Hi friends!, I´m a blender 3d hard surface modeler, and I want to buy a resin 3d printer in the near future , I want some advice to prepare my meshes for 3d printing be it on blender or using or learning another 3d software, Usually I use subdiv and quads on all my meshes but I read somewhere that that is not the case in meshes used for printing and that they gotta be airtight. Please give Me some advice
Hello!
One of the countless tasks we made for clients was 3D printing.
We always used https://www.shapeways.com to print the models… but I now noticed they filed banckrupcy 
… they were the best around. Each material had the technical specifications including the minimum and maximum size, size of details, etc.
They also had a tool that highlighted the problematic areas. You would load your model to them and if it turned out all green is because it’s good to go.
They apparently are now a completely new company.
Anyway, yes, the model has to be 100% watertight, can have only one material with one texture (the color) that needs to use UVmaps as coordinates.
Apart from that the important is respect the supported dimensions of each material.
All we did was for clients, except Layla from Clash On Little Pond that we printed in Playmobil size. It was the only model we ever made that came with some flaws (walls too thin made some parts vanish), but Shapeways full refunded it. A refund I did not requested, I did mentioned that the model had some issues, but was to alert them, so that this wouldn’t happen on future models.
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But we 3D printed with them dozens of tools, silver earrings and necklaces, company logos, etc… actually clients did, but with our models 
Generally, yes, meshes should be airtight. Topology does matter if you want clean models/prints, and its probably best to keep modelling the way you always do, as it’ll be converted to tries when you export as an STL anyway.
The biggest thing to consider, for printing in general, but particularly with resin, is resolution.
When modelling for 3D print, you should always model with flat shading enabled. That way you’re seeing a more exact representation of your model. If you can see all of the individual faces, then that’s what will print. Subsurf is great, but you’ll need to make sure that ‘Apply Modifiers’ is checked when you export, otherwise you’ll end up with a low poly mesh that will print with all of those faces visible.
Some slicers have anti aliasing, but there’s only so much it can do.
Resin models also need to be hollowed out, with the addition of drainage holes and supports. This can be done before hand, but most slicers will be able to handle that for you, so you don’t really have to worry about it in the modelling/prep stages.
Thank You very much Rogper, very useful information.
Thank You friend , I did not know about flat shading, I will investigate about all that drainage thing, complete newbie here, Thank You.