Over the course of the last few jobs I have run, I have noticed a big problem with part sizes off the machine. I am constantly off by .015-.030". Uniformly, all interior features are too small, and exterior features are too large. The amount of over or under-size condition is constant regardless of features size (for example, a 3.00" hole may measure 2.980, whole a .332 hole measures .312, both .020" small)
My machine is 2’x4’, but I am working in the corner. Ive confirmed all bolts and grub screws are tight. I checked a commanded move vs actual with a dial indicator and its perfect. I know the limitations of the design, and not to expect too much, but I have had much better results than this before. I have nailed 1" brass discs to well within .005". Something has changed, but I dont know what.
Is this amount of “slop” in the gantry normal? Try not to pay attention to the test indicator (which has a .008" travel and maxes out when I push the tool). It seems to me the entire gantry is moving. Is it pipe flex, belt stretch?
EDIT: Also, the code is good. I did the trig on the G3 moves in the code and its commanding the tool to the correct position.
EDIT 2: Also want to mention that the most recent jobs I have run in which I am seeing this issue were 1/4" birch ply with a 1/8" 2-flute mill. 40ipm rough, 20ipm finish. .063" DOC. .005" finish pass @ full DOC.