3Dプリンタの資料。

http://reprap.org/wiki/G-code#M92:_Set_axis_steps_per_unit

http://3dp0.com/calibration-pyramid/

http://tsurezurelife.com/st/printrbot/entry8.html

http://nexus7fan.blogspot.jp/2013/01/printrbot-plus.html#more