Which printer to build? Recommendations required

Hi,

I am into 3D printing (or plotting, in fact) for some time now, but only worked with karthesian types. Two friends asked me to help them building a delta type printer, and after reading a lot of stuff, pages, wikis, I still got no idea which printer would be a good go, or even where to start.
To make it even worse, we don't know exactly what we want...
One of the friends build a 120x80x30 cm^3 CNC milling machine, and he wanted to remove the motor and replace it with a Mendel90 extrusion head, but I fear the precision of the CNC mill is too low to produce good prints. Anyway this thing is much too slow to produce anything within a day. IIRC the max travel speed is 25mm/s, although it looked faster. And we didn't check any acceleration settings, but when feeding some dry run GCode, the whole thing was shaking and rattling. I think the Z mount with motor is about 2 or 3 kg.
I told them to build a karthesian printer, like the P3 with a steel frame, preferrably using the toolson edition, but they insist on a delta machine. We need a heated bed, and probably a chamber or housing, because we want to print ABS & PET. I assume it's the same for karthesian & delta printers. The bed should have at least 200mm, better would be 250 or 300. Same for heigth. Anyone got a good recommendation where to take a look?

TIA, Inhumierer

dc42 blog about his big delta is a good starting point. I'd look for Kossel XL all_metal parts and go for linear rails. The critical parts are the carbon rods. I've built a big one with standard 6mm rods and Traxxas rod ends and it turned out to be too fragile for a heavy 3-color Diamond hotend.

Thanks for the hint, this one looks very promising.