Edit: Added Diagrams. Added comment about advantage for lower corners
According to “About the No Judgement category”, it’s for ‘anonymous or “intimidated” users’. I’m definitely not one of those any more, but I decided to post this here because it’s one of those “way out there” ideas that probably doesn’t have much promise. I originally thought I would prototype this idea before reporting it to the group, but I’m not sure when/if I will get to it, so I really need to get it out of my head and onto the forums.
So the concept is to put a more rigid connection between the sprocket and the sled. The way I thought of doing this is to tension the chain using a beam, kind of like a bow. This pre-tensioning would reduce the catenary sag of the chain. In theory, it might improve the accuracy of the machine. Edit: Also, because you can push on a bow, it would eliminate the control issue in the lower corners.
One challenge for this concept is that a straight chain would have very little engagement with the sprocket and would likely slip. By making a serpentine path for the chain around an idler, then around the sprocket, then around another idler, the engagement can be increased.
The other challenge is that a rigid connector means that there will be a long piece sticking out when the sled is pulled near to one of the motors. It is certainly not a concept for a tight space!
So feel free to throw rocks, suggest improvements, prototype, whatever. This idea now belongs to the community.