This is a derivative work from MBI's open source parts files - http://www.thingiverse.com/thing:4973.
This is a first attempt to print a replacement for one of the plywood struts which commonly get broken on the ABP during assembly.
I broke mine by fat fingering it while assembling my Thing-O-Matic in Mar. '11. I'd been trying to get this into CAD and learn how to use some idle CNC machines at a local college. But, the MBI files were hard to use several months ago. Rev. F is cleaner. If you work with their files it will help if you delete the hidden block libraries. They are useful for MBI's design efforts but, they will get in your way for use to manufacture the parts. No big deal. Just a hidden caveat.
05/05/11 - I printed the ABP strut replacement. This is the strut with bushing holes. I'd broken a small tang during our original assembly and had just epoxied it together but, my sons did not like that kluge of a fix. I told them that it was acceptable for this low stress member but, they wanted to print a new one. So, after reading in Thingiverse about Webca and others having printed their entire bots [http://www.thingiverse.com/thing:3285] we decided to plunge in with the challenge of printing one replacement part.
In my pictures - if the part looks warped it is the black paper that the part is sitting on. The part is very flat.
2/2012 - Part will and does print accurately. The file is good. My mistake as a noob. See new picture in red.