|Monthly Tech-Tip |
Turn this upside down and center it over a precision plaster or 3D printed form of the outside shape of a mug. This creates a mold that drops down in our Shimpo cuphead. This opens slightly along one side for easy release from the plaster after set. It is held together by paper clamps during use. The upper flange can be glued down to a smooth surface with a clay slurry. If you would like this 3D file in Fusion 360 format, it is available in the Files manager in your Insight-live.com account.
The grey outer shell mold on the left was printed in two parts and glued together (at the shoulder). It's vertical split enables me to open it a little. The center model of the outside contour of the mug (on a two-step base) was made by casting the plaster inside another two-piece 3D-printed form I had made (we had to use a heat-gun and scissors to get the PLA printed form off of that plaster). It smooth the surface on the wheel using a metal rib and trimming tool. Then I stretched a rubber band around the first step at the bottom (because the shell was a little lose-fitting). Now the outer shell mold fits perfectly and clamps tightly in place. To cast a jigger mold it is just a matter of soaping the plaster model and the inside of the shell and pouring in a mix of 1300 pottery plaster and 900 water.
I prepare to attach these by simply touching them to the top of the slip (it is sticky and coats the underside evenly). Then it is just a matter of setting it in place and and it glues down in seconds. I make these a little larger diameter than the top of the opening (e.g. 2mm) in the plaster mold, producing a small overhang on the cast piece. During the time in the mold, the clay slurry creates a thickness against the plaster walls but also extends upward above the top of the mold (inside the spout). A while after pour-out I am able to make a cut and lift the spout away leaving an over-hang, over-height and thickness that all play to enable jiggering the rim to the exact contour I want.
This is machined out of aluminum. We also have drawings of a 3D-printable shell-mold for making molds that drop into this. And methodology for printing the outside contour of pieces to be jiggered.
Shell jigger mold drawing
Project to Document a Shimpo Jiggering Attachment
Make your own jiggering attachment for your potter's wheel. Here are the plans and lots of help to get you going with molds and techniques.