Enclosures for the midnight engineer

[HLA-27b]

Casting is fun...

...if you don't mind molten metal on your feet 

Where I live, it's almost cheaper to to submit your model to the foundry and have it cast for you. What I learned from the foundry guys is that thin features are no good for casting in sand. They have some aspect ratios for surface area/volume but it isn't trivial arithmetic. So if you ever dream of cast enclosures think thick features, and I mean thick ass features. For example for a bearing cover the size of a CD they refused to make it thinner than 6mm and they will charge me for the failed parts too, unless I raise the thickness to 8mm. The failure rate was around 40% so next time around I raised the thickness to 8 and brought snacks and drinks too.

If you want more delicate parts there are two ways to go. Either lost wax casting or injection molding at high temp. Both are expensive. But there is slight possibility one can make lost wax casting at home.

[ivan747]

BRILLIANT! As much as Dave's uWatch and uCurrent designs.

[Conrad Hoffman]

Semantics has some very good points.

FWIW, every company I've worked for that paid the big $$ for a mold would have saved money if they had every injection molded plastic part CNC machined. The success of products isn't predictable, product life today is very short even if successful, and nobody ever paid off the molds and went on to make profits. Even with low volume aluminum tooling it's too expensive.

I've never vacuum formed, but believe it's a very good alternative.

CNC machines are super fast if the people know what they are doing. I'd always get a quote to have the whole thing machined from a block or maybe a cast part made of ABS or similar. Always talk to a good shop before making assumptions about cost.

I've cast very good gears and such using silicone molds. No doubt you could do a nice enclosure, but once you get beyond about 10 parts, it's way too tedious. The resins and colorants are also quite expensive.

The 3D printed parts I've seen over the years just aren't of sufficient quality or durability for anything other than prototypes.

Sand casting is great for heavy wall stuff that needs a lot of machining but lost wax is capable of much finer detail and smaller sections. There are people who do lost wax commercially and it's very very good, but could be too expensive.

I typically use PacTec enclosures if I want plastic and Lansing enclosures if I want metal. These are both good commercial quality, reasonably priced, decent looking and I wouldn't consider anything else until volumes hit several hundred.