DC Voltage = AC Voltage x 1.414"

I'm not a power electricity guru by any means, but I thought your DC Volts were equal to your incoming AC Volts once you rectify and smooth it with a capacitor? Is there a way to use the existing transformers or would I need to find a different transformer that has other tap voltages?

[Al_The_Man]

Larkin is correct of course, With 210vac you will get around 300vdc!
Are those 3ph transformers? I would have expected it on those drives.
If so, check to see if they are star connected and would be around 160v from star point to a phase?
Otherwise you may have to source another transformer.
Or another alternative if they ARE 1ph transformers with a 200v secondary is to take turns off until you get down to what you want, it is a bit messy on a square EI type transformer, but I have done this in the past, the secondary is usually wound on last, and as a rule works out to around 2-3turns/volt.
Al.

[barchdesigns]

They are 3 phase transformers indeed. They feed 185V 3 phase AC power to the Fanuc DC Servo Drive. Using those would probably be out, but what about this:

If that AC to DC conversion is true, then I believe I should just be able to put a Bridge rectifier and capacitor on the first phase and ground coming into the machine similar to the viper drawing from the manual, correct?

I run a rotary phase converter for main power and the first two legs to ground are 118VAC and 120VAC, with the third leg being wild.

So 120VAC x 1.414 = 170VDC which is what the drive calls for. I should probably throw a breaker or fuse on there for safety as well. Would this work?


Can anyone confirm the wiring of the Fanuc drives? If you look from left to right on the power connections of the drive I see what I think to be:

E - Ground
R,S,T - 185V AC 3 Phase Input
12, A - 100V AC E-Stop loop?
1A1, 1A2 - DC Motor Output
E - Ground

Does the front Honda connector have a 0-10VDC signal for VCMD? What else would be in that Honda connector? Maybe the generated tach signal? If I understand correctly, the Motor Encoder signal connects back to the Fanuc 6M control unit, the control unit then figures out where the drive needs to be and sends the appropriate 0-10VDC VCMD signal to the drive board?

The other white plastic connector has three red wires which are two 18V AC lines from the transformer (18V, 0V, 18V). I assume this is to power the logic circuit board side of the drive?

[barchdesigns]

I ended up finding the pin out diagram for this particular drive. This answers a lot of my questions on the control side.

So the main question is can I use the first phase to ground 120VAC with a bridge rectifier and capacitor to get the 170VDC for the Viper drive?

[Al_The_Man]

This is what I mentioned in post#6, about using the star ground and one phase.
The only thing you have to watch then its that the DC side is not grounded at all.
The alternative, and what i would be inclined to do is remove the star from ground and have an isolated secondary.
Al.

[barchdesigns]

I bought a Viper V200 Servo Drive and will be powering it from a "rectified and smoothed" single phase of the machine. It looks as if you can get Fanuc used servo drives for a few hundred dollars and new for about $2,500. So far I have about $300 into the servo drive between it and the power supply caps and rectifier.

Viper V200 Servo
2x 12,000uF Capacitors
Bridge Rectifier

The parts will be here soon. I'm not sure when I will be scheduling the drive swap yet, but I will probably do lots of off machine tests and reporting back here before I go ahead and replace it out for good.