Virtually every electronics project will end up in an enclosure. The project box is an essential, unsung hero of the electronics world, and how you design yours can be the difference between your installation coming off without a hitch or disappearing in a cloud of blue smoke.
LAYOUT & PREP
To get a sense of how big your enclosure needs to be, where your components will fit best, and what’s going to work for your external connectors, start by laying out all of your parts in real space. If you don’t have all of your components on hand, draw or print out their footprints from datasheets scaled to the appropriate size.
Printouts can also be helpful in laying out holes — you can mark the centers of the component holes in your printout and tape them to your enclosure temporarily. Mark the centers with a punch and a light tap with a hammer to create a divot in the enclosure’s surface to help when drilling.
ENCLOSURE TYPES
Enclosures can take a lot of forms, from off-the-shelf boxes for quick, simple projects, to custom 3D printed cases with clever snap fasteners built in. What format you choose should be guided by what kind of environment the enclosure will experience.
A sandwich enclosure is a good compromise between speed and security. A sandwich enclosure is simply two boards separated by standoffs with your components between them.
One popular method is to laser cut the base on which the components will be laid out, and 3D print a lid to secure to the base using snaps or screws.
Creating your own custom enclosure from scratch offers opportunities for clever design elements, convenient fasteners, and secure connections, but it can require substantial investment of time and effort.
Experiment with different arrangements for your components and different configurations for your enclosure. It’s easy to create a puzzle box that’s irritating to put together, take apart, and service.
Drilling Holes IN Plastic
Chances are your next project box is going to be made of plastic. Plastic is easy to find, light, strong, and cheap. However, it can be a little frustrating to drill.
You can find specialty drills made just for plastic. They’re pretty cheap and their biggest appeal is that they keep the plastic from climbing the drill flutes as it approaches the end of the hole.
You can get a high-quality hole using just about any drill bit as long as you use a drill press and clamp your piece down before drilling.
To get accurate holes, make sure to scribe the hole’s location beforehand and mark it with a center punch. The divot a center punch leaves in durable plastics like nylon and Delrin is an ideal starting point for small drills.
Quick Tip
For hard plastics that might shatter from the force of a center punch, you can twist a starting divot into its surface with a ⅛” twist drill. Just give the drill a few turns until some chips form.
FABRICATION & ASSEMBLY
There are many fasteners and connectors that make it easier to put your custom case together.
HEAT-SET THREADED INSERTS
Useful for attaching strong threaded holes to FDM printed enclosures. These can be melted into a hole in your print using a soldering iron.
CAPTIVE NUT
You can quickly get a fastener inserted into your print by creating a cavity the same profile as a hex nut, just a quarter of a millimeter wider. A screw coming in from a through hole opposite the cavity will get caught by the hex nut.
HELICOILS
A method for adding metal threads to any hole. Run the proper size tap into your hole and then follow it up with the helicoil insert. These are a convenient feature for plastic parts that will see a lot of service and their screws installed and uninstalled dozens of times. You can replace helicoils if they ever wear out without having to re-drill the hole.
TOOLS
Here are some helpful tools to make your next project box the best you’ve ever built.
HEAT GUN
It’s simple enough to shrink heat tubing with a lighter, but when you can get a heat gun for less than ten bucks and find yourself making strain relief wraps for a hundred bundles of wires, you’ll be glad you’ve got one on hand.
WASHERS
Washers are one of the dirty little secrets of fabrication. Did you accidentally buy screws that are a few mm too long? Did you accidentally drill a hole that’s a touch too large for your fastener’s head? Washers to the rescue.
STANDOFFS
Having standoffs on hand saves a lot of headaches when it comes to connecting circuit boards to just about everything. Buy a cheap set that includes a few different lengths of male/male, male/female, and female/female standoffs.
HAND COUNTERSINK
For cleaning up small holes, nothing beats a hand countersink. You can even find ones with deburring tools built in for cleaning up the edges of freshly cut pieces of metal or plastic.
MINI FILES
Sometimes you have to take a nibble out of a case to get a wire fitting through correctly. You can get sets of small files with different profiles that are great for this kind of mod. They usually come in cheap plastic bags, but they store really well in a pencil case.
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