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5 axis rotaional backlash in Postbuilder

I'd like to add a small rotational move to our A axis for every A (positioning) move to remove some of the machine backlash.  What would work for me is to simply move the A axis additional 5 degress and then move it back to the target position.

 

This would be done in the Postbuilder on one of my posts only.  I do not really worry about not seeing this move in my verification, etc.

 

What would be the best solution to do this?  Should I simply catch the A value when it changes, add 5 degrees to it and then output another A move after that with the A -5 degrees?

It's kind of quick and dirty but I think it would work?

Or is there a better way of doing it?

 

Thanks for suggestions,

Jerry M.

NX8.5.2

 

3 REPLIES

Re: 5 axis rotaional backlash in Postbuilder

That would work, probably how I would do it.  There no G code for uni-positioning (or it doesn't do the A axis)?

I'm assuming A changes only on rapid moves (not while cutting)?  (i.e. do you ever do 4 axis contouring?)   So you need to check only rapid moves & drill cycles (not linear moves).

 

Make sure for drill cycles you check both cases (with and without "Avoid" motion between the holes) - without avoid you might have to do a G80/A(too far)/A(correct)/G8x cycle

 

Ken

Ken Akerboom Sr CAx Systems Engr, Moog, Inc.
Production: NX10.0.3.5 MP5 + patch/TC11.2
I'd rather be e-steemed than e-diseaseled


Re: 5 axis rotaional backlash in Postbuilder

I would create a block for A axis monitoring - maybe

 

get_A_axis

 

then issue a do template to see if A changes:

 

set tmpflg [MOM_do_template get_A_axis CREATE]

 

Then if info exists and not "" - A needs to change. Then return 1 in conditional code for a couple following blocks and if you have say [expr $mom_out_angle_pos(1)-1] (will change modal A word - so will be output) and $mom_out_angle_pos(1) (will change modal A word so put out.)

NX10.03
Windows 7 Pro

Re: 5 axis rotaional backlash in Postbuilder

Just thought of another case you might want to check...

 

After tool change, do you force the A out?

Do you want to be able to restart the program "safely" at any tool change (or other places)?

Then even if A doesn't change, you'll have to set a flag to re-do the A uni-position output.

 

i.e.

(end of previous operation)
G0 A30
N10 (OPERATION 2)
T2 M6
T3
G54
(you would want a "G0 A25" or "G0 A35" here)
G0 X1.23 Y2.34 A30 B40
G43 Z3.45 H2

 

Ken Akerboom Sr CAx Systems Engr, Moog, Inc.
Production: NX10.0.3.5 MP5 + patch/TC11.2
I'd rather be e-steemed than e-diseaseled


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