Re: [CAD_CAM_EDM_DRO] Tuning steppers

> From: "Joel Jacobs" <jj@...>
> With the eval CNCpro I could get 30 ipm easy,
> with emc and freqmot I can barely get 15 ipm - and the motor 'growls' - and
> the drivers get quite a bit warmer - due to the not-smooth pulse train. Now
> I do only have a pentium 100, and I had to set the 'PERIOD' variable in
> freqmot from 20 to 100 just to get the GUI working and that may be the
> problem but how much computer does it take to run a stepper motor?

If you want to run in a windows environment (X or Microsoft), and also
generate the step pulse train entirely in software, the answer is that it
takes quite a fast computer. Systems like Ahha, Flashcut, and the Bridgeport
BOSS use external pulse generator hardware which frees up a lot of CPU time.
Other systems like CNC Pro, Stepster, DanCAM, and DeskNC run under DOS where
they execute with 100% priority. Since DOS gives a user program complete
control over the computer, step pulse generation and user interface
interaction (limited) can be accomplished simultaneously, although they won't
be able to achieve the performance of a system that uses external pulse
generating hardware.

I've made a spreadsheet that shows the relationship between INPUT_SCALE,
PERIOD, and the output frequencies available. It's at:

http://users.erols.com/mshaver/stepfreq.xls

> I see there are instructions on linuxcnc.org for installing emc on a 486!
> How could that possibly work?

It won't work for steppers, it might work OK for a servo system.

> So you guys running emc and freqmot - what speed computers are you
> running it on? What value 'PERIOD' do you use? I'd like to know what it's
> going to take to make this thing work?

I retrofitted a Bridgeport BOSS machine and got 54ipm with an input scale of
4000 using a 350MHzP2 with 128MB of RAM. I think I had PERIOD set to 11 or
12.

E-mail me your phone # and I'll give you a call. I bought a board that has an
8254 on it with the idea of integrating it with the EMC software to solve the
problem you're having. I might not get around to this for some time and it
might be a good idea to send you the board to see if it helps you.

Matt