High temperature engineering plastics

[PonoBill]

So I've been slinging filament everywhere. I blame some of it on Maui Humidity (I'm facing four days of steady rainfall as I type this), but mostly it's because I don't know what the fuck I'm doing. Most of the 3D printing I've done previously is PLA, which has a low glass transition temperature, a parameter that I previously assumed meant it melted, but doesn't really. Suffice it to say the characteristics of PLA make it super easy to print well, all you need is a basic recipe of printer settings and off you go. Occasionally I venture forth into more exotic stuff like PETG, which is almost as forgiving, and ABS which is not. I made some enormous messes with ABS and just set it aside--I didn't need it, and it didn't like me.

So now I'm trying to print much more exotic stuff, which is rumored to be much stronger and stiffer than the weenie stuff, though some people claim otherwise, probably because they don't know how to print it any more than I do. I've done some small prints that were very promising, and one or two bigger prints that were fairly amazing. But printing polycarbonate and nylon--either reinforced with Caron Fiber to just straight up, is a random thing for me right now. Sometimes cool and satisfying, sometimes a mess and enraging.

So I've been digging deeper and deeper. It turns out that these higher-temperature materials naturally have a greater aversion to large temperature differences throughout the object being printed. An object that is 100C on the base and nearly 300C up top is in great danger of warping, splitting, yanking itself apart, and otherwise driving me nuts.

One solution is heating the enclosure they are produced in so the temperatures throughout the object are quite a bit closer together and the entire print stays close to the glass transition temperature--effectively being annealed while it's being printed. The main reason current hobby-level printers don't heat the enclosure is a patent on doing just that which has been enforced vigorously (and the simple fact that most folks are happy printing PLA garden gnomes and LOTR figurines). The folks selling 3D printers for 1500 bucks can't afford to pay the license. The folks selling printers for 250K can. But of course, nothing stops me from adding heaters to my enclosed printers, and heated enclosures to my open printers and doing prints that approach, and even exceed the strength of injection molded plastic.

This is all fairly promising. I did a little jury-rigged heater last night and printed a solid cube of polycarbonate 150mm per side. It lifted a little at the corners, but this would have distributed itself all over my printer in the recent past.

The fancy-schmancy 250K printers hold the print volume at 100C or more, but I'm thinking a lot of stuff inside my Bambu would run out the bottom if I did that. so I'm shooting for 80C. We'll see how it goes.

For the seven other people on the planet who find this interesting, there's more info on this from two somewhat irritating but very experienced pros here:

https://youtu.be/QtEnWsSdbN4

And this other goofball. I feel comfortable listening to these guys. These are my people (unfortunately):
https://youtu.be/rMrMkKBxNZs

[PonoBill]

Unfortunately, it looks like simply adding insulation and heaters to a Bambu Labs printer is probably not going to be satisfactory, or at the very least will shorten the life of the printer. The case is aluminum, but all the structural parts are injection molded plastic and there are a lot of electronics inside the box--the control boards, power supply, etc.. So this is going to take a lot of fiddling unless I confine the heating to perhaps 80 C and add some cooling fans and isolation of the main electronics from the case. The plastic looks like it might be glass-reinforced ABS or Nylon. It's not super special stuff, so any temperature much higher than 100C is likely to cause dimensional problems and perhaps softening of the plastic. The glass transition temperature (Tg) of the plastics used is likely to be somewhere about 120C, and can potentially be exceeded without failing completely, but bad shit will likely happen. So 80C is where I'm aiming.

That adds a bit to the challenge and limits the likely outcome, but the alternative--spending 20K for a high-temperature printer with an enclosure than can be heated to 200 C -- is not going to happen. I am, after all, just screwing around here.

[sflinux]

I'd be worried about starting a fire if the printer was left unsupervised.

PCL has an even lower melting temperature than PLA, and is biodegradable.
You can make PLA biodegradable by embedding the enzyme proteinase A.
https://news.berkeley.edu/2021/04/21/new-process-makes-biodegradable-plastics-truly-compostable/
Without the enzyme PLA takes 100-1000 years to degrade.
https://makershop.co/what-is-the-difference-between-pcl-and-pla-filaments/

[PonoBill]

A legitimate concern. I have the printer on a steel table with nothing above it--the ceiling in that section of the garage is 17 feet high (the garage has a storage loft) and I have an ABC fire extinguisher ball capable of extinguishing electrical fires in energized devices hanging over it. The heater is a PTC heater, which means Positive Temperature Coefficient. I have a thermostatic control for it, but it's also self-regulating--as it gets hotter the resistance increases. If I just plug it in and leave it, it won't go above 120C. It also has a passive high temp cutoff set for 130C just in case the laws of physics get suspended. The printer is in a metal and glass case and connects to both my phone and iWatch. If it has any alarm or failure it buzzes me. I can turn it off completely from my watch or phone.

And still, I generally hang around when it's printing.

People who know me would be astounded by these precautions. I'm a bit of an idiot when it comes to safety. But people who know my wife aren't surprised in the least. She doesn't care how stupid I am at my shop in Hood River, but if it's going to be in the house--as it is here--she needs to be convinced it's OK.