Multi SCARA printer

Hello, I search for methods to speed up 3D printing and had the following idea. Please tell me your thoughts about it.

Speeding up a 3D print could be done by multiple hotends working at the same time.

So why not build a 3D printer with the printbed in the middle and at each side one or two SCARA printers (so 4 or 8 in total), printing at the same time. The printbed is moved as Z axis.

Advantages:
- especially for big prints there should be much faster prints, because there are few collisions
- possible mix of material and nozzle diameters without filament change
- possible addition of abrasive methods like a minirouter
- SCARA because it has few conflicting belts, pulleys etc. The room is restricted to one area

Disadvantages:
- Software must coordinate the SCARA printers to create a single print and avoid collisions
- hotends must be designed small
- you need 3 motors for each SCARA, so 12 or 24 motors and drivers in total

What do you think?

Edited 2 time(s). Last edit at 06/05/2018 04:45PM by JoergS5.

First I thought about whether Harmonic Drive or cycloidal drive is exact enough for 3D printing.

The commercial harmonic drive solutions have a repeatable resolution of 1 arcmin (those drives are very expensive btw). If I calculated correctly:

harmonic drive radius 35 mm, perimeter 219 mm, precision 219/360/60 = 10 micrometer
For a SCARA arm of 300 mm this is about 0,1 mm precision. With two arms adding imprecision we have 0,2 mm maximum error.

This seems to be too low for 3D printing.

But I am not sure whether the precision is different for the different harmonic drive radiuses. There are drives from 35 to 107 mm radius.

An additional absolute positioning system could be necessary or a better solution.

The results of some research so far:

- parallel scara is more precise than serial scara and I expect it to be more stable also (serial scara in videos are often shaking). I will concentrate on parallel. Harmonic drive is too expensive for me, I will decide between planetary or cycloid drive, 3d printed if it's good enough.

- one problem is that firmware does not support parallel scara yet. I'll try to give input

- I underestimated the problems I didn't know they exist: variable acceleration and type2 singularity (maybe more to come...)