Chassis Builder's HOW-TO
Start: Buy the Box
Get an enclosure that will afford ample volume for the electronics inside,
and ample area for knobs, lights, buttons, etc. on the outside.
You will also have to decide between plastic or metal. Metal is always better;
it is sturdier, and provides a convenient ground. (Make sure anything you
are mounting in a grounded chassis contacts it only when you want the component
to be grounded!)
For modular systems, a rack mounting system may be convenient. There are
standard parts available to build a rack-mount chassis.
If you can have separate front and rear panels from the rest of the chassis
body, this is a plus. It allows you to only machine those parts without the
rest of the body getting in the way.
Map Out Placement of Chassis-Mounted Stuff
Figure out where all of the knobs, lights, etc will go and how much area they
will take up. Sometimes it's easiest to make paper cutouts the size of the
components, and arrange them on the chassis to decide on placement. Make sure
that the knobs themselves have enough clearance from each other, and
allow suitable room for you to place whatever markings or labels you need to.
Machine the Chassis
Drill the holes and generally cut and mutilate your box until it looks the way
you want it to. If you have access to a milling machine, USE IT. Things such
as large square holes and slots are much much easier to complete with one.
Otherwise, it's up to you, and a drill, and some creativity to figure out
how to do such things. One useful tool is called a ``nibbler'' tool, and
is a godsend for cutting square holes in metal.
Put all the components in their newly-machined spots, making sure that they
fit, and that all screw holes are properly aligned. If everything works out,
then file and sand the front so that it's relatively smooth. About 300 grit
sand paper works well. It won't look nice at this point, but that's ok,
because now you will...
Paint the Base Coat on the Chassis
I recommend some good spray enamel or epoxy paint. If you want to put primer
on first, then more power to you. Get a nice even finish, which may (probably
will) require multiple coats. Multiple light coats look better than one heavy
coat. To prevent the paint from pooling and drying weirdly, make all of the
surfaces to be painted vertical or at least not horizontal. Note: you will
now have to worry about dripping, but at least the coat will be smooth.
Paint can dry with a texture if it is allowed to pool on a horizontal surface.
This doesn't look nice.
Labeling the Chassis
Now you'll want to put all of the labeling on that will be needed for your
switches, indicators, and knobs. You can paint some of this with masking
tape and hobby enamel paint, but this is usually very difficult to do well
for very small things. Dry-transfer lettering and other marks are an
excellent way to mark your box after a little practice with them. Be careful
of dry-transfer marks, though, as they are prone to scratching or rubbing off.
This will be remedied in the next stage.
If you are really intent on producing a quality-marked chassis, and/or will
be printing on many identical chassis, silk-screening your labels might be
an idea. If you have access to silk-screening facilities, a laser printer
printout is all you need to make the screen. After that, alignment will be
the trickiest part. After everything is set up, however, you should be
able to do many boxes pretty quickly and accurately. I haven't actually
tried this myself, but I think it should work.
The Finishing Touch: A Clear Coat
This is especially important if you have any dry-transfer labels! They
will eventually rub off otherwise. Get some nice, clear spray paint. Acrylic
paint is nice. Spray the entire outside of the box. This is mostly to protect
all of your labels, the most vulnerable and important part of your chassis.
Once you have done this, your chassis should be ready to go.