## Day 328: 3D printing… ugh

Well it’s time, in a few short days I’ll be doing a marathon session of courses for the summer interns. I admit it I bit off a lot! I’m doing three solid modeling courses, so the basics, plus a 3D printing class. Today we’re talking 3D printing because, well it’s a headache even though the prints themselves can be worth the pain. I know if I can pull off printing what I’m working on now it will be worth it… I hope.

First rule of 3D printing, we don’t talk about 3D… wait how did those rules get in here. Half of you wont get that reference and that’s fine. Anyway for real, the first rule is what can go wrong will go wrong, I know someone else stole that rule first, but it applies to 3D printing as well.

I printed a set of dogbones! Dogbones are what we call the strips of material that we use for material testings, typically (but not always) they get pulled apart by the ends, so the ends are wider and have enough material for the machine to grip them, then the centers come to a thinner part, we do this because we don’t need to pull apart a big piece to do material testing, we can do it on a small part and use fancy math to figure out the toughness of a beam for example. So they are shaped like a dogbone, hence the name. In fact here’s the set I just printed.

This brings us to the second rule of 3D printing, orientation matters! Notice I printed the same dog bone in two different directions, because a 3D printer works in layers, if we apply force parallel to those layers the part will fail faster than if we applied the same force perpendicularly. This has a lot to do with crack propagation and material properties, but basically while the layers look solidly joined, they are not! So the dogbone standing up will break much easier than the one I printed laying down (if I apply a bending force to the center dogbone, which is what I’m doing for part of my class since I don’t have the fancy material testing equipment I need in my home).

There are so many different 3D printing technologies out there now it’s hard to keep track of them all frankly! However, most of them are subcategories of a larger group, for example my printer above is a FDM printer (Fused Deposition Modeling), but we can also use fancy polymer liquids and shine light to create a solid object (SLA or stereolithography printing), we can use a laser to heat up a powered material (SLS or selective laser sintering), we can even use the same tech you use to print your homework (seriously, it’s called multijet printing).

Of course, there are spin offs to these, like we have printers (Markforged) for example that can print continuous fiber into the print creating a composite material, but really it’s a FDM printer with a twist. While SLA and SLS use different materials, they both are laser based printing tech, they just go about it in different ways. What I’m saying is that these are very mature technologies so advances in how they do what they do are incremental not exponential (computer processors are a good example of exponential growth, or pretty close to it).

In any case, the difference now between a home 3D printer like mine and a commercial unit is mostly price and customizability, my printer will put out parts just as good if not better than some of the commercial FDM printers for example, however my printer is a giant headache and I am constantly troubleshooting it. Whereas a commercial unit isn’t customizable, but will produce parts very reliably. It’s a tradeoff for sure, I like the flexibility I get with my printer, but I also can appreciate not having to fix it every ten minutes.

Luckily the 3D printing course is after my solid modeling course, 3D printing can take forever! I have two different prints I want to do for example and they are both about 4 days worth of non-stop printing. Both prints won’t be done for my class, but that’s fine as long as I can get them done… if I could get my printer to cooperate, I wouldn’t mind so much. Unfortunately, printing long prints like that can create problems, in my case print failures like the one I had last night. I’ll get it eventually, but that’s the price of flexibility.