*Making Professional Quality Project Boxes*
Okay, you know how to build stuff, but does it look like it was built in your shop, or store bought? When I started working in my current job, almost 14 years ago, our lead engineer showed me some techniques I'll pass along to you. This isn't complicated, and can easily be done at home with tools you probably already have at home.
You will need some sort of CAD program for your computer. Lots of options here. You can even use Microsoft Word to make up a basic grid to drill holes. The key thing here is you must print at 1:1 scale. So when you specify 1" spacing between holes, that's what prints out on paper. Look for free versions of CAD software online too.
For under $20, you can get a decent digital caliper. Measure all the components that you plan on mounting on the front panel (LEDs, Switches, etc.), and you can accurately place them in the drawing program. Move them around until the spacing looks good, and avoids any clearance issues inside the box. The nice part is you can print out the layout, and set it on your box to get a feel for how it will end up, BEFORE you start drilling.
Those are the basics, let's get to specifics.
Got my project box ready to go. Printed out a layout drawing of where I want the holes to be. Note that I put crosshairs in each of the circles. This makes finding the center when drilling easy. The layout is printed on regular paper.
Cut the layout sheet to size. With a can of spray adhesive, spray the back of the layout sheet, then apply it to the panel of the project box. If you do this with the adhesive still wet, you can move it around some.
This adhesive goes everywhere. I use some butcher paper on the workbench, and give the sheet a spritz. Don't get too carried away, or it will saturate the paper, and be harder to remove later
Lift the layout sheet off the butcher paper, and apply it adhesive side down to the top side of your panel. Press firmly to get out any bubbles. Allow the adhesive to set for a few minutes.
Using an automatic center punch, I mark the centers of all the holes.
A Unibit drill bit mounted in a drill press does a nice job of drilling the holes squarely, and accurately. Tends to have all the common sizes, so one bit usually will take care of an entire project with multiple size holes.
The holes are all drilled in nice even rows.
On some softer aluminum, the metal can blow out a bit on the backside of the panel when drilled. A deburring tool can quickly clean off the flashing. Pomona brand project boxes have a harder grade of aluminum, and this step isn't required.
An optional step for a finished project.
Once the holes are all drilled and cleaned up, peel off your layout sheet. Use isopropyl alcohol to remove any residue. Print out a second layout sheet. Get a piece of adhesive backed repro film (translucent), and put this into the sheet feed of a copier. Put your layout sheet into the copier, and press the button. The idea here is to copy your layout sheet onto the top side of the repro film.
Cut the layout that was printed onto the repro film. Peel the backing, and carefully apply to the panel. This sheet must be put on straight as there's no moving it around once applied. When you're satisfied with the placement, take a sharp X-Acto knife, trim the edges, and remove the material from the holes.
I use Krylon #1311 Matte Finish spray to seal the printing on the film. Several very light coats will do. If you put it on heavy, it can dissolve the print from the photocopier. Allow this to fully dry (hour or two).
Now you can apply all the components to your panel. Switches typically have a nut on the face side, and backside of the panel. The one on the top is to set the depth, the one on the back is used to tighten it in place. If you tighten the one on the face side of the panel, you'll tear the film, and scratch the aluminum.
Wire it up, you're done.
Some simple examples of my other projects.
An aircraft helmet tester...
A breakout box for an aircraft helmet...
And an ECG interface box. This was done a little differently. Rather than use the Repro Film, I replaced the front panel with a piece of thin plastic used for making laminate signs. The outer skin is black on both sides, white plastic inside. An engraver mills away the top layer, exposing the white material inside. I have a 4x8 sheet of this in my shop, so decided to use a piece of it as a panel. Rather than getting fancy, I simply cut it to size, drilled holes, then used a label maker for the labels. A very quick way to make a project.
My latest project, a multiple zone emergency light controller. Power goes off, a relay drops out, and all the zones illuminate if armed. Simple project, but ends up looking nice with the simple technique shown here.
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