I have several ideas for solving the problem of internal paint scratching: 1) the easiest approach would be to avoid mechanical stress on the paint by masking areas where case parts meet. That would create a bright band since light is reflected on the two walls before being absorbed by the paint on the inside of the inner wall, but may not look too bad. Here's one of the cases with the paint scratched off in one corner:
http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-scratch.jpg One issue is that the PCB is also held by the case and thus rubs against the inner wall. This could perhaps be solved by adding a gap and constraining horizontal PCB movement via some structures away from the wall, e.g., a pair of columns, similar to the LED "pipe". 2) a similar approach would be to add a gap between the case parts and holding them together with screws. One problem with screws is that making precise holes for them would require a two-sided milling process, which exceeds what my machine can do. 3) applying the paint on the outside. This would largely protect it from internal scratching but it would be exposed to scratching from the outside and also the "object inside acrylic" effect would be lost. I tried this on a set of parts with bad geometry (the case wouldn't close properly when the PCB is inside.) First, the bottom half: http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-out-back.jpg The paint is a bit bumpy. This is what happens if you get it right: http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-out-front.jpg Perfect reflections - good enough to defeat the camers's auto-focus (it even did it two times in a row.) Not sure why the two are so different. Maybe I didn't mix the paint well enough - I'm still new to all this. This is what the case looks like with the drop of masking fluid I used for the LED window removed. The damage in the upper front edge comes from difficulties removing the part from the workpiece, again caused by bad CNC settings. This is what it looks like next to a case painted from the inside. http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-out-compare.jpg I'd say the result looks quite acceptable but less fancy than the other one. It also seems to attract dirt a lot more. 4) a mixed solution: paint the top surface from the inside (so that the LED/OLED window looks nice) and paint everything else on the outside. This means that I need good masking at the edge of the top surface: http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-mixed-mask.jpg The result: http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-alt-mixed-result.jpg The masking worked rather well and the result looks promising. I'd be a bit worried about paint easily getting rubbed off at the edge. I think I'll aim for approach 1 for now. This means that I'll have to add a few holes in the PCBs, make the cases a little wider, and put some columns into them. - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
