Quick and Easy Project Case

This project shows how to build a simple project case out of hardware store materials in about an afternoon. It is particularly suitable for projects that need user controls or displays. For this example, I built a case for the amazing "Wacky sound generator" from www.musicfromouterspace.com.

By looking at the number and type of controls you have planned for the project, make a rough sketch. You can make it pretty rough- I have included mine as an example. Note that you want to design it "flattened out" and plan to leave space for bottom attachment of the circuit board as well as a place to attach the bottom plate. Take note of the "tabs" going down the sides of the main box- they are how the final metal portion of the case will attach to the wooden sides, and they must be far enough apart not to interfere with one another when the case is bent.

Once you are satisfied with the basic layout, create a measured version to use as a component and console layout. You can use the examples I provided as a template for your own designs. I used the open source program "Inkscape" to produce my template- it is a nicely featured peice of software, using SVG as its file format. (see http://www.inkscape.org/) Pretty much anything that has measuring tools can be used to create the layout, or you can use regular drafting tools on paper, although it is a lot easier if you can make copies as you go.

The point to to make an "open bottom" box, which is folded from sheet metal on all four sides, but that stiill has an opening on the bottom for acces to the PC board and components (including a battery, if desired) inside. The 4-sided box is then secured to the wooden sides with screws via a series of small tabs down the vertical sides.

A couple of useful tips- first, create the component layout in one layer, and place the console markings and layout in another layer. This makes it easier to make all the needed templates later in the process. The second tip is to use your component layout to make sure that the hidden portions of the console components do not interfere with one another. I measured the size of the petentiometers, for example, and then I made a measured circle to represent them in the layout, so that I knew how far they would extend and I could see how they were going to fit, and make and required changes.

Also, make sure that the drill holes are marked, and that they are the correct size. Clearly mark the centers of each, to simplify punching/drilling later. Also, another layer with text indicating the drill size to use is a nice feature- you can enable that layer when you print the component template.

Once you have made the template, print it or make a copy, and cut it out. By folding the paper into the rough shape you want, you can ensue that the layout is correct, and that the tabs do not interfere with one another when the box is assebled.

When you are satisfied with the template, you can use it to generate the measurement for a pair of wooden sides. Measure the meight from top to bottom of the case, leaving some clearance on the bottom of the case. I left about 5mm or so, but more is okay too. I left almost no clearance at the top, with the wooden sides ending at the peaked top of the case. With the measurements in hand, you can either create a template to cut the sides from, or you can directly cut the sides from whatever you are using for the sides. I used 3/4" plywood for my sides, simply because I had a lot of it around as scrap. It is overkill, and I would suggest 1/4" as a good size, and easier to work with, at least for small projects. Use your judgement.

From the template you create, or directly, cut out the wooden endpieces, verifying that they are a matched pair when you are done. I used a miter box to cut mine, but a table saw probably would have been better. A perfect fit is not required, but, of course, the final appearance depends on getting clean aand even cuts. I clamped my endpieces together and sanded the edges with a sandpaper block to make sure that everything came out evenly. The sides of mine were already painted white when I cut them, so I left it as is.

Once you have cut the endpeices, and you are satisfied with the template, you can prepare the template. You will need something to use as the body of the box. I use thin stainless steel from the "furnace duct" section of the hardware store. it is cheap and easy to work.

You need to glue the paper pattern to the sheet metal using a removable adhesive. I like 3M Post-it glue stick, which sticks pretty well and is easy to remove. Spread the adhesive all over the back of the template, and then press it glue side down on your sheet metal. You can use a roller or the palm of your hands to make sure that it is attached securely. If some comes up. just add a little more glue and push it back down again.

Once you have attached it firmly, you are ready to cut out the template. Note on my example, I did not put the tabs in explicitly, but rather left space along the edges to cut them out as needed. it is probably better to put them in by design, but I did not do it this time...

Now cut out the template according to the plan. I used standard straight aircraft shears to cut out the straight cuts, and I used a "nibbler" to cut out the tabs. In retrospect, I should have nibbled more off than I did, but the box still came out okay.

Once the basic form has been cut out, use a punch to mark the center of each circle to be drilled out. This is where marking the center of your drill spots with crosshairs really pays off. It makes it a lot easier to get the exact center of each hole. note that I have also punched some marks by eye on the tabs to make places for securing the edges of the case.

I drilled the holes with a little drill press (dremmel tool in their drill press stand) starting with a very small bit and working stepwise to larger bits. I should have used a "step bit" as the larger holes still came out ragged, and needed to be cleaned up later in the process. Since the holes are meant to be locations for potentiometers, there is no harm done, but for higher precision applications, more care and better tooling are necessary.

In order to make the bends in your box, start with the outermost bends, and align the bend line with the edge of your workbench. Clamp a straight-edged piece of wood over the top, again aligning to the bend line. Now use another straight peice of wood as a lever to make a neat sharp bend of the appropriate angle in the metal. For subsequent bends, repeat the same technique. As the box starts to close, or for harder to reach bends, you can substitute narrower peices of wood, angle iron, or even the narrow edge of a taller piece in order to get enough room to move.

At this point, you should also bend the tabs inward, perhaps with the help of a couple pair of pliers. Be careful here, as the edges are sharp and you can cut yourself.

This is another step where having the right tool (a sheet metal brake in this case) would be really helpful, but for something of this precicion, it is really not necessary.

Now is the time to check your design to ensure that the box is correctly and symetrically bent. If I was not so lazy, I could have made the endpices more attractive than mere squares, by cutting them off to more closely follow the contour of the metal box. Alas. I did not. Adjust the bends by hand on your box of neccesary.

Align the endpieces one at a time, and mark the screw-holes with a pen or pencil. I used a nailset to pinch at these marks, and then I drilled them a little way into the wood endpieces on my drill press. You can then attach the ends, working with a stuby screwdriver (or right hand driver, if you have one) through the hole in the box bottom to screw the metal to the wood with short self-taping woodscrews.

At this point, I also cleaned up the holes with a deburring tool. If I had used a step-dril or something similar, this step would have not been necesary, but it worked out just fine for this project.

Now, work with your console layout file to generate a matching console label. This is the place to put the indexing marks for the potentiometers, label the lights, and add all the cool decoration for your case. If you have a suitable printer, you can even doo neat designs in color. If your printer ink is not waterproof, though, be sure and coat it with the appropriate sealer. Krylon makes a nuber of good products- find one that works with your printer inks an use it.

I chose to use my laserprinter, and I printed onto Avery 8.5x11 labels, which worked out just fine. Once you are happy with the layout, print onto the label paper, and then cut the labels out.

Carefully align the label on your case, and seal the label down. I used light marks where the drilled centers were to go to help me align the label before I sealed it to the case.

Now is the time to insert the control components into their respective holes. Most potentiometers and switches are secured by a coaxial nut and washer that must be removed before the shaft is inserted into the corresponding hole on the board. I made my leads extra long to allow the board to be handled while the controls are inserted to ease servicing and adjustment. I does make it a little crowded in the box, though. Once each component is secured, tighten the nut and washer with a wrench of the appropriate size

I made standoffs out of nylon tubing and nuts/bols of the correct size. Make sure and give you board ample room above and below the components for clearance. I mounted my circuit board on the botom plate for the box, so that it can then be screwed into the bottom of the box once the board is secure. I had to be careful to make sure that there was enough room for the board to mate to the bottom of the case with enough clearance to allow the board to pass through the hole. I had to do a little adjusting after all, to make sure that it fit correctly.

Once the circuit board is attached to the bottom plate, and the connecting wires safely inside the box, attach the bottom plate onto the bottom of the case with self-taping sheet metal screws.

Attach the knobs and admire your creation!