First experiences with glass filament

Thanks to highball for reminding me to share my own! PS, haven’t forgotten about scanning the coin either.

I helped make this stuff while visiting TVF last month:

And it has quickly become one of my favorites. It just has a lot of interesting properties: It’s lighter than PLA, has a high fill but is still flexible and very strong, looks cool, and sinters overnight in one step. I don’t have much time, but let’s try to get a bunch of images on:

Check out that sparkle. When it prints, it does so super smooth with great detail! But I also frequently fight with clogs on my creator pro with 0.4 mm steel nozzle. I even upgraded to an all metal hot end to try and fix it, which turned out not to help much. What did help, was lowering the temperature from 220 to 200 or less. I think that the plastic and glass has a tendency to separate when left sitting in the nozzle, and a lower temperature helps somewhat. I have properly taken off my nozzle and removed a solid plug of material at least a dozen times though.

As soon as I get a new computer I will do a proper scan of the surface of it before and after sintering, because it looks awesome.

Debinding and sintering. I did five, varying only with peak temperature (units in Celsius):

0-204 over 30 minutes
Hold at 204 for 2 hours
Ramp to 482 over 2.5 hours
Hold at 482 for 3 hours
Let cool for 2 hours (possibly unnecessary)
Ramp to sintering temperature over 4 hours
Hold at sintering temperature for 2 hours

Note that this is all over just one sintering cycle, without covering in the second step or adding carbon or anything. Glass is already bound to oxygen! Really simplifies things!

peak temperatures tried so far (first based on this paper). 700, 800, 900, 1000, 1100 Celsius.


700 just falls apart when you take it out.

800, 900, and 1000 are white and porous, with decreasing porosity and increasing strength:

Note that there WAS isotropic shrink, which was totally unexpected to me — my understanding of sintering involves production of vapor, which I didn’t think glass would do. It also isn’t fair to say that it “melts” at these temperature, but rather just softens. Either way, binder goes bye-bye and glass gets stuck together.

Here is a video where I use the porosity to make coffee:

I tried it so you don’t have to!

One problem is that the aluminum oxide refractory gets fused to the surface of the glass:

This is a problem because uhhh this is a problem. Especially for eventually making transparent pieces. So I’ve been experimenting with using magnesium sulfate as refractory material instead of aluminum oxide, with the idea that, even if it gets stuck, it would dissolve in water afterwards.

This worked but it shrank and became like plaster, being a pain to get out afterwards.

You can see the comparison though, in aluminum oxide on the left and mgso4 on the right. No sticking!

Next I want to take the temperature past 1100, the part where it starts to become solid glass, with the goal of transparency.



This confirms some hunches I had about the refractory sticking to the surface. Like I said in the other post, I’m going to try steel shavings (so you don’t have to :grin:).

Also my thought was to go around 1600f (first attempt was 1310f) which is near the mid-high range softening point for Pyrex and hold a lot longer, bring down to the annealing temp of 1050f and hold then gradually bring down to room temp.

So I haven’t managed to make transparent glass, but I’ve confirmed that lower temperature of the nozzle has really helped with clogs on my 0.4 mm nozzle.

What I’ve done is printed a bunch of “coverslips” for microscopy purposes. The idea is a colleague of mine was (is) supposed to grow cells on them to see if they can make 3-D structures. It’s also become my standard test piece for glass on account of the file prints reliably so I hit the button a bunch of times and now I have them :slight_smile:

Magnesium sulfate refractory is not a golden bullet, especially for higher temperatures. In fact it does something weird when the slips are heated to 1300C:

They’re like, little yellow potato chips. What?

Meanwhile here is with aluminum oxide:

Those little spots are bits of oxidized iron impurities in my prototype batch, I think. It’s trying to become transparent, I can just tell! But I need a better refractory :frowning:

Lower temp the way to go for sure. Appreciate you noting that because I’ve had one hell of a time with those plugs and have replaced my ptfe tubing a couple times now

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woo hoo! Yeah, I was taking the nozzle off with every couple of meters of filament before making the change. Was just able to print a couple of big dogbones though (didn’t want to risk it before being able to consistently print larger amounts). Will pull apart and compare with pure pla this week

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New (looong) video all about glass, including for instance my boiling water in it on tuesday:

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Sweet will watch it later today :+1: