I have been working on a circuit board design for a RepRap heated bed. Far tidier than mk1.
The maths really did my head in I tell you !
I have made circuits in the past with Toner transferr, but only small ones.
Trying to do 200 x 200 mm just don't happen.
The Thermal expansion pulls the tracks off the paper :(
This is the best image I managed after 4 attempts.