|Monthly Tech-Tip |
Print these three, pour plaster into them (after soaping) and you have a cone slip casting mold. Part 2 has a separate upper to enable printing it upright without support structure (producing a much higher quality surface). Hold that top cap on with a rubber band to cast. The separate cap also makes it easier to extract the plaster mold after set. If you would like this 3D file in Fusion 360 format, it is available in the Files manager in your Insight-live.com account.
Supply chain problems are hitting everything. Even cones. It turns out one can make these! The shape of a self-supporting cone is easy to draw in 3D (I did it here in Fusion 360). It is a 25mm equilateral triangle base lofted to a 3mm one 65mm straight up on the front side. And then a cut-out across the front. By using 3D printed press molds and plastic clay I can press these by the dozen. What about a recipe? Cones melt short of being glazes but beyond being porcelains. I chose L3685Z3 engobe as a starting point, it has a linear vitrification curve spanning a wide range. Approaching this on the material level, not as a chemistry project, I did three iterations of adding Ferro frit 3110 to the engobe. Shown here are the second, "A" and third, "B" (on the right is an Orton cone 6). B has too much frit, A does not have enough. You likely guessed what I did next: Mixed A and B. The result was almost perfect, bent just a little too much. If you would like this 3D file in Fusion 360 format, it is available in the Files manager in your Insight-live.com account.
This is recipe L4532D. We are still working on the molding process, whether to press the plastic clay or pour slip clay into a plaster mold. Or both. CAD files are available in the Files section of your Insight-live.com account so you can 3D print your own cone molds or shell molds. Pressing into the 3D printed PLA forms is potentially much faster and easier if it can be made to work. The issue is that the pointed ends are quite delicate and either crack in the mold or break during handling. The cross-section is also a very uneven thickness and requires special techniques to prevent cracking or warping during drying. The casting process is working better, the cones are more durable and drying is not an issue. Mold release has been a problem but we are finding that using ball clay instead of kaolin produces a better casting and releasing slurry (for example, the L4532F recipe).
The rear cones are Orton 5 and 6. The front ones are the L4532F recipe, it is bending too much at six and not quite enough at cone 5. The L4532F recipe employs ball clay instead of kaolin, which is making for better casting properties and better dry strength. It has also greatly reduced the cost, removing the need for Veegum. The difference in bending for this one-cone range is also looking similar to what an Orton cone would do.
Pyrometric cone casting shell mold drawing
Make Your Own Pyrometric Cones