Gas station without pumps

2023 January 26

3D-printed clay-extruder die

Filed under: Uncategorized — gasstationwithoutpumps @ 10:18
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In UCSC’s soon to be fab lab (and an existing one), I talked about two of the fab labs on campus and mentioned that I was planning to try using the DSI studio in the basement of the “Science and Engineering Library” (which no longer has any science or engineering books or journals, so should be called the “Study Space on Science Hill” instead). On Monday, I got certified to use the Ultimaker 3 printers and attempted printing the clay-extruder die I had designed:

The Scott Creek extruder is designed to work with ⅛” aluminum dies, with no allowance for different thickness of dies. So plastic ones have to be made with an ⅛” flange, with the body of the die as a plug that goes into the extruder tube.

I printed the design in PLA with a 0.4mm nozzle and 0.2mm layers, with 4 walls, 20% gyroid infill, and 20% infill overlap.  I chose gyroid infill, because the stresses on the die would be both compressive and bending. I was worried that the 3mm flange might not be strong enough, especially as I expected some stress raising around the inner edge of the ring that holds the die in place.

The die printed fine, with no visible blobbing and only tiny amounts of stringing, easily brushed away.

On Tuesday, I took the die to my ceramics class and tried extruding some clay with it (I had a scrape on one of my fingers and did not want to get my hands wet practicing throwing pots). The die worked just fine and showed no damage from being used—the photo above was taken after the die was used and cleaned. So it seems that the 3mm flange is thick enough not to cause problems (at least for a few uses—I’ve no idea how long the die would last in production use, and I don’t really care). Next week I’ll trim the soap dishes, stamp them on the bottom, and leave them to dry on the greenware shelf.  Trimming should not take too long, so I should have time to try throwing again.

If I design other clay-extruder dies, I think I’ll make the bevel on entrance to the die bigger, so that there is more “wedging” of the clay as it is pushed through the die.  I had intended a wider bevel, but I had a bug in my OpenSCAD code, where I had used a constant “3” instead of the parameter “extend” in one function, and I had not noticed that the bevel was narrower than intended in the final STL file.  Of course, there wasn’t really room on the die for more bevel (unless I made the soap dish even smaller), so perhaps the bug was not such a bad thing.  I’ll have to think about how I could modify the OpenSCAD program to make the bevel large in the middle of the die, but reduce it near the edges, so that the die entrance does not get too close to the sides.

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