Why can't we have FDM printers print in Metal Filament?

[BradAngelo]

Can someone please explain this to me... There are 3D printers that extrude melted plastic filament. Why can't we make 3D printers that extrude melted metal filament? Can't we create extruders that get hot enough to melt metal, lay it out on a flat surface and cool it, layer by layer? I know it's probably not something that is easily done, but is it not possible?

[Davo]

Have you noticed the difference between what happens when you use a soldering iron on ABS and what happens when you use it on solder?

Not all materials have characteristics that lend themselves to FDM.

[Flixtix]

Davo said it as well as I could myself. Metal is a liquid, whereas ABS is more of a gooey substance. If someone could figure out a way to make the consistency of the melted metal thicker that it normally is when melted, FDM might work.

[Compro01]

No, because you don't extrude melted plastic filament. They heat the plastic to it's glass temperature, which makes it soft and fusible. Metal doesn't do that.

[greatestalive]

I honestly think one day it will be possible. Someone just has to find a way to do it.

I came across a website where this guy is trying to develop an idea for a metal extruder.

Here is what he came up with so far. (from his website: http://www.genericmaker.com/2014/03/...metal-fdm.html)

Hotend & nozzle metal

• Able to withstand 700-1100C
• Not going to interact badly with molten aluminum, zinc, or copper
• Hard enough that a 0.5mm hole is still 0.5mm after extruding a bunch of molten metal through it

Hotend design

• Thermal expansion from worst metal shouldn't cause a jam
  
  • worst case expansion * worst case tolerance + magic extra tolerance
  
  
• Minimum amount of metal is molten at any given moment.

Nozzle design

• Metal should extrude with minimum turbulence
  
  • Nozzle 10x longer than diameter of extrusion?

Coldend design

• Thermal transfer up filament should be minimized

Heat break design

• Heat leakage into the coldend should be minimized
• Filament must be supported enough that it won't bend under the pressure of extrusion
  
  • Ceramic sheath? Stainless tube?
  
  
• If the heat break can't withstand the full pressure of extrusion, the hotend will need to be anchored to the coldend externally

Extruder design

• Filament should not be marred (eg, by a sharp gear) to minimize the risk of jamming in the cold end or damaging any components
• Filament must be pushed with enough force to extrude
  
  • Need to find data on how soft metals are at various temps

Filament research

• Find filament of multiple metals in the same diameter & tolerance (at/near extrusion temperature after thermal expansion)

Conclusion

In my mind, this hotend looks a lot like an E3d hotend made from steel or titanium, but with a directly mounted extruder and a lot more cooling (possibly water cooled?). It would be heated with a high temp heater cartridge (maybe?) and have a much heftier heat break, possibly supplemented by external thin steel wires.General questions

• How will molten aluminum interact with titanium? Would it be an appropriate nozzle material? How about steel?
• Any idea how to figure out a graph of extrusion force vs temperature for aluminum (w/ a given diameter nozzle)?
• How horrible is it going to be to deal with thermal expansion across this entire design? If more than one metal is used, everything needs to be matched up for expansion, yes?
• What sort of surface will be able to handle the thermal stress of being printed onto?
• How can part adhesion to the print bed be maintained with high levels of material shrinkage?
• Ceramics are exciting and could open a lot of opportunities, but I have no idea where to start with designing and specifying ceramic parts.
• I know there are some additional issues I haven't mentioned here and certainly some I haven't even considered. Feel free to chime in an any of them!

[WildZBill]

A novel idea that I have considered is suspending metal particles in a fluid, flowing the fluid through a nozzle with an electrical charge at the tip that would cause the metal to be attracted to the work. Of course you would constantly recycle the working fluid.

[3dkarma]

I'm aware of two ways to 3d-print in metal that are fairly close to FDM.

The first uses a two stage process. First stage is to print a clay made up almost but not entirely of metal particles. You use a paste extruder, such as this one from thingiverse, loaded with a metallic clay such as this (which evidently sees a lot of use by jewelry makers). Second stage is to fire the piece in a kiln. You end up with a metal piece.

The second uses an arc welder as the hot end of the extruder. Welding wire is fed to the business end the same way it's done in a normal arc welder. Lots of current is pumped through and hey-presto: 3d welded metal. Article here.

[Markum_Debreeze]

A novel idea that I have considered is suspending metal particles in a fluid, flowing the fluid through a nozzle with an electrical charge at the tip that would cause the metal to be attracted to the work. Of course you would constantly recycle the working fluid.

Bill, I'd love to see if this could work. In theory it would, but would there be a mess involved? Please try it. I beg you to

[Feign]

A novel idea that I have considered is suspending metal particles in a fluid, flowing the fluid through a nozzle with an electrical charge at the tip that would cause the metal to be attracted to the work. Of course you would constantly recycle the working fluid.

Sort of like a directed electroplating process, but with a flowing fluid rather than a suspension? There would be very little way to control where the metal plates at the fluid runoff from the point of intended deposition... Actually, I seem to remember a kind of vapor deposition additive manufacturing that blasts a charged work surface with charged metal particles. I thought it had lots of potential, but never saw a followup of it since the initial report.

Of course, just using an automated MIG welder setup like 3D Karma mentioned.

[LambdaFF]

Sort of like a directed electroplating process, but with a flowing fluid rather than a suspension? There would be very little way to control where the metal plates at the fluid runoff from the point of intended deposition... Actually, I seem to remember a kind of vapor deposition additive manufacturing that blasts a charged work surface with charged metal particles. I thought it had lots of potential, but never saw a followup of it since the initial report.

Of course, just using an automated MIG welder setup like 3D Karma mentioned.

I think it has been developped to repair helicopter magnesium gear boxes in australia.