Dual gcode stream with mesh-leveling. What's best to build?

[o_lampe]

Hi guys,
based on @dc42 's latest article (link) about implementing dual gcode streams, it is still unsolved how to use two tools concurently and have mesh levelling at the same time.
Nevertheless, I thought about the kinematic options we have to build a printer with inbuilt independent Z-axes. (no mini-Z axes like my hashPrinter would need)
A fixed bed would be the key, I think...

My first idea was to use two delta effectors on a square bed.
The delta kinematic also works with 90 degree tower angles.
So it would somehow be possible to build a rectangular frame that guides both delta effectors.

Another way to have independent Z-axes is two SCARA arms working on the same bed.
The SCARA builds I've seen are quite few and have their own difficulties and limitations. (eg. printable area)

Then there's a rotary bed printer, which could host two vertical towers. @CNCModeller could tell us more about feasibility, I hope?
I have no idea, how well it could print with two tools, given the dynamic rotation required to print at fixed speed?

Last not least, there's the good old bed slinger with two Z-axes.
Worth a try, since it isn't rocket science to build one.

I also tried to figure out a CoreXY printer with fixed bed (Voron-style). But it's quite difficult to build two independend CoreXY gantries both moving in Z direction without interfering. So I skipped that idea.

What I would like to discuss are the pros and cons of each candidate.
How to setup RRF3.5 (tool definitions, Z-probe(s), heightmap(s), etc) and slicers to make it work?
First goal would be printing two different objects simultaneously, both with mesh-leveling.
No collision detection so far.

Thanks for reading
Olaf

[o_lampe]

@o_lampe
I think the bed slinger is a pretty limitted option. We could only do copy prints or switch between tools as it's already possible with RRF3.4

[CNCModeller]

@o_lampe so a polar (rotary bed) machine is effectively a bed slinger, so independent towers would just allow ditto printing IMO. However you would need to be able to do mesh adjustment for each tower for it to work given each tower would be in a different sector of the bed.

All the best
Barry M