Hi Stefan. Holy smokes that's a lot of work! I feel a bit bad, because I had a feeling when posting that video that you were going to get a lot of requests 😅, and I lack all the testing equipment to do it myself. Thank you so much for doing this. I completely agree, we only scratched the surface of what can be done with FDM, this method and remelting in general. When you remelt the parts in kapton you get really shiny surfaces and you can see exactly where the bubbles form (if the filament is transparent. You can also join different parts together whilst remelting. I've experimented with embedding laser printed transparencies in transparent parts (works really well!), but you can also embed inserts etc. Also I've done some tests where I have a shell of PVA surrounding the part, which keeps the original surface texture. One final thing, all these parts are actually watertight, so you can use FDM to prototype pump housings, heat exchangers and other stuff like that (as long as you design it in such a way that you can get the salt out). 3D printed watercooled pulse jet maybe? I would encourage everyone in the 3D printing community to try different methods AND POST THEM on the internet to create prior art and avoid any of these techniques falling in the hands of patent trolls! Best of luck to all!
Kudos to you! You didn't only inspire me but also thousands of others. I would not have done these tests so quickly if it wasn't for your work. Thanks and keep on sharing your work!
Great work by yourself and Stefan to introduce this as an option! I'm curious: rather than printing in a PVA shell, have you tried simply dipping the parts in PVA glue (white glue) letting it dry, then doing the sand re-melting process and finally dissolving the outer PVA coating in water? This might allow people with single extruder printers to quickly and easily make extremely strong parts that still have a great surface finish!
@@GoughCustom I was thinking about that, especially since hot glue lets go of any surface when wetted with ethanol and for some reason I can't get my PVA to remelt
Regarding materials - what do you think about fine copper powder. russian.alibaba.com/g/fine-powder-copper.html it is good heat conductor and doesn't make and reactions at these low temperatures. it is used as paint addition.
@@amicloud_yt While I agree in part, there are casting methodes that use similar things too heat resistant enamel. You dip a part (out of wax) into the liquid, let it dry onto the part, and do this multiple times to create a hard shell. Then you poor in a liqid that melts and replaces the wachs. This can be done with a lot of parts at once and reproduce extrem fine details often whitout any post prosessing. While using salt is a really cool technique I think casting a part (with the help of 3D printing the desired shape) or using better materials for printing has more advantages. If you simly care for a more homogenous part you could use SLS (selective laser sintering, printing with powder).
Tried this as well two years or so ago, the thing I found out is that even with 100% infill setting there are still air gaps in the part that flow up to the top during the remelting process. The thing I came upp with is just adding an extra cylinder or cone shape to the models top so you have extra material to be sure the part would be 100% plastic after the heating. Just some small cleaning required.
@@seth7745 ah yes, I'll just jump in my rocketship. Plus that wouldn't fix the problem, it would just create imperfections inside the print instead of completely filling them.
You should try it next with foundry casting sand. If you're still set on salt you can process the salt into a fine powder more easily by filling a two liter bottle approximately 1/3rd full of salt and then adding steel ball bearings and putting it onto a rock tumbler turner to make a simple ball mill.
@@D__x Always looking for fun experiments! :P Looking at reference materials, it seems like 51-55Mpa for IM ABS. If I look at Stephan's bar chart, it looks like he's measured 40Mpa for FFF.
I think free spirit reached 90% of injection molded parts. Stefan didn't. I guess he used way to high temps for the parts. Free spirit didn't heat them up as much.
As a mechanical engineer I appreciate the scientific approach and notions. This is actually the only channel that performs tests that has useful results. Huge respect for building a tensile test rig and for performing bending tests and themal tests. There's too many variables that aren't taken into account in those luggage weight pulling tests, and not to get started on the repeatability... Keep up the great content! Btw. did you get a measure of the grain sizes?
Well said. I agree with you from industrial and academic standpoints. However, let's all remember that this is a RU-vid channel being viewed by mostly hobbyists (not industrial manufacturers nor academic laboratories). I want to say the same as you to CNC Kitchen: "Keep up the great content!"
The Very populr channel @ProjectFarm does tests and record keeping of every ind. buiding multiple custom rigs per show. Its VERY Impressive.. I too appreciate The Scientific Method.
Try Epsom salt. I have used it to anneal 3D prints with great results. I first dehydrate it in the microwave on a plate lined with parchment paper which results in Anhydrous (without water) magnesium sulfate. It's like ultra hydroscopic glass. I break it up into small chunks and it grinds pretty easily into a very fine powder (like baking powder). This packs really well and has the benefit of adding zero moisture to the process, being considerably cheaper than salt, less corrosive, and results in fine detail surface finish. The powder is water soluble just like salt. I also use it as a very effective desiccant for storing my filament.
I might actually have a suggestion to make here. I don't 3D-print, but over the past couple years I've had to take to grinding down salt for medical purposes in a similar fashion to what you describe. I found that after finely powdering it, it had a tendency to stick together because there was too much moisture in the salt itself. This can easily be solved by pouring the salt into a flat pan and then baking it at a medium heat for a few hours, at which it will have a consistency closer to fine, dry sand, which might help for when trying to get it into all those little crevices.
Don't want to intrude on your personal life and feel free to say no if you're uncomfortable answering, but I got really curious. What did you use the salt for medically? Take care :)
@@idekman5427 Rinsing out my sinuses. I mix a specific amount of salt in with a specific amount of warm water but I found that most types of granulated or crystalline salt didn't well fit into the measure, so I ground it up. Then because it was too wet it got stuck in the jar I keep it in, so I started roasting it. The end result could very well pass off as some kind of powdered drug, but it works real well.
@@PackthatcameBack Back in South Africa we called an activity used to clear sinuses "see snot klap" Which translates to "sea snot slap" In short, we go to the beach and get smacked in the face by waves.
Wikipedia says it's fine salt to speed up dissolution.. But seems Winsor is making a coarse version from what I can see. windsorsalt.com/product/coarse-salt/ So I guess it depends on the brand.
This is not just a blender. It can cook and refrigerates meals. It tells you what ingredients to put in and prepares recipes. There are plenty of recipes avaible online. Yes cuz it is connected as well.
@@jeroenvandend yeah thats a thermomix .i dont have one but i was pretty sure it can refrigerates. A friend of mine did an ice cream once i dont know how.
You should try Starch (Stärke). It is used for making the forms for haribo gummybears etc. they get a very smooth surface and it melts at 200°. So this is already very fine, holds the form very well, cheap, heatrestistant. Maybe another video? :)
@@EliTheDriftPanda you dont have to melt the plastic. Hardening usually uses 100° or so. It should work. It softens at about 80-100 which should rebind the layers.
@@the23er in salt, the suggested temperatures were way above 200°C and even with Stefan going lower than suggested, the whole thing was heated close to or above 200. I'm not sure about the thermal conductivity of starch, but I doubt it's precise enough for you to reasonably use it for this purpose. Even if it were, you'd have to pay way more attention to the process, increasing post-production costs (be it your more active time or higher print failure rate if you don't intervene quickly enough). Softening at 80-100° doesn't change this, because the issue is not the individual layers being deformed or similar. This technique is specifically meant to give your prints a solid, moisture reducing atmosphere to remelt the layers into one continuous object. That's why Stefan made special note on how the breaks looked and the difference between clear layer lines in the controls as supposed to the homogenity of the tests
Have you considered trying a ball mill to get the finer granularity? There are a few ways to make them cheap, such as a coffee can with marbles inside. It might also help with the dust issue.
To grind salt properly, first dry it thoroughly in the oven, this will minimise the formation of clumps. Then, use a ball mill with stainless media for the grinding. Load the jar and let it working overnight.
Hi stefan, I work in a solid state chemistry lab and when doing solid state chemical reaction it's super important to have the smallest possible grain sizes. It's common practice to use an agate pestle and mortar to get ultrafine particle sizes. We often also add a small amount of a liquid that will not dissolve the powder, and evaporate dry, to really facilitate the grinding process. I would recommend something like 99.9% IPA for salt. This process can be labour intensive, but it works extremely well. There are some manufacturers that sell automatic agate pestle and mortar grinders for this exact reason.
You guys are way overthinking this. Take the printed part, flour it, dip in egg wash, then panko bread crumbs. Repeat twice, then deep fry in vegetable oil. Peel off and eat breading. Done.
@@free_spirit1 Was thinking the same thing. He tried plaster, but I believe the water was an issue. Must be some material out there to use as a binder that won't effect the PLA and can be dissolved afterwards. Smarter people than me will figure it out.
Try using diatomaceous earth instead of salt. It comes in a very fine powder, is relatively cheap when you buy bulk and it has excellent thermal/insulating properties. Also, I’ve found that if you can find a vacuum sealable container that fits the part, you can run a vacuum after compacting by hand and it will get into all the missed crevices. Another thing I’ve been working on is using these heat resistant vacuum seal bags to be able to heat with water immersion. Still some stuff to work out with it though, such as getting a workable thermometer in the bag that can be seen.
Alas, like sand and plaster, diatomaceous earth aka kieselgur is NOT water soluble. As free spirit 1 pointed out, the powder used for this application has to be water soluble, because the process makes the grains in contact with the melted plastic mix and merge with the surface part. In the end, the part needs to be washed in warm water so the grains incrusted into the surface can dissolve and be completely removed, leaving the part with a smooth surface finish. If you use a non-soluble material even with a small grain size, those will remain stuck and give a rougher surface finish.
@@fluxcapacitor that could work if you actually want more manual control over the finish afterwards! Do you have any experience with marble powder by any chance?
For a better surface finish you should try silicon dioxide nanoparticles. Sounds fancy, but its actually the food additive E551. The grain size is about 50 to 200 nm. It has a melting point of 1700°C and is used as drying and release agent. Since it is a food additive, it is pretty save to handle, but you should not breath it in. Sadly I cant say something about its compactibility.
When you mentioned Talcom I realized that cement could work. It is usually ground to a very fine powder. It's cheap in bulk. Would help suck out extra moisture. Not flammable. etc. Have you also tried plaster of Paris with this method?
Bingo. I second the motion on dual extruder with HIPS. Will also try using non-dissolvable high temp formlabs resin printed to fit the inner diameter of a PETG tube. One of my goals is to preserve dimensional integrity as well as surface smoothness of PETG
Print the outer layer from a high temperature material, and the main part from a low temperature material. Melt the inner material but not the outer material, then peel off the outer layer. Just requires two materials which won't bond well to each other.
You can probably get away with using ordinary coarse salt then, as you don't care about the finish of the outer layer. Not sure about the problem of grains of ordinary table salt not being able to stick together though, maybe adding a heavy weight or some kind of clamping container would solve this?
I did this with PVA, it werks :) Preserves the original texture of the part when the PVA doesn't melt. (I'm using pva that prints at pretty high temperature). I'm going to do another one and try to get the PVA to melt as well during remelting, see if it makes a smooth texture. Now that my thermocouples arrived I should have a bit more control over the process.
I really love that you are doing real science with controls and graphs. It makes it so much easier to understand what is going on. Thank you, professor!!!
A ball mill would be excellent in making the fine salt. Edit : I would also like to see what happens to CF Nylon. What would be also interesting is using Epson salt that has had its water bonded to it boiled off. It make a powerful desiccant and can protect the parts like nylon when it is up in temperature. Don't forget to probably hold the nylon at a temp to dehydrate it before going to the melt stage. You will need a hammer and ball mill to powderize that stuff as it cools down into hard cement.
You beat me to it. I was going to suggest getting an inexpensive rock tumbler, the appropriate balls (would ball bearings be appropriate?) and just let it run for a couple weeks.
Yea I second the ball mill idea. Cheap and safe way of getting more fine salt in one go. Also consider a desiccant or dry nitrogen to store the ball mill in while running or run it at temperature i.e. 50 to 70c? To dry it.
Wow. You guys are just amazing. A comment from another video that induces another investigation, which at the end opens another dimension to create funcional parts with better properties. Hats off to all of you! Thanks!
Hi, I managed to easily make powder salt. Mix equal parts of regular salt with water then put it on a blender or food processor. After blending for some time you can transfer the mix to a regular pan and boil the water away (for safety, with some kind of lid that lets the vapor out). You can process all of the salt in one batch, and what you get in the end is dry fine salt.
I needed flour salt a few years ago for silver refining and i just put the coarse potassium chloride chunks into a coffee grinder and then finished grinding in a mortar and pestle. Sure, it was a tad laborious but it came out unbelievably fine.
@@turtledruid464 , sand will stick to the melted up surface of the part. Salt has the great advantage of dissolving in water, so you get back the pure plastic surface with little effort.
I have an idea. To avoid those gaps in the material, those pieces can be printed with extensions, so that when the material melts, it flows or descends and fills the gaps.
I'm wondering if this method could also be used to fuse parts together. You could maybe connect two parts with a dovetail connection and the melt them which may lead to a permanent link
This version misses, or rather, improperly tackles an important step. The grain size of the salt. What another person did, in a different write up- not free spirit, my mistake-, was hand ground the salt, likely in a mortar bowl. This allowed him to get an extremely fine grained sample. Your blended sample could have done better with grinding, where you can sieve through to under 400 micron. Sieve is also an important step, to maintain a consistent grain size, for consistent surface finish, and allow the transparency shown in the other users channel. And as always proper PPE, any dust is bad, but the salt especially so.
Good point. Fine and consistent salt is important, though doing several kilos in a mortar is not very practical. I'll be doing more tests on that topic.
@@CNCKitchen Definitely sieve for consistent grain size tho and the surface finish would probably look superb. A ball mill would be the easiest option if you have the budget.
Use sodium carbonate. Sold in any supermarket in the washing powder section, cheaper than salt, dissolves in water, melting point is 850C. Super fine grains. Don't confuse it with baking soda, its melting point is just 50C. Also - consider applying a bit of talcum ("baby diaper powder") with a brush to the parts - they will separate more easily and surface will be better protected.
wait wait wait, could you just use talc powder instead of salt? It's really fine and as i found, it's melting temperature is also about 800 degrees C, would be really cool if it worked
also some information about baking soda: "Baking soda, or sodium bicarbonate (NaHCO3), is a chemical that can undergo a decomposition reaction when heated. At temperatures above 176 degrees Fahrenheit (80 degrees Celsius), sodium bicarbonate starts to break down into three compounds, forming sodium carbonate (Na2CO3), water (H2O) and carbon dioxide (CO2)." So you can basically put the baking soda into the oven for some time at the temperature higher than 100 C and get sodium carbonate
I'm sure you could use talcum powder but on Amazon that stuff's expensive, 500 grams is $30. You can get 4500 grams of sodium carbonate for $20. Sterile talc powder has a grain size between 0.399 μm and 100.237 μm with a mean at 26 μm. Sodium carbonate is slightly larger at 115 μm, you might be onto something coating the part in talc powder and then packing in sodium carbonate. Edit to add if anyone decides to use talcum powder wear a respirator and be very careful about not breathing it in as it is not water-soluble and can lead to lung damage and cancer with prolonged exposure. Also sodium carbonate can cause you to go blind if it gets in your eyes and it can cause scarring in your lungs. Wear a respirator if you're going to use either of these powders and avoid creating dust when working with them.
@@88Timur88Bahmudov88 if you check the packaging most powders these days are talc free. Be sure to check out the safety data sheet for this and any other powder you intend to use. Sodium chloride (table salt) is relatively safe even if mishandled, and almost any chemical is safe if handled properly.
I'm sure someone has said this already, but I did a Ctrl+F in the comments and didn't see it. I found fine powdered salt sold as "popcorn salt" on Amazon, hopefully that helps someone, maybe a fellow viewer from the US. I also wanted to mention, I've learned that printing at 100% infill prints infill at the speed of top/bottom layers (at least with Cura) but any non-100 value will use your infill speed, even if it's effectively 100%, like 99.999. Big fan of your videos, you cover a lot of great printing topics, thanks for all your hard work!
@@alejandroperez5368 vapor smoothing done carefully enough doesn't make any meaningful dimensional difference, it just takes the high ridges and averages them into the valleys a bit. Though it is very easy to go too far and make a massive mess destroying the part, its quite possible to do it without doing so - but its hard to get highly consistent just right results. So I'd love to see if the salt crust messes the process up too much.
the porosity and vapor smoothing would likely result in a interesting finish that is not 100% smooth as I theorize the vapors would puddle in the pores.
Perhaps you could try it with baking soda. It's available at much finer grains off the shelf compared to salt, and should also draw water out of the print similar to salt. When I tried it myself, I got the same foamy surface you did, but with finer bubbles. There was discoloration of the pigmentation as well, but I'm not sure whether that was from a bleaching effect or poor temperature control on my part.
@@JuLian-cq2qv I was intiially concerned about the CO₂ issue as well, but could not observe any change in shape of the top surface of the mold, so I think that it was probably able to escape without damaging the mold.
I'm thinking Sodium Carbonate is much more fine and is easy to make and or buy instead of Salt? Heating the Baking Soda turns to fine Sodium Carbonate. Maybe it's stupid idea.
Use a flour sifter to remove the final large particles. After you pack the part in the salt, you could vibrate it to get it to settle in really well. This is kind of like black sand casting.
What I can notice is that melting and solidifying removes any gaps in the printing process, giving the pockets after the melting and cooling process. The best solution in this case is to make negative molds. 3D print your part, polish the surface in manageable pieces, put your pieces together and then make a high temp mold. Afterwards, you can take plastic pieces and make a funnel to get the pieces to melt into the mold.
@@buckithed It was 3d Jake's clear PETG. I mixed small portions of seasalt in blender. Now grain size is really small, more like dust😃. You have to ditch part really well in the salt in order to get off with least amount of deformation. Also make sure that printer really prints at 100% infill. In slicer I put 100% infill but it still did get squeezed in process of remelting.
May I suggest experimenting with cement as a medium? Also, if you have an ultrasonic cleaner lying around, try using that to compact the material while filling.
I don't know if someone else had made this suggestion before. Not that i've read untill now. I would add a vibrating table to the process of compacting the salt. Think that'll be usefull to compact the salt evenly without relying in human force and, maybe settling a more consistent result. i believe that this test has a lot more potential to give us answers
@@Yrocsrelles the thermomix bowl is grounded therfore there would be no ststic buildup. but salt is hydroscopic so it is more likely to be caused by humidity.
The advantage of using salt is that it's easy to remove the outer layer with water. If the stone powder is really fine and compacted might yield a better outer shell
@@BaristaPablo "stone" could be any mineal - like he used plaster before he can switch to bentonite or talcum, which is very cheap and also can be washed off in water afterwards
@@CNCKitchen What about spraying the part with a saltwater solution to coat it with the dissolvable salt, then pack it in a material that transfers heat better like greensand, silica, or talc? Also, would love to see how much stronger/stiffer? This method would make nylon prints.
Very interesting results. I wonder if dipping the parts in a clay slurry, let them dry, then dip them again until you build up a shell would work. Look up the lost wax process for metal casting. The salt lets the plastic expand as it becomes hot so you might need to put some sprues on the part for the plastic to expand when hot and contract when it cools.
You found something pretty big. If you had small beads of PLA and remelted them in salt you could create beats with a high surface are for a variety of application. Some that immediatly come to my mind would be biofiltration in ponds and aquriums and immobilaziation of enzyms and katalysts on the highly porous surface to use them in a reactor. Someone could even immobilize microorganisms like yeasts in those pores and use them in some sort of fermentation process.
Hey, i did the same thing with plaster-powder in my kitchenoven at 210°c with Pla for 1h in a glas and ist worked perfektly ! I even can reuse the powder aslong ist stays dry. That video opend a new horrizon for me , thank you very much :))).
I think maybe the plastic needs some kind of coating to keep a cleaner outter layer after melting. The salt results look great for strength, but surface details are also important, especially if making the part for a cast.
Did you consider using a vibrating table to compact the fine salt around the printed items, so to avoid having air bubbles around complex objects? after vibrating it you can still proceed with layered top-down compaction. Also, it would be nice to use boron salts, but you could also go to a marble cave and collect some marble powder (it is usually mixed up with water due to the stone cutting process, so you'd need to wash it, filter it and dry it beforehand). It is not soluble in water though. Baking powder would be soluble, but I think it would release CO2 bubbles when heated, so it's a no-no...
Salt density is notably higher than PLA density (2.16 vs 1.24) so if you're vibrating the compound (like to extract bubbles from poured concrete) the printed parts will rise to the top as if they were bubbles. You can try this fun experiment by placing a river pebble on top of sand in a beach bucket, and burying a cork at the very bottom: when you vibrate the bucket, the pebble will sink into the sand, while the cork will rise and pop out!
@@mariosebastiani3214 Right. With the risk of reintroducing air when finally removing the finger, but air above the part is not as bad as air under admittedly. However the other problem is the powder cannot be fully packed down by doing this. One could mitigate the issue by using very thin removable metal rods, properly securing the part temporarily while vibrating.
Came back to this after seeing Integza’s home sintering of 3D printed metal aerospike jet. He was using carbon layer on top of the supporting granular sand-ish material to prevent oxidation. I think you can re-melt ABS at much higher temp without little or less oxygen to get insanely strong parts, it won’t turn brown unless it’s the pyrolysis.
The electronic stuff seems like a waste of money or even a liability though (failure point). Would be nice to just have dumb products of high quality or more features.
I wonder if one could add some kind of membrane between the 3d print and remelt material, such that it doesn't affect the surface finish as much. For flat surfaces maybe something like aluminium tape, or maybe a thin layer of silicone?
There are water dissolvable filaments, so if you have a printer that can do multi material, you could print an exterior layer of it that will fully dissolve with the salt.
@@TerminianLinkVT Yes but that stuff would just melt off during the remelt and mix into the part. Whatever is used to coat it would need to be able to tolerate the high temperatures and keep shape.
Did you try dipping the part in salt water, then letting it dry before compacting the fine salt around it and remelting? There was a mention on free spirits site how this might be a good way to get perfect grain free surfaces. Seemed like a good idea.
this is actually very smart, i was thinking a similar thing: 1) get salt water and boil off the water at no more than 100C, which should coat the part, and then put the salt-coated part in a lot of salt and anneal 2) first use a conventional postprocessing adhesive (like spray adhesive) to adhere salt to the side, then bury and anneal. The general theme being: don't let the packed salt directly touch the surface
The main benefit I'm seeing from salt is that it's water soluble, so it's easy to get off your parts. Something like green sand will give you more cleanup work, but it might be worth it. Three experiments I'd try if I were investigating it: - it would be interesting to try non-melting powdered sugar ... it's supposed to have be temperature and moisture resistant, but perhaps easier to get hold of? Shame the working temperature is just a bit over the point where normal icing sugar could be used - how about using an ultrasonic step, to get the salt to flow into gaps, prior to compacting? - just as an off-the-wall thought ... instead of trying to crush salt in a blender, how about throwing it in a rock tumbler for a while? it's slower but you can probably throw a large batch in and just forget about it for a while, so it might work out.
So I realize a bunch of people have made a bunch of suggestions, but I went and dug around, and the melting point of talcum powder is only 1C lower than salt, and plaster of paris is a whopping 650C higher than salt. And both of those come from "the factory" with a very very fine grain. Might be worth considering. I say, 3 years after the video came out... :D --- Oh, you mention that in the video. I guess I should watch to the end before asking questions. :D
You blended salt with a thermomix?! That can't be good. I would really suggest using something like a ball grinder, it can grind even rocks into a powder without any damage to the parts.
There might be some in very limited scenarios. Risers are a bit more complicated in metal casting because they are designed (often through trial and error) to facilitate the injection process, to balance flow rates through the die, to deal with the metal cooling or swirling in portions it shouldn't, etc. Much of that is already being handled, here, by the printing process, itself. The dimensional changes are mostly coming from the salt grains creating voids for the plastic to seep into once made liquid. Injection molding is part of my upbringing, and it's still more of a dark art than many people realize. There are around 80 diecasting factories in the world (for metal) if that gives you any idea how powerful yet small the trade is. You might be able to use that method to, say, use a high degree of infill and then create a riser where you can add bulk material to it. However, there would be no inherent pressure aside from gravity, and you would be trading one void for another in the packing. I suppose you could play around with some kind of springloaded injector. Once the mass goes liquid, a spring would push the plastic into the voids left by infill. Venting, however, would likely be necessary to allow displaced air and gas to escape. It may be able to do it through the packing, but this method would be closer to what is called drop forging or sand casting.
What an interesting and weird hybrid process! I wonder if this could be improved by wrapping the 3D printed parts in some higher temperature foil to avoid the mixing of salt. Or maybe spray painting them with some sort of (flexible?) paint coating. I'm also wondering why lost form casting metal works without mixing in the sand particles, but here it's a problem. I think if I needed this for a specific part to be really strong I'd rather look into how to use the 3D printer to make a mold for epoxy based casting.
It may be worth trying fumed silica or fine mesh silica. Fumed silica is easily found online, and the fine mesh silica can be found at most local pottery supply stores where clay artists purchase materials.
Anyone have a good reference for the thermal conductivity of talc? All I can find is paywalled articles (why is scientific information is so locked down in this Information Age?).
@@spagamoto I googled for thermal conductivity of talcum powder and a quick scan through the freely accessible pdf put a compound of 30v% of talc at 0.59W/mk thermal conductivity but cannot find anything else as of yet
I'm thinking kaolin, ball, or bentonite clay might also be a good option. It's already finely powdered, compacts easily, & has a sintering temperature far above those required here
I don't know Kaolin, Betonite might shrink so some pre processing might be necessary. This could also mix with sodium silicate The grog I use (fire clay) is not far off Bentonite, I use fire clay in stovevs, it shrinks like mad from wet, hence the grog.
Or maybe even baking soda with the advantage of washing it out of the pores with a vinegar solution... looks like 320 mesh from a quick internet search.
When i watched the video i was thinking about oil bound sand for metal casting and talkum powder.. Both are very fine, can be compressed and should work without preprocessing
Following idea: use a silicone mold for the remelting I've created silicone molds from 3d printed designs for making Christmas themed chocolate. The pouring of the silicone works reasonably well and the silicone should be able to withstand temperatures of up to 200C. The molds can also be reused for the next print with the same shape. Would be worth a try. Maybe I'll give it a shot with one of the molds.
I think the ultimate technique is to undersize the part (enough to account for the coating) and coat with some thermoset polymer like epoxy. That ensures the salt doesn't mix with the outer later. Also, if your part geometry lends itself to it, you can print it empty and coat+fill the part.
Have you tried greensand like they use for sand casting? That holds together really well and in theory should work really well for this kind of process.
@@MLP4242 Could also use delft clay. You can actually make your own casting sand and pick the grain size. Some people can reproduce fingerprints so I can’t imagine there would be a problem with resolution. With metal the bigger grains are better at expelling gases so generally the larger the castings the more corse the material used will be.
I use a ball mill (basically a rock tumbler) with round porcelain balls. This process is like the process used in mining to prepare ore for processing. The resulting material I sift the material through a 100 mesh screen to equalize the grain size.
Hello I'm a chef and I wanted to let you know about easy way to make powdered salt you can use sea salt and a coffee grinder. Or any machine capable of turning something into a fine powder you can use table salt however I find it's more consistent when you use what we call sea salt or kosher salt in America. Besides3D application printings it's a great way to get restaurant quality taste at home for anything that requires it, popcorn, french fries and any food where you want the salt to melt on contact.
Im curious if adding a bulb of material(3d printed to the part) on the top of the z access would allow for excess material to flow down and fill voids/air pockets in the part. Maybe add this material at different heights to make sure it begins melting prior to the rest of the part.
I already tried this and it doesn't work that well, you can see that the plastic doesn't flow as well and the salt bonded layers won't let the plastic move that good.
I was thinking about the same. It would be interesting to try to print the shell of the object (minimal infill), put a metal funnel over it with grounded failed prints and heat it only from above at the beginning. Like sand casting of sorts.
Hi. I was aware of that. Anything that melts quickly by the hot aluminium (even polystirene) can be used. I was thinking about melting the PLA slowly, with the model encased in something that can take that heat without deforming or letting liquid or gases out and also being reusable. Something like plasticine perhaps, but with no oils in it. Or clay. I believe it can be rehidrated after being backed at 250 Celsius for hours, but I dont know if it can hold its dimensions.
A good question to ask is if the sodium chloride is reacting with the offgassing styrene byproducts to cause the discoloration or is it a result of the heat.
i used polycarbonate for the same process. PC turned brown after 45min in 220°C. changed to 180°C and 20min and it came out perfect. noted the time is correlated to the size of container.
My thoughts are that this works because, firstly the compacted salt acts as firstly a structural support to support the melted material so the object can retain its shape, whereas if you just baked a 3d printed object in the oven it would just melt and deform freely with no support. Secondly, salt has the ability to draw out moisture in the parts which may explain some of the surface bubbles on the outside of the object and the uniformity inside the object as seen in the test parts that snapped. Thirdly the properties salt allows for great absorption of heat allows as you mentioned in your video "salt takes along time to heat up" this in turn acts as an "insulation" from the direct heat in your oven allowing you too evenly cook the whole object at a much more even temperature without burning the outer layer, while allowing you to melt the inner layers together promoting layer adhesion. This process is similar to how you would sous vide food (submerging food in an airtight plastic bag and cooking it a set temperature over long hours to get a precise even cook temperature throughout, amazing technique to make perfect doneness on steaks :D). It would be interesting to see if you can do something similar with clay (also a good heat conductor) or other heat insulating mediums rather than salt as a the support structure medium and the heat transfer medium, this would allow us to determine if the moisture drawing properties of the salt plays small or a big effect in this process. Great video, thank you for sharing your results!
I come from a pyrotechnics background before 3d printing. I would suggest getting a ball mill to powder the salt. You can get much lower micron/mesh size that way. I believe it's more uniform as well but fact check me on that.
I have an idea, Mark Rober has a video about making sand a non-Newtonian fluid using ultra sonics - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-My4RA5I0FKs.html In theory, wouldn't this allow the sand to better adhere to the part? It would act as a more efficient and much faster version of what you're doing with compacting the salt and shaking it around, I bet you could "activate" the salt, sink the part into it, turn off the vibration, compact it down as tight as possible, and then anneal it. There are ultrasonic vibrators that you can purchase from Amazon, people use them to make cookies, I might just pick up one and give that a go and report back with the results EDIT: He doesn't use vibrations, he uses air injected into the sand from underneath, however (imgur.com/V1DyB2H) here you can see when the ball is ejected from the sand, it still has sand perfectly contouring around it, I bet a similar setup could be achieved with sand, just let the part rest in the middle and turn off the vibration and I think it should adhere quite nicely
A combo salt oven + fluidized bed would be a pretty slick commercial product to make post-processing prints a snap. One could even sell the premilled salt.
I don't think this would work, because you do the exact opposite of compacting. But using vibrations might do the job. The main issue here is to get the frequency right. I'd say this might be grain size dependant, which makes it difficult. I kinda like the idea mentioned in another comment, using a vacuum bag. Combing both vibration and bag would make that compacting way more efficient.
Definately a good method! But expencive, and you might as well use the resulting silicone molds to cast items from epoxy filled with chopped fibers to achieve strengths absolutely unattainable it "budget" 3d prints :)
Brush on with ht silicone leaving a vent on top with some additional plastic on top, place it in normal salt in heated vacuum chamber. The salt will act as heat distributor and support. Venting in vacuum will get the bubbles out. Maybe some moisture will go into the salt during the process. Overkill but science needs sacrifice :)
@@CNCKitchen Plaster will recristalize with sodium carbonate forming calcium carbonate. If the latter cannot be rubbed off it will dissolve in weak acids.
@@prolfinator It could work, but handling would be difficult, since Portland cement is very alkaline. Washing would be difficult as well, as wet cement dust can be quite dangerous.
I think I'll try this technique using glass beads for blast cabinets in an argon atmosphere. Glass beads can be purchased in extraordinarily fine diameters and the "melting" point should be sufficiently high to work. Perhaps the argon will prevent porosity.
I would really recommend using a vibration plate while filling and compacting the salt as it would do a much better job filling in the voids of the model.
I'd love to see a comparison of a single material (PLA) and how it reacts being remelted in different materials. Sand, greensand, salt, talc, flour, corn starch or even something more exotic like graphite. :D
Should add fine metal powder to that list. The metal would bind to the plastic part, but it would have a very tough abrasive resistant surface if used.
Well, that is very, VERY interesting, in a rather unusual way. By itself, it will not work: the *salt* method is uniquely great because it clumps and maintains shape w/o a binder (which gives nasty vapors under heating). But! When you add a bit of graphite to the salt, instead of baking the stuff for hours in the oven, you can can bake it for 5 minutes in the microwave! More that it, carbon or grafite filled plastics will take even less, and if you print them in a zebra stripe or coaxial filament - is is very likely you'll be able to fuse the layers but maintain hollow structure! There is a paper online where they did just that, but using a very thin nanotube coating - you don't even need to bury the model in salt... but it is complex. Still, very interesting and worth experimenting with.
This is such an interesting result! I wonder if it's possible to make parts that retain the strength of this method without the disfiguring of the outer surface
@@kundeleczek1 I was considering the use of silicone as a coat. It could be high temp. silicone, but maybe standard silicone is enough. It can be brushed onto the part. Off course this is not a cheap fix, but very effective!
@@kundeleczek1 Yes, silicone is soft, and I wouldn't expect strong bonding between the print material and silicone. You will only have to brush a protecting thin coat of silicone on the print. The salt would create the necessary support during annealing. After cooling down, I would expect that it's possible to peel off the silicone skin. If not, you will have to use a wax release on the print. I haven't tested this :-)
This was a very interesting experiment. I know my input is late on this but it would be great to see an revisit on this subject with other powder like substances. Salt is highly corrosive and though the idea to make something like this work is there, the surface layer would never look that great no matter how thin the grains of salt would be. I would love to see this experiment done again with powders like Corn Flour for example, or Talc Powder (also known as Baby Powder), which are very thin, non corrosive and safer. Not sure what kind of temperatures they can handle though so this would be really interesting to see the results. Keep up the god work Stefan. :)
