A cyclone dust separator extracts dust and debris using a vortex effect instead of a filter. The debris is collected in its own container (easy to discard in trash) and as a result it greatly reduces the clogging of the main shop vacuum bags or filters.

This device is particularly useful for CNC/Machining/Woodworking environments but the applications are more varied.

This design is in a very experimental state, no data on the efficiency at this time (standard cyclonic theory should apply), but some testing shows it does a good job with aluminum chips from my CNC.

Note: As my first attempt at cyclonic separation, this was designed independently / from scratch but in the meantime thing 119410 was uploaded here so I'll credit that (not just because the design is sufficiently similar and was uploaded earlier, but I'd also like to integrate some of its features in my design now).

How to get custom STLs

Printables does not support online customizable designs like thingiverse, so you have to generate the STL on your machine, it's actually simple (3 steps, 3 keys) 
1. Download OpenSCAD  (it's free, open source, available for Mac, Linux and Windows). Either official or nightly builds work.
2. Open the .scad file and change the parameters to match your needs
3. Press the following keys, in this order:
   - F5 (Menu -> Design -> Preview) 
   - F6 (Menu -> Design -> Render) 
  -  F7 (File -> Export -> Export as STL)

Print instructions

Just print out of your least favorite filament, preferably with a wall thickness of 2 or above to resist abuse in a shop environment (my first printed cyclone with 1mm wall thickness cracked at the first serious drop).

A Shopvac version of this (45mm input hose) might require a print volume of 8x8x8 inches or more.

The design seems very resilient to decompression: a powerful vacuums (eg "5HP") might implode typical PET bottle (like the one in the image) but the cyclone retains its shape.

I have not yet experimented with smoothing (of the interior cyclone) but in theory it should help increase efficiency because the decreased friction.