20cm X axis, 30 cm Z axis, 100 cm Y axis. or switch the X and Y axis, it doesn't really matter. Need some visualization for that?
That's a Pompeii gladius, full scale, printed on this bot. Yes, it's big.
I've chosen to base this printer off the D-bot Core XY printer. As far as I can tell, it's the best design for printers with one very long axis; the only thing being thrown around the long axis is the print head carriage. This decreases the inertia and will produce better prints. Also, the torque from both the X and Y motors will be used at all times. This will work, and it might work well enough to get rid of the bowden cable.
There will be a few changes to the design. I'm getting rid of the cantilevered bed design and putting four steppers on the Z axis. I'll be using an aluminum (mic6) build plate. That's heavy, and I'll need the extra support and torque from the motors. The Z motors will not be independant. Instead, I'm using this shitty breakout I designed.
A Heated Bed
For large 3D printers, the heated bed is the largest problem. A 200mm x 200mm heated bed draws about 80 Watts, or about 5 W/cm^2. The same power density for this printer looks like this:
Yeah, 43 Amps of 230 mains to get the same power density as the standard RepRap heated bed. This is the problem with large 3D printers.
I can do a heated bed with ~1W/cm^2, which brings the power requirement down to something sensible. For now, though, I'll just print in PLA while making provisions to get a silicone heated bed and a 230V outlet installed.
I've begun printing the parts for the D-bot, and since enlarging it is basically only a matter of ordering more extrusion, there aren't many modifications necessary. Once the parts are printed, I'll spend the $150 on extrusion, $250 on hardware, and get assembling. The print bed is the biggest challenge, but the Hackaday design lab has a shopbot.