On 5/14/24 14:34, Eric Keller wrote:
Do something cheap because I'm not convinced it's the beam. I've done
troubleshooting on things like this, and sometimes it's stiffness and
sometimes it's not stiffness. But it really doesn't make sense that it
would sit there and ring after a move, so you also may have some
tuning to do. Possibly a notch filter?
Eric Keller
Boalsburg, Pennsylvania
On Mon, May 13, 2024 at 4:50 PM Todd Zuercher via Emc-users
<emc-users@lists.sourceforge.net> wrote:
Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on a gantry router
without adding too much mass? What is there now is a 4" x 8" rectangular 3/8"
walled extrusion that is 145" long.
Under normal jogging commands the two servos control the ends of this gantry
reasonably well, but while the axis is homing the thing shakes and wobbles
terribly bad.
This, on 3rd or 4th read, sounds as if the two servo's are not in tune
with each other. Tuning servo's is not my strong suit, (and the only
servo I had was destroyed by the new autotune pid in linuxcnc, it
found settings that mde it ocillate and fried a $125 motor in around a
minute. But this would be a lot easier to synchronize if stepper/servo's
were used. Rigged with a home switch, maybe a prox switch since its non
contact, with logic rigged so they can back away from home and move in
sync the rest of the day, getting sync is running toward home until the
switch trips on that end of the beam, run toward home until both ends
have tripped, call that home. From then until powerdown, both motors
getting the same step/dir signals will be in sync till the powerdown. No
fighting because the two servo's are not in an identical state of tune.
Hanpose has nema 34 and 42 motors of 12 NM, probably with more torque
and speeds than your servo's. The best description is that they just
work. And they use much less power than regular steppers to get the job
done. A diff you can see in the power bill if replacing burn your hand
regular steppers.
How fast and how strong are the servo's you are using now? Gear ratio's too.
Also If I put a dial indicator in the center of the bridge and hit
the bridge forward or backward it will flex and wobble enough to
displace the dial indicator +/-0.03 and it takes nearly a dozen wobbles
to dampen it. But on the ends the servo's only have a few thousandths
of give.
I'm less concerned about the actual stiffness and more worried about dampening
the wobble.
Todd Zuercher
P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php>
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
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Cheers, Gene Heskett, CET.
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