RE: [CAD_CAM_EDM_DRO] Servo as a Sherline spindle motor ?

Hi Alan,

I've tried an ELS on a Sherline lathe and not had any problem threading
once I added the spindle tracking code. This was using the original FROG
stepper on the Z axis which was way under powered and ran on 24VDC.
Upgrading to a 280oz-in motor with a 42VDC power supply the ELS's own
micro-stepper driver had no issues with turning threads on the Sherline.

But I agree that the spindle motor on the Sherline, although it operates
closed loop, is quite underpowered for threading. You're really between a
rock and hard place. If you run the spindle with the slow speed belt
combination at mid range where it has decent torque then the stepper motor
has to turn that fine pitch 20TPI lead screw really quickly. If you slow
down the spindle the closed loop controller tends to let it wander a bit
and it just doesn’t have the torque.

IMHO, the least expensive option for a Sherline would be to create a
planetary type back gear pulley arrangement that let's you run the motor
at higher speeds but keeps the spindle speed down so the stepper motor on
the Z axis isn't running at the high end of it's speed range (again the
low torque end of the stepper).

Eventually I plan on changing my DB-200 Lathe DC motor over to a Treadmill
motor with a UHU DC-Servo drive. I have a version of the ELS that I've
been testing that creates a variable speed step rate for the spindle so I
can just tell the UHU to hold the motor a given speed and then threading
with the fine pitch DB-200 lead screw should work nicely.

The motive behind the spindle stepping rate though was really to use the
DC-06 Digispeed step to voltage converter that Peter Homann donated to the
project for the VFD on my SouthBend.

John Dammeyer

Automation Artisans Inc.
http://www.autoartisans.com/ELS/
Ph. 1 250 544 4950

> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Alan Rothenbush
> Sent: Wednesday, December 17, 2008 8:06 PM
> To: CAD CAM EDM DRO
> Subject: [CAD_CAM_EDM_DRO] Servo as a Sherline spindle motor ?
>
>
> Thanks to all who responded to my question about my 5mm
> pulley bore. I have some coming and I'll try to bore them
> out and cross my fingers.
>
> That pulley is destined for the end of a double-stack NEMA17
> stepper that will be used to drive the cross slide of a
> Sherline lathe that I'm FINALLY getting around to CNCing properly.
>
> One thing I'd like to try on the Sherline is CNC threading.
>
> I see two ways to do this.
>
> 1. Put a servo on the spindle and write a bit of custom code;
> no real problem, or
>
> 2. Put a nice fat motor on the spindle (so there's no worries
> about it slowing down) and use one of the "spindle sensor" options.
>
>
> Option 1 is certain to work AND I have all the bits at hand;
> spare gecko G320, a choice of servo motors, and some L series pulleys.
>
> The one little fly in the ointment is that the choices for
> servo motors are
>
> . one that's SEEMS a wee bit small or
> . one that's WAY WAY WAY TOO BIG and would be wasted in this
> application.
>
>
> The smaller motor is an older EG&G Torque systems ME2610. It
> is physically pretty close to the same size as the stock
> Sherline _AC_ sewing machine motor, if that means anything.
> (It's an old lathe).
>
> I can find no specs on the PRECISE motor, but I did find some
> specs on a similar motor from the same manufacturer (same
> dimensions, similar part number). That motor is rated at 29
> OzIn continuous, 150 OzIn peak. This does not seem like a
> whole lot of torque to me.
>
> On the other hand, I can't stall it with 36 volts driving it
> by grabbing the 1" pulley, so maybe 150 OzIn is more torque
> than it seems.
>
>
> Anyway, I'm looking for thoughts, opinions and experiences;
> all comments gratefully accepted.
>
>
>
> Alan
>
>
>
> ------------------------------------
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com,
> wanliker@..., timg@...
> Moderator: pentam@... indigo_red@...
> davemucha@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com
> to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider
> this to be a sister site to the CCED group, as many of the
> same members are there, for OT subjects, that are not allowed
> on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
> POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
> EXCEPTIONS........
> bill
> List Mom
> List Owner
>
> Yahoo! Groups Links
>
>
>
>
>