How to Make a Glowing Metal Sign (For Pi Day!)




I wanted to make something special for my girlfriend's annual Pi Day party, so I decided to use some sheet metal I had on had to make a glowing π sign at TechShop. Here's how you can make something similar yourself!

Materials Needed: The sign in action:

Step 1: Design the Vector File

Using Illustrator to draw a shape you want to cut is simple enough. However, if you're interested in saving metal (as I was since I had a limited amount of stainless) it may be possible to nest two letters into one square of sheet metal. In order to do that with π in the font I chose, I realized I'd have to widen the gap between the legs.

To do that:
  • Draw the letter at a size that you think will fit onto your sheet.
  • Turn the text into an outline with Text > Create Outlines.
  • Draw a line across the corners of each let, then use Object > Path > Divide Objects Below.
  • Now, select the whole thing, and copy / paste to create the second copy, then rotate and move that selection into place.
  • Finally, nudge each leg to make more room, making sure to work on both copies simultaneously in order to ensure that the two copies stay exactly the same size. Keep toying around until you have an image that fits nicely.

Step 2: Cut the Shapes and Polish

Cutting with WaterJet is pretty straight forward - just follow the recommended procedure for your particular metal. However, with a complex shape like a letter (especially π) there is good chance that a leg could flap itself up during the cutting and hit the cutting nozzle (which is dangerous and expensive), so make sure to add solid tabs around all the thin pieces!

Once both sides of your sign are cut and dry (hah), take and angle grinder to them; I used an old 150 grit flap disc that was probably actually around 300 grit. Get all 4 sides nice and shiny!

Step 3: Cut Holes! Make Standoffs!

You've got two shiny pieces of metal that match up... time to attach them to each other!

Use a center punch and hole punch, make holes around the circumference of the back piece of your sign. Through these holes will go the standoffs (bolds) that will provide both structural integrity to the sign and a place to affix the light strip inside the sign.
The exact locations don't matter too much (since they're on the back of your sign), but make sure you provide standoffs around any sharp corners or curves the light strip will have to go around.

Next, in order to affix the nuts on the back (interior) side of the front piece to which the standoffs will attach, lay the back on top of the front piece and use a marker to mark each circle.

Now affix the 1/4" nuts to those spots. The best way to do this is probably brazing. I was in a little bit of a rush, however, and have never brazed stainless before, so I decided to take a shortcut by using Cold Weld (JB Weld is the standard in the metal-glue category; Cold Weld is what I got from my neighborhood hardware store). Note: Although the glus is strong enough in general a few of my glue joints failed under the torquing pressure of tightening the nuts. I re-glued them, but that's another reason to braze the nuts.

Finally, assemble the sign. Through the back of each hole, stick a 2" bolt. On the other (interior) side of the metal, loosely add a 1/4" nut. Once all the bolts are in place, lay the back piece on top of the front piece and screw in each bolt. Finally, tighten up each interior nut against the back of the sign.

In my case I used a threaded rod with an extra nut instead of the bolt, partly because I wasn't sure how "thick" I wanted the sign to be. However, I wouldn't recommend doing that for three reasons. First, cutting the rod is a pain (it moved around to much to cut effectively with all the power saws I tried, so I ended up cutting it with a hand saw. Second, it's harder to tighten up the sign when there isn't a standard distance to tighten each nut to. Third, the back of the sign just doesn't look as clean as it could. :)

Step 4: Light It Up

This is the easy part!

Wrap the LED strip around the standoff with the lights pointing out.

Use zip ties to keep it tight and affixed to the sign and itself. Position it towards the front of the sign so the strip itself is less visible and more light reflects off the inside-back of the sign.

Step 5: Celebrate Pi!

Turn it on and enjoy!



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