Paste Extrusion For 3D Printing Glass And Eggshells

A variety of red and black glass objects are shown on a white background. In the foreground, there are two black spiral-patterned earrings. To the left is a red and black shape with three points on the top. On the right, a deformed glass sheet is shown bent over concentric red and black glass rings. In the center top is a red glass vase with a roughly-textured exterior.

In contrast to the success of their molten-plastic cousins, paste extrusion 3D printers have never really attained much popularity. This is shame because, as the [Hand and Machine] research group at the University of New Mexico demonstrate, you can use them to print with some really interesting materials, including glass and eggshell (links to research papers, with presentations in the supplemental materials).

To print with glass, the researchers created a clay-like paste out of glass frit, methyl cellulose and xanthan gum as shear-thinning binders, and water. They used a vacuum chamber to remove bubbles, then extruded the paste from a clay 3D printer. After letting the resulting parts dry, they fired them in a kiln at approximately 750 ℃ to burn away the binder and sinter the frit. This introduced some shrinkage, but it was controllable enough to at least make decorative parts, and it might be predictable enough to make functional parts after some post-processing. Path generation for the printer was an interesting problem; the printer couldn’t start and stop extrusion quickly, so [Hand and Machine] developed a custom slicer to generate tool paths that minimize material leakage. To avoid glass walls collapsing during firing, they also wrote another slicer to maintain constant wall thicknesses.

The process for printing with eggshell was similar: the researchers ground eggshells into a powder, mixed this with water, methyl cellulose and xanthan gum, and printed with the resulting paste. After drying, the parts didn’t need any additional processing. The major advantage of these parts is their biodegradability, as the researchers demonstrated by printing a biodegradable pot for plants. To be honest, we don’t think that this will be as useful an innovation for hackers as the glass could be, but it does demonstrate the abilities of paste extrusion.

The same team has previously used a paste printer to 3D print in metal. If you don’t have a paste printer, it’s also possible to print glass using a laser cutter, or you could always make your own paste extruder.

10 thoughts on “Paste Extrusion For 3D Printing Glass And Eggshells

    1. Coarse (on the nanometre scale) glass frit is nothing compared to fibrous CF and other asbestos-like nanoscale javelins. Even if you use powder frit (rather than the 0/00 that appears to be in use here) with an actual silicosis risk, the powder is contained within the paste. This is unlike in FDM, where the filament is heated and offgasses, carrying with it aerosolised filler material (including your CF fibres).

      Maybe hold off on pooh-poohing risks until you actually understand them (e.g. cancer is a secondary risk to asbestosis when it comes to aerosolised nanoscale fibres).

  1. This introduced some shrinkage, but it was controllable enough to at least make decorative parts, and it might be predictable enough to make functional parts after some post-processing.

    Which is to say that more research is needed in order to make the shrinkage uniform.

  2. This is for all the writers and editors, not just you— I really enjoy the writing, but then I run into “we don’t think…” I’m getting so tired of the “we” (and please stop calling it “royal”: look it up, it’s called the editorial “we”). Many of the writers here do it, but not in a way that makes any sense. Did you ask anyone else if they think that the eggshell printing (which is pretty cool) is a useful innovation? Isn’t it really just you? Own your opinions and stop saying “we” as if it lends more credence to your personal views. It isn’t journalism: it’s disingenuous, insincere, and insinuates that the whole staff of a respected tech blog agrees with you. It’s a cheap trick, and beneath you (plural). I’m actually interested in the biodegradable eggshell printing, but your article is biased towards it being irrelevant, so you didn’t give it a fair write-up. I don’t care if the (editorial, not royal) “we” is a part of your style guide, it’s incorrectly (or untruthfully) being used to signify the agreement of the staff or the readers. I mean, think about it: you write about an innovative 3d printing process using paste extrusion with novel materials, but you think only the glass material is innovative and insinuate that everyone agrees. Let the opinions battle it out in the comments where they belong. (Unless this is just super-deep trolling: Benchoff?)

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