Geeetech

Hi there.
I'm trying to get to the next level of printing skills. At this point, my 20mm test cube looks like this.
The "z-banding" I think I can fix.
But the side wall isn't straight. It is concave by large amount.
How do I improve on this?

can you take some pictures to show me your configuration ?

In order to increase the rigidity of the whole printer, I build a plywood box around it. The top of the acrylic frame is now glued to the wooden structure. so are the bottom feet. The frame is much more rigid than it used to be. (Photo 1). The second photo shows the bed that I have. Instead of the original spring and screw, I have replaced it with rigid wood spacer against the acrylic base plate. I'm printing with both abs and pla, but the test cube shown in my original post is from PLA.
Thanks.
TB

Woo....it's a huge work I think But I think is not the rigidity ,on the contray, I think your threaded rod maybe a little warp , you can try rebuild the rod and tighten the coupling in the end of the rod, slide the hotend up and down for several times to make it smooth .