The STRENGTH of 3D prints REMELTED in SALT
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- เผยแพร่เมื่อ 1 พ.ค. 2024
- Everyone is currently talking about 3D prints remelted in salt, but how strong are they really? I printed parts in DasFilament PLA, ESUN PLA+, DasFilament PETG and ESUN ABS, and remelted them in salt. I've also been looking at different salt grain sizes and the temperatures that are necessary to properly re-melt the parts. Let's find out, if we can get 3D prints with the strength of injection molded parts!
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Chapters:
00:00 Introduction
02:40 Which salt?
04:55 Putting parts in salt
06:53 Heat treatment
10:07 Dimensional change
10:48 Strength test
17:14 Promotion
18:29 Outro
#3Dprinting #remeltingInSalt #science
DISCLAIMER: This video was sponsored by Audible. - วิทยาศาสตร์และเทคโนโลยี
Those benchies that weren’t printed at 100% infill look like shipwrecked benchies that you’d find in the deep ocean
You could design your prints to be filled with salt as well as having it packed around them.
@@Wingnut353 not sure if you know what’s going on here
Cause they don't float
@@Wingnut353 ?
Those are the ones that look the best
Bake your salt for an hour in an oven BEFORE blending. This drives out the moisture first.
Wouldnt the salt just absorb water out of the air anyways while he's trying to pack it or break it up in preparation for packing?
@@spacegooley3796 Yes, but providing you work fast enough you should be ok.
@@michaelakerman7609 If you coated in a heat resistant enamel (that held the shape of the part), when baking maybe you wouldn't even need the salt
@@WaynesStrangeBrain sounds like a nightmare for moving parts
@@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.
Or do it in zero gravity so the bubbles dont rise.
@@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.
Try a little bit of over extrusion, I made a vase mode turbine blade much stronger by over extruding.
If the bubbles don't rise you don't increase density or get rid of stress concentrations
Do it in vacuum
"expensive blender" is the most accurate description for a Thermomix i've heard so far
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
Fantastic idea to use a PVA outer layer.
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.
Brilliant video. Excellent job!
Thank you very much!
Happy to see my favorite TH-cam content creators in cooperation :)
Of course you'd be watching this video too 😂😂Love you man; you're an amazing role model for all engineers
Hey Destin, Are we going to get a "3D printing on a submarine" video next? ;)
@@mnp2169 He already showed us how they slice a pizza
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.
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? :)
200°C as a melting temperature is lower than some of the oven temperatures used - it sounds a bit too low to risk it...?
@@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
As in cornstarch? It's a very fine powder, inexpensive...... and definitely worth a try. Oh yeah..... it's non corrosive...
@@the23erwhat video did you just watch?
Nice job. Free spirit deserve a shout-out for telling us about this amazing technique. 90% strength of injection molding is amazing.
Is it thought? I thought he'd achieved 90% of the non-crossectional strength? Is that actually the same as IM?
@@JohnDriggers So we need to injection mold test samples? 8)))
@@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.
Thanks for the shout out!
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.
@@idekman5427 Maybe he is making bath salts.
@@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.
@@alaskanalain which is more or less what sterimar is.... :)
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.
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.
Could you produce and upload a video demonstrating you process?
@@VaticansHolocaust I would be glad to. I have been working on other projects lately so it might be a while.
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?
You don't watch enough you tube. Shame on you for being a ME with out having done your number crunching
@@rrtsduf what the hell is this comment supposed to mean
@Steven Tran - Doesn’t every German home have such a test rig? 😁 Cooks use it for pasta testing and meat tenderness testing... endless uses!
Well said. I agree with you from industrial and academic standpoints. However, let's all remember that this is a TH-cam 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.
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.
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.
Also heating it while under vacuum seems like the optimal way if you can manage this in some way.
Aren't there specific sous vide cooking thermometers that are basically made for that purpose?
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?
I was going to recommend this as well. Just be careful with how much dust it can produce
I'd be very interested in seeing more videos about this, and especially testing different "fillers" instead of salt
The salt you want is called "pickling salt". It's much finer than table salt, has no anti-clumping agents, and is available in bulk at low prices.
Really? Around here, pickling salt is extremely coarse. Can barely run it through a pepper grinder
@@Yankeeprepperasshat Yep. It's very fine grained so it dissolves quickly in cold water. I've never heard of pickling salt that is coarse.
@@Yankeeprepperasshat Same here. It looks like the salt you'd put on a pretzel.
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.
@@devilwarriors5164 That's my city's salt mine, awesome to see someone mention them!
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.
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.
Großartig! Nach Deinem Video über das Tempern von PLA und dem umständlichen Eingipsen hatte ich genau diese Idee. Danke, ersparte mir viel Frust!
Germany:
✓Computer controlled blender with touch screen
✗Popcorn salt
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.
ive got one its an awesome tool XD
I like that behind the touchscreen is a series wound motor, as AvE would say Will it Chooch?
@@equakebilly isn't it just a thermomix, I've got one to but it doesn't refrigerate just heats
@@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.
What if you used a dual-extrusion to print an outer shell of a different material, then have it dissolve away? Maybe HIPS?
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.
Excellent concept - or perhaps some sort of release agent, spray/dip in wax, the wax would melt sooner and cause the salt to form a smooth crust
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.
Awesome video as always! :) ... For fine (and uniform!) grinding salt it might be worth looking into either burr grinders (espresso coffee) or dedicated flour grinders (should take care of the dust as well).
very high quality information here
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?
Remember to wear respiratory protection if trying those materials. You dont want those inside your lungs.
I think it's a great idea, needs testing
Haaa... Finally, the most awaited print post processing method...
Will be testing mine in the next weeks.... Thanks for testing Stefan.
Wow. Your videos always impress me. Love it.
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 think you can skip the blending step. I think the salt dissolving is what makes it fine.
@@stinkiaapje It can become saturated and no longer accept more salt into solution. Not sure what that point is, but worth a mention.
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.
a cheap burr grinder with a ceramic burr would be ideal
You could also use calcium chloride, it loves to absorb water. Here in Canada it is sold in huge bags during winter.
@@marc-andreservant201 What about Gypsum powder dried out
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!
Thanks!
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!!!
3:47 lacks "Salt smoke - dont breathe it!" :‐D
I've used a ball mill to grind materials to a very fine powder. I think that would work really well for salt.
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
You also could melt in steel rods for structural strength in left out channels
@@gandhizehner this could be difficult as the steel rods might sink and tilt over until they rest on the salt, when the plastic is molten.
@@gandhizehner no need the steel will be strong enough, no need to melt it into the rods when cheap epoxy would do just as well.
@@mattbechberger3298 Easily fixed by oversizing the rods so that they extend outside the part and into the compacted salt.
@@LanceThumping that may not suite the final product, having rods sticking out at both ends, not ideal
Lots of work, but it's much appreciated. Thank You
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 :))).
Wow! Each video on this channel is incredibly detailed and precise, keep it up Stefan!
Glad you like them!
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.
Ahh the trusty mitutoyo absolute series👍 love seeing good grade equipment being used
Great tests. I'd love to see what it does with nylon, both in strength and impact.
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Now try clay slurry and sand multiple layers @
@CNC Kitchen i think you made the same faux pas like you did on the plaster. i mean the task of the surrounding medium (plaster,salt, whatever) is just to hold a tiny object which weight is under 50? gramms. So there is no need to surround it with 20x of plaster or salt. try tin find the edge, the smallest amount of powder which works for the size of the object you want to test. This means use smaller buckets or other forms which fit better. (You can find cheap stainless steel forms/dishes/buckets for kitchen supply in so called "1euro stores"(or similar concept stores like thomas phillips or Pfennigland))
another idea is use silicone and add a mm thick layer on the parts (let it dry ofcourse), and then put it in the sand/salt, this can make the porous surface disapear
are you romanian
I think the original guy said he used a real coffee grinder not a mixer/blender to get the fine salt. So he grinded a lot of salt till it was just really fine and now reuses it all the time
If all you need is a fine power that can stand a little heat then limestone dust (whiting, calcium carbonate) would be a lot easier.
You could also use something like sea-lite aquarium sand. It's fine enough that it's used by chemists as a filter material.
@@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.
maby sodium chloride powder?
Maybe just use baking soda 🤷♂️
@@381delirius Baking soda decomposes into washing soda below those oven temperatures. So, no.
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.
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. :)
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.
@@CNCKitchen You could try getting a kitchen grain mill from amazon (normally used to make flour), they shouldn't be too expensive for an experiment
@@CNCKitchen You could use a wet grinder, like Alex used in grinding Cacou Nibs: th-cam.com/video/g-F8zL3Ufi4/w-d-xo.html
Ball mill. With ceramic media for preference (steel would probably stain the salt and then the parts).
Definitely excited for a follow up with the other casting media.
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.
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.
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.
@@cchamilton1985 wow, talc can cause lung problems? I didn't know, it's used for baby's skin, so i thought it’s completely safe 😅
@@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.
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 tried this a while back. I used a cobbled together ball mill to pulverize the salt and it worked really good.
You are a researcher and a scientist by the very definition of what you have done here.
Next time I want to see this with different powder substrates!
YES BEEN WAITING FOR THIS EXPERIMENT
Well done stefan may try it I use my printer to make mechanical parts regular printed parts are 90% fail this will give them the strength need I am mostly interested in that outer layer I maybe a new way to get perfect adhesion to paint or resins
Just saw you in the last video for the first time... Nice to finally see a face to the voice! Moin moin und grüße von der côte d'Azur!
I still haven't gotten my first 3d printer. I subscribe to several channels on the subject, but only passively/occasionally watch any of them. I have to say, this channel was suggested by the YT algorithm a few weeks ago, just after watching Naomi's Creality belt printer prototype vid. I keep coming back and watching your uploads when I see them in my sub feed. It's well presented, concise, consistent, and most importantly interesting.
Not that it matters, but the shaker screens used to sort rocks after the crusher at a rock quarry or asphalt/concrete plant, usually has 3 or more screens in a (huge) box. The ones I've worked on are around 10 meters long in the direction material travels, around 2 meters wide and the box is around 2.5 vertical meters not including the stand that holds it at the right height for conveyer belts. Inside, the entire shell surface has bolted on steel wear plates. The screens are progressively smaller the lower they are in the machine. There is just enough room to belly crawl between each set of screens. The screens are made for the width of each machine. They are around 1.5 meters long and just butt against each other. The sides of the screen have a steel flange with a 90 degree angle. This is clamped/bolted to the sides with plates. Under these plates but on top of the screen there is a strip of silicon around 10cm wide and 2.5cm thick. This is how the "seal" is made and how excessive screen wear at the clamps is avoided. The bolted plates and hardware get replaced periodically as needed, but the screens won't fail at the edges.
The entire deck is tilted down at 30 degrees. It is steep, but possible to sit/lay on it when replacing the screens. The box is mounted on the bottom to heavy springs about the size of automotive truck springs and there are smaller height versions with rubber bumpers on the sides of the box's frame in case the vibration has a bad resonance or material gets distributed badly.
Anyways...the real reason for all this blah blah blah...the machine is free to shake and oscillate pretty violently. It does this using two large motors. One spins fast with a small eccentric weight, the other spins slowly with a weight around 10 times the size of the other. If either motor fails, the machine fails and overflows in minutes.
Inside the silos that store both dry material and hot wet asphalt there is a shaker system that is very similar with two motors only smaller and less violent. A scaled version of a shaker like this would work well to yield a precision screened grain size.
The shaker screen part of the plant usually has water sprayers to suppress dust. However, one other thing of note with asphalt plants specifically, the rock must be heated in a giant "drum" - a cylinder on it's side. The thing is around 20 meters long and 3 meters in diameter. Inside material travels up hill at a ~5-10 degree angle. Shelves ("flights") inside the drum take material to the top of the drum and drop it in front of a burner that blasts a flame the size of the drum down it's length. Yeah..THAT big. The burner is as big as a car. As the material dries it travels up the drum. The flame temp and drum rotation speed control the process. The hot black liquid asphalt is added at the exit of this drum once the aggregate is the same temp as the liquid asphalt.
If you think about this, it makes sense that this drum produces an enormous amount of dust that has to go somewhere. That somewhere is a giant "bag house." Its a metal box the size of a small studio apartment with high ceilings. The box is connected to the exhaust from the drum with a large air duct. Both machines are always directly beside each other, and the air duct to the bag house is vertical. Only the particles that can float in air go in, and this is tuned to allow as little as possible too. The drum burner is run as close to stoichiometric as possible to meet emissions regulations and usually burns natural gas in most plants.
Inside the bag house there are 2 sections. There is a deck around 20cm from the top of the box. This deck is covered in a matrix of ~10cm holes spaced as close to each other as structurally possible. Inside each hole is a tube like wire frame that extends the full height of the box. They are very long. On the outer surface of the wire frame are high temperature "socks." They are a heavy, Kevlar like, material, and look nothing like a typical air filter.
The whole machine works like this. The dust from the drum is dumped into the lower chamber of the bag house. The upper chamber is connected to a massive airflow circulation system, - the size you'd expect from a skyscraper. This system sucks air out of the top of the bag house pulling all of its air through the hundreds of long socks inside the structure. Around once every 2 seconds the entire airflow system is reversed and a powerful pulse of air is sent in reverse to clear off anything stuck to the socks. The dust is pulled from a trough in the bottom using a screw auger.
This dust is a waste material that usually goes into industrial 2 ton bags and gets trucked away eventually.
Here is my point: this dust is unlike anything I've ever seen elsewhere. Once cooled, if you put your hand in it, you would swear your hand was in water. If the humidity outside is low, you'll be able to put your arm in up to your shoulder just like a tub of water despite that depth having a massive amount of material probably a half ton or more. The only use I know of for this dust is making terracotta roofing tiles. After the stuff has sat for a few weeks it turns to a solid you can barely stick your fingers in. Ultimately the dust is a clay like substance once wet. If this dust gets into water a special mucus like coagulant is required to get it out of solution. Most of it will not settle out of solution otherwise. The only other way is to let all water evaporate. The material itself is not hazardous chemically, it's just the clay and rock dust that were not dissolved and washed away at the rock quarry's crushing plant.
If someone were to call up an asphalt plant and ask the operator for a 5 gallon bucket (or few) of the stuff for a 12 pack of beer on a lazy early afternoon when the plant isn't in production, I bet any operator would be happy to oblige. I don't think you will find a finer grain medium than an airborne dust capturing system.
Just an idea.
-Jake
Great suggestion, but a little long.
For those of you looking for TL;DR, asphalt processing produces a very fine dust, as a waste product, that might be very good for use in this process.
Edit: Original comment isn't perfectly clear whether this is asphalt processing specifically, or general rock crushing/grading.
@@Kineth1
asphalt specifically. Rock crushing plants/quarries use a water based system to control dust.
For ABS, can you try and vapor-smooth the parts after annealing? I am curious to see what that does to the post-treatment outer layers
It makes them everything but dimensionally accurate
@@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.
Would be interesting to see if that works and that would also tell us if we dissolved all of the salt out of the surface.
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.
I use a high pressure air compressor to blow off salt from my annealed parts, also with the pressure up high enough and with a smaller nozzle, it can even be useful in removing pesky supports in hard to reach places
"It's better than investing in injection molding that costs more than your car" Exactly!
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.
I know you are joking but you might actually be on to something here. You are basically describing a form of investment casting
@@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.
Would there be any benefit to adding a riser, like with metal casting, of sacrificial material to the top of parts to fill in for any shrinkage?
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.
Wonderful video, thank you for all your hard work!
Some other thoughts: I'm curious to find the effect of the porous layer on the specimen's ultimate strength. A change in surface finish has an effect on the endurance limit for rotating members (S-N diagrams & endurance limit modifiers), but I'd bet it changes the material property on the exterior of the part. I'm assuming a skinny part (2mmx5mm CSA) would be more effected by the finish than a wider one (5mmx5mm CSA) by ratio of area effected vs homogeneous material. There also seems to be a difference in how much the exterior is effected: the PLA has a thicker porous exterior (13:31) compared to ABS (16:02). Maybe it's because salt is more chemically inert with ABS at those temps?
One way of getting a very fine powder is to use flour. Of course, how to keep it from burning. I put some in a vacuum sealed mason jar and it worked just fine. I guess this means parts have to be smaller than your jar and you need vacuum sealing equipment (I have a food saver) but it is an alternative.
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.
Just commented something similar. Fine for ABS, but might hydrolyse PLA. Also, it might lose CO2 and thus change its shape is used as a pure salt.
@@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.
@cnc kitchen can we get your thoughts?
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.
Take a look at foundry sand. Its highly tampable, extremely heat resistant, and less likely to react with the plastics.
Also, the best way to powder anything, is to get a ball mill. I use alumina and tungsten carbide ball mills to powder rocks for my experiments, and sand is super simple.
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.
What kind of coatings are out there that will stand up to salt and the remelt temperatures?
This is a fantastic and in-depth investigation as always. I am interested to see if talc would be more effective....
Interesting 👍‼️
🤔
I would definitely be interested in a video about remelting in talc
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
Kind of a DIY HIPping process. Makes sense. Well, without the P.
Having a matching pressure foot to either impact or push on sand might improve results and decrease temps needed.
Really great experiment and seemingly good results.
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.
I got clear finish with clear PETG. Temperature of oven was set to 150°C and it was there for about 1 hour.
what filament did you use, and how did you make the salt?
@@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.
you can ball mill the salt... it will produce quite fine powder...
I'll try.
Fantastic video. I too have been curious about talc and green sand. I also have been wondering how this salt method compares to coating the parts in a thin coat of polycrylic paint or porous sealing vacuum impregnation. For my salt I used a burr grinder and was able to reduce the table salt effectively by targeting Turkish coffee which is best with a d50 of 50-100um. I agree with your assessment that more than one small part or longer than a short run is not viable.
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.
Hi Stefan, Will it work with talcum powder? The grain size is really small, cames "ready to use" and is cheap...
really great video! Love your content, very professional! Would be interesting to see this method with different material! Do you think this would be possible with plaster powder? Like you did a while back but using the methods in this video?! I believe powdered salt isn't the best material, I'm sure we can find something more readily available that maybe even works better.
Exactly my idea (I could not stand watching him torturing his blender with salt). Plaster (gypsum?) poweder is already fine. Maybe washing parts afterwards would be problematic, who knows.
Could you have gotten better results if you'd used your vacuum pump to compact the salt powder?
You could vary the outside faces of the part a fraction larger and then use acetone post processing to smooth the finish. might be amazing.
These will be awesome techniques for 3D printed firearm technology...
My thoughts exactly.
Nice to see like minded people here. Wondering how this will work with carbonfiber PLA.
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.
just a guess but this is probably way to coarse
@@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 would really love to see this looked at some more, the PETG results were very interesting. I am very curious how this would affect something like CF reinforced PETG. I hope we can get a followup on this at some point.
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
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?
I wondered the same, maybe something like a sprayed on clear coat
Same thoughts here, maybe a thin layer of oil could prevent salt to dissolve into plastic. This is a question for a chemist
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.
@@LanceThumping Oh yeah that is true. I would definitely go with like aluminum tape or something similar at that point.
Looks like grain size isn't only to blame. Might be caused by wet salt or inpurities in the salt. As dry salt does not clump together.
Or vapours coming out from melted plastic cannot escape between grains of salt.
@@KAMIKADZE441 the vapour can defenetly escape, salt is quite pourus. good thinking
I think the clumping you saw was from the static charge built up in the blender
@@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.
@@henry67278 dry salt clumps together , thats why the industry puts in additives to avoid that: en.wikipedia.org/wiki/Anticaking_agent
Seems to me that annealing would be best suited for sanding down the pieces for a smoother finish over all. Depending on your use case the strength may also be nice but for my use case I need the ductile property that PLA+ provides without annealing with also decent strength.
Great video. Have you tried creating a salt sludge, place the parts inside and make the sludge dry? it could be a solution to all the grains problem even if it would mean huge extra work.
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
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.
I think it's "just" the Butadien gasing off and getting bad.
Excellent, a very usefull and good investigation, thanks from Colombia
This is fantastic. Would be worth it for types of mounts for my bike. Ive had to use specialized resins so far.
0:30 - i love this remelted Benchy! 😍 It's looks like ship wreck! 😀
Litterally searched for this comment. I was thinking the same.
Rock Dust ... Stone Powder ...
$5-10 per kilo.
No corroding.
No grinding.
No rust.
... but perhaps stone-coated plastic parts?
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
how about a lime/calcium based powder that could be removed with an acid wash like vinegar.
..non water dissolvable. I think that's the problem.
@@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.
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.
Use a ball mill for grinding the salt. You can build one yourself EZ with a 3D printer. Marbels work great as a grinding medium :)
Have one myself build form pvc pipes, wood, bearings, a rubber drive belt and a old hand mixer. Works great.
I have some very fine aluminium oxide here usually used for polishing, this should be pretty usable for this purpose.
Aluminium oxide is insoluble in water so it would be harder to post process.
I've talked about Talc and mixing it with sodium silicate, I suspect you could this with Aluminium (Aloominum) Oxide.
Needs to be dissolvable in water otherwise you just get a bunch of metal stuck to the surface tho
@@DrakeOola although it may give a cool shiny surface :) or glittery either!
@@DrakeOola On the other hand, that may be desirable in some situations.
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
You would need to cote printed parts with substance that will separate salt from part and salt need to be ultra fine.
@@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!
@@Fischertek you would need to spray thin layer on a print to avoid print disturbing. Isn't silicone to soft? How would you remove that silicone?
@@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 :-)
@@Fischertek @cnckitchen you need to check this out
Super fine iron powder would also allow for the pieces to be magnetic. And it's used in cold casting already which implies that it can be compacted to hold shape as this method is reminiscent of casting to begin with.
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!
@@fluxcapacitor You're right about the floating problem, but it is easily solvable by keeping the PLA part down with a finger.
@@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.
@@fluxcapacitor Or directly printing the part with a protruding rod on the top, easily removable after the remelting.
Yeah just pop over to a marble cave