Digital Phase Converter for lathe

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

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liveaboard
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Re: Digital Phase Converter for lathe

Post by liveaboard »

I rewired the old forward/off/reverse drum switch on the lathe to switch the VFD the same way.
Because it's in a handy spot and robust.
Also, I was used to it, and it's easy to operate by feel while keeping the eyes on the work.
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Bill Shields
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Re: Digital Phase Converter for lathe

Post by Bill Shields »

I hate to continue to remind folks that gearboxes and back gears do more than change speed...they multiply torque.

Having a VFD that gives you full motor torque at low speed is great until you need 4X motor torque to drive a big cutter..the VFD is not going to multiply torque at low speeds...

you will still need the gearbox or pulley arrangement to provide this increased torque ..and occasionally reverse the motor when using back gear.
Too many things going on to bother listing them.
whateg0
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Re: Digital Phase Converter for lathe

Post by whateg0 »

If I ever get around to finishing the conversion, I'll have infinitely variable speed and the back gear. Monarch used the BIG DC motor to do that but the drive was completely disassembled when I bought it so I just replaced the whole kit and kiboodle. Never have gotten the back gear out back in. I'm also fortunate that the back gear doesn't require reversing the motor to go forward. I think I read somewhere that the new rebuilds they do use a 7.5 hp motor to get sufficient torque to eliminate the need for a back gear.
John Hasler
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Re: Digital Phase Converter for lathe

Post by John Hasler »

From what I can tell the spindle motors in high end CNC machines these days are usually polyphase synchonous motors with their own drivers.
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Bill Shields
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Re: Digital Phase Converter for lathe

Post by Bill Shields »

John: you are correct for many CNC machines...but I thought that we were discussing a retrofit for an existing lathe..

Putting one of these newer motors into service in an existing lathe would be prohibitively expensive.
Too many things going on to bother listing them.
rrnut-2
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Re: Digital Phase Converter for lathe

Post by rrnut-2 »

One other thing to bear in mind, with some machines you shouldn't slow the motor down. For example, in my Clausing Colchester lathe the motor drives the spindle and the lubricating pump for the head stock. Slow the motor down and the lubrication stops. The head stock gearing does the forward/reverse function. I do use a VFD for the 3 phase and I wired the front controls so they operate the VFD.

Jim B
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