how do I paint panels?

[Muts]

Hi All,

I'm at the very beginning of my Home Cockpit. I finished my DIY CNC for cut and engraving panels. I didn't found information about the painting of the Panels. How do you do that and what is your experience? What translucence of the top plate do you use. I try at the moment Acrylic with 68%.

 

Thx for help

Edited February 16, 2021 by Muts

[agrasyuk]

tried several processes through the years and narrowed it down to the below. I use laser , you will need to do your adjustments.

painting with rattle-can spray paint.

 

For the face plate I use engraving material called lasermax. it's a white polystyrene sheet  1/16" thick (that's about ~ 1.6mm) painted black at the factory. Light plate (mid layer) is a 1/4" (~5.2mm) transparent acrylic. this thick layer provides rigidity and ability to tap thread into it if you need it. prior to cutting the lightplate it gets a coat of white spraypaint to help reflect the light. cutting the lightplate happens upside-down so the LED locations are marked for "drilling". "drilling" I touch with a larger drill bit into the lightplate creating a conical depression to let the light in and help it spread. 

Faceplate and lightplate are carefully aligned under clamps and cemented with solvent based acrylic adhesive.  Notice at this point the protective film is still on the faceplate. I mask the underside as well and spray several layers on the sides (and sides of switch holes) to block the light. make sure sufficient drying time between layers is observed, attempting to repaint  in under 48 hours resulted in several ruined panels (had to strip paaint and start over). Remove protective film from the front, sand the edges with 600-1000 grit wet paper  from the paint buildup and paint one final time , blending the edges. this way the face is not glossy.  

all this assumes you have capability to put the panel back into the machine precisely - engraving happens as last step.

 

shown without layer of white on the lightplate. for this panel self-adhesive aluminum tape (shiny and very reflective) was mounted onto the backplate. 

 

 

it's a long process but the result is worth the effort. good luck and make sure to share your work

 

 

Edited February 16, 2021 by agrasyuk

[Muts]

That's looks really nice. Thank you very much for this detailed answer. This is very helpful I will study it.

[agrasyuk]

I'm working on AHCP panel. I can't get to painting due to low temperatures in the garage .
here is more images for anyone's reference.

 

Faceplate + Lightplate assembly prior to paint. in this case i'm working with a piece without protective film. this means the front will have thicker layer of paint then usual. while this is not an issue on mechanical engravers in my case i'm most probably going to make additional pass for best clarity of engraving ( I engrave at the lowest consistent power I can get out of the machine).

backplate to be painted as well.

 

 

backside. LED drill target marks are visible. it does take quite a few of those to shine through the polystyrene sheet with the intensity and consistency that I like. 

while not absolutely required I will be hand painting the inside edges to block light bleed from the switches. 

perhaps you can spot the 4 blind holes (not through the faceplate). Larger ones are 7mm recesses to clear for M3 nuts on the backplate, that will hold the interface board standoffs behind the switches. 2.5mm holes between switch row 2 and 3 will get tapped to M3 to hold two more screws holding the faceplate to the backplate. usually I tap thread before I glue the plates, in this case I forgot. for this situation I have a shallow tap ,  not ideal but gives enough of usable thread. 

 

Edited February 19, 2021 by agrasyuk

[LooseCannon]

What type of laser are you using to cut your panels?  I have a 15w 450nm diode on my 3018 Pro which is sufficient for engraving, but I have been unsuccessful cutting through 1.6mm white cast acrylic.  I suspect I need to upgrade to at least a 40w CO2 laser, but I'm worried that may also not be enough.  I've seen Youtube examples of 10mm thick clear acrylic being cut with no issues on a 50w CO2.  I could use my CNC to cut the panels, but I really find the laser so much easier to operate and I really like the uniformity of the engraving.

[CorporalCarrot]

Cutting white acrylic with a 450nm laser is always going to be difficult, as it is smack bang in the middle of the blue light range.  The reason that CO2 lasers cut white translucent acrylic and even clear acrylic is more to do with the fact that the light is around 10,500nm, which is beyond red and into the infrared range, and isn't visible to the naked eye (which is why you need to be even more careful with then).  For a laser to cut any material, it needs to get enough energy into the material to sinter it completely (i.e. vaporisation). White acrylic tends to reflect blue laser light and passes through clear acrylic, so the energy goes everywhere except where you want it!  You need to use the right tools for the right job!

 

WRT to painting panels, the method noted by Agrasyuk is very effective, but not the only method.  Like everything in life, there are pro's and con's!  The test I made of the Agrasyuk method (which is expertly explained by The Warthog Project here.)  I find that this method can make the backlighting very spotty with variablity in light intensity.  If it's done well and you  get the right number of LEDs in the right places, it works, but it is also easy to get it wrong.  I use a method similar to Craig S, where the LEDs are stood off the front panel, which provide a much more consistent illumination.  I personally integrate 1206 or similar SMD LEDs onto custom PCBs, which i either make with my own equipment on copper clad boards, or order the more complicated ones from JLCPCB (as it is just easier and more time efficient!)

 

I have both a top end Hobbyist CNC router (which has both a 25,000rpm spindle and a 6w 450nm laser), and I have also recently bought a cheap 40w CO2 laser from ebay for £280.  I had to spend some time (5 to 10 hours) setting it up, commissioning it and I even had to re-align the mirrors, but is good value for money IMHO.  I am happy I went with a high end hobbyist CNC router to begin with, as it was capable of doing everything (albeit with some drawbacks such as machine maintenance and mess from acrylic swarf), but the 40W laser can cut out panels much faster with less mess.

 

I can only suggest you think about what money you have to invest in equipment and then decide on which method suits you the best!  Remember, there is no right or wrong way!  (but there are easy and hard ways of doing things XD).

 

Good luck!

 

P.S. The other tip I would suggest is to cut the basic panel out first, then paint it.  This means that all surfaces  (including inside the holes) get  evenly painted.  I then engrave the panels.

Edited February 23, 2021 by CorporalCarrot

[agrasyuk]

I I started with small K40 laser as well.  I now use a. Bigger machine with true 40Watt of power output (Chinese manufacturers liberally overstate capabilities ).  Both can cut through 1/4" acryl in one pass if properly aligned and focused. 

 

As to uniformity of light, true on what CC said. Needs good LED positioning . Things get significantly better with reflective back though

 

 

[LooseCannon]

Thank you CC and agrasyuk for the good info.  I've had a difficult time finding answers specifically related to cutting white acrylic with various types of lasers.

 

The 3018 seemed like a good value for getting my feet wet in the hobby, and it has been fun to learn on, albeit very frustrating at times.  I've been looking into CO2 lasers and that seems like the next logical step.  My workspace (garage) is limited but it should be able to accommodate a 40W and allow for proper ventilation.  

 

You answered my biggest concern with the K40 laser as I had also seen a number of videos detailing the questionable output claims by the mfgs.  

 

And thanks for the tips regarding backlighting the panels -- good to know.  I've been watching Craig S. and Romeo Kilo's videos and have learned a lot from both as well.  

 

Cheers!

[CorporalCarrot]

The chinese 40W CO2 laser I bought, while needing effort to setup it up and re-align the mirrors (the laser wasn't even reaching the last mirror on delivery), cuts 3mm thick black, white (opal) and clear (100% transparent) acrylic in one pass at a speed of between 10 and 16 mm/s.  As Agrasyuk mentioned, you just need to make sure the laser is focused on the surface properly.  This means you need to have the surface of the material about 5cm from the moving head (your mileage might vary, depending on the model you buy etc.).

 

I've ordered some bits from amazon to help overcome this;  The main thing is a lab stand, in place of the really crappy clamp it came with.  I've also ordered a Nemo17 stepper motor and lead screw, to power the table up and down.  I'll be using an Arduino and something like a tool touch off sensor (going to 3D print my own) to automate setting the height to get it consistent everytime.  The stuff arrives tomorrow and I'll post some pictures and info on it, once it's finished (probably by the end of the weekend).

Edited February 24, 2021 by CorporalCarrot

[Muts]

I made a little bit progress on my prototype panel but I have to improve the engraving. I have LEDs with 85 mcd. In my opinion it's not enough. What are you using? How much mcd has your LEDs?

[agrasyuk]

LEDs from china have mcd? I'm not even sure what it is , lol. I just buy a 3mm flat top (wide) models 500pc bag and use that with whatever mcd they provide.

When you need more light  use more LEDs . You also want to play with exact positioning to try and achieve uniform lighting and avoid hotspotting

 

[Muts]

I made a test with LED green 75mcd, 800mcd and 3000mcd. Between 75 and 800 is not a big difference. 3000mcd its very bright and the color looks much better.

[CorporalCarrot]

mcd (or millicandella's) is how bright the LED (or more accurately, how much light is given off).  With regards to the colour, it is specified by wavelength (usually nanometers - nm).  The third metric which is important to consider when buying LEDs is the dispersion pattern, or viewing angle.  This is sometimes quoted as a single angle (i.e. 120 degrees) but sometimes has graphical plots on on the datasheet.  If you buy two LEDs from different manufacturers that have the same brightness (mcd), wavelength (nm) and dispersion pattern, then they should be pretty much interchangeable.

 

For the application of backlighting, you want LEDs with a large dispersion pattern, 120 degrees or more.  This is especially important for you, as your LEDs are very close to the top of the panel.  Having a wide angle will help reduce spotting of the light and make the light more even.

 

The last thing you need to keep in mind is the brighter the LED, the more power it is likely to draw.  LEDs are pretty efficient, but they still give off heat.  A 3000mcd (or 3cd) LED is likely to give off 0.1 to 0.2 W of energy, some of it as light, some of it as heat.  If the LEDs are embedded in the plastic, make sure that you don't keep getting brighter LEDs (I've seen small 3mm LEDs upto 15,000mcd), because at some point you will start heating the plastic and melting it (worst case is that it could be a fire risk)!I 

 

I still advocate backlighting which is stood off the panel by at least 1".  It results in a more even spread of light, and you can use twice as many cheap SMD LEDs with low light output to achieve a much better result. (8p per SMD LED compared with 20p per through-hole LED - these are quality LED prices, not budget ones; you can get them cheaper).

 

Just my humble opinion...