I was tasked with refreshing an existing product line. We wanted to add a number of features to our basic [radio] monitor-receiver. Things like adjustable digital audio levels, a different L/R filter and GPIOs. One novel change is the use of a multi-colored background LCD screen. The idea is that the 'white' background would turn red when an alarm is triggered making it easy to see the error from across the room. The problem: the LCD has no bezel. No way to mount it. Enter 3D Printing 🙂
It started with the idea of gluing the lcds in place, that lead me to design a jig that would hold the LCD screen in position…It failed. Glue was not enough.
We kept with the idea of glue though, trying different brands and polymers but it was known that some-sort of brace was going to be needed. Since I was redesigning the PCB anyway, why not add a mounting/alignment point on the board? This took the form of two holes in the center of the front of the board. Now I could design a brace. The idea was to make a simple brace that pressed the LCD into the front of the chassis to help the glue.
I was sending away for the brace designs to be 3D printed, but after two iterations, I convinced my boss it was worth buying a machine. We got a PRUSA MK3S (well technically it was a MK3 but I upgraded it when the 'S' variation came out).
With a printer in house, the iterations of design were fast and many. I tried brackets with hooks, press-fit, curved back, inverted backs, long flat surfaces, minimal surfaces…none of which worked great. Finally I 'bit the bullet' and designed an entire wrapper for the LCD. Enter the red Bracket, a bracket that, with hot-glue, held the LCD in place properly. Well that was until we took the prototypes to the Las Vegas NAB convention and the warm weather and constant running of the radios showed the glue failing. The LCDs were becoming misaligned. The corner kept rising. Hot Glue just isn't going to work but what do we do?
Then I saw it, a true mounting point that's always been there. Not just an alignment hole, it's one of the four PCB mounting screws. With a taller screw and a little help from the lid, I was able to take glue out of the equation and use physical mounting hardware instead. This design actually holds up. There is a little too much support material for my liking but I think the design is decent.
All in all, I think I wen't past 70 design iterations to get to this point. The fun isn't done though. The leading edge of the PCB is a little thick and that makes it harder for manufacturing to install the brackets quickly. Now that we have a winning design, the next iteration will be a PCB change with the alignment holes and leading edge pushed back.