Making our own kilns posts using a hand extruder

Posts don't need to have thermal shock resistance like shelves do. And they don't need to be as refractory. They don’t require tensile strength. And they don't require powerful pressing or extruding equipment to make them. Any potter who is mixing glazes or clay bodies already has the materials to make them.

3-D printing has suddenly made it easy to extrude round or square or even complex hollow shapes and tubes. This is possible because it is now easy to make highly precise compression dies for extruders. They can be made out of a variety of metals and plastics.

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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 (click the link below to go straight there).

Thin walled kiln posts using a hand extruder

Shown is a tube hand extruder die (with a floating core). It was 3D printed using ordinary PLA. These posts weigh 23g/in (vs 81g/in for the commercial one shown). The posts were cut square-ended using the length patterns shown. Commercial regular posts will support the weight of a city bus but we are supporting pottery - so a thinner more energy-efficient version seems appropriate. This new drawing has been uploaded (visible in the Files panel in your Insight-live.com account). This drawing is more parametric than version 1, it enables setting the post width, wall thickness, draft of the float and position and angle of the float supports. This clay is normal pottery stiffness and contains ~20% grog and sand. We are experimenting with various refractory mixes (e.g. L4543).

By Tony Hansen
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