Author: Garth Whelan

I recently bought a bambulab X1C 3d printer. This was inspired by how long it takes to machine many small parts for hobbies that could be adequately done with a 3d printer for much less effort. Design is much easier when you can iterate with 5 minutes of work per iteration and a few hours wait.

Work has been really busy recently so I decided to take a break from hobby engineering and do less ambitious fun things in my nights. I’ve been interested in learning to post-process 3d prints the way people do for props, and also for better 3d printed molds. This was kind of an experiment in that – I used a well recommended filler primer from Rust-oleum to try and hide layer lines and turn the 3d print surface into a good surface for painting. It seemed to work fine, but when I tried to make a nice layer-less surface for casting into it was clear how bad PLA is for sanding. There’s a Bondo product I’m going to try next.

Anyway, I like mushrooms and I found a guy on cults3d selling very nice mushroom models (https://cults3d.com/en/users/gazzaladra/3d-models), so I bought a bunch, printed them and spent a night painting them with my SO. Painting is harder than I remember; I haven’t painted since I was a child and mixed colors always turned out different from how I expected. However these are mushrooms so it’s realistic if they look a bit gross.

I get the impression that things are much less decorated than they used to be. This has been explained to me as because of the increased cost of labor, which has some issues but to me wins out over other explanations. Some other explanations I’ve heard are that people are overstimulated in life and don’t buy decorative stuff so they have a place to recover, that plainness and lack of decoration is the new class signalling, and that a different civilization is responsible for all the nice stuff we see historically but don’t see built any more. These may later explanations may be more correct but they are unverifyable, while the first points to a specific effect that is definitely true. An issue with the first explanation is that the ultimate cost of e.g. nice decals, impressions onto stamped metal, has also been made lower due to technology, but maybe less so than the thing itself. Regardless, I appreciate nice looking things and soulful things and want to live in a world with more of them.

Costs can be split into manufacturing costs and design costs. Something neat to me about additive manufacturing is that for a lot of methods, decorations are free, or atleast very low cost. The decorations can also be different for each object produced. For example, Desktop Metal has a binderjet printer that prints wood (sawdust+binder) and dyes the material to resemble different types of wood (Forust). Because it’s a binderjet printer, small model changes for e.g. fake engravings don’t affect print time or cost, and because the material is already volumetrially dyed having custom colorations and patterns and images should also come free. This is the best example, but all binderjet printers and resin LCD printers should have basically free 3D decorations, and many 3D printer methods that allow color have the same print time cost regardless of the color used. Of course, all these methods rely on 3D printing actually being a competitive way to design a mass produced product, but in my impression that’s already what a lot of 3D printing companies are betting on anyway. There are also many cases where literally the same object is sold from different places with several fold differences in cost so I think it’s very possible that most people would be willing to pay a small premium for custom items.

This leaves design costs. While I think there’s some human intervention required, there’s a lot of neat generative deep learning work that could be used to take the load off of human artists. For example, given a model of an object to print, a human probably needs to label visible surfaces vs. critical surfaces (surfaces which must remain unchanged for function). At the lowest end of engineering difficulty, aesthetic patterns or simple random textures/tilings can be applied. There are manufacturing methods which produce results like this already, where every customer gets a slightly different object in a nice way. At higher levels of engineering difficulty, generative deep learning models could produce stylized and themed decorations according to the desires of the consumer. I’m still thinking this side of everything through, so I’m collecting examples of technologies and art. While I have some experience making and training generator deep learning models, it’s not something where I’ve ever been happy with the result.

I was a bit interested in making a personal stamp (like for sealing letters), so I threw together a design in Blender, printed it, and cast it in silicone. Just a note, I was incredibly impressed with Blender’s sculpt mode-it felt like I was playing with actual clay, and no matter what I did the result was always a manifold mesh. I have plenty of experience where programs can’t even maintain manifoldness after boolean operations on relatively simple shapes.

For the stamp itself, I think I used smooth-on’s ecoflex gel (don’t remember now). Silicones are nice because they are generally non-stick, so no extra mold-release is needed. When cast, they often can transfer details finer than the eye can see and this level of detail is used for some types of lithography.

As 405 nm floodlamps and SLA resin were more common where I did this than waxes, I used resin first. I was pretty happy with the results.

I also tried beeswax (not show), shellac and polycaprolactone, but wasn’t as happy with either of those.

Traditionally, sealing was was made from shellac and beeswax with pigments. Modern sealing wax is literally hot glue. As I didn’t get anything melted to work well I wonder if it was because this used of a silicone stamp instead of a metal one.

I was thinking this would be neat to turn into a small self-contained device, with stamp material (resin or wax), stamp and activator (405nm light or heater). Maybe wedding planners would be interested in it.

After a bit of fuddling I’ve gotten some inductively coupled plasmas started. These pictures are each around 1E-1 torr. The two coils are 0.5uF and 5uF respectively. They are driven with a signal generator (@13.56 or 27.12MHz)->100W shortwave amplifier->MFJ 941B tuner->BNC aligator clips. The plasmas were started with ~500V 20kHz AC on different feedthroughs.

Tuning was difficult but was made easier by monitoring radiated power with a SDR. It helped to add a 220pF capacitor in series to move the impedance closer to something that a tuner would normally be used for. A 275pF capacitor would have yielded a resonant circuit at 13.56MHz and 5uF but the real part of the impedance would still have been mismatched. Using the balun tuner output failed, presumably because the 1:9 turns ratio moved the impedance further out of range. I also tried using a homewrapped ~10:1 inductor around a ferrite core (because the real impedance here is tiny compared to 50 ohms) and got some less impressive plasmas.

I’m basically using the setup from here, with a used 700mm focal length telescope mirror. It’s a very clumsy setup and I’m very happy I got any results. Seeing it with your own eyes is kind of magical.

In this setup, light from a point source (LED covered in tin foil with a pinhole) is brought to a image half on a razor blade and the images are taken from behind the razor blade. Something that causes changes in air index of refraction (through heat from candles here) is in the light path. If there were no index of refraction changes in the air, one would see a uniform field of half intensity, but because the thing to be imaged changes the air’s index of refraction, you can see its effects.