What are the tolerances and surface quality?  More importantly, what do they depend on?  <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10691293" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10691293</a> asked this already and you didn&#x27;t answer, but this is the #1 most important issue for whether this is a useful service for other than decorative purposes.