Re: Jake's 4x8 CNC Build
I'm not an engineer / machinist but my understanding is that at least the majority of movement will occur at the time of machining. I could be wrong. I spent quite a while trying to get a clear answer on whether a steel weldment will continue to move in weeks / months / years after machining but could not find a clear answer. It may also depend whether the piece is subject to certain conditions (mainly vibration) during it's use.
If you can machine both sides multiple times (side A then side B then side A then side B and so on) you may get to a stable flat piece. The movement should get less each cycle as there should be less residual stress. (This is largely based on first principles, so take it with a grain of salt).
When surface grinding it is common to take light passes then flip the part, and repeat the process a few times.
7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)