Shear Calibration

There is some z axis offset which isn't linear across the print bed, meaning it isn't a fault of the calibration process. When drawing a straight line on a single bed, the print tip will rise a fair bit off the bed and then come back down within the same line, same bed.

Calibration still needs to be done more accurately but currently the whole thing is too fragile to spend too much time on calibrating.

Potential causes:

• Print bed is not planar
• Forces on arm by the things like the wires to the extruder are not linear throughout space (unlikely, arm takes a lot of force to move)
• Calibration error
• Arm ik/fk does not match reality

Planned solution

1. Create a shear calibration process (grid of maybe 5x5 or higher storing z offset at each point) (estimate 4h)
2. During plan execution:
3. Do FK to find where the print tip want to be
4. Apply z offset for that x-y point
5. do IK and updated print tip point
6. save to JointTrajectory (this step would probably be done during Jtraj2ROS). (estimate 4h)