1

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 hollow complex structure with 0.2 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. 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 5mm 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.

Niculae George Razvan
  • 13
  • 3
  • 1
    While yes this is very different, my initial thinking is that it may not work. Not being thoroughly experienced in this, I would imagine that the PLA would melt and lose its shape before the copper inside would fuse together. Maybe someone else could elaborate if I am correct. – agarza Apr 28 '22 at 13:06
  • Of course it will melt. I'm counting on it. It is supposed to melt. I feel sad for not being properly understood. 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. I'm not sure. I don't know. That's why I'm here. To understand what I'm about to do, better. – Niculae George Razvan Apr 28 '22 at 13:15
  • I guess I didn't explain fully. The PLA will melt **before** the copper fuses together. PLA has a melting point of ~200C while copper is ~1000C. So the PLA will melt (and probably burn off) before the temperature gets hot enough to melt/fuse the copper. – agarza Apr 28 '22 at 14:50
  • Yes. I know. 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. I'm not sure, what you see in the process as a problem. The PLA will have to melt. It has to melt. It will not probably burn. It will definitely burn. It is designed to burn and leave nothing behind(that's why 0.2mm walls). The only remaining thing in the furnace climbing above 500C will be copper powder inside a cavity in a box. – Niculae George Razvan Apr 28 '22 at 14:52
  • Hmmm... I think I'm beginning to see what your process is (coffee hasn't fully kicked in yet). – agarza Apr 28 '22 at 14:57
  • Can you at least tell me what this madness is? English is not my native language so I can't even begin a google search. I don't know what to search for. What is this that I'm describing? It's not because I'm not extracting any ores. It's not any form of because it doesn't involve any liquid material being poured anywhere. It's not because I'm not pouring nor forcing any metal into a mold. – Niculae George Razvan Apr 28 '22 at 15:20
  • Perhaps it's a little bit related with but I want to actually melt the powder, not just bind it without liquefaction. It's not because i'm not injecting anything into anything. My powder is already there. I'm just melting it. I have no idea what to google. What on earth is this mad idea in my head which I'm describing? Just give me one single word to search for, besides the self-criticism I've expressed so far. – Niculae George Razvan Apr 28 '22 at 15:20
  • Putting the PLA and powdered metal together into the cavity made by the plaster isn't going to work. What's going to happen, at best, is that the PLA will float to the top and get burned off and/or escape, and the copper powder will compact down and leave more than half your mold empty. At worst, the PLA won't burn off evenly and will leave defects in the metal. If you have a large sacrificial cavity at the top and fill _that_ with copper powder, it might work. – user10489 Apr 29 '22 at 22:36

2 Answers2

7

I think this is just an overcomplicated lost-PLA (investment) casting.

What you're asking for is to create an object, create a mold around it, and then burn out the object and replace it with metal. Traditionally this is done with wax, and called lost-wax casting, but the same can be done with anything that melts/burns away, including PLA.

Rather than worrying about burning hairs and pressure and compaction of metal powder, print a model, and use the correct kind of plaster (a search for "investment casting plaster" will get you going down the right path) to make your mold. Heat the metal powder in a crucible, instead of the mold itself, and pour it through the expansion/extra material tube you were talking about.

Greenonline
  • 5,831
  • 7
  • 30
  • 60
Tal
  • 328
  • 1
  • 9
  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/136045/discussion-on-answer-by-tal-the-weirdest-diy-3d-metal-printing). – Greenonline May 04 '22 at 17:56
0

I don't see why it wouldn't work. It doesn't seem to be the optimal way but I haven't tried it.

Only thing that might be an issue is that PLA doesn't burn away clean (not for me anyway) which can leave defects in the product. But there are filaments specifically made for casting which apparently burn away with no residue.

This is assuming you can actually successfully print a complex object with walls that thin.

Kilisi
  • 1,207
  • 2
  • 11