I built a 3D printer back in 2011 when 3D printing at home was just beginning.
I started with a rough kit shipped from an other maker that I improved in many ways. I added linear roller bearing for the rails, a chain to maintain cables, a holder for the plastic, a case with a fan for the electronics , and other parts to hold things in place. See photos and videos below.
This printer printed the first part of the Poppy project back in early 2012.