My wife decided to try and use Diatomaceous Earth to rid our house of some tiny silver fish. The powder is cheap enough on the big A, but the applicator was like $10 USD. Firing up FreeCAD 0.20 was able to design a two part applicator the bellows in FLEX and the base in PLA in a few hours using 40 cents of material yielding a $9.60 savings. Alas, my first attempt of attaching the bellows to the applicator with a set of tabs on the bellows resulted in more powder blown out the joint between the two parts then produced at the business end. I finally had to learn how to screw in FreeCAD. A sketched triangle, an additive helix, a subtractive helix and two incompatible mating parts later, here is working fine powder applicator.

Can be used as a camera lens duster too!