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Fanuc Welding servo positioner headstock

kineticmx

Aluminum
Joined
Mar 10, 2014
Location
United States, CT
I'm looking for a small headstock for a fanuc welding cell. Its a small Arcmate 50 and all the headstocks I am finding are way too big (not to mention expensive) for my application.
Looking for 6-8" platter and I will have no more than 200ft-lb moment load on the headstock.
I still need to buy the servo amp so I can pretty much drive any Redcap servo motor without issue.

At first I was thinking possibly build one from scratch, but why not adapt a standard rotary?

Thoughts on some old 4th axis pulled from a VMC? Not sure how fussy I would need to get with electrical isolation. Just ground using a graphite brush on the edge of the rotary faceplate and go for it?

I really don't know what sets a welding servo headstock apart from a regular CNC rotary. Roller cam, worm gear, harmonic? I think a worm gear would be best suited for this application. Mostly worried about frying bearings from stray current or heat damage. Would appreciate your thoughts.
 
Hello!
you will need to adapt the mounts or electrical connection to integrate the servo amplifier with the rotator.
The worm gear is really well suited for welding applications due to its ability to provide high torque and precise positioning at relatively low speeds. It also provides natural locking to prevent unwanted movement under load.
your design must provide good electrical insulation to avoid damage from stray currents. This may include insulation between the servo motor and the mechanical components, as well as between the rotator itself and the welding machine. spare parts you can look at globy.com Using a graphite ground brush can help reduce the risk of damage from electrical currents, but make sure it does not create additional friction or wear.
When selecting an old 4th axis from a VMC or other rotary device, pay attention to its mechanical condition, especially the condition of the bearings and worm gear. Damaged or worn components can reduce the accuracy and reliability of your welding headstock.
 
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I'm not a robot guy but I've been looking into them, so please take experienced advice over mine.

There are so many Fanuc robotic parts/components on eBay, I'd just look into those and see if something fits.

200ftlb moment is actually a lot if you're anywhere close to it.

If you just need positional moves you might be able to work out a timer mechanism with two separate controls (robot & rotary), and maybe a limit sensor, but it'll cause more issues than an integrated system can. If you need it to rotate while welding I think it would be almost unjustifiable. Adapting mechanical hardware is easy but adapting drives/controls is probably a total nightmare for most people and a huge time consumer. I would only stick with native architecture for robotics. Fanuc has more drives out there than probably every other automation company combined. I would try hard to find a Fanuc rotary versus buying any generic rotary. If the connectors don't hook up, the signals aren't readable by the robot control, and the rotary isn't designed for welding, it will make for a very expensive and time consuming failure of a project in my opinion.
 
I'm not a robot guy but I've been looking into them, so please take experienced advice over mine.

There are so many Fanuc robotic parts/components on eBay, I'd just look into those and see if something fits.

200ftlb moment is actually a lot if you're anywhere close to it.

If you just need positional moves you might be able to work out a timer mechanism with two separate controls (robot & rotary), and maybe a limit sensor, but it'll cause more issues than an integrated system can. If you need it to rotate while welding I think it would be almost unjustifiable. Adapting mechanical hardware is easy but adapting drives/controls is probably a total nightmare for most people and a huge time consumer. I would only stick with native architecture for robotics. Fanuc has more drives out there than probably every other automation company combined. I would try hard to find a Fanuc rotary versus buying any generic rotary. If the connectors don't hook up, the signals aren't readable by the robot control, and the rotary isn't designed for welding, it will make for a very expensive and time consuming failure of a project in my opinion.
There are almost no Fanuc headstocks for sale used, typically packaged with robots. Not paying 8k for a welding headstock. Hence my question, what would you do to take a typical rotary with a fanuc servo and make it not fry itself in a welding application. I can get a regular worm drive headstock for under 2k. 8k plus servo amp, cables and software would damn near double my investment so far.

 
I'd be more comfortable with a brass slipring for low speed high current. Robots often use fancier welding power supplies with more complex feedback that is far more sensitive to ground resistance.

I'd personally just get a hollow output low backlash worm gearbox that fits your servo and make a plate for it, and have some spring loaded brass (or graphite, if you use enough of it) on the portion of shaft extending through the gearbox.
 
I'd be more comfortable with a brass slipring for low speed high current. Robots often use fancier welding power supplies with more complex feedback that is far more sensitive to ground resistance.

I'd personally just get a hollow output low backlash worm gearbox that fits your servo and make a plate for it, and have some spring loaded brass (or graphite, if you use enough of it) on the portion of shaft extending through the gearbox.
This is the one I'm eying. It is roller bearing, but so long as I get a good ground I'm not too worried. And it is hollow so I can pass the shaft (tube) you mentioned through it and have a grounding mechanism hanging out the back. Thoughts?

 
This is the one I'm eying. It is roller bearing, but so long as I get a good ground I'm not too worried. And it is hollow so I can pass the shaft (tube) you mentioned through it and have a grounding mechanism hanging out the back. Thoughts?

Seems like all of the hard work would be done for you there. Just make sure to ground it well and I don't see any issue.
 








 
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