Weird Center Height Calibration

[Chaoite]

Hey! So I was calibrating my printer with a dial, and I've noticed something odd. Using the towerCal script found in the Rostock max V2 user manual, there is a difference in height between when the machine initially lowers to the center with a height of .2mm and when the script is complete and the dial returns to the center. The difference is about 0.004". The odd thing is that this is repeatable, and the dial will go to the exact same place every time, keeping the .004" difference. Anyone else notice this or what it is?

[Xenocrates]

Does doing this repeatedly increase your slop? It may well be that especially if you don't lift between points, that the indicator is engaging differently from being moved along the surface rather than straight down, or it might be that there is some backlash/slop/lash in the mechanisms, and that it become evident in the case of the three towers moving independently rather than in sync (Obviously they all move at once, but different speeds, directions and distances)

[Chaoite]

Im not farmilar with slop, and the dial changes between runs, but only by less than 0.0005'. However you could be right about the backlash, how would I check for this?

[Xenocrates]

easiest would be to push the effector plate around a bit with the motors engaged. If it moves somewhat, and you note this on the dial, then you have at least some backlash/slop. Then the question becomes how to go about eliminating it. If you have the old generation all metal U-joints, then consider replacing them, as there are major improvements available. For the newer injection molded U-joints, a few rubber bands or such around each arm pair can help. If they're the tricklaser arms, either replace the Traxxas joints as they've grown worn (Unexpected, as you seem to be relatively new to the forums, and most people seeing that sort of issue have multiple hundreds of hours of print time, and had marginal joints to start with), or tighten/shorten the zero-lash straps. For the new SeemeCNC ball-cup arms, you may be seeing relaxation in the molded sprint (An unprecedented issue, but it could potentially happen), or some other mechanical issue (Belts, pulleys, ETC).