The incredible utility of 3D-printing handle case molds

These molds are 3D-printed from PLA filament. They are part of my 2019 year-long casting-jiggering project to reproduce a Medalta 66 mug. A quick soaping, 325g water, 475g plaster and a fifteen-minute set produced these two plaster molds. When casting these solid they can be ready to apply in an hour after pouring (using the slip clays I have). While it is amazing how well these molds work I learned several things for version 2.0. The two halves mate with a tiny amount of play, it would be better not to have the natches, that enables sanding the mating surfaces flat for a perfect fit (simply lining up the outsides lines up the insides). Spares are not needed either, a 3D-printed dual pour spout would be better. A draft on the side walls would also make it easier to get the plaster molds out after they set.

Related Pictures

Final cast-jiggered cone 6 mug beside original 3D-printed mock-up

This is a product of a casting-jiggering project I did in 2019 to recreate a 1960s Medalta Potteries mug. The first step was drawing a profile in 2D (using Adobe Illustrator) and then working with a Fusion 360 freelancer at Upwork.com to create a quality 3D drawing. 3D printing this mock-up was possible after that, using my favorite 3D slicer, Simplify 3D. The mug was drawn "parametrically", that is, measurements and geometric relationships were built-in such that changing contours and the size preserved the original design. The first production mug, made about a year later, is on the right. Molds were scaled up 10% from this mockup size so that final pieces would be this size, however the firing shrinkage of the clay turned out to be about 12%.

3D-Printed master mold, handle mold made in it, first cast

The halves fit together well. Even with a thick handle like this, the mold splits for me in less than an hour when casting solid (and in half an hour when cast hollow). The cast handle is very sturdy and easy to cut and glue on to leather-hard mugs. As a parting-agent I use Murphy's Oil Soap on the 3D-printed PLA mold, this makes it fairly easy to extract the freshly-cast plaster molds (the sidewalls have a draft of about 5 degrees). The PLA mold is very durable so it is practical to use the end of a knife to get soap residue out of the recesses (when cleaning). If I do not remove the soap bubbles sufficiently before pouring in the plaster, corners are poor quality (so the mold produces a more visible seam on the cast handles). Notwithstanding that, the open plaster mold shown produces excellent quality handles.

Links

Projects	2019 Jiggering-Casting Project of Medalta 66 Mug
Glossary	Slip Casting A method of forming ceramics. A deflocculated (low water content) slurry is poured into absorbent plaster molds. As it sits in the mold, usually 10+ minutes, a layer builds against the mold walls. When thick enough the mold is drained.
Glossary	3D-Printing Standard 3D printing technology (not printing with clay itself) is very useful to potters and ceramic industry in making objects that assist and enable production.

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