Re: deepgroove Z-axis

Well it seemed to have "sort of" loosened up initially, and I ran some
experimental projects with the Z set slow. The problem seems to still
be here though. The binding on the lowest end of the axis is limiting
the Z-rate, and somewhat unpredictably as well.

Looking at it, with the deepgroove2 controller and the 280oz steppers
and mach3, the z-axis is limited to 20in/min on the lowest part of the
screw but sometimes even that jams. And that's with the acceleration
set at 5 or 0.5, doesn't matter. Higher up on the axis, 30in/min is fine.

It's not the drive channel. Switching the motor to the X or Y output
gives the same problem at the same speeds. Tried to clean it and give
the slide and screw more oil too. And again this is a
right-out-of-the-box problem.

I did try removing the motor and unbolting the bearing block/motor
mount so I could just lift the axis up and down by hand, and tried it
again with the motor attached. Yeah, I think there's more friction
down low and it really shows up with the motor attached. Not a
specific binding point felt but yeah noticeably more friction at the
bottom.

So, it's a slide problem. Not a leadscrew, because I was sliding that
assembly up and down without turning the screw. Nor is it a problem
with the head's guides mating to the slide too tightly either because
it's only present at the bottom of the slide. So I'm concluding the
slide's dimensions are just slightly "off" at the bottom somehow.

Would a break-in help? I could just set it slow and make some G-code
to run up and down over this area for a few thousand cycles. Or is
this serious?

Danny

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@...> wrote:
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Danny Miller <dannym@> wrote:
> >
> > I'm setting up a deepgroove CNC kit with the 280oz steppers, the
> > deepgroove controller, and Mach3.
> >
> > I am having some trouble with the Z-axis.
> >
> > I've got the parallel port pins set up ok. The directions go the
way I
> > expect.
> > I configured it at 32000 step/in and the travel seems to agree
with the
> > Mach3 location measurements.
> > X and Y axis did fine at say 30in/min acceleration 4.
> >
> > Z, not so much. I was running 5 in/min acceleration 0.5 and it's
still
> > kinda dicey near the bottom of the travel. It's difficult to get
it to
> > go up without skipping when it's near the bottom of the travel. Also
> > even mid-screw going up you lay a finger on it firmly and you can
stall
> > it, not sure if that's "reliable". And 5in/sec is REALLY slow,
but 10
> > is less reliable. At first I wanted to attribute that to the obvious
> > weight of the spindle head and motor since it seemed to be a going-up
> > problem, but in fact it won't go all the way down without getting
stuck
> > either. About 3/4" from the table, going down, and it stalls out.
> With
> > the controlled off, I can tell it's harder to turn the knob in the up
> > direction than down as expected, but I don't feel a specific
> > obstruction or odd-feeling resistance. Couldn't really compare the
> feel
> > when it's at the "bottom" vs higher side-by-side because there's so
> many
> > turns between them.
> >
> > I played with the freq, no real change.
> >
> > Next I pulled the motor. It does go up and down freely now. The nut
> > can kiss the table. The head can go up and down at 30 in/min.
> >
> > Is this a normal problem for the z-axis? What can I do about it? Is
> > there a break-in procedure I didn't find?
> >
> > Danny
> >
> Move the Z motor over to the X or Y axis and jog using that axis and
> see if it does the same thing. If so it's probably mechanical in
> nature. If not you may have a bad drive or the current limit is set
> wrong on Z.
>