Triple (x3) your Layer Strength by Annealing 3D Prints in Plaster!

In the past, I've already tried many different techniques to fuse 3D printing layers together by annealing or coating but never had great success. This time I embedded PLA and PETG 3D prints in plaster and then annealed them at temperatures over their melting point to see if we can fuse the layers together and how their heat resistance changes. Let's find out more!

💚 Support me 💚
Join as a YouTube member!

🎙Check out my PODCAST with Tom Sanladerer

🎥 Related videos:

🛒 Equipment used in this video (Affiliate Links):

⚙ My gear (Affiliate Links):
🎥 CAMERAS & LENSES
🎙AUDIO
🔴 LIVE STREAMING

Chapters:
00:00 Introduction
01:50 Test Setup
02:50 Embedding
03:56 Drying
05:00 Promo
06:34 Plaster Removal
09:00 Mechanical Tests
12:50 Temperature Tests
13:56 Summary
14:21 Outro

DISCLAIMER: This video was sponsored by Autodesk.

[CNCKitchen]

Don't forget to share this video on Facebook, Reddit, Twitter, and other platforms!

[MegaScienceguru]

this man single handedly has helped the entire 3d printing community on multiple occasions, thank you Stefan

[Coloneljesus]

Before putting in plaster, coat with a sealer and then mold release. Avoids moisture absorbtion and reduces cleanup.

[free_spirit]

Use SALT. I get EXCELLENT and consistent results by doing this process in finely ground salt (ideally near powder, if you have the patience to grind it that fine). The finer the better. Pack a stainless steel container tightly with salt and the part. In the oven the salt kind of hardens and the part is not allowed to deform at all. After the remelting I just demold and wash the parts and the fine crystals embedded in the wall just dissolve. I'm left with a part surface roughness that is dependent on the coarseness (or fine-ness) of the salt. The solidified chunks of salt easily return to powder by crushing them with your hands and it can nearly be reused ad infinitum since you lose very little salt at every run. The parts are super strong and water/airtight. I use the technique mostly for printing watertight containers and small pressure vessels. Can do really thin walls too.
Beware, try to buy preground salt, cause grinding a few kgs of salt in a coffee mill or blender will overheat the motor (i broke my blender this way).
Feel free to credit me if you try the technique. Also take a shot for every time I said the word 'salt' in this here comment.

[tinayoga]

The higher temperature capability of the PLA after annealing is the most interesting result from these tests.

[Seecalator]

Hey Stefan! I did a bit porcelain casting back in university. This is the technique we used to get (mostly) bubbly-free plaster molds:
Start with water inside an somewhat wide and shallow container.
Slowly add plaster using a sieve and let it dissolve into the liquid. Don't stir!
Repeat until the plaster stops dissolving and is resting on the surface.
You can now give it a light carefull stir, but it does not need much at this point.
In the end the plaster should have the consistency of a thick gravy, which makes pouring it into your mold pretty easy.

[shenqiangshou]

The temperature tolerance improvement on PLA is astonishing. That is much more interesting to me, since we have so many techniques for designing and printing parts in their optimal orientation, but if the material fails due to temperature, then there is nothing you can do. So massive kudos for figuring out this step.

[pyxiscarena]

Hello,
I use the same technique but
with some difference:
1) I don't use Plaster of Paris,
but two-component silicone,
much easier cleaning.
2) I don't use vacuum, but
I put under pressure at 5 bar.
Have nice day. :)

[MakeTestBattle]

1. Coat the parts in a hydrophobic mold release.
2. Cast the parts individually in custom printed casting containers so there is an even plaster layer around the part. You will use less plaster and have more surface area to volume so the cast will dry quicker. More even heat distribution during annealing and the plaster may be less likely to crack.
3. Cast the parts with the container on a vibrating bed to agitate the bubbles out.
4. Use an ultrasonic bath to clean the parts. Maybe investigate if you can use IPA to dissolve plaster instead of water.

[rickarddt]

As a mechanical engineer that studies strengths and stress analysis (but now specialise is thermodynamics) I find this first principle practical approach first class. I use the same formats to show improvements or steps backwards. Overall very refreshing to see.

[wesmatchett]

Did you consider some type of release medium coating the part prior to covering with plaster? Like an oil or powder coat. Oil would also reduce absorbing moisture from the plaster.

[AwestrikeFearofGods]

Great video! Try painting on a watered down layer of gypsum plaster to capture fine details. After letting it dry, paint a thicker layer of gypsum plaster mixed with sand. The plastic parts should heat up more quickly and evenly if you don't submerge them in a large volume of gypsum plaster. Besides adding strength, sand should reduce the degree of shrinkage, steam bubbling, and cracking that occurs when calcining gypsum.

[fredlight]

I've used this technique with ABS once - I dubbed it plaster self casting - and it seemed to work great. My wife's food processor (like a thermomix / hot blender) had a plastic coupler that wore out. The part undergoes a lot of stress, coupling the heated blender to the motor. I kept printing out replacements, but they'd last at most a couple of months before shearing along the z plane. The self-cast piece has been going strong for a year now.

I printed at 100% infill. For plastering, I kept the container small, kept the mix runny, sprayed the part with vegetable oil and spent 5 minutes manually jiggling and vibrating to get the bubbles out. I left it for over half a day for it to set. Then I bake 2 hours on high in the oven and left for another half a day to cool before hammering to get the coarse plaster off. Finally I soaked in vinegar and then used a water pik to blast the rest of the bits off. There was no evidence of bubbles or deformation, even on the finer gear teeth.

One thing that would be interesting to see: what happens if you use this on solid clear plastics - clear PETG, ABS and PLA?
If it's really re-melting inside, it should make these internal plastics fuse together into a single blob and it should become much more translucent and clear. Any takers to run the experiment? Maybe something cool like a crystal skull model?

[dontask]

I saw that bread and forgot what you were talking about....
That looks good!

[Thecanadiancarguy]

I use jewelry investment and ABS printed @100 infill. I dip my parts 4-5times to build a shell around the part to keep the shape, and simplifies removal and speeds up the process vs encasing the part in a block.

[ZappyOh]

I have annealed parts embedded in two-part concrete-molds made specifically for this purpose.
This way I can anneal many parts quickly, and there are no difficulty in inserting the parts or retrieving them afterwards.
This procedure is, off course, best suited for relatively simple geometries.

[Guardian_Arias]

How about leaving a port open to the infill and inject an epoxy into the cavities basically making the print 100% solid.

[igorfedik]

Thanks for testing this! It seems like it should work for PETG with 100% infill and heat-resistant mold release. In order to avoid bubbles cover the parts with just a thin layer of liquid plaster solution. And when it hardens submerge it in bulk plaster.

[supersupreme]

Here is finds, you might know already. I was printing huge containers with PETG, first of all PETGs are different, but I found the one which sticks to hot glass without anything else. Sometimes after bed cooling down, tension in printed item is so high, that it cracks glass, so you need to remove it while it still hot. Secondly, I noticed that printing at highest temp without cooling for PETG makes it the most strength, if you break it it shattered as glass, so layers adhesion is equal to strength of material, but when you print at lower temperature without cooling and lower speed therefore, it retains it plasticity while saves property layer adhesion. So with this setting PETG is like welding to part, rather than placing layers.
When you print big parts, "places of welds" have a time to cool down, so if you want to print small parts you need pause printing after printing each layer, to let plastic to weld to each other. Also at high Temps PETG expands and while extruder on a side even with huge retraction, PETG will runout, as the result not enough/constant extrusion for next layer.
Like anyway.

[fluxcapacitor]

Instead of annealing PLA inside a solid plaster envelope at a certain temperature tuned for this specific process, wouldn't such a solid envelope allow to completely melt the PLA at a really higher temperature, like for casting? Except the PLA part would already be right here inside the mold from start in a solid form, instead of being casted into it in as a liquid at a later time. In the end, the part would perhaps look like injection molding? What do you think?