Hi everyone,
I'm happy to report that I now have my fourth axis spinning. Not quite
as fast as I was hoping for, but it works. Now the issue is getting it
to move a specified number of degrees via gcode. Basically what I'm
getting is much smaller changes in the A value than the actual number of
degrees it spins.
It probably sounds like the INPUT_SCALE setting in the ini file is
incorrect (and it probably is) but I've tried lots of changes to it
without success so I think it's time for a couple of hints! Here's
what the mechanics of the rotary axis are:
200 step motor w/24 tooth sprocket --> 95 tooth. I make that out to
be a 3.9583:1 reduction.
Then, a 28 tooth sprocket on the same shaft as the 95 tooth drives a 145
toother on the actual rotary axis. Another 5.1785:1 reduction.
[Sounds like a nightmare when you write it out that way, but it's smooth
and stiff and mechanically it works well, so....!]
So the overall reduction is somewhere in the vicinity of 20.498:1, which
would translate into 11.387 motor steps per degree.
INPUT_SCALE is supposed to be the number of steps per UNIT (which is 1.0
on the ANGULAR axis), but setting it to 11.387 or 11.0 makes things go
really sloooooooow and I cannot for the life of me adjust the
MAX_VELOCITY to anything that moves it at a decent speed without
immediate following errors.
Note: with INPUT_SCALE set to 4100 (the approximate number of steps
needed for 360 degrees) I get a good spin speed but the A values are all
out of whack with respect to the rotary table. I have tried lots of
combinations of INPUT_SCALE, UNITS, [TRAJ}ANGULAR_UNITS and cannot seem
to get it right.
One other thing: when I try to get rid of the UNITS tag for the 3rd
axis and use [TRAJ]ANGULAR_UNITS (as it suggests in the manual) I get this:
Starting emc...
iocontrol: machine: 'TOWS CNC' version '1.4.2.4'
task: machine: 'TOWS CNC' version '1.4.2.4'
emc/ini/iniaxis.cc 192: can't find [AXIS_3] UNITS, using default
Traceback (most recent call last):
File "/usr/bin/axis", line 2299, in ?
unit = float(inifile.find(section, "UNITS")) * 25.4
TypeError: float() argument must be a string or a number
<sigh> sorry this is so long-winded...anybody have any suggestions?
Thanks a lot.
regards,
Pat
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