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mission:resources:picojet [2014/05/04 09:21] – [Mold] chronomission:resources:picojet [2015/02/02 18:12] (current) – [Mold] chrono
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 ==== Mold ==== ==== Mold ====
 +
 +To create something out of liquid silicone we need a mold. Luckily, once you have figured out what exactly it is you want, you can create a mold out of almost anything you find, rests of wood and any other materials you can manage to get. Keep in mind to build it as tight as possible so that the silicone won't pour out. You can see on the images how this happened here because it wasn't tight enough. At the same time, remember that it should be easy to disassemble later, to get the final product out again.
 +
 +{{:mission:resources:img_20150116_091145.jpg?210|}}
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 +{{:mission:resources:img_20150116_091213.jpg?210|}}
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 +{{:mission:resources:img_20150116_091452.jpg?210|}}
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   * created out of wood   * created out of wood
-  * use clay (sulfur free) to cover holes and edges+  * used clay (sulfur free) to cover holes and edges (easy to apply and cheap)
   * Nylon string to hold heater element in place above the mold   * Nylon string to hold heater element in place above the mold
   * Use wood to create tube-bearing holder-pockets   * Use wood to create tube-bearing holder-pockets
   * drill a hole into the wood to place the sensor element   * drill a hole into the wood to place the sensor element
- 
 ==== Ghetto style silicone processing ==== ==== Ghetto style silicone processing ====
  
-The biggest challenge are the tiny air bubbles which inevitably occur while mixing the portions/color pigments (greatest part) and when the mix is finally poured into the mold. +To get a usable, final product made out of silicone, we need to take care of the tiny air bubbles, which inevitably occur while mixing the portions/color pigments (greatest part) and when the mix is finally poured into the mold. 
  
 **So how do we get them bubbles out?** **So how do we get them bubbles out?**
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 Once the portions are mixed, there usually is only a small time window to pour the mix until it starts to bind, but that is not enough time for the bubbles to "naturally" hover up and leave the silicone. The key hack for ghetto silicone molding without vacuum gear is to stretch time and luckily, silicone makes this easy for us: Once the portions are mixed, there usually is only a small time window to pour the mix until it starts to bind, but that is not enough time for the bubbles to "naturally" hover up and leave the silicone. The key hack for ghetto silicone molding without vacuum gear is to stretch time and luckily, silicone makes this easy for us:
  
-When you put your final mix into the freezer for 24 hours it slows the binding process almost to a complete standstill which gives the trapped air enough time to leave the mix. After 24 hours pull out the frozen mix and pour it carefully and slowly into your mold. Put the whole mold with the silicone into the freezer for another couple of hours to give the air, trapped by the pouring process, time to leave. Then just carefully take the mold out and let it bind for 24 hours. Keep the size of the freezers you can easily access in mind when designing/sizing your molds :)+Put your final mix into the freezer, it slows the binding process almost to a complete standstill which gives the trapped air enough time to leave the mix. After 24 hours, pull out the frozen mix and pour it carefully and slowly into your mold. Put the whole mold with the silicone into the freezer for another couple of hours to give the air, trapped by the pouring process, time to leave. Then just carefully take the mold out and let it bind for 24 hours at room temperature. 
 + 
 +<WRAP round tip> 
 +  * Mind the size of freezers you can easily access when designing/sizing your mold 
 +  * Make sure your mold is tight and sealed, so that the silicone can't get out  
 +</WRAP>
 ==== Heating-Element ==== ==== Heating-Element ====
  
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 === Calculations === === Calculations ===
 +
 +First, we need to figure out how much energy we have to put into the fluid in order to get from room temperature to 45°C:
  
 <x 14> <x 14>
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 </x> </x>
  
 +Now we can determine how much heating power we need to deliver that amount of energy in a reasonable time-frame:
  
 <x 14> <x 14>
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 ==== Heat Reflector ==== ==== Heat Reflector ====
 +
 +Since the heater radiates the energy in all directions we want to reflect the heat going to the bottom upwards again, so that we don't waste energy there. Tests have shown that rescue blankets for cars (the gold/silver foil) can help with that, so a piece of this foil was inserted between the bottom glass and the silicone footer (silver side up, as this side reflects heat).
  
 ==== Prove-of-Concept Test ==== ==== Prove-of-Concept Test ====
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 === Impeller === === Impeller ===
 +
 +This was the first approach, by simply cutting the tubes and some ABS material in a half-circle shape and then gluing them onto the tube. The next test should be, if we couldn't just print something with [[mission:resources:picoprint|our 3D printer]] to make it even more comfortable.
  
 {{:mission:resources:picojet-tube-impeller-single-open.jpg?640|}} {{:mission:resources:picojet-tube-impeller-single-open.jpg?640|}}
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 {{tag>research lab spray etch machine pcb picojet silicone picofab}} {{tag>research lab spray etch machine pcb picojet silicone picofab}}
 +
 +~~DISCUSSION~~
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