[simpits-tech] backlit panels 101

[Marv De Beque]

The back plate is aluminum.  The switches mount to the back plate.  Back
plates are made from 0.070" thick aluminum painted black.

The light plates are about 0.250" thick.  They are cast acrylic.  Lamps are
embedded into the cast and the wiring embedded into the cast, too.  There is
a small circular connector embedded into the casting that is 0.250" round.
It is a coaxial style that looks a little like the old RCA Phono plugs on
stereos, but smaller.  The press into the receptor that is mounted on the
back plate.

Lamps are spaced about 1.250" to 1.500" apart.  You can't see them from the
front or back, but the real panels have a silk screen of their positions.

The light plate is mounted to the back plate with two or more 6-32 by 1/2"
black oxide Phillips pan head screws.  There are aluminum inserts cast into
the light plate that have an integral washer on the top side.

The light plates are first painted white, then a coat of black is added to
all sides.  I do not know the exact technique to make the letters, but they
are probably engraved using a laser or something.

Holes are tricky for plastic.  To drill plastic, use a low speed drill
press.  Add water as a coolant using a squirt bottle.  Heat is the enemy  Do
not force the tool through the work, let it cut through.

You can dress the drill's end in a grinder.  Flatten out the cutting edge of
the drill so the edge isn't so steep as to grab the work, but plow through
it.  There are drills made just for plexiglass that you can buy.

The back side holes are counter bored.  You need a milling machine to do
this.  This is done to allow the retaining nuts for the switches and
controls to clear the light plate.  The counter bored holes are not painted
and allow light to leak out around the switch.

Cutting acrylic is tricky.  Blade speeds should be low.  Water as a coolant
helps reduce melting.  A low speed band saw will work, but most tools do not
like fluids added as a coolant.  I cut mine dry with a medium blade
(something like a wood cutting band saw blade).

Edges are finished with a belt sander allowing the work to cool so melting
does not occur.  A wet belt sander is best and gives a very nice polished
surface.

The light plate is clear acrylic.  The edges have a very slight rounded
corner to them.

Paint like something to grab onto.  You can very lightly scuff the surface
with a fine sand paper (400 grit).  Clean with alcohol and dry with a lint
free cloth.  Spray paint white.

Text does have slightly rounded ends, but not fully rounded.  Chardater
height is about 0.140" high.  An example of text width is the word MASTER.
It is about 0.430" wide.  It is a proportional font.  That is, two letter M
with the letter I between then (example MIM) are closer to each other than
the letter M between them (example MMM).




-- 


> From: "Ido Dekkers" <idekkers@clicksoftware.com>
> Reply-To: simpits-tech@simpits.org
> Date: Wed, 19 Jun 2002 13:36:19 +0300
> To: simpits-tech@simpits.org
> Subject: [simpits-tech] backlit panels
> 
> 
> Can someone explain exactly how a panel is built :
> 
> 1. the backplate - aluminum ? black painted ? holes just for the switch or
> also for the lights? how thick ?
> 2. the faceplate - plexy/acrylic ? engraved on the front/back ? the black
> color on the front/back/both?
> 3. the lighting -  little bulbs in the faceplate ? how do they sit -
> glue/connector ? how many ? what spacing ?
> 4. the switches - on backplate / faceplate ? how are they connected ?
> 
> for making the faceplates :
> 
> 1. cutting the material : fret/jig/other ? how to smooth the edges ?
> 2. making holes so it wont brake ?
> 3. painting - preparing the surface, what kind of color ?
> 4. engraving - how ? how deep ? and for the never ending dispute - do the
> fonts have strait or curved edges ?(f16 panels)
> 5. is the original material clear / milky
> 
> 
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> Thanks!