Quote
Solidus Labs
The play in the z axis on the print head is caused by the rotation on the shoulder pivots. The play is very bad around the edges of the print bed where the arm angle is small and the horizontal pivots are close together. I added a spring to mitigate this but I think it is making movements nonlinear.
I'm unsure of your use of the word “play”, I tend to think of it as the fit up between two parts being loose.
21. Are the arms consistently rising or falling at the extremes of the print envelope?
If there is change of altitude in the Z axis at the outer perimeter of the print envelope it can be accounted for,
maybe not perfectly but to a degree that it's inconsequential to our needs.
Empirical test:
Mount a dial indicator onto the end effector.
Measure the Z axis change from the center to the outside edge of the print envelope, centered between two arms, and near the pivot.
If there is an elevation change in the Z axis it can then be accounted for with either math or by adding a cam to the pivot, i.e tilting the axis of the shoulder pivot.
Shoulder pivot cam:
By angling forward or backwards the shoulder arm pivot a cam profile is created.
Ex. if you angle the shoulder pivot towards the center of the print envelope the end effector will rise as it moves to the outer perimeter of the print envelope.
If this is a solution, you can print a bracket with the required angle.
Bed leveling sounds like a cleaver way to solve this problem.