another EMC Glitch?

Speaking of glitches.....

I think the G92 offset thing is still with us. I have a modified version
of BDI 2.14 (I think) that Paul installed so mine is pretty new.

I had to do a dive for the e-stop yesterday.

I haven't figured out exactly what's going on but M30 program stop
removes an offset from the GUI- but it seems to be still there in
the controller at least sometimes.

I set G92 Z0 after jogging the tool to the work surface usually.
My Z0 is normally at the center of travel. If I do the next plank
and reset Z offset I am apt to have about double the amount I want
with no indication in the display.

With 2500 lb force capability in my machine I could some real damage.

If anyone knows where this offset stuff is in the source code I could have a
look.
This is a bad thing. Must be a canonical function or something.

On a similar note I have the spindle force detector about ready to
breadboard.
I am just doing it analog for now. It's pretty simple- acceleration force
and
spindle force are separated by analyzing servo current and tach signals in
real time. Just doing some summing, multiplying, differentiation,and square
roots
with op amps to see if it works. The only rub is that transmission friction
forces
have to be considered as well, and they are not constant. But with a simple
linear
approximation for friction , but I think I can have estop go off with about
a
200 lb spindle force, while maintaining the 2500 lb force capability for
rapidly accelerating the gantry. That would help a bit with things like
this G92 weirdness or an operator error.

If it works this could be performed with no accelerometers or force sensors
on the spindle (at least with servos).

Kind of an electronic shear pin...



Les

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.alltel.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.alltel.net/~leswatts/shop.html