VFD lathe retro
VFD lathe retro
(OP)
I've got a lathe that has an extremely complex gear box that has failed in multiple ways. A 2-1/2HP motor was the original prime mover. We have a 7-1/2HP VFD motor which is even plumbed with an integral 3ph blower. We'd like to replace the 2-1/2 and the transmission with this motor and a VFD - belt driven. Any suggestions or concerns you guys can think of?
Keith Cress
kcress - http://www.flaminsystems.com





RE: VFD lathe retro
Are your power feeds and leadscrew driven from the transmission? Even if they're separate you need to be able to keep the speed down a bit for screwcutting on a manual machine.
Does the transmission drive a lube oil pump for the main spindle? There's usually a sightglass on the head somewhere if there is a pump.
There are a lot of folks more knowledgeable than me over at Practical Machinist, a real mix of enthusiasts / home workshop owners and professionals. You might get a proper answer if you know the machine type. And of course there's our very own forum281: Machines & Machining engineering full of experts.
Oh, and please tell me you haven't broken a Monarch or CVA - I would love one of them for my home shop!
RE: VFD lathe retro
RE: VFD lathe retro
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RE: VFD lathe retro
Compositepro, Jeff; Yeah I realize the torque issue. That's why I'm asking you guys. There is a final gear ratio that we're banking on helping us here. Unfortunately as-is it's very limited because the sheave we go to is next to the drive tail so it can only get so large.. (about 4.5") It's less than 2:1 though so I've warned the guy that we should put in an intermediate shaft for more reduction. Essentially being geared way low and then taking advantage of the motor's 6kRPM name tag would be a better way to go. I'm trying to figure out what the minimum reduction would have to be to get us in the ball park with the original drive now that our motor is 300% of the original. It should be at least 1/3 the reduction of the original gear reduction correct?
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD lathe retro
By the way, for some reason when I read your original post I didn't even read the name. Had I known it was you Keith, I wouldn't have bothered explaining the torque issue... sorry.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD lathe retro
RE: VFD lathe retro
Comp; I'm told this lathe is "all about accuracy and smooth function NOT hogging out 1/2" cuts of steel". So I don't think loss of some torque is going to be an issue. As you say, something will always limit you. :)
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD lathe retro
It would even be nicer to have it turn on a lamp when the torque gets near the limit, so the operator will know to back off the depth of cut a little, or sharpen the tool.
The other warning would of course be smoke from the belt; you want to set the torque limit a little under that.
Mike Halloran
Pembroke Pines, FL, USA
RE: VFD lathe retro
Most higher function drives will have the ability to indicate a torque warning, but limiting torque sometimes involves allowing it to override the speed command, so be careful about that.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD lathe retro
Looks like the second one down:
http://fac-staff.seattleu.edu/fshih/web/14_misc.as...
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD lathe retro
The CVA would be my first choice for a smaller machine to sit alongside my old Holbrook which is on here somewhere: http://www.practicalmachinist.com/vb/antique-machi...