Materials science and engineering fascinate me, but I know absolutely nothing about the fields. Between that and the fact that there’s so much YouTube content on 3D printing, it’s inevitable that I’m going to end up watching some of it; and one thing that’s stuck with me (so to speak) is the problem of getting better adhesion between layers.

So I thought about it. Inside my own entirely unqualified head. And it’s left me with so many things I want to try that I’m now too afraid to buy a 3D printer because I can see how it would absorb my entire life and leave me unemployed and homeless. Presumably living in a cardboard box with custom-shaped PLA patches covering the holes where the rain gets in and begging on the side of the street for any spare filament passersby might have on them.

So let me just post all my ideas on the internet where they can ruin somebody else’s life instead of mine.

Egg-crate foam

z += sin(x) + sin(y)

By warping the slicing this way the filament has to follow wave patterns and this eliminates continuous shear lines and it increases the contact area between layers because those wavy beads are much longer.

stretch goal: woodgrain

Small variations in height, but variations themselves varying over z axis so that it gets thinner and thicker as well.

Weaving

While you can’t do fundamental over-under weaving; consider the way string is wound onto a spool in a helical winding pattern which gives it that herringbone finish. That’s kind of a weave, right? I think this can be unwound to a flat surface, or laid out in a flat ring, but I haven’t fully thought through what it does to shear lines. That’s probably a thing I could experiment with without using a 3D printer.

Helical beads

Rather than printing straight, smooth beads, it may be productive to roughen the surface so as to improve adhesion for the next layer. This might be done by jiggling the print head back and forth subtly while it’s drawing a notionally-straight bead, or perhaps by tracing a sort of skewed helix, giving the sort of finish you get from arc welding.

The localised movement and reduced progress of the print head and the extra manipulation might also help to heat and massage the filament into the layer below at the same time as producing a rougher surface for the next layer to bind to.

Injection

Leave tiny voids in the shape of interlocking rings, and squirt filament into the holes from the top. This allows the placement of small vertical joins between layers, knitting them together and hopefully helping to overcome some of the weakness of poor layer adhesion.

It might be possible to do this a bit better by pausing to raise the temperature of the filament above normal printing temperature. Some of the problems will not be applicable in this injection case, and the extra fluidity and extra time before setting will help with penetration. Also, if the filament is especially fluid then it may squeeze into the gaps between layers and form spurs which make it harder to pull out.

The rotisserie

Make an adapter to translate the bed movement axis into rotation of the workpiece. Then slice the object into concentric cylinders rather than planes.

This change in coordinate system represents a change in overhang constraints. This should make it possible to print christmas-tree-like overhangs. The outline is not restricted to being cylindrical, of course, and the points of the overhang can be drawn as higher (actually “outer”) layers which become disjoint in cylindrical coordinates.

I’m also wondering if the curving of the layer lines might help with strength.

and another thing

I wonder if flux could be a thing the way it is with soldering. Some kind of solvent emedded in the filament which helps etch the previous layer of filament and spread some heat around or raise the heat capacity temporarily to improve adhesion before evaporating or flowing out of the way.