Which methodology for building complex models?

This is just a question that occurred to me this evening: when you are designing a complex model in OpenSCAD, do you start with a lump (like a cube) and use difference() to take chunks out of it, or do you use union() to combine components until you get the result you want? Up to now I've taken the first approach - using difference() - but I was wondering if I'd be better off combining parts using union().

Obviously both functions will get used in any complex design, but do you start by cutting bits out of a lump, or start with a base and stick bits on? Or doesn't it really matter in the long run?

I use a mixture of both. Typically I use difference to make some individual components and then union to glue them together. Sometimes with another difference at the top to make holes that go through multiple components.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

This query about design philosophy came about when I thought I'd completed my design, then realised that I needed to put 4 pillars into the left-hand chamber to support a circuit board!



I know how I'm going to do it, but it made me think that there must be a better way to start something like this. It's a bit like asking for directions in the countryside... "well, I wouldn't start from here".