[kragen]

Hysteresis is, in general, predictable, though sometimes compensating for it is impossible. Are you speaking from experience in measuring SG90 hysteresis and gear wear or are you theorizing?

(I'm theorizing, because I think theorizing is valuable, but I want to be careful to distinguish theoretical predictions from reports from experience.)

The broken 3-D printer idea is brilliant. Unfortunately, right now there's only one broken 3-D printer for sale near me on MercadoLibre, and it's an SLA printer, so it only has one degree of freedom of positioning. However, it won't be a thousand times more precise; typically RepRap FDM printers like the Prusa or Creality have positioning errors on the order of 0.1 mm, and a thousand times less precise than that would be an error of 100 mm. The BrachioGraph drawings seem to have an error of about 2 mm, only about 20 times worse than a bog-standard RepRap, and actually, 20 is less than 1000.