Week 7: Molding and Casting

PART I | Learning 3D CNC and Different Molding Materials

  1. desktop CNC

    This week we used the smaller CNC machine (also ShopBot but smaller).

    The operation is basically the same as the bigger ShopBot.

    We learned how to cut 3D path this time, with initial rough mill and then with finishing mill.

    Here is a sheet for speed and feed on both roughing and finishing (1/8"endmill on solid wax).

  2. molding materials

    We learned how to cast OMOO onto the wax: part A and part B (1:1) should be stirred individually, and they will be mixed together for 3 min before they get poured into the wax mold.

    Then, we learned how to cast plaster onto the OMOO mold: plaster to water should be (4:1 or 5:1), let water sit in plaster for a while before start mixing, then pour into OMOO mold.

PART II | Design and Toolpaths

  1. design

    Since I have not set on my final project yet, I decided to experiment with casting a small vase for a single strand of wild flower.

    I made the model in Rhino and export it as an stl file.

    It is just a boolean difference between two four-sided pyramids.

  2. toolpaths

    I loaded the stl file into ShopBot Partworks 3D.

    I followed instructions (input model/material size, set thresholds, load tool for roughing and finishing, feed and speed).

    Then I saved rough and finish toolpaths individually as sbp files.

PART III | Milling and Casting

  1. milling

    I first hotglued my wax block onto a osb board, and then I screwed it into the milling bed.

    I opened ShopBot3, and I zeroed x,y and z axis.

    Then I loaded my roughing file in and began milling.

    After roughing is done, I vaccumed the bed, and went on to finishing milling (no need to zero again).

    I vaccumed and unscrewed my wax board from the milling bed. Here is my wax mold, ready to cast the omoo mold.

  2. casting

    I mixed omoo part A and B 1:1, then poured them into my wax mold (agitating for a while).

    Then I waited for 90 minutes before I took the omoo mold out from the wax mold.

    For my first cast, I tried plaster(Hydrostone superx). I mixed about 4:1 plaster to water, using islander method.

    I poured the mixture into my omoo mold (agitating for a while).

    Then I let the plaster sit overnight to soldify.

    I failed to find a small flower on my way to school today, so it turned into a pencil holder instead.

    I plan to do my second cast in metal, and I will update later.