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  1. #1
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    Lightbulb The weirdest DIY 3D metal printing

    I have a very eccentric, weird, unusual and strange idea. I need some advice and serious professional help.


    I'm interested in 3D printing in PLA a sacrificial hollow complex structure with 0.2mm thickness walls (Yes! That thin!). Fill it with very fine copper powder with a little borax powder thoroughly mixed. Use superglue to join halves or other shell pieces together, making sure the powder is very well compacted inside the shell. Then, in a separate container I want to make some thin plaster of Paris (calcium sulfate with a lot of water). Mix in it, some of my trimmed hair (about 5 to 10mm in length). No joke. Seriously. Please, I'm begging you with all my heart, hear me out! There's a very good useful reason for doing it. I then place the object (3D printed flimsy crappy shell filled with copper powder) in a DIY drywall box and pour in the plaster over the 3D printed shell object until the box is filled and object completely covered. Leave it to dry and completely solidify for a day. Then I bake the entire thing in a furnace making sure I'm over the copper melting temperature and voila! 3D printing in copper very complex intricate models with ease. Can it be that easy? Or am I deluding myself? The hair purpose, after it will burn inside the plaster while in the furnace, is to create very thin tubules or air holes for water and gases to escape and to prevent cracking of the plaster under intense heat. I don't want to use hay because the straws are too thick. I have to use very thin organic straws. I just can't think of anything more accessible than my hair. Do you know of something even thinner and more accessible than human hair? Please let me know. I know it sounds and looks very odd, weird and strange. I'm opened to alternatives or other suggestions, otherwise I wouldn't be here making a fool of myself with such an insane ridiculous idea.


    I was thinking to add some form of additional volume above the object, which is connected to the model by some thin hollow tube. All this volume (like an empty cube (shell) ) will also be filled with very fine copper powder providing additional melted copper to the model, in the case if the powder was not very well compacted inside the shell model.


    Could this absurd ridiculous insane crazy idea work? I have never heard of anything like this. This is so bizarre and strange. It seems to be some form of odd mix of multiple techniques. But besides all this, will it work in the end? Will the plaster hold while some of it(depends on the model) will be inside molten copper? Or do I have to mix in the plaster, not just hair, but also some individual singular fine strands of steel wool?


    I don't know who and where to ask such a thing. Am I in the right place? I don't know what this idea is, I don't know how to name it, I don't know how to ask or formulate this idea, I don't know how to google it or search it. I don't know anything. I really need some guidance, help and advice.

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Even though it's a thin shell there is a good chance the PLA will convert to enough CO2 to blow up the mould before the Cu melts. Solids convert to about 1000x more volume as a gas which is a lot more to handle than the small amount of air that will be trapped inside the mould.

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    Niculae, welcome to the forum.

    I suspect this is more of a casting/foundry process than a 3d printing one.


    1) I am not experienced in using plaster (or hair ), but have you thought of sand instead?
    "Green sand" is usually what people use at home for casting.


    2) What will happen to the PLA at 1000°C ???
    I suspect it will initially puddle down the bottom under your copper powder,
    then it might boil up through the middle, then it would carbonise.


    3) If you get the copper hot enough to fully melt, the air might bubble up through the powder.
    So your 3D print might need extra material on top, to allow for copper sinking down in the melt?




    Interesting idea. I have thought of 3D printing a pattern for casting, but never a hollow one!


    Maybe experiment with powdered Tin before trying Copper?

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by nigelpearson View Post
    2) What will happen to the PLA at 1000°C ???
    I suspect it will initially puddle down the bottom under your copper powder,
    then it might boil up through the middle, then it would carbonise.
    PLA is (C3H4O2)n

    PLA starts to soften at about 80ºC, and starts to melts at 150-160 C fully being melted at around 190C
    According to Wikipedia and, Ainali et al in a Polymer article on the thermal decomposition of PLA.
    Thermal degradation starts around 300ºC and depending on the type and amount of filler used is complete by around 400ºC
    Degradation products will gasses containing lactides and phenols which will convert to CO/CO2

  5. #5
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    Quote Originally Posted by BobL View Post
    Even though it's a thin shell there is a good chance the PLA will convert to enough CO2 to blow up the mould before the Cu melts. Solids convert to about 1000x more volume as a gas which is a lot more to handle than the small amount of air that will be trapped inside the mould.

    I posted this same mad idea on 3dprinting.stackexchange.com and they were confused saying that the PLA would melt and lose its shape before the copper inside would fuse together. Of course the PLA shell will melt. I'm counting on it. Didn't I said the word "sacrificial"? It is supposed to melt. The sole purpose of the 3D print is to create the required cavity inside the solidified plaster. After it will melt it will probably leave only some carbon residue at the very bottom of the mold, or it will completely evaporate. So I'm using the PLA JUST to make a mold (cavity inside the plaster in the box). Then when it's placed in the furnace, the hair, the PLA print, all organics will slowly burn away as I approach 1000C to melt the copper powder. It's designed to work this way. The PLA will have to melt. It has to melt. It is designed to burn and leave almost nothing behind(that's why so thin 0.2mm walls). The only remaining thing in the furnace climbing above 500C will be copper powder inside a cavity in a box.


    I am very well aware the plaster mold, even after 24hours of drying up and solidifying, it will still have some water(or humidity) trapped inside. When I place it in the furnace, it will break apart and crack. If only I could create enough air-holes very small tubules inside the plaster mold to prevent that. Hmm... If I poke the plaster with a thin needle while still soft, I might distort it and I won't have enough of these air holes for gases to escape. Heating the box SLOWLY in the furnace will probably solve the cracking issue. If the heating is too fast, the gases from PLA decomposition(CO2) might build up enough pressure and break apart the mold. Slow heating might be the solution, but additional thicker(larger) air holes(vents) on top will also help prevent that.


    I am really struggling to think harder and harder for this ridiculous ingredient hair replacement inside the plaster but I just can't find anything else. Even though dandelion puff has "straws"(thin cylinders) thinner than human hair, I can't use it, because it will clump(coalesce) together inside the plaster when mixed. Hair will disperse more evenly in comparison (if it's trimmed and short 5 to 10mm max, otherwise it will not).


    Quote Originally Posted by nigelpearson View Post
    1) I am not experienced in using plaster (or hair ), but have you thought of sand instead?
    "Green sand" is usually what people use at home for casting.

    Green sand contains some water to hold its shape while casting. My eccentric method requires placing the entire mold for a piece inside the furnace at all times. If the green sand mixture looses its small amount of water (in my furnace), then it will lose its property to hold a specific shape. That's why I'm using plaster instead (plaster of Paris-calcium sulfate-melting point 1460C). Just because the plaster won't melt in the furnace, doesn't mean it won't crack or distort (of which I am very extremely very and again very very very well aware of). Trapped gases inside the plaster are the culprit for such things. If only I can have thousands upon thousands of tiny air holes in the plaster mold to facilitate the venting of the gases...If only the plaster will be more "spongy" looking at a microscopic scale...If only the plaster will look like a Swiss cheese but at a microscopic scale...If only I could somehow create thousands upon thousands of microscopic tunnels or long spaghetti "caves" inside the plaster mold ....If only these tunnels, holes or caves will be around 75 micrometer in diameter or less...if only...


    Instead of ridiculous absurd human hair ingredient in the plaster mixture, I could use dried leaves from the herb Dill(Anethum graveolens) found in every garden or grocery. However the leaves (without the central stem) are thicker in diameter than the human hair. I am open to other suggestions. Please feel free to advise.


    This weird new method I'm proposing doesn't involve casting at all, because I'm not pouring liquid metal anywhere. So the word "casting" can't be used at all to describe this strange new method.
    Someone on 3dprinting.stackexchange named it "overcomplicated lost-PLA (investment) casting". I disagree. I don't know how to name this method thus I don't know what to google. The closest google-key-word-search I could get is <<<powdered-metal-sintering>>> but I want to actually melt the powder, not just bind it without liquefaction.


    I am hoping for people to actually see THROUGH my method instead of advice like: "Stop fooling and goofing around. Be like everybody else!"


    Quote Originally Posted by nigelpearson View Post
    2) What will happen to the PLA at 1000°C ???
    I suspect it will initially puddle down the bottom under your copper powder,
    then it might boil up through the middle, then it would carbonise.

    When the PLA slowly melts in the furnace, since it's just 0.2mm, it will more likely diffuse in the inside walls of the mold (because they are porous), than to melt and form a puddle at the bottom. Just as easily as placing the extra powder chamber on top, I could place a dummy chamber at the bottom of the mold of the model to catch the melted PLA if the model is complex and large, and thus prevent surface roughness. I don't think the 0.2mm PLA walls of the model will melt at the bottom. Since it's so thin (little quantity), it will probably diffuse more in the powder copper than in the plaster walls(inside the mold of the model). Thus the piece coming out from the furnace will probably have a unique strange looking surface, porous due to trapped leftover unburned carbon from the PLA print. This effect could probably be reduced by leaving in the furnace the box containing the plaster mold, for more and more hours, giving more chances for the leftover unburned PLA to escape as gases.


    Why some people see this strange new method as overcomplicated is a mystery to me. For me is quite the contrary. What I'm proposing could be 10 times safer and cheaper than anything in existence (Provided if what I'm proposing does work, because I don't know for sure and that's why I'm here). What I'm proposing doesn't involve any metal foundry equipment. Doesn't require any crucibles at all (thus this mad idea can be made in any size you want, without constantly melting hot crucible after another to finish your part). This method doesn't involve any gloves, apron or tongs whatsoever, no dexterity or safety procedures while handling and pouring dangerous liquid metal. Besides the DIY furnace (of which TKOR showed us that any idiot can make in no-time) absolutely no other equipment or safety procedures are required. I prefer to make a DIY electric furnace than a gas one.
    The drywall-box containing the solidified plaster mold placed in the furnace can't really be considered a crucible because I'm not handling it. I turn on the furnace. Forget about it. Remember about it. Turn if off. Forget about it again. Next day I remeber I have a box left in the furnace, I take it out, it's cold, I brake it and reveal the piece inside. I just don't see why some sees this method as complicated. There are many people who mixes all kinds of stuff in their plaster, including steel wool. I see an advantage in safety to patiently compact copper powder in a PLA shell than to handle dangerous hot liquid metal and cast an object. I'm really sad and sorry that some people don't see that.


    Quote Originally Posted by nigelpearson View Post
    3) If you get the copper hot enough to fully melt, the air might bubble up through the powder.

    Not if I gently and very slowly raise the heat of the furnace (that is why I prefer an electric furnace than a gas one, because I can have a little more control over the temperature curve)


    Quote Originally Posted by nigelpearson View Post
    So your 3D print might need extra material on top, to allow for copper sinking down in the melt?

    I already addressed that. It does have an extra box on top of the model (but still everything inside the plaster and inside the mold). This box will be filled with additional copper powder, because no matter how hard I try to compact it inside the shell(without distorting or ruining the PLA shell), I can't achieve the density of a solid metal, therefore, when the copper powder will melt, I know it will occupy less space, thus it needs extra powder to fill the entire mold.


    Quote Originally Posted by nigelpearson View Post
    Maybe experiment with powdered Tin before trying Copper?

    I intend to DIY the powder through various chemical means, since fine metal filings could be too rough. I don't intend to grind copper for such an experiment and then sieve the filings. Anyway, whatever the procedure, the copper powder has to be pure copper. It can't be Copper(I) oxide or Copper(II) oxide, since these oxides melt at 1235C and 1326C which are way to close to the 1460C when the plaster mold will start to disintegrate. I don't intend to operate the furnace beyond 1100C (pure copper melts at 1085C, the borax thoroughly pre-mixed in the powder will help drop this melting point a little bit). Perhaps I will leave the furnace on continuously for many hours at 1100C(or even less to prevent degradation of the mold)but never beyond that. That's why I prefer electric furnace. With a gas furnace I just can't easily and cheaply get the level of temperature control required. Being an electronic engineer, I find it more easily for me to accurately control a DIY electric furnace than a gas one. In general, a relay is cheaper than an electrically actuated gas valve.
    You are right. I should probably start with something simpler and safer at first. Like powdered tin.

  6. #6
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    I do find myself wondering how much of that decomposing PLA will then form some sort of copper carbonate (of a very impure tupe). I would also be concerned about the voids in the copper powder being enough that when the copper finally does melt, it sinks down in the mould leaving an air gap.

    Michael

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    The other significant factor you're forgetting is a 0.2mm thick layer of PLA will have significant flex, so anything made out of it it will bend/fold/sag somewhat, like a thick plastic bag, this will happen during the printing and as soon as you put anything inside it. You could of course add PLA bracing but that will just generate more gasses during the melt.

    Before you do anything else I suggest trying to print a simple 25mm square box with a 0.2mm wall thickness and check how much it deforms.
    Then maybe print a double walled box and report back on the dimensional accuracy of the prints.
    Pictures would be useful.

    Unless you can do that any further discussion is moot.

  8. #8
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    Quote Originally Posted by Michael G View Post
    I do find myself wondering how much of that decomposing PLA will then form some sort of copper carbonate (of a very impure tupe). I would also be concerned about the voids in the copper powder being enough that when the copper finally does melt, it sinks down in the mould leaving an air gap.

    I already said that as I slowly go beyond 200C the PLA will slowly difuse into the copper powder, forming a temporary layer of copper carbonate (as you stated), but since this will also melt way before reaching 1000C, it will eventually decompose forming copper oxide {CuO} and carbon dioxide {CO2}. CO2 will gas away and leave, but the problem is with CuO at the surface of the model which will not melt unless I reach 1326C, which I won't, thus leaving (as I already said) a unique rough surface on the finished metal part once it cools off. Besides, there are some special filaments specifically made for casting, which apparently burn away with no residue. Again, as I already said (the third time now), the model has a chamber above it attached to it. This chamber is also filled with copper powder and then eventually sealed off and completely submerged in plaster. Once the copper powder slowly melts, the trapped air within the powder will rise to the surface, through a small tube, in this upper chamber replacing the extra copper in there. If I repeat this for the forth time, I will lose my mind (like if that didn't happened already judging from these crazy ideas I'm proposing)




    Quote Originally Posted by BobL View Post
    Unless you can do that any further discussion is moot.

    You are right. I don't know when I will try this. I have this idea for some time now. I will get back with results, when, or if, I actually attempt this. Perhaps in the meantime, someone likes and entertains this idea to actually try it. I will be greatly satisfied if my mad crazy idea can inspire someone out-there.

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    Quote Originally Posted by NiculaeGeorge View Post
    I already said ... which I won't, thus leaving (as I already said) .... Again, as I already said (the third time now), ... If I repeat this for the forth time, I will lose my mind (like if that didn't happened already judging from these crazy ideas I'm proposing)

    ...I will be greatly satisfied if my mad crazy idea can inspire someone out-there.
    You will find that if you ask a question about something like this, the same comments will be repeated because we do get people who are so hell-bent on doing something they pay no attention to what responders have said. The more it is mentioned, the more likely responders think it is an issue

    I was going to try this over 40 years ago just using a clay mould and a mix of copper and tin powder (including a hopper of powder to fill the voids). I did not as apart from the cost of the powder, the other thing that occurred to me was that with all those small powder grains, there is an enormous amount of surface area. Surface area = oxide opportunities, so the resultant 'casting' would likely be riddled with imperfections.

    I know a commercial operation who laser sinters using metal powders, specially prepared in neutral environments so oxide is minimised. They can not handle the powder in atmosphere due to the fire hazard that it represents.

    Good luck.
    Michael

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by NiculaeGeorge View Post
    You are right. I don't know when I will try this. I have this idea for some time now. I will get back with results, when, or if, I actually attempt this. Perhaps in the meantime, someone likes and entertains this idea to actually try it. I will be greatly satisfied if my mad crazy idea can inspire someone out-there.
    Its fine to have crazy ideas (I have many myself) but maybe its better to test a few things out before putting them on the internet.
    If I get some spare time (Ha!) I will try and print a cube with a 0.2mm wall thickness.
    I'm not holding my breath.

    I just realized I dont have any nozzles smaller than 0.4mm so the trail will have to wait till I buy more parts for my printer.

    I checked the smallest nozzle I can use on my printer and its 0.2mm and with that the smallest object wall thickness possible is 0.2mm. The other thing that is critical is such narrow wall thickness will severely limit the extent of any off-vertical (slopes) printing without support.
    If support is used, removing the support will almost certain destroy anything with a 0.2mm wall thickness.

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    This morning I upgraded my 3D printer slicing program from "Cura 4.13" to "Cura 5.0 (beta)' and stumbled across a 3D metal printing process that starts with a conventional 3D printer. For the unaware, a 3D slicing program converts a 3D drawing into the necessary code for a specific printer.

    The most common metal used is copper with the filament consists of between 60 and 90% metal with the remainder being plastic.
    For the 90% metal material, the printed object can then placed in a furnace and heated under control conditions which sinters the metal.
    There are services that will do the furnace part (at a price ie $$$)
    The filament is very expensive but a) it is copper and b) its early days.

    This filament has been available for some time BUT, due to shrinkages, accurate sizing of the final sintered product was a hit and miss affair. The shrinkage is not necessarily even in all directions so just upsizing the object did not always provide an accurate final result.

    According to the blurb Cura will now accurately oversize specific directions to allow for shrinkage.
    The are still many hurdles to overcome but they are getting there.

    Here is a bit more info from https://thevirtualfoundry.com
    Virtual Foundry Copper FilametThe “Copper Filamet” from Virtual Foundry is in a league of its own. With 90% copper content, the goal of this filament is to create 3D printed projects made completely with copper by using PLA merely as a “vehicle” for the metal.
    The idea is to print with the Copper Filamet using a standard FDM printer. Some measures will have to be put in place, such as using a nozzle with a wider orifice and printing at slightly higher temperatures. Upon finishing the print, it is then placed inside a sintering furnace to melt the plastic and leave behind a 100% copper object.
    Some shrinkage will be expected because of the loss of plastic material. The finished copper print will effectively be porous and not super durable. However, this is far and away the easiest method of creating something made of pure copper. The copper can also be treated with an oxidizing agent to develop a green patina.
    As you would expect, this is probably the most expensive copper filament that you can buy. You are also going to need a furnace – not exactly something that hobbyist 3D printers have at home. This technology is more appropriate for professional users, the production of one-off parts, and rapid prototyping.
    According to the Virtual Foundry Website
    Next, we will submit three other metal-infused filaments for review: Stainless Steel 316L Filamet™, Rapid 3DShield Tungsten Filament, and Aluminum 6061 Filamet™.
    Other interesting develop include
    - a medical grade TPU (flexible plastic) with embedded silver compounds for antibiotic properties.
    - SiC and ceramics
    A list of some materials and sinter temps here https://thevirtualfoundry.com/produc...103.1651357618

    As I said - early days but rapid development is underway.

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    I'm not seeing how this it a lot different to lost wax casting.(well other than trying to remove two steps)

    Print your object with infill.
    Pour your plaster around it.
    Drill a hole in the top.
    Heat to burn the PLA out.
    Fill with your powder.
    Reheat to melt powder.

    What am I missing?

    BTW All the times I recalling seeing plaster used there is a step after pouring the wet plaster in a vacuum chamber to remove air bubbles.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Stustoys View Post
    I'm not seeing how this it a lot different to lost wax casting.(well other than trying to remove two steps)

    Print your object with infill.
    Pour your plaster around it.
    Drill a hole in the top.
    Heat to burn the PLA out.
    Fill with your powder.
    Reheat to melt powder.

    What am I missing?

    BTW All the times I recalling seeing plaster used there is a step after pouring the wet plaster in a vacuum chamber to remove air bubbles.
    In practice you are right, for simple objects it's no different

    IMHO having to deal with plaster, multiple heats, vacuum chambers, powders etc are a PITA.
    Compare that with print, and then stick object in a furnace - DONE!

    The lost medium method is currently superior because it should produce a stronger final product - but as I said its early days.

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    You could try electroforming - as I understand it you 3D print the shape/form you want, electrodeposit a coating of metal/copper onto the shape and when it is thick enough melt away the plastic 'form' leaving behind a copper/metal shell


    https://www.homemodelenginemachinist...-prints.33998/

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by BobL View Post
    In practice you are right, for simple objects it's no different

    IMHO having to deal with plaster, multiple heats, vacuum chambers, powders etc are a PITA.
    Compare that with print, and then stick object in a furnace - DONE!

    The lost medium method is currently superior because it should produce a stronger final product - but as I said its early days.
    Sorry I missed part of the process. the printed object does need to be supported by casting sand while it's in the furnace.
    Still probably less messy than dealing plaster.

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