Y Axis Auto-parallel

Y axis auto parallel involves adding a half-carriage as an extra piece to the X Axis Universal Axis. This was done from v19.02 onwards to prevent the y axes from jamming if the 2 axes are not parallel. By adding an extra half-carriage at the end of the X axis, with rods of the X Axis inside this half carriage - we are allowing the X axis to slide in and out of the Y2 axis (Y1 axis attachment point is fixed). This constrains the X axis at the Y2 Axis in the Y direction, but does not constrain the X axis at the Y2 Axis in the X direction - thereby preventing any jamming due to the distance between the Y1 and Y2 axis not being the same.

When the Y1 and Y2 are not parallel, some non-parallel can be allowed as the Y axes flex. This increases motion resistance. Once the resistance is high enough - the stepper motors cannot overcome it and motion jams, resulting in layer shifts.