Hello!

Today I came back to client's site to finish the plasma table and now
I am desperate to understand, what is wrong with this machine.

I had control box and motors with me at home, where I had plugged
motors directly in control box and got everything working 1st or 2nd
of january. All the following days I turned the control box every day
to check, if motors behave properly. And they did - I could jog them,
they moved ok, when I told to home all joints (since there were no
homeswitches attached, I always interrupted that procedure with Esc
key). Everything seemed just fine.

Today as I arrived, I plugged all the cables in control box and
plugged motors to their cables, so now the difference is that motors
are not plugged directly in control box, but through their cables,
which are from 7 to 11 m long.
And now I see several things that I completely do not understand:
1) if I set bldc value positive, motor will turn sometimes positive,
sometimes negative direction. This is changing as I restart LinuxCNC
application. I _do not_ change any settings between these attempts to
run LinuxCNC, so I have no explanation for this;
2) when motion is enabled, mostly encoder 0, but very few times
encoder 1 will report a positive velocity, which corresponds to more
than 10 motor revolutions per second, but:
a) motor _is not_ moving;
b) it drops to 0 as soon as I set _any_ bldc value to a non-zero
number, for example, +0.01 or -0.01;
c) machine frame is grounded, control box case is grounded, signal
cable shields are gounded;
3) One motor does not turn as good as I would like, so I tried to
adjust lead-angle value. As I change it back and forth, trying one
value, then another and then returning to previous one, each time it
will behave differently with one and the same value - in one case it
can go up to 200 mm/sec with bldc.value = 0.7 and -80 mm/sec and
trigger overcurrent on 7i39 with bldc.value -0.70 and next time it can
do completely opposite. I am playing with values in range of 90 to 100
degrees and increment them by 2.

Does anyone have any idea, what is all this about?

-- 
Viesturs

If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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