Forcing objects to touch the build plate makes it needlessly difficult to print vertically stacked part.
It would be great if Bambu Studio had some tools to automatically stack prints vertically with a single interface layer between them. But until then, allowing objects to float atleast makes it possible for designers to stack parts by modelling the interface layer. Right now it’s only possible to vertically stack prints with hacky workarounds.
Not a lot of hoops to jump through, but easy enough to do if you combine the objects into an assembly. Once in an assembly, you can move each object to where ever you need them while in the objects view.
Unfortunately this is not a good solution for stacking prints with an easy-to-remove interface material because parts of the same object (assembly) that touch get merged together by the slicer so they won’t have any walls separating them. If you make a stack this way and model the interface layer as it’s own part you will just end up with one tall object with slices of interface material at regular intervals. When you separate your print along the interface boundaries you will find exposed infill at these layers instead of a solid top and bottom surface.
If you are making your own interface layer as its own part, yeah I can see why this wouldn’t work out for you.
Another alternative if you are needing to have a different interface material is to add supports to the underside of the top object. The bottom side of the upper object is considered a bridge, which we can leverage. In my pictured example, I have a 1mm gap between the two flat squares and painted on support on the bottom side of the top object. From here I can change the material of the support and make other tweaks to improve the bottom print quality. I could then stack up and up and repeat the same procedure.
Unfortunately generated supports don’t work for more complex shapes with curves and concavities. I’ve tried every support setting and it’s not currently possible to strictly limit support to a single Z height on models of moderate complexity. Because of the interface material change requiring purging, having bits of support all over the model instead of only at a few layer heights makes a huge increase in print time.
I am sure I read here in the forum that the latest beta of Bambu Studio has a new toolbar item that will provide a solution for this.
I can’t remember which post it was on as it was an update to an older post if memory serves.
If I am remembering correctly, you can choose the items you wish to align/stack and choose how that should be and it does it for you.
Here is what my part looks like with the manual generated support:
Those little blobs of green in the concavity almost double the print time.
Mind linking the model? Would be easier to see what’s going on from my own computer.
You can grab it from Coat Hanger by Murata - MakerWorld
If you look at the profile called 4-pack you can see the hack I’ve used to make the stacked print work. But this would all be much much easier with floating objects.
First of all, these hangers are pretty cool. I’m going to have to print a few to see how well they hold up. Very neat design!
I ran into your exact same issue when I stacked them and tried to paint on the supports. For some reason it tries to build the support scaffolding inside those joint areas. For those complex joint areas, this method will not work. But for many more simple models it should work just fine.
I decided to take a bit of a different approach. I made 2 copies of the base model, flattened one along the z axis as far as it would go and then merged all 3 objects into once assembly. I then stacked them on top of each other, with the flattened piece in the middle. I changed the material of the middle object, essentially creating an interface layer.
This looks like it will work. Though I’d probably still classify this as a hacky work around 
