Take This 3D-Print Post-Processing Method With A Grain Of Salt

There’s a lot of folklore around post-processing of prints from FDM printers. Proponents swear by their methods, which are generally intended to either strengthen the part or to improve its appearance, or both. But do they actually work?

Knowing that a collection of anecdotes is no substitute for actual data, [Stefan] from CNC Kitchen has again performed some valuable experiments, this time testing the strength of parts that have been annealed in salt. This was a follow-up to his recent experiments with baking prints after entombing them in plaster, which yielded mixed results in terms of strength gains. Viewers commented that common salt makes a good medium for annealing prints, so he set about finding the right kind of salt. It turns out that the finer the grain, the better — powdery salt packs tighter and leaves little space for the softened plastic to flow — but that powdery salt is not easier to find. He ended up making his own by pulverizing table salt in a blender. He also had to play around with temperatures and times until coming up with a good process.

The results are impressive. PETG, ABS, and two varieties of PLA prints tested with force applied perpendicular to the print layers all showed marked increase in strength after breaking, to the point of nearly matching the strength of parts printed with the layers parallel to the stress. As with the plaster, parts were printed at 100% infill; a Benchy printed at 20% was notably unseaworthy after annealing. Surface finish on the annealed parts is an interesting combination of pitting with white residue — not unattractive but still a bit weird.

Salt annealing might be a bit cumbersome, but it’s a neat method to add to all the other post-processing tricks that people have come up with for their 3D prints. Continue reading “Take This 3D-Print Post-Processing Method With A Grain Of Salt”

Making An Ultrasonic Cutter For Post-processing Tiny 3D Prints

An ultrasonic knife is a blade that vibrates a tiny amount at a high frequency, giving the knife edge minor superpowers. It gets used much like any other blade, but it becomes far easier to cut through troublesome materials like rubber or hard plastics. I was always curious about them, and recently made my own by modifying another tool. It turns out that an ultrasonic scaling tool intended for dental use can fairly easily be turned into a nimble little ultrasonic cutter for fine detail work.

Cheap ultrasonic scaler. The blue disk is for adjusting power. Foot switch not shown.

I originally started thinking about an ultrasonic knife to make removing supports from SLA 3D prints easier. SLA resin prints are made from a smooth, hard plastic and can sometimes require a veritable forest of supports. These supports are normally removed with flush cutters, or torn off if one doesn’t care about appearances, but sometimes the density of supports makes this process awkward, especially on small objects.

I imagined that an ultrasonic blade would make short work of these pesky supports, and for the most part, I was right! It won’t effortlessly cut through a forest of support bases like a hot knife through butter, but it certainly makes it easier to remove tricky supports from the model itself. Specifically, it excels at slicing through fine areas while preserving delicate features. Continue reading “Making An Ultrasonic Cutter For Post-processing Tiny 3D Prints”