Drive Cage

Your drives will need to be securely mounted in your enclosure. Space-saving designs can use direct attachment of the drives; either to the case walls or to rails made of acrylic and cemented or screwed to the case walls. Think carefully about access to your hardware. It’s possible to paint yourself into a corner this way. Chances are you’ll want to remove your drives at some point, so give careful thought to how to provide access to both sides of the drive. Mounting drives with screws in one side only is risky.

For more flexibility, a removable drive cage is a desirable option, although it adds to the complexity of your design somewhat. You can choose to use a drive cage from a metal case, which has the advantage of having holes drilled in the standard locations for you. Or you can fabricate a drive cage from acrylic or other material. If you only want one or two drives, a drive cage may not appeal to you, but for larger case plans you may even want two cages to accommodate both standard drive widths.

If you want to stay with a single drive cage, using longer screws to mount the 3-1/2 inch drives is a viable option. Hole placement is different for the different drive sizes, though, so plan carefully in order to place the drives where you want them.

Power supply

Power and size are the two main tradeoffs for selecting a PSU, but cost gets into the game just to make it more interesting. ATX PSUs are widely available. A 250W ATX (or AT, if that’s what you need) PSU should be very inexpensive, and widely available. But the large size of these PSUs makes them less attractive to case builders going for the small size.

ATX, FlexATX, and mATX motherboards have a couple other options available. On the expensive end, server-grade PSUs (so called 1U PSUs) are available up to fairly high wattages, say 300W, but can cost over $100. If you have a power-hungry or overclocked rig, this may be your only option. For those with systems drawing less power, MicroATX (more properly called SFX, but more commonly called MicroATX) PSUs are fairly common and inexpensive. You’ll find that they are fairly uncommon above 150W (although you can try looking around, they may be more common as time goes on). 150W may be perfectly adequate for a moderate system, and using a bigger PSU would just generate more waste heat.

Removing the enclosure from the PSU can shave precious millimeters from the space it occupies, especially with MicroATX. It’s up to you whether it makes sense to use a ‘naked’ PSU in your design. In return for the slight extra space, you forfeit your warranty and expose yourself to hazardous voltages (as if you cared). Seriously, safety is an issue, and if you aren’t comfortable, the easy solution is to leave the PSU enclosure in place. You may need it for the mounting holes anyway.

After selecting your power supply, you’ll need to give some though to where and how it will be mounted to the case. It’s typical for PSUs to be screwed into metal cases, and the hole placement is standardized for the different form factors. You can work with the standard hole placement or ignore it entirely. Bear in mind that installing the PSU usually involves supporting it before the mounting screws are in place. Providing a shelf or rail for the PSU to sit on can simplify the installation and protect other components from being damaged by a dropped PSU.

Inside Access

Building an acrylic box is simple enough, but you’ll need access to the inside in order to install or change system components. Consider this when you place components and select mounting options. You may want to add RAM in the future, and removing every drive in the system may not be convenient.

At minimum, providing access involves having one removable access panel. And that panel has to be secured during normal operation, so mounting hardware is usually involved. Think about how you want to secure the access panel. Plastics shops sell hinges that are quite clear and match an acrylic case nicely. Ordinary cabinet hardware will serve the same function. You may want to use screws or thumbscrews and a handle or a cutout to allow gripping the access panel.

Beyond the access panel or panels, you need to provide adequate room in the enclosure to maneuver components into their final install positions. This can have an effect on your drive and PSU mounting strategies, so try to visualize how all the components will be installed before you commit to your design. It also doesn’t hurt to have alternatives or at least to stay flexible during construction. Test fitting pieces with masking tape and doing trial installs of key components can help you see a planning deficiency before you’ve committed it with adhesive.

If you plan to use expansion cards, you will need to provide card slots. Keep in mind that lots of peripherals are available in half height versions now. This may lessen the impact on your design of using expansion cards. A full-size system can borrow a back panel from a metal case, or leave the entire card area open and use a piece of aluminum L-channel secured to the case as support for the cards. (L-channel is a form of aluminum rod with a lengthwise bend at a right angle–it’s lightweight and rigid.) Cutting individual slots for cards is another option, especially if you just need one slot for a video card.

Port cutouts will be needed in any case. If you use an integration motherboard, these may be the only cutouts in your case other than the PSU access. Making individual port cutouts is labor intensive, so you may want to use a blanking plate with a single rectangular cutout for the entire port cluster.

Construction Technique

You really need to consider the purpose of your system. If it will be mobile (like a car system or a LAN rig) you should give some thought to ruggedizing the enclosure. If the case just sits atop your desk it can afford to be an aesthetic marvel at the expense of durability.

There are a few things you can do to make your case more rugged. Using the technique of screwing acrylic panels to an aluminum support framework gives rigidity and protection to the corners. Extra durability comes from using aluminum L-channel pieces on the outside of your corners. Using thicker acrylic panels will also add rigidity. Acrylic is quite rigid at .250-inch thickness. Thicker material is available but it gets expensive quickly, and heavy too.

A case made entirely of .250 inch panels glued solidly without reinforcing frame will still be quite rigid. The same case made of .125-inch panels will feel insubstantial, especially as any of the dimensions get longer than six inches or so. Internal reinforcing structures, metal or acrylic, can help add rigidity to a case with thinner walls.

One technique that merits special discussion is using screws rather than adhesive to join the case walls. Several people have successfully used this technique, but it can be difficult to get a hole drilled into the edge of the material and then tapped, and in perfect alignment with the corresponding hole in the piece to be joined. Add up all the drilling and tapping for two screws (minimum) per joint and it’s a difficult job. Using screws also requires use of thicker walls. I personally find gluing the edges much easier. Once you get a little practice, it goes quite quickly, and it produces a perfectly clear joint that’s quite strong, with no visible pin or screw to detract from your case’s appearance.

There are a few secrets to getting a perfectly glued corner, and we’ll discuss those in the next article. But one thing that is worth noting now is that getting a clean corner requires very flat edges. If you plan to cut your material into panels with a jigsaw, you’ll have substantial work to do cleaning and smoothing those edges to prep them for the adhesive. Edges cut with a table saw need to be sanded smooth, and router cuts may need minimal prep, just a deburring. If you get your panels cut professionally, ask for edge finish, they’ll be ready to glue when you get them from the shop.

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