Machining time is expensive, so at some point it makes a lot more sense to just pay for the tool that will produce the exact part you want for a fraction of the price. For low volume stuff Hammond Manufacturing makes a variety of plastic and aluminum boxes for electronics projects.

No to mention, if you want a unique industrial design for your product to stand out then you are going to need custom tooling.

Another approach, for low volume and if the target user can do a little assembly, is to make something out of laser cut plaques of plywood or plexi. It's simple to make and easier to ship (because it's flat until it's assembled). The Ikea way, if you will.

I do this for my personal projects (volume < 5) and the results are nice and functional. You can also cut holes for buttons and whatnot and you get something well tailored for your needs.

If it can be 3D printed, is (commercial?) 3D printing more affordable/efficient for such low volumes ?

In my experience it mostly depends on the size of the piece. Commercial 3D printing can produce beautiful and strong objects, but they are size limited and the price goes up fast with the size.

Laser cutting can be quite big and make a large volume box, if that's what you need. And transparent plexi is nice (if it fits your needs).

> Out of curiosity, wouldn't it be easier/cheaper/faster to use some existing off-the-shelf design and drill/machine some holes if you need it slightly modified?

For small production runs, definitely. There are standard aluminum extrusions for boxes with PC boards. You slide the PC board in, and provide custom flat end plates with holes for connectors and controls. Here's one of mine.[1] The end plates were cut on a laser cutter. Here's a supplier in China.[2] For small boxes, the aluminum extrusion alone should cost a few dollars.

Somewhere above a few thousand, custom injection molding becomes cheaper. Amusingly, these are better boxes than plastic injection molding, but don't look like consumer products.

[1] https://github.com/John-Nagle/ttyloopdriver/raw/master/board...

[2] https://www.alibaba.com/product-detail/CHANGHE-electronics-a...

You are right, it is faster,cheaper and absolutely possible to take the existing enclosure and modify it. OEM enclosure suppliers will gladly add or remove a few openings on their design for a few thousand. They will modify or build a new mould just for your new product, and it works just fine as long as PCB can be designed around their enclosure.

I posted somewhere else on this thread, but if you're planning on getting your products certified, using an off the shelf enclosure can be troublesome if the manufacturer can't/won't provide test samples. We wound up using an enclosure from Bopla which we got certified.

Yes. Or use a vertically-integrated service like Polycase that will do that for you. But you lose the customization of a fully custom enclosure, so it's a tradeoff. And if you're doing high volume, it's more expensive. Upfront costs are only a few $100 for ABS; more for aluminum, or if you want full-color printing.