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Molding and casting

Week 12

PLAN


Making an object from molds is a time-consuming process that requires several steps:

  • 1. Draw a 3D model
  • 2. Cut the 3D model on the wax
  • 3. Make the silicone and pour into the wax. (It takes about 24h to dry)
  • 4. Make the resin and pour into the silicone mold.

    • 3D Model



    As a first experience I decided to make a simple and small object, because cutting into the milling machine is a process that always takes a few hours.



    I thought about doing a 3D pawn on the Rhinoceros and separated it in half to later make a mold and counter mold.



    In rhino to shape the pawn I made several cylinders of different sizes one above the other and I put a cone to make the spinning spout.

    Then I divided the pieces of the Pawn into two pieces and joined them together with the "join" command.



    To do the negative of the pawn I started by drawing a box with the size of the wax bar I was going to use to make the mold and subtracted two larger pails from the bar.I put each part of the pawn into the holes and put it together.


    Then add four grooves on the end of the cube to allow the silicone to fit into each other.

    MILLING WAX

    A "matt-carving wax" wax block was used, where the two parts of the pawn are cut, as we can see from the images.


    The template was exported to stl and I installed MeshCAM which prepares the stl file for g-code.








    In MeshCAM it is necessary to define stock, supports, tools, retract height, program zero, set max depth and machining region and finaly generate toolpath.



    I defined three types of toolpath cuts:

  • 3.0mm End Mill, which quickly disintegrates
  • 1.9mm Ball Mill, which is finer and more accurate than the previous one
  • 2.1mm End Mill, to give the final finishing





    • Then the g-code is exported in three different parts, depending on the three types of drill bits to be used:

  • Rough Operation
  • Waterline Finishing
  • Pencil Finish









    • You should export the files on format : Basic Gcode-MM (*nc).












    I opened Easel.inventables which is the software that uses Carvey, and started by cutting the resin in three steps.





    After 3 hours, my final wax object was finally done!




    SILICONE MOLD






    Now is the time to prepare the silicone.


    The silicone used was of the Mold Max 30 type.












    To prepare this type of silicone we must mix 100 parts of type A and 10 parts of type B.


    So I started by putting 100 grams of type A silicone in a plastic cup measuring with a scale.










    At the initial 100 grams I collected 10 grams of silicone from the top B and mixed thoroughly, for about 5 minutes, to avoid creating bubbles of air in the silicone.











    After mixing, the beaker was placed in the vacuum machine in order to remove the air bubbles inside the silicone.












    After ready the silicone was poured over the molds in wax.


    It is necessary to pour the silicone slowly and close to the wax molds to avoid creating new air bubbles.


    The silicone takes about 24 hours to dry.







    After the silicone is dry, I have a mold and a counter-mold where I will pour the resin, which is the last step to obtain my final object.

    RESIN




    For the resin I used Smoth-Cast 300 resin part A and part B.

    And I mixed 100 parts A with 90 parts B to obtain the resin.












    Then it is only necessary to stir for about 2-5 minutes until we feel the resin start to heat up.


    Then the two parts of the mold are closed and the resin is poured into the hole in the mold.










    The resin is quick to dry, takes about 10 minutes.

    This is a very quick and simple process!













    The first pawn I made, although it went well, the resin did not reach the tip of the pawn, not giving it to rotate it.


    As a solution, I made a small hole in the tip of the mold, so the resin does not create a vacuum and go down to the tip.


    The second piece I did, it came out perfectly, and it turns very well. :)


    VIDEO

    Find the files used and download here:


  • week12_spinningtop.3dm _Rhino3D Files

  • week12_spinningtop.stl _STL 3D print File

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