I promised more details on keeping the paint out of the OLED window. This is the journey so far:
The masking piece (not masterpiece) ----------------- Exhilarated with how smoothly the CAD-to-CNC process worked in the end for cases, I decided to also try this to solve another problem: to keep paint from the display area. For this, I made a little piece of acrylic the size of the OLED panel, complete with a raised base for extra strength, and a nice little knob to handle it. The piece snugly fit into the bezel, so it would be exactly where the OLED will later be. Here it is, already with paint applied: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win01-paint-mask-painted.jpg The next picture, with the piece removed, illustrates the two things that were wrong with this idea: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win02-paint-mask-result.jpg First, some pain merrily crept under it. But worst, the resulting window is the wrong size ! There's a lot of panel around the OLED's active area, and it doesn't look pretty enough for us to want to put it on display: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win03-paint-mask-case.jpg Ewww. What was I thinking ? The whole idea relied of course on the ability to use the bezel as a mechanical guide, so I couldn't just make the piece a bit smaller. Back to the drawing board. Masking the masking liquid (or trying to) -------------------------- So I sought the help of an old ally, the masking fluid. If I could make a mask for that, it would in turn keep paint from obscuring the window. One issue with this is that the mask now has to have an opening. A mill can cut perfectly pointy corners if there's more "outside" than "inside", but if this isn't the case, the corner will be rounded due to the mill having a non-zero diameter. So I couldn't use the sturdy 1/8" (3.175 mm) endmill I chop wood and acrylic with, but had to use something small, e.g., the 35 mil / 0.89 mm bit I cut PCBs with. Alas, this one is also quite short and it would take forever to grind down a block of acrylic with it. But it does cut PCBs really well, so this is what I used. Here we have the case top from the previous experiment, now about to receive the paint that's been missing: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win04-masking-mask-before.jpg Fits nicely. On with the masking liquid: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win05-masking-mask-liquid.jpg A deep, reassuring blue. Looks as if it's gonna work ! After letting it dry for a while, I took off the mask. This is what I found: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win06-masking-mask-revealed.jpg Even though the masking fluid is quite viscous, it clearly had no difficulty at all getting under the mask. With the help of a straight piece of PCB and a knife I then manually trimmed the masking fluid. This didn't look too bad: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win07-masking-mask-trimmed.jpg And the result was quite acceptable: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win08-masking-mask-result.jpg Note that a little paint still crept into the window in the upper right corner. Okay, that did not go as smoothly as planned but it worked in the end. I had a second case to make, and I decided to try to do better this time, e.g., by trying to apply more pressure on the mask. Masking the masking liquid (trying again) -------------------------- The previous case looked a bit austere. So I thought of also making a window for the slider, e.g., to paint over later in a different color. I designed another masking piece, milled it, held down the masks firmly with a toothpick-like stick, and applied the liquid: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win09-masking-mask-again.jpg A deep, reassuring blue. This time it certainly must have worked. Let's see what it looks like from the other side: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win10-masking-mask-creepy.jpg Oh no, not again ! Ah well, more cutting to to then. But let's be smarter this time and cut the masking fluid with the mask still in place, so that the PCB can act as guide. Well, to make a long story short, the cutting was so ineffective that the entire layer of fluid merrily detached from the case - in both cases ! http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win11-masking-mask-removal.jpg All I had to show for my troubles were the ugly knife marks. Going dry --------- Having had it with liquids, I decided to return to good honest masking tape. Since the area is quite small and not easily accessible, I didn't use painter's tape from the hardware store but something specifically made for small stuff. To have an indication of where to place the tape, I drew the outline of the case and the position of the windows, and placed this under the case: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win12-masking-tape-applied.jpg After painting, the inside looked good: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win13-masking-tape-inside.jpg Now, let's check the outside: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win14-masking-tape-outside.jpg Argh ! Not the creepiness again ! This is what the case looked like after removing the tape: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win15-masking-tape-result.jpg I then removed the extra paint with the help of thinner. This is not very precise and dulls the plastic a little, but the overall result is tolerable: http://downloads.qi-hardware.com/people/werner/anelok/tmp/case-2015/case-2015-win16-masking-tape-case.jpg There are of course still the ugly knife marks, but there isn't much I can do about them. They also don't stick out in real life as much as they do on this picture. (And neither does the OLED ever look so blue. This is from the photo where the supply voltage was too low for proper operation.) Conclusion ---------- While I prevailed in the end, the process requires way too much improvising for my taste. Maybe another possibility would be to make an acrylic piece the size of the display's visible area, plus spacers to maintain the correct distance from the bezel. To facilitate removal, the spacers would have to be split. I suppose I could use a small vise / clamp to put more pressure on the window mask as well. By the way, what's the general opinion on having a window in the slider area as well ? I was thinking of painting it in some light yellow. - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
