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Author Topic: Looking for help with a spindle motor.  (Read 1237 times)

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Re: Looking for help with a spindle motor.
« Reply #10 on: April 08, 2022, 12:54:28 AM »
I don't have a signal generator but I do know the motor turns. 
It was working with the printer port up to 600 rpm.  After that the computer just couldn't handle it.  Fell flat on it's face.

You told me that.  Go back and refresh your memory at the initial post and your reply.
Somehow I'm missing one of the basic fundamentals with the ESS.

In my defense, I've been working on this two and three minutes at a time in between the work I'm supposed to be doing.  ::)
Re: Looking for help with a spindle motor.
« Reply #11 on: April 08, 2022, 06:52:16 AM »
Why use a stepping servo motor to drive a spindle?
Re: Looking for help with a spindle motor.
« Reply #12 on: April 08, 2022, 01:02:30 PM »
Why use a stepping servo motor to drive a spindle?
It's small (nema23). 
It's very affordable.  Well, it was until it became apparent the ESS would be an essential ingredient.
It has great torque for its size and the torque curve is flat over its entire rpm range.
The rpm will be spot on and stay there if the power demand increases.
It's controllable for soft start and end.
All of this assumes, of course, that I actually get it to work the way its supposed to work.

Right now I'm using a sewing machine motor.  It has good rpm and torque but the rpm is manual and is really vague.  I have to use ipm rather than ipr.  The rpm has to be changed manually between tools so it needs to be constantly tended.
Re: Looking for help with a spindle motor.
« Reply #13 on: April 08, 2022, 03:00:31 PM »
What lathe is it?
Re: Looking for help with a spindle motor.
« Reply #14 on: April 08, 2022, 04:34:58 PM »
It's a home built.  Built around a pair of Parker 404XR linear actuators.

Made for light, precision work.  Jewelers lathe type stuff.
The specs will make you kinda giggly.
8 um (.0003") accuracy over its entire travel.
1.3 um (.000051") repeatability.
Re: Looking for help with a spindle motor.
« Reply #15 on: April 08, 2022, 04:44:50 PM »
Hi,
may I suggest a couple of experiments that will tell you if the ESS and servo are working as expected and also inform you as to how
to set up both to your satisfaction.

Start by assigning your servo to a rotary axis, say A or B , just as an experiment.

Lets say you have set the servo set to 2000 pulse per rev. A rotary axis has units of degrees, so the Steps per Unit value in the
A axis motor tuning page would be 2000 / 360 =5.55 Steps/unit. the max velocity in units would be 3000 (rpm) x 360 =1,080,000
units per minute, and make acceleration 10% of that, say 100,000 unit/s2.

Now try an MDI command of
G0 A360000

This should cause the servo to rotate 1000 turns at max speed and acceleration then stop. Does it do so?

Craig
My wife left with my best friend...
     and I miss him!
Re: Looking for help with a spindle motor.
« Reply #16 on: April 08, 2022, 04:57:56 PM »
Good idea.  I probably won't have time to try it today.  I'll check back and let you know what happens.
Re: Looking for help with a spindle motor.
« Reply #17 on: April 08, 2022, 05:24:33 PM »
Well those sewing machine motors run up to 5k rpm I think and can generate 3/4 hp, much more suitable than a 130W servo motor IMHO for a lathe.  If precise spindle control is needed for threading then I think Mach4 can process both spindle encoder and index pulses.  Nice looking little machine though.
Re: Looking for help with a spindle motor.
« Reply #18 on: April 08, 2022, 08:31:04 PM »
Hi,

Quote
Well those sewing machine motors run up to 5k rpm I think and can generate 3/4 hp, much more suitable than a 130W servo motor IMHO for a lathe.

On the basis of power output I'd have to agree. There are some countervailing arguments which may prove otherwise.

I've been using servos (Delta B2 series) for a year or more now and they never cease to amaze me how much power they produce, it seems rather more than the
nameplate would suggest. I think the feature that we overlook is a servos overload capacity, commonly three or four times its rated output. It would certainly not
work to design a system that required that overload capacity, but that capacity can and will be exploited and so make you believe that it has much more power
than you guess. On this basis I would suggest that this wee servo could well behave as if its a motor of 260W, so a little over 1/4 hp.

The second area that suggests a servo is better is because it can be position controlled. Things like rigid tapping become possible when you your spindle
has positional capability rather than just  a closed velocity loop.

I have a second hand 1.8kW Allen Bradley servo that I use as a secondary spindle motor. It has so much more torque than my regular 24000 rpm asynchronous
spindle, I use it for steel and stainless. Mostly I use it in velocity mode, ie just a free running spindle with a closed velocity loop, but I can and sometimes do use it
in position mode as a C axis which allows me to do rigid tapping. For instance:

g1 c3600 z-10 f10000
c0 z0

Will result in the C axis, ie the spindle, rotating 10 revolutions at a speed  of 10000 /360 = 27.8 rpm while the Z axis does a coordinated move of -10mm., ie a pitch
of 1mm per revolution. Then the C axis will stop, with deceleration, and coordinated with the Z axis, and then unwind ten revolutions with the Z axis coordinated
to back out of the thread at 1mm per revolution.

Note this does not require any specialised Gcode or any extra motion control support, it just relies on the coordinated movement of two axes which Mach does that and more all the time.

Craig

My wife left with my best friend...
     and I miss him!
Re: Looking for help with a spindle motor.
« Reply #19 on: April 08, 2022, 08:38:42 PM »
Hi,
even if the wee 130W servo doesn't have the power then get yourself a 750W Delta B2 series servo ($435USD) and it will 'kick anus all day long'.

Craig
My wife left with my best friend...
     and I miss him!