a Nami Orb (Physical Design)
(c) Kelly Heaton and the MIT Media Laboratory, 1999.
For specific information about the materials used in this project and where to buy them, go here.
|First, a CAD design was created and machined on an NC lathe (thanks to Peter Morley of the MIT Machine Shop). This positive was affixed with super glue to a glass base, and a metal ring plus two brass tabs were arranged outside of the positive for mold registration during casting. Everything was carefully glued in place and cleaned thoroughly.||Next, a piece of cut aluminum tube was placed over the entire set-up (the positive and registration tabs). The height of the aluminum tube was chosen to accomodate the overall height of the final mold.|
|Craft putty was placed around the entire outside base of the aluminum tube to prevent any leakage during the mold-making process. The insides of the aluminum tube were sprayed thoroughly with a mold-release agent. Next, a flexible silicon molding material was poured into the aluminum tube until the material covered at least one or two inches above the top of the positive (this process is not shown). Prior to pouring, it is highly recommended that the silicon be removed of air bubbles by placing it in a vacuum chamber. To prevent introducing air bubbles, the silicon was poured in a slow, even stream into the lowest point of the mold chamber. This was allowed to cure over night.||Once the silicon fully cured, the mold and aluminum tube was detached from the glass base and registration tabs. The silicon mold was then pushed/slid from one end of the aluminum tube to the other. Once flush with other end of the aluminum tube, the mold was set it down flat again with the positive facing upwards (as shown above). Several tall aluminum pins were Super-glued to the bottom of the positive (to provide an escape for air bubbles during casting). Special care was taken not to disturb the positive inside of the silicon.|
|A new layer of silicon was poured into the aluminum tube, covering the positive by approximately one inch. The material used for this layer has a higher durometer ("hardness") than the first half of the silicon mold. This was for two reasons: (1) the top half of the mold did not need to be as flexible as the bottom since it does not contain the majority of the positive; and (2) the difference between the materials made it easier to prevent adhesion between the two parts of the mold.||The second layer was left to cure for approximately eight hours, and then the mold was removed from the aluminum tube. At this point, the positive was removed and the mold was ready for use. To make a casting, the insides of the mold were first sprayed with a release-agent. The casting material was then poured into the white silicon base until almost flush with the top of the mold. Then grey top was then carefully fit into place using the registration tabs for correct orientation, and the excess casting material was allowed to escape through the air release holes.|
|A mold for the o-rings was created using pre-existing o-rings of the desired size. These were suspended one inch above the base of a plastic container by attaching two bent pieces of metal to the inside of each ring. The metal stands were then glued to the bottom of the plastic bin. This enabled the mold to be poured in two parts: (1) the bottom layer of polyurethane was poured until the tops of the metal stands were just level with (but not covered by) the rubber; and once this layer cured, (2) a second layer was added on top to completely cover the entire assembly by at least one-half inch thickness of rubber (for mold durability).||The above photo depicts the two halves of the o-ring mold. Notice that the polyurethane rubber used to cast the o-rings has adhered to the mold; this could have been avoided by increasing the cure time of the o-rings during casting, or by using a silicon material for the mold (instead of polyurethane). The holes left in the rubber by the metal stands were useful both for releasing air bubbles and excess material during casting; however, it was still necessary to excercise quite a bit of effort and caution during casting to prevent the introduction of large quantities of air.|
|Here, the final products are shown assembled to create a hard resin base with a soft, opalescent bumper.|