Hi Tweakie,
Right, I ran a few tests and record a bit of position information first. I turn the machine on and zero'd the tool to each edge of the vice I had in, then ran a simple movement program with G00 and G01 commands. The machine lost position from the zero points by X: 3-4mm, Y: 3-4mm, and Z: 16mm.
I then changed the Velocity and Acceleration values as you said by 50%.
Original Values
X: Velocity=6000, Acceleration=300
Y: Velocity=6000, Acceleration=300
Z: Velocity=5100, Acceleration=300
New Values
X: Velocity=3000, Acceleration=150
Y: Velocity=3000, Acceleration=150
Z: Velocity=2550, Acceleration=150
I then ran the same simple program (after re-zeroing), and repeated the program a few times. It still lost position, but not as much this time. X: 0.5mm, Y: 0.5mm and Z: 2.4mm
Should I reduce by half again? or do we need to look at something else now?