Are there bottlenecks? What’s left to do?
Sure! At the moment this would be the low stiffness of 20x20 extrusions and MGN12 rails. However, since I want to keep the MGN12 for the moment, there is no alternative to 20x20 extrusions either. When the next lock down comes and I am bored, I will upgrade to 40x40 extrusions and HGR20 rails (and SFU2005, and.. , and..).
With the current design using nut holders from China the ball screw axes are overdetermined. I am planning to design a nut holder with slack to “free” it. Coming soon..
The frame is supposed to be screwed onto a heavy and plane plate (e.g. 20 mm sealed plywood in my case). An important part of the stiffness of the frame comes from that connection. If you want/need a highly mobile machine maybe this one is not yours.