On 12/22/24 07:02, Nicklas SB Karlsson wrote:
lör 2024-12-21 klockan 19:47 +0000 skrev andy pugh:
On Sat, 21 Dec 2024 at 18:24, gene heskett <ghesk...@shentel.net> wrote:
That leaves the backlash in the gearshift, which are nylon gears in a
go704.
That shouldn't matter if the encoder is on the spindle.
It detects the encoder reversing to know when to reverse the Z direction.
If it cuts on both directions, then perhaps there is a lag introduced
by something in your HAL. Or maybe there is slack in the Z drive.
If encoder position is measured to drive z direcion there will be some lag. Though
"prediction" may cancel out lag
except then speed is changed for example the then direction is changed.
Nicklas Karlsson
Of coarse the direction changes, its rigid tapping. Explain how this
effects vertical position of tool please.
turn off motor power while the rigid tap is being performed, then
grabbing the spindle and turning it by hand, the tracking in both
directtions is followed by Z quite accurately. The encoder is on the
motor with a 14/1 nominal gear ratio in low gear. 7/1 in high gear. It
turns out the gear backlash is maybe 2 degrees, but this doesn't fix the
index timing when the direction changes, possibly as much as 15 degrees
when working with an ats-667 as an index pulse generator. Depending on
how sensitive the individual ats-667 is. But I am getting sloppy
threads, like its cutting on the backout stroke. So something is putzing
with the z timing vs direction.
I have motors and controllers on hand to put closed loop stepper/servo's
on all 3 main axises. at which point I'll hack my hal to invert the
signal edge detected for index, steering it with the encoder direction
wiping out that potential 30 degres of electronic lash. There's two sigs
from an ats-667, first is the reset as the screw approaches, second,
opposite polarity is the accurate one, switching exactly as the screw
crosses the center of the ats-667, a state it maintains until the screw
approaches from the other side of the ats-667 again as it comes around
on the next turn. BTDT.
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
