[dingo117]

Hi Dingo - I think you need to rethink the config. To move radially 0.25mm at 6m radius requires a move of 0.00119deg. If you used a std 200step stepper this would require a gearbox with a 1513:1 ratio to achieve that move. The calculations will have to consider the r value and adjust for this delta move at every radius difference. I think it's way too complex plus the structures will need to be enormous to be stiff enough. Keep it simple. Peter

i was thinking of using a ball screw like a piston to move the arm but i have already decided to not do a crane and started planing for a standard gantry style machine, just refining the dimensions a bit and what i actually want to do with it. i will be posting soon for some advice!