Top-down and Bottom-up 3D printers

[jeffmorris]

Most 3D printers that use filaments print from bottom to top and most 3D printers that use resin materials print from top to bottom. How do projects stay on the bottom of the printing platform on those printers that print from top to bottom?

[ServiceXp]

I think in the same way, bed adhesion.

[awerby]

Yes; basically the "raft" is the first thing to print, which clings onto the bed as it's gradually lifted out of the tank full of goo.

[Geoff]

Most 3D printers that use filaments print from bottom to top and most 3D printers that use resin materials print from top to bottom. How do projects stay on the bottom of the printing platform on those printers that print from top to bottom?

Same way your normal printer does, the base layer has to have a good adhesion to the bed, which is done in several ways, i.e a raft as werby said.

You can turn your 3D printer upsidown and it will still print pretty much exactly the same, in fact in some tests I've gained an advantage because parts that were lifting slightly are now not simply due to gravity.