glue & sawdust 'powder' printer ?

The maker space I belong to has a big, fast, moderately precise 3 axis mechanism (from an old bulk data storage center) they want to convert into a 3D printer. I don't see much use for a bigger fused filament 3d printer (due to long print times and high cost), but something that is faster and lower cost that could kick out BIG models on the cheap, even if with loss of precision, might be fun and even useful.

My idea for implementing this was to take a waste product we have tons of (sawdust) and use it as the feedstock for a 'powder' printer, by spraying down wood glue (or similar) to bond the sawdust layer by layer. Has this ever been tried? Or maybe something similar? Any inherent reasons it would not work, or massive challenges to over come?

As a demonstration of concept, I was considering cutting some 'stencils' to spray glue through onto the surface of a powder bin (using a garden sprayer) and building up a model by hand, layer by layer (probably try 2mm layers using a laser cut jigging system). Does that seem a valid demonstration?

or another possibility is figure out how the wood feedstock is made and find a way to combine the fine grains of wood into plastic feestock. or one could make paste extruder that feeds wood paste.

I'm not looking to print wood, per se. Just for a fast, cheap printing method. Wood paste would need to harden between printed layers, and I don't know of anything (aside from thermoplastic) that sets that fast and is cheap. 'Powder' printing has the advantage of being self supporting, doesn't it? That not only allows overhangs, but allows for using binders with drying time that (greatly) exceed the time needed to print one layer, right?

Are there other (affordable) materials suited to this? Plaster comes to mind, but I'm hoping for something less fragile & lighter.

This is a cool idea. You can check out OpenSLS for some ideas on handling the sawdust. A simple spray nozzle or off-the-shelf painting system could be used to apply the binder. You could definitely do this. There is also Pwdr.

This probably isn't quite what you had in mind, but you might get some ideas from the Stone Spray Project.

Also, the stencil idea sounds great. It is so simple to try with materials that are easy to obtain. I like it.

Use droplet deposition with a UV cured resin, i.e. light activated polymerization.
To enhance resolution, and quality, I would dry the saw dust first, and classify it with a screening process before using it.

Sustainable Composites Limited
[www.suscomp.com]

Quote
MattMoses
This probably isn't quite what you had in mind, but you might get some ideas from the Stone Spray Project.

Stone Spray was actually EXACTLY what I had in mind originally, but then I realized we already throw out literal barrel fulls of sawdust, and that having the 'support powder' around the model during printing offers a lot of benefits. Not to mention the hideous mess free-spraying glue and sawdust would make inside an enclosed space full of potentially delicate machinery.

One thing that may prove challenging is most glues shrink when they dry. Not sure how what impact they would have. I had considered using damp sawdust (to keep dust down) and Gorilla Glue (which is water activated) but that glue actually 'foams' quite a bit as it dries, which might be even worse. Probably take quite some experimentation with different glues to get right, and unfortunately none seem to specify shrinkage.

Edited 1 time(s). Last edit at 04/23/2014 01:24AM by sebwiers.

Quote
A2
Use droplet deposition with a UV cured resin, i.e. light activated polymerization.
To enhance resolution, and quality, I would dry the saw dust first, and classify it with a screening process before using it.

Sustainable Composites Limited
[www.suscomp.com]

That looks like exactly the glue I need! Tossing some UV lights in over the work is no problem, and it sounds like using UV cured resin would also avoid issues with it hardening where we don't want (IE, inside the machine). The non-toxic stuff you linked to is also a big bonus. To bad it's not cheaper.

Agree that screening and drying the sawdust would be ideal - research I did on making 'molded wood' from sawdust and glue suggested the same. We can probably modify our dust collection system to do that automatically (IE, separate and save the finer dust in a heated bin).

Edited 1 time(s). Last edit at 04/23/2014 01:23AM by sebwiers.