week13 add content

content/WeeklyAssignments/week13.md

++++
+title = 'Week 13 : Casting & Molding'
+fa = "flask-vial"
+faVariant = "solid"
+toc = true
+weight = 13
++++
+
+### Summary
+
+This week I designed a 3D mold on Fusion 360 from an STL of a chess piece found
+on [cults3d](https://cults3d.com/en/3d-model/game/set-pieces-echecs). I then
+produced the mold in PLA using a Prusa printer. In the end, I cast a Smooth
+on polymer, as rigid as possible.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Mold_Final.jpg" alt = "MoldFinal"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_Final.jpg" alt = "CastFinal"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+***
+
+### Assignments
+
+#### Group Assignment
+
+* Review the safety data sheets for each of your molding and casting materials,
+then make and compare test casts with each of them compare printing
+vs machining molds.
+
+#### Individual Assignments
+
+* Design a mold around the process you'll be using, produce it with a smooth
+surface finish, and use it to cast parts.
+
+***
+
+## Mold Design
+
+To design the mold, I had two options:
+
+* 3D design the mold and produce it.
+* Design the negative of the mold, which will make a first mold that
+will be used to create the mold for the part.
+
+I decided to go for the simpler option as I'm a neofite in practice, if I have
+time I'll try the other method!
+
+For this week, I've decided to produce a chess piece, the queen to be precise.
+
+To do this, I first need a 3D model of the part. I find a design that
+suits me on the [cults3d website](https://cults3d.com/en/3d-model/game/set-pieces-echecs).
+
+I import the part into Fusion 360, which will be the starting point for the
+mold design.
+
+<img src = "./img/week13/ChessPiece_Model.jpg" alt = "ChessPieceModel"
+width = 40% class="mx-auto d-block">
+
+The idea then is to create a solid around the part and use the part and
+combine functions between it and the solid. The result is a solid hollow with
+the negative of the chess queen.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Mold_Model_1.jpg" alt = "MoldModel1"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Mold_FunctionAssemble.jpg" alt = "FunctionAssemble"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+I now need to work on the mold to make it easy to use: to be able to open it
+to remove the part after casting, and to have notches to align the two parts.
+
+I use the "split body" function to have two pieces.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Mold_Model_2.jpg" alt = "MoldModel2"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Mold_Model_3.jpg" alt = "MoldModel3"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+I then work on one of the
+two halves by extruding polygons (better for alignment). I then make a new "combination"
+to remove the extrusions from the first half on the second.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Mold_Model_4_Part1.jpg" alt = "MoldModel41"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Mold_Model_4_Part2.jpg" alt = "MoldModel42"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+Finally, I chamfered the edges for a smoother finish and I add a 0.75-mm offset
+in the holes so that the two pieces can fit together.
+
+<img src = "./img/week13/Mold_Model_5.jpg" alt = "MoldModel5"
+width = 40% class="mx-auto d-block">
+
+My mold is ready to be made! I need to export the STLs for import into
+the Prusa software.
+
+## Mold Production
+
+I import the STLs into Prusa to generate a gcode for 3D printing. In the
+parameterization section, I set the size of my mold according to the size
+of the part I want. I also set the precision along the z axis. Better precision
+could result in smoother rendering, but 3D printing takes much longer. I decide
+to go for an in-between precision of a tenth of a millimetre for 8h of printing.
+
+<img src = "./img/week13/Mold_Creation_Prusa.jpg" alt = "MoldPrusa"
+width = 80% class="mx-auto d-block">
+
+The printing process went smoothly, and the result can be seen below!
+
+<img src = "./img/week13/Mold_Creation_Printed.jpg" alt = "MoldPrinted"
+width = 60% class="mx-auto d-block">
+
+Now I'm ready for the final step, which is casting the polymer into my
+mold to create my chess queen!
+
+## Casting
+
+For the choice of polymer, there was a huge choice available between the FabLab
+and my research laboratory, so I decided to use a material that my colleagues
+had already used, to have a little confidence in the result. It's called
+[Smooth-Sil 960](https://www.smooth-on.com/products/smooth-sil-960/)
+and has a hardness of 60 A, the equivalent of a car tire.
+
+<img src = "./img/week13/Casting_1.jpg" alt = "Cast1"
+width = 60% class="mx-auto d-block">
+
+I start by calculating the volume needed to make my part. I'll need about 10 ml,
+which isn't much. So I decide to make more to make it easier to measure and to
+make sure I've got enough (even if I have to make another sample on the side).
+As the ratio of A to B is 10:1, I need to be precise. In total, I'm
+aiming for 25 grams of polymer.
+
+I start by taring my container and adding element A.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Casting_2.jpg" alt = "Cast2"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_3.jpg" alt = "Cast3"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+I then add element B in a 10:1 ratio, so here I need to add 2.25g of element B.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Casting_4_2.jpg" alt = "Cast42"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_4.jpg" alt = "Cast4"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+Then mix gently to prevent bubbles from being encapsulated in the polymer.
+I've got 45 minutes (pot life) to mix, vacuum and cast, so I'm not worried.
+
+You can see that despite my precautions there are bubbles. It should be noted
+that the polymer is not very fluid, which favors the encapsulation of bubbles.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Casting_5.jpg" alt = "Cast5"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_5_2.jpg" alt = "Cast52"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+To get rid of as many bubbles as possible before casting, I pass my
+container through the vacuum chamber to create a vacuum outside the
+polymer, which will stretch the air outwards. I'm careful to protect the
+outside because there's a risk of overflow, although I don't have much volume here.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week13/Casting_6_vac.jpg" alt = "Cast6"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_6_vac_2.jpg" alt = "Cast62"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+Below is a short video showing the bubbles escaping from the polymer.
+
+*add video*
+
+After about twenty minutes under vacuum, I can take my container out of the
+vacuum chamber and fill my mould. The mould is fixed beforehand so
+that it doesn't move. I try not to create a new bubble by pouring the polymer gently.
+
+<div class="row">
+  <div class="col-md-4 align-self-center" markdown="1" >
+    <img src = "./img/week13/Casting_7.jpg" alt = "Cast7"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-4 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_7_2.jpg" alt = "Cast72"
+class="mx-auto d-block" >
+  </div>
+  <div class="col-md-4 align-self-center" markdown="1" >
+      <img src = "./img/week13/Casting_8.jpg" alt = "Cast8"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+Now that the mould is full, I have to wait 16 hours for the polymer to cure.
+
+*add end*