Multiple plates per panel

[birdyguy]

Hello everyone,

Silly question here, but why are there two to three plates for each panel. I'm building my own panels for overhead and I've noticed some panels are sold with three plates of plexi and not sure why this is. For the lighting area of the overhead for instance..there is the main colored plate, then a clear plate of the same size and then a white plate of the same size.

I'm thinking that the clear plates are most likely used for mounting standoff switches. The third white plate not really sure what it's purpose is. Would appreciate if someone could shed some more light on this for me.

[tiburon]

I think it might be because the real thing is about 6mm thick without the mounting plate. So there's a aluminium plate (the clear plate I'd say) for mounting all the hardware and a lightplate (white) to diffuse the backlighting. So you just have to paint the sides of the plates to get a reasonable thickness.
Does that make sense ?

[birdyguy]

Hi tburon,

Yes , that makes sense. Thanks.

[Westozy]

How I build my backlight panels! The top "lightplate" panels are made from 3mm white acrylic, this gets painted in the appropriate RAL colour then the panels are engraved through the paint. The light from white LEDs penetrates the 3mm white acrylic for a good result. The second layer panel is cut from 3mm clear acrylic and this is used to mount the switch hardware and these plates have their edges painted. If the panels were machined from a single piece of 6mm acrylic the backlighting is dull and not to good at all. This is how most vendors are doing it these days if the panels aren't IBL.

8643
Cheers Gwyn

[birdyguy]

Thanks Gwyn. Very informative. I don't have access to an to an engraver so what I'm doing is printing out the overhead bitmaps that you sent me long ago (thanks much again) , then peel off the backs of the printouts and stick them to the acrylic . I then spray them half dozen times with clear coat. Seems to work quite nicely for now.

So my understanding from reading the above comments, two plates should be plenty.

[tiburon]

What's IBL ?

[jonesthesoftware]

I'd just like to add that you need to select white acrylic NOT Opal as Opal gives grey characters when not backlit. 3mm White acrylic comes in 2 grades of light transmission, approx 4% and approx 16-20%. Make sure you tell your supplier you want the 16% variety. IBL is internally back light.
regard
geoff

[fordgt40]

Another way with better results, albeit more "tricky", is to use clear acrylic which you then spray white after it has been cut to shape. Then subsequent top coats can be applied. The tricky bit is setting the laser to cut through the top coats but not the white base coat
The benefit of this approach is more even lighting as the white initial coat traps the light inside and gives a better spread, also, the white engraved letters stand out better. I have not tried this method, but it was outlined to me by one of the "best" private panel makers

[RadarBob]

The way fordgt40 has described is pretty much how the original light plates are done.

I rubbed back some of the paint layers on a broken original to find out.

On the one I looked at, there was a large depth of matt white, followed by a matt black blocker layer and then the top colour.

I tried making my own copy using 6mm clear acrylic, machining out the back to
accept very small white leds (instead of the filament lamps) mounted on a pcb.

The back of the acrylic is also painted (white) and the technique relies on introducing the light in the centre of the acrylic between the layers and creating a spread.

I was quite pleased with the results, but I found:

There is a lot of careful machining involved with drilling blind holes in the acrylic
-The large recesses around switches and knobs are particularly tricky.
- I used all sorts: End Mills, Forstner bits, Mad bits etc to do it - One slip and you've had it!

It's very slow going - Lots of paint coats and waiting.

If you use rattle cans, it cost a fortune.

The paint needs to be well cured before you try to engrave it otherwise it tends to tear and look a bit ragged - Don't know what paint they use but it is very hard anyway.

You need a good sharp engraving tool

Some white paints look a bit yellow even with a white led.

If you use leds mounted horizontally you need to work out their positions carefully and angle them towards the area in which you want the light to spread - You also need to keep the distance from the text to the leds fairly consistent or the lighting is overly uneven.

Was an interesting experiment, but I decided that it wasn't practical.

Best Regards,

Rob

[fordgt40]

Rob

Very informative, thanks. Perhaps this method has too much grief and risk attached :sad:

David

[RadarBob]

That was my conclusion David.

I think it could be done, but it would take forever - And on balance, given the many other things to be done in a build, not worth the effort imo.

Pity, because the results were quite authentic.

Glad my findings were of interest though.

The blind holes for the leds weren't too much of a problem as there was enough depth in the material to use a standard drill bit - It was the ones around the switches/knobs that were most problematical due to the diameter.

A lot of the drill bits/cutters suitable for the material have spurs to keep the cut centered - But you don't want them to break through - So I tried starting the hole off that way then switching to a milling cutter to get the flat bottom.
-But I found it tended to snatch and chatter - Bit scary to be honest!

I don't know how they do it on the real thing - But I suspect they use a stepped cutter.

I tried a small test panel to evaluate the light effect- And then went on to try one in anger - But to be fair, I picked a fwd overhead engine start panel - Which is probably not the best to start on.

-At least it wasn't a multi-colour!

I think the technique might have a place for small one-offs if you have a machine shop with a vertical milling machine - But not for the amateur with a pillar drill.

I guess an alternative approach might be to use two pieces sandwiched with different sized holes - But I'm not sure what would happen to the light at the interface in the centre.



Rob

[jonesthesoftware]

A simpler method is to use 3mm white acrylic front plate sprayed and engraved or stuck on letters, masked and sprayed. Only needs through holes for switches/buttons. Then use 6mm clear lightplate with through holes. PCB on back. Much easier to drill and file. Glue plates together with super glue or chloroform(trichloroethane). Superglue safest as chloroform dangerous and dissolves paint/plastic.
Use MATT acrylic household paint. Cheap water based no solvents. Fianlly coat with MATT clear varnish which unfortunately is solvent based and stinks so do it outside not in the kitchen
geoff

[jnr641802]

I Have made my 747-400 based o/head (inputs only)using the very simple way of white acrylic/drilled /mini sticky letters/blank sheet,no's,circles ,lines etc/2x undercoat/3x top coat/peel off letters/one long strip led lights left to right etc behind installed panels.The effect is pretty reasonable in my opinion especially the backlighting which is evenly spread.The cost per panel is very low,and the 15 or so panels took about 4-5 hours each to make .

regards Jim