Creating a jig

Probably the most important tool when constructing the cube is the jig. It hold the wires and LEDs in place when you solder them, making life a whole lot easier. This jig is used to create a pillar of LEDs; 8 LEDs stacked on top of each other with all their cathodes connected.

I've bought a piece of wood, about 44 mm wide and 20 mm thick, and cut it into pieces. I've cut off eight pieces of 20 mm to hold the LEDs, and two pieces of 80mm to go on each end. The bottom part is about 250 mm. In the 8 "columns" I've drilled 5mm holes, 1 cm from the top. The distance between the hole and the edges of the columns determines the distance of the wires to the LED.
I've drilled three 3 mm holes on both ends to hold the wires. The position of these holes should match the top and sides of the columns, so the wires will touch the columns.

This was just a prototype I made to figure out the what works and what doesn't. I recommend taking your time for designing and constructing the jig, as it will eventually determine the quality of your cube.

Plan your cube; think about how large you want it to be. I'm going for a 1 inch spacing between all LEDs. This means that the front of a jig column should be one inch away from the front of the next and previous  jig column. The width of the columns shouldn't exceed 20mm, this leaves just 5 mm of space between the pillars of LEDs. As you can see, the design of the jig determines the dimensions of the cube. And make SURE you keep plenty of room between the bottom LED and the end of the jig, you'll need this extra wire to install the pillar.

Things that went wrong:

• I'm not that great with wood, I used a hand saw and a portable electric drill. The result is far from perfect. Next time I'll use an electric jig saw for cutting and my Dremel workstation to drill straight holes.
• Use glue. The columns rotate a bit, so next time I'll glue them first, then drill holes from the bottom before screwing them in place. This should keep them perfectly in place.
• Make the columns thinner. The space between the columns is a bit too small to comfortably put the LEDs in and out; they tend to get stuck.
• Make the columns narrower. Right now I'm creating pillars that are 20 mm wide, I think I'm going with 12 or 15 mm instead, so I'll have more space between the pillars.

 Here's the result of my first test with the jig:

 Not too shabby. I had to put quite a bit of force on it to get it out of the jig so it's a bit bent. A few more lessons learned:

• Make sure you have plenty of clearance between the columns, one of the LEDs got stuck.
• Make sure you bend the legs of all LEDs equally, or they might push the wire away making it difficult to solder other LEDs. I'm probably going to create a jig for bending the legs as well.
• Place the LEDs before you place the wires, it's much easier that way.
• When done, cut the wires at the top of the pillar first, then pull the pillar back so the LEDs are freed, then cut the wires at the bottom of the pillar on the outside of the jig, this gives you another extra cm of wire.
• Straightening the wire is done by inserting them into the jig, tie their ends together and rotate the bunch. This will put tension on the wires and that will make them nice and straight. Don't put too much tension on them or they will break!

And a few things to keep in mind:

• Test your LEDs before you put them in the jig, make sure they work and that the brightness is the same as the others; you really don't want to replace a LED when your cube is already constructed.
• You can use a wire stripper to strip the wire, but I like to use a snap off knife. Just place the wire on a surface, place the knife on the wire and hold it almost parallel to the wire, then gently pull the wire along the knife and half of the insulation will be stripped away in one go. You can peel the other half off easily.
• The wire I got is pre-tinned, and it looks great! Much better than bare copper in my opinion.
• You can straighten the wires a bit before inserting them in the jig. Use two pliers to grab both ends of the wire, then tug on them gently a couple of times. Don't do this too hard or too often because the ends will suffer from metal fatigue and break.
• WASH YOUR HANDS! You're not going to get lead poisoning from breathing fumes, only lung cancer. But the lead does get on your hands, so make sure you wash your hands thoroughly before you eat, drink, rub your eyes, scratch your <insert bodypart>, etc. Also clean your working surface and don't put food on it.
• Don't breath the fumes, it's not exactly healthy. Using a small 12V computer fan is enough to blow most of the fumes away from you. Keep your mancave/shed/living room well ventilated.

That's it for now, once I'll have my final jig done I'll add another post on this subject.