Originally shared by Andreas Hölldorfer
Started building a tool head for a “wool” printer like described by this paper http://www.disneyresearch.com/project/printed-teddy-bears/
this is my approach for needle moving. Still very work in progress:
http://www.youtube.com/watch?v=j8raLljA-Kw
Interesting concept. I’m asking myself why car pistons are not made with this approach .
@David_Malnar My experience with this is it works only this way,
if you move the rack it blocks sometimes, but never if you move the gear.
That is probably the right answer.Just a little out of tolerance would stop (break) your car 
There’s also a TON of reciprocating mass
Maybe it would be better to make a wool printer with pistons
@David_Malnar I thought about this but I think for the same stroke it would bigger and you need more parts what makes it difficult to print. And I think for the size you get more torque out of this one. (no prove just a feeling)