[CAD_CAM_EDM_DRO] Re: Resonable Stepper Speed under simple Unipol ar drive ?

Thanks Guys

I just wanted to know that I wasn't completely insane.

This is on an old Jet 9X44 Mill running 3:1 on the original
lead screws.

It works great as a CNC machine it just slow a snail on a salt lick.

I have tried to drive the system with the following drivers:
Mach1
EMC (Linux)
Wave Tek (pulse generator)

What I found was that if I pass through the resonate point at just the right
acceleration I can get the motors to around 400-500 rpms. But it is imposable
to operate near the resonate point with the L/R drives.

Also I found that PC power supplies (IE: CHEAP Switcher) don't work without a
significant amount of bulk capacitance to filter them. I ended up with 50,000uf
of filter caps on each one to keep the regulators from oscillating.


Thanks all
Mark


-----Original Message-----
From: ballendo [mailto:ballendo@...]
Sent: Friday, August 15, 2003 2:23 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Resonable Stepper Speed under simple
Unipolar drive ?


Mark,

90rpm for a size 34, triple stack motor seems a bit slow...

Mach1 does not have the most stable pulse train, as Art will tell
you. Partly why he recommends using microstepping drives... Mach2 is
better, if you can use it.

So, first try another cnc controller if you can. Perhaps Turbocnc?
The older dos based controls had better pulse trains consistency, and
your motor needs a little help<G>

Second thing to check is whether your power supply is up to the task;
is your motor getting the amps it needs? Double check your ballast
resistor calcs...

And finally, for me at least the older superior slo-syn motors in
this size top out at about 200-220 rpm with a unipolar setup. And
that was with 34 volts, using a Dan Hudgins (DanCAD3d/Dancam) driver
design with 2n3055 output transistors and some tricks with
capacitors...

From the specs you list, I'm guessing these motors are the old round
sky blue type... Magnet technology wasn't where it is now, and you
may find it worthwhile to trade up to newer motors. You can get 550
oz. in. motors in a 34,double stack size, which likely will give
better performance (less rotor inertia), depending upon the machine
you're connecting to...

With your existing motor(s), I'm thinking you'll see maybe 120-150rpm
with a dos-based control, or other pure pulse train (You might want
to wire up a 555 oscillator; many kits available if electronics
aren't yer thing)

Hope this helps,

Ballendo

P.S. Are you using a computer power supply (switching type)? You may
want to add a filter cap to it's output, as switchers and unipolar
sometimes don't play well together... (add a smaller hi-freq cap as
well) Perhaps one of the electronic gurus here can give you more info.

P.P.S. If you have half-step available on your drive, be sure to try
it. Although the torque changes every step, the shorter distance
makes for less ringing at each step, and you may be able to extend
your upper limit due to a change of the resonant freq..


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Mark Thompson <Mark_T3@v...>
wrote:

> Hi all
>
> What is resonable expectation for stepper speed when running
> a Unipolar drive ?
>
> Specs:
> 12V supply voltage
> 4.3V @3.5 Amp motors
> Ballist resistors to control current
> Unipolar mode
>
> M93 series Slosync motors
> 400 oz/in
>
>
> Currently under Mach1 I can achive 225-250 full steps/secs unloaded

before it

> resonates and slips phases.
> Under load I can get around 300 full steps/secs before it resonates.
>
>
> Does this sound typical or do I have problems ?
>
> Thanks
> Mark

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