This morning while the laser was still setup on the X axis I decided to run the machine in to warm up the ballscrews. I ran it at 150ipm for 1 hour x and y axis' using M11, M12 reciprocating axis motions (just back and forth infinite).
holy sh*t the screw expanded a lot. it is 0.007" / 40" under this condition. I noticed that the fadal factory SV tables usually biased the ballscrew about 0.005" / full travel (in this case its a 4020 so 40" x) towards the short side. I see why now.
I don't always operate in a condition where my screws experience 150 ipm all day long, and there may be plenty of downtime during the day - so I will probably just pick a number in the middle between 7thou and 0 (cold cal). and I will bias my SV table accordingly.
here's the data of Cold vs Hot screw. what a pain in the a$$.