Re: Runaway z axis with steppers

["Tim Goldstein" <timg-at-ktmarketing.com>]

Don't remember all the details, but this is a problem that has crept up from
time to time. I have had it happen on various of the old RH 5.2 builds.

Tim
[Denver, CO]

----- Original Message -----
>
>
> Hi Don.
>
> Thanks for that confirmation.  I was beginning to think that it was me!
> What input_scale value are you using on Y?
>
> Ray
>
>
>
> On Saturday 07 September 2002 01:32 pm, you wrote:
> >   Hi Ray,
> >
> >         Yes, I have this problem too on a BDI/TNG implementation. But
> > it is on my Y axis. Setting the P to 1500 minimized (eliminated?) it
> > for MDI and AUTO commands. But it still happens after the first or
> > second manual command to the Y axis.
> >
> >       73, Don...
> >
> >
> > -----Original Message-----
> > From: Ray Henry [SMTP:rehenry-at-up.net]
> > Sent: Saturday, September 07, 2002 11:26 AM
> > To: Multiple recipients of list
> > Subject: Runaway z axis with steppers
> >
> >
> > EMC List
> >
> > I posted this a while back to the developers list at sourceforge but I
> > don't think that that list is working so I'll post it here.
> >
> > Attached is an ini from Tim <tim.smith-at-electrolux.com.au> that does
> > some goofy stuff here.  I'm not exactly going to call it a bug, rather
> > the odd behavior is the product of certain combinations of values in
> > the ini file when used with freqmod.o.  The same behaviors are not
> > obvious with steppermod.
> >
> > I'm started testing this with TNG with no machine attached to the
> > parport. I think I'd be afraid to start much of a machine with this
> > setup because it trips up the stepper math and creates an oscillator
> > that tends to push an axis slowly in a single direction -- even when no
> > motion is commanded.  With the attached ini file, I see this behavior
> > after a couple of quick jogs of the Z axis.
> >
> > I've also tested this behavior with BDI-2.16 and my Grizzly minimill
> > and it seems to behave the same as the TNG.
> >
> > Here is what I did to exhibit the problem.
> >
> > Startup using timsfreq.ini.  (attached)
> > Start the machine and home out.
> > Start scripts->IO_Exercise to view parport 0x378. (default)
> > Issue a couple of quick jogs in Z
> >
> > Once the problem shows up with the IO_Exercise display and I press
> > estop, the step pin seems to latch but the displayed position runs
> > wild.
> >
> > The problem seems to go away if scale is set about 20 with a proper
> > deadband.  It also goes away or changes the way it works with larger
> > gains and different combinations of velocities and accelerations.
> >
> > With some small adjustments, the problems seems to change into a simple
> > dither between adjacent steps but as it is, all of the steps are in the
> > same direction.
> >
> > I need someone to see if they can reproduce this problem and work with
> > me to clearly define the nature of it.
> >
> > Ray
> >
> >
> >
> >  << File: timsfreq.ini >>
>
>