What should I think about if I want to design something modular?
All printers are designed with an idea of WYSIWYG for sure. Depending on:


printer - type/quality/settings/configuration/assembly precission
filament - type/quality/shrinkage
user skills - manual/using app proficiency
model complexity
environment conditions and so on


you can get different results.

I venture to say users know their printers (after some time and by trials and errors) so they know how to manage dimensions to compensate all above so you will get this knowledge too.

Mathematical formula can describe shrinkage of the material, all other elements are very hard to describe (mathematically) in a general way.

Of course someone can simplify it and say: more money you spend better effects you'll get. It's sometimes true ;)

So all your modular things will be better and better if you will increase (what is to be increased) in above points especially "user skills".

Is engineering paramount? It depends of whay you gonna create. If your modular things have to lock itself, have to have threads, screws and such stuff then this is engineering. Is it the most important part of the design? Not necessarily.

I would say 3D printing moved engineering to next level. I'm talking about this or this. Is it still art or engineering? :)

This is my receipt:

think > imagine > design > rethink > redesign > give it a try > get back to thinking

good luck