Make your own pyrometric cones? Why not!

Self-supporting cones are a must in each firing but they are expensive. Fortunately 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 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.

Related Pictures

Success: My homemade cone 6 is bending the same as the Orton

This is recipe L4532D. 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 uneven thicknesses require 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).

Drawing and first test cone mold for slip casting

We will have converted the recipe into a casting slip for this. Results will be posted here when ready. This method could be quite practical since it is relatively easy to 3D print a form to enable casting a multi-cone plaster mold. This is version 1.0 of the mold, it works sometimes, but the sharp angle on the spine of the cone is hampering release. It was also printed on its back to avoid the need for printed support, but next time I will do it upright and make the top a separate piece. And it should be possible to cast them back-to-back that way Orton presses them. If this works we will make the 3D drawing available for download in your Insight-live account (in the Files manager). There is a lot of interest in this project, many manufacturers need to cut costs and this could be one way, cones are very expensive in some parts of the world. And hard to get.

3D drawing to print shell mold to make plaster pyrometric cone molds

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 a printed 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.

Making your own kiln posts, is that even practical?

Supply chain issues during Covid made it difficult to get posts. I wondered if I could make my own. I have access to the same ceramic materials that post manufacturers use. Firing to the highest temperature they will ever experience should make them dimensionally stable, for me that is cone 10. In the past it was always a hassle to make the extruder die, but not anymore. An ordinary 3D printed PLA template will easily withstand the pressure in a hand extruder (even if printed with infill). The precision tapering possible is amazing. Notice that the floating centre has a tapered bridge to help clay knit together as it flows around it. What about a refractory plastic body? I started with L4543, it is cheap to make and dries quickly with minimal shrinkage. To cut posts to length with a square end I print sleeves to slide them into. I you would like the 3D drawing it is in the Files manager in Insight-live.com, it is parametric and easy to change.

Links

Glossary	3D Design 3D Design software is used to create dimensionally accurate objects by sketching 2D geometry and transforming it using tools to rotate, extrude, sweep, etc. The software generates the polygon surface.
Glossary	Pyrometric Cone Cones are ceramic and bend through a narrow temperature range. They used to be actively used to determine when firings were completed but now are used to calibrate electronic devices.
URLs	https://insight-live.com/insight/share.php?z=ZhRPJJH2Bg Pyrometric cone pressing body development project
URLs	https://insight-live.com/insight/recipes.php?OpenFile=woXZ17PTMw Pyrometric cone press mold drawing
Projects	Make Your Own Pyrometric Cones

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