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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 00:19] – tjhowse
@@ Line 25: / Line 25: @@
 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 did not exist when I took the panel out of the mould. It formed shortly after I put it in the sun for this test. It seems to have been formed by some combination of:
+I was reasonably happy with this result. There is some white discolouration on the solar cells visible in that photo. That discolouration wasn't present when I took the panel out of the mould. It formed shortly after I put it in the sun for this test. It seems to have been formed by some combination of:
   * UV radiation,
@@ Line 49: / Line 49: @@
 ==== Failure ====
+Following from my success investing the solar cells in resin I decided to cast the electronics to the back of the  cast panels.
+{{:projects:blinker:work_logs:pasted:20220418-000335.png}}
+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.
+I had previously sought advice from knowledgeable folk, like Zak Crow of [[https://hsbne.org/|Hackerspace Brisbane]], on the details of using castable resins. They had warned me of the dangers of pouring too much resin in one go. I got cocky and poured too much in one go, with bad results:
+{{:projects:blinker:work_logs:pasted:20220418-000736.png}}
+The resin shrank and cracked as it set. I was able to chip off most of the prominent chunks.
+{{:projects:blinker:work_logs:pasted:20220418-000947.png}}
+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. :(
+==== Dissolving cast polyester resin ====
+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:
+{{:projects:blinker:work_logs:pasted:20220418-001232.png}}
+It had no effect.
+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:
+{{:projects:blinker:work_logs:pasted:20220418-001220.png}}
+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.
+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.
+==== Better casting mould ====
+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://github.com/larsch/lasercut-box-openscad|box generation library]].
+I happened to be rendering some beeswax at the time, so I dipped the panels in wax before assembly.
+{{:projects:blinker:work_logs:pasted:20220418-001908.png}}
+{{:projects:blinker:work_logs:pasted:20220418-001920.png}}
+==== Resin selection ====
 ==== Videos ====