projects:blinker:work_logs:9_resin_casting
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projects:blinker:work_logs:9_resin_casting [2022/04/18 00:00] – tjhowse | projects:blinker:work_logs:9_resin_casting [2022/04/18 00:22] – tjhowse | ||
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===== The Plan ===== | ===== The Plan ===== | ||
- | I wanted to run a medium-duration test of the electrically-complete blinker before going through all the trouble and expense of encasing it in aluminium and glass. I decided to cast the electronics in transparent resin. This would be reasonably mechanically and chemically robust, but it would degrade in sunlight over a few years, turning yellow and crumbling. | + | I wanted to run a medium-duration test of the electrically-complete blinker before going through all the trouble and expense of encasing it in aluminium and glass. I decided to cast the electronics in transparent resin. This would be reasonably mechanically and chemically robust, but it would degrade in sunlight over a few years, turning yellow and crumbling. |
===== The Results ===== | ===== The Results ===== | ||
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Not too bad! | Not too bad! | ||
- | I was reasonably happy with this result. There is some white discolouration on the solar cells visible in that photo. That discolouration | + | I was reasonably happy with this result. There is some white discolouration on the solar cells visible in that photo. That discolouration |
* UV radiation, | * UV radiation, | ||
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==== Failure ==== | ==== Failure ==== | ||
+ | Following from my success investing the solar cells in resin I decided to cast the electronics to the back of the cast panels. | ||
+ | {{: | ||
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+ | I used the same cardboard box as previous, however I smeared vaseline over the inside to prevent the resin soaking into the cardboard. That part worked great, aside from the thin layer of goo over the resulting casting. | ||
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+ | I had previously sought advice from knowledgeable folk, like Zak Crow of [[https:// | ||
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+ | {{: | ||
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+ | The resin shrank and cracked as it set. I was able to chip off most of the prominent chunks. | ||
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+ | {{: | ||
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+ | And I attempted to cast a new layer over the top to seal it all up. This new layer cracked off as it set, knocking off the backflow protection diode in the process. :( | ||
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+ | ==== Dissolving cast polyester resin ==== | ||
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+ | I wanted to try to salvage the electronics trapped in this failed casting. I had noticed that isopropyl alcohol made the surface of the cast solar cell a little tacky, so I submerged some chunks of solid resin in IPA overnight: | ||
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+ | {{: | ||
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+ | It had no effect. | ||
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+ | I also tried Methyl Ethyl Ketone (MEK). Nothing happened after an hour or so, so I added a splash of IPA to see if their power combined would have any effect. I left it overnight and found this in the morning: | ||
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+ | {{: | ||
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+ | The resin had started to crumble away. I'm not sure if this was the effect of the MEK+time alone or a result of the MEK+IPA+time combo. | ||
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+ | I was able to salvage the diode from this cast block, unfortunately I dropped it into the carpet in my office and it was gone forever. | ||
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+ | ==== Better casting mould ==== | ||
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+ | Getting good dimensional control with a cardboard mould was hard, so I cut one out of 3mm plywood. The pattern was generated by a great OpenSCAD [[https:// | ||
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+ | I happened to be rendering some beeswax at the time, so I dipped the panels in wax before assembly. | ||
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+ | {{: | ||
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+ | {{: | ||
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+ | ==== Resin selection ==== | ||
==== Videos ==== | ==== Videos ==== |
projects/blinker/work_logs/9_resin_casting.txt · Last modified: 2022/04/18 05:02 by tjhowse