I have a JGRO style machine, that I am in the process of taking out the slack, and modifying the structure to remove some of the play & flexure. There are a lot of posts that show mods to do this, but I would appreciate it if someone could post some accuracy figures and if modifications were made, which mods gave the most improvement.
Here's where I stand:
When I cut 2" squares, they are undersize or oversize about .030" to .040" depending on which direction I cut. Right now, I still have the basic JGRO structure, and ther only thing I have done is to re-set all of the bearings to remove the play.
I tooks some static measurements with a dial indicator: I have a .035" flex at the router bit when I apply a 10 pound side load on the bit (pulling toward the 1" pipe that runs parallel to the base). The flex at the gantry wall is about .012". I put some clamps on the pipes to eliminate any looseness that would be hard to eyeball, but there was not any improvement.