On 01/23/2020 11:07 PM, David Berndt wrote:
Hello All,
I'm having a bit of an issue with some geometry not coming
out as expected. I suspect it's related to backlash and
cutting forces moving the table a bit but I don't have
linear scales to monitor/correct for that sort of thing so
I'm left wondering a bit. I was hoping that being able to
see what backlash comp is doing on screen as my toolpaths
run might enlighten me some. Is there any pin or ?? that
can be monitored to give me more insight?
What motion control system are you using? Mesa, Pico,
software stepping?
In any case, there is some position output that can be fed
into Halscope to read
the real-time position and graph it.
The problem with backlash compensation is that you are
trying to cover up a defect (usually slack in the leadscrew)
with software that can't actually read the slack. So, any
force from the cutting tool can put the table on either side
of the slack, and the computer can't sense it. Also, when
changing directions, it requires the motor to instantaneously
jump from one side of the slack to the other. So, the best
fix is to remove the slack. Depending on the mechanism,
Acme nuts can often be sliced in half and compressed or
otherwise adjusted to reduce backlash. One problem with
Acme screws is that there can be more wear in the middle of
travel, making it hard to adjust out the slack throughout the
range of travel. Dual ballnuts can be set up with a preload.
Jon
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
