SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

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2js4rx7
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SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by 2js4rx7 »

HI
my mind is melting trying to figure out what servo spindle options i can use to power my cnc lathe conversion
it currently has a big old 10hp 3 phase motor and belt drive to the gearbox input but looking to drive straight to the rear of the spindle
have been looking at chinese servo spindle motors around 5-7.5kw
was also wondering if a normal servo motor could be used ?
something like an estun emb-75d and pronet-75d driver?
will the driver have the correct inputs to receive both step/direction and velocity modes from an oak board ?
it lists a 0-10v input on the spec sheet for the pronet 75d but not sure how you get the step direction into it ?

option 2 is retain the 10hp 3phase with a vfd
and assemble a seperate servo arrangement that is either clutched (belt driven) or gear driven and can be brought in and out of mesh when c axis movement is required and set this up using the 4th axis on the oak board ?
pics attached show this idea.
other pics are of the dsg lathe im converting
thanks for any help daniel
Attachments
MoreCAxisSubServoDetail.jpg
GoodwayC_axis_thumb.jpg
CAxisSubServo.jpg
IMG_20180904_122901.jpg
IMG_20180904_122846.jpg
IMG_20180831_154541.jpg
martyscncgarage
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by martyscncgarage »

My .02 for what its worth.

What are you trying to ultimately accomplish with the lathe and C axis?
Are you going to fit some sort of live tooling to it?
Is the C axis just positional or is it going to to have to rotate while the live tooling is cutting?
What kind of material are you cutting?

I would think a large enough servo motor and servo drive (which would be dependent on what you are trying to do and what kind of material you are planning on cutting) could get really expensive.

Engaging and disengaging a servo motor when needed would be more economical...but again, what kind of cutting forces is the machine and they C axis going to see?

OAK should control what you want to do...but need more info on the application.

Just some thoughts...
Marty
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mrprecise
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by mrprecise »

I would keep the original motor, and drive it with a VFD; Simple speed control with 0-10v. Since we are not talking about high rpm's with big lathes, the original motor will last forever. The older motors were much better than what is make today.

Put a small timing belt drive on the inside face of the spindle pulley 1:1 ratio to a jack-shaft in bearing support. Mount the 2000 ppr quadrature encoder with a coupling to the jack-shaft.

Install an air-clutch on the back side face of the spindle pulley; timing belt drive the input of the clutch with a 750 watt servo mounting an inline gear reduction perhaps 10:1; you already have the encoder reading position. This should be plenty of torque, in a small space. The clutch will have to carry lots of torque, so it should be a in/out locking, not a friction drive. It is not going to engage when the spindle is turning anyhow.

Simple is best.
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by Magneto »

What did you end up doing on this project? I'm on a similar trail for two machines.

Having researched it out, I'm surprised that there's not more support for C-axis / mill-turn conversions on the CNC aftermarket or more explicit direction from Centroid. Siemens, Fanuc, Mazak and Okuma seemed to have solved it by using spindle motors with multiple windings that can switch into servo mode.

Centroid forums keep referring to an A-Trump lathe conversion that can do it, but not a lot of detail on how it was done - the text seems to suggest that the spindle is velocity driven and position driven via a servo motor, but reference a mechanism of some kind.
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by cncsnw »

The Atrump lathe pictured in the Centroid video had a third servo motor that was engaged and disengaged from the spindle on demand.

For normal turning operations, the servo motor was disengaged and the lathe's native main spindle motor was used.
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by Magneto »

Thanks, Mark. Sounds like the mechanism the page refers to is a clutch, then. We'll plan accordingly and be in touch with you if you've got room for the work and don't mind the travel. :)
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by cnckeith »

Uwe found a nice electromechanical clutch to use in his C axis build. https://www.youtube.com/@TheSuntravel/videos

The Centroid Atrump C axis machine used a roller engagement scheme where the servo motor was engage and disengaged by moving along a slide with air cylinder controlled by output. the 'pulley' on the servo was actually a polyurethane roller and the wheel connected to the spindle what a large diameter knurled wheel. the roller was pressed against the knurled wheel when in C axis mode.
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by aamir »

Magneto
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by Magneto »

Nice. Researching both now. Will follow up soon. Thanks, fellas.
aamir
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Re: SERVO SPINDLE MOTOR OPTIONS MILLTURN CAXIS LATHE

Post by aamir »

CTB is economical and has variety of features.for both C axis and for drill tap m.c
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