Makelab Charleston has started a Morgan derivative
To address the sagging when the extruder is at full extension, you could extend the central rod upwards and then support the first joint in the extruder arm at the bolt, as the triangle formed by the z-axis extension, the extruder assembly’s parallelogram arm (between the first bolted joint and the axis) and the suspension hypotenuse will not change as you rotate the tubes to get your extruder’s delta from the origin.
I thought about this before I attempted the firmware correction, and after some experiments I found that most of the sagging can be contributed to the following:
1. The treaded rod onto which the Psi arm connects flex right at the point where it exits the pipe shaft. The only way around this is to redesign the arms so that the Psi arm mounts to the Copper pipe in stead of the rod. This would make the toolhead mounting a bit more tricky since the bearing will have to run at the bottom of the toolhead. Not impossible though.
2. The rest is made up from the arms leaning into the bearings. The 608 bearings have play, but at least it is predictable, allowing us to fix it in the firmware. Compensating in the hardware would not be possible, because the arm turns.
The PLA arms hardly flex at all, not noticeable anyway.
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