Bertha Mark 4

I've been playing with a Delta-style 3d printer for some time now - Bertha.  Most of the development work has been posted up on private mailing lists or in Google+, but I'd like to make it more public here, where a new user can easily stumble upon it years from now and still follow from the beginning.

Bertha is derived from the Rostock and later Kossel printers, as well as borrowing ideas from every other printer I've seen.  It will be developed as close to the spirit of the Reprap project as I can manage.

So far, I have designed the alpha plastic parts (www.github.com/paenian/bertha), and am satisfied enough with them that I've just ordered the metal bits.  I'll try to document every part of the process here.

For Bertha Mark 4, I have decided to build another machine from scratch rather than try to add more bracing to Mark 3.  I'll post more on Mark 3 over the next few days, while waiting for mark 4 parts to arrive.

Paul