Re: Runaway z axis with steppers

[Ray Henry <rehenry-at-up.net>]

Don

That is interesting because I've never seen it happen with large numbers 
in the input scale.  Does the 1 mm pitch mean that you are using a 1 in 
the units variable?  Perhaps you could send copies of your [TRAJ] and the 
offending axis ini stuff.

Ray


On Saturday 07 September 2002 03:21 pm, you wrote:
>   Hi Ray,
>
>        The input scales on all three axis is the same on my machine. It
> is a 1 mm pitch machine, with 10X microstepping steppers. All three
> axis have input_scale and output_scale set to 2000.  0.   .
>
>        If I remember correctly, the problem would happen on the MDI
> commands too, until I set the I and D to 0, as well as the the P to
> 1500.
>
>       73, Don...
>
>
> -----Original Message-----
> From:	Ray Henry [SMTP:rehenry-at-up.net]
> Sent:	Saturday, September 07, 2002 2:08 PM
> To:	Multiple recipients of list
> Subject:	Re: Runaway z axis with steppers
>
>
>
> 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 >>