When you have your machine on casters, the inertia of the gantry moving around can shift the table on the casters, at least during rapid movements of a heavy gantry. This can also shift your workpiece.
Casters are not a bad thing, but make sure you can retract them or lift the table off the casters.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
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