Can someone shed some light in why FDM (Fuse Deposition Modelling) is not possible with metals?
Has anyone attempted any experiments with it?
Can someone shed some light in why FDM (Fuse Deposition Modelling) is not possible with metals?
Has anyone attempted any experiments with it?
Yes, it is possible and it's done all the time. It's more commonly known as welding.
We did TIG welding on our Hyrel printers back in 2017.
Note: I work for Hyrel.
First of all, it is possible in multiple ways:
The most akin to FDM is using an automated MIG-welder, building up weld beads upon weld beads using an arc to melt the metal and keeping the puddle in position by carefully low speeds and coordinated movements. With a little ingenuity, even a TIG could be used, if you manage to feed the filler rod.
Converting a MIG is possible even on a hobbyist scale, as this hackaday 2021 article shows. However, research into something like that is in research since at least 2018, and Hyrel experimented with a TIG setup in 2017.
The items created this way have a rather rough surface, yet they do have upsides: The created metal is easily machineable and can reduce a lot of waste. It might not beat machining from bar stock at the moment, but it can beat steel casting in price, though not in quality. However, automated welding also has the chance to have defects. In some applications, it is used industrially, for example, to manufacture specialized stock for machining with minimal waste or from a special material.
Oh, and it is even rather simple to repurpose 3D welding robots to 3D Weld a gap closed bead to bead, akin to how you'd 3D print in FDM.
There are filaments that contain about 80% of metal powder. These highly abrasive filaments contain a binder that is thermoplastic. You can print on a somewhat modified machine with those. That's called BMD - Bound Metal Deposition. This method is industrial by 2022, and often post-processes the part to remove the binder.
Usually, this post-processing is done in a kiln or sintering oven, melting or cross bonding the metal between layers more than with the plastic binder, and simultaneously at times burning out the binder. This technique exist since at least 2018, as this answer shows.
For many metals you would need to run the hotend around 1000 °C. Aluminum melts at a lower temperature but needs to be in an inert atmosphere, such as argon. Solder melts at the right temperature, but tends to stick to most metal nozzles. It would start dissolving a brass nozzle thus enlarging the nozzle opening. Lockheed has a titanium alloy printer that melts powder with a laser. I would assume they need an inert atmosphere since titanium reacts with nitrogen as well as oxygen.
It is completely possible, there are 3d FDM printers that could do that with the Ultrafuse 316L. You could print filament that has metal in it, you just need a special nozzle for that. The pure metal-printing printers use an industrial heater/extruder that can reach up to 230 °C.
I have tried some stuff. It depends what problem you're trying to solve.
You can get metal infused filaments, both aluminium and copper infused filaments print fine. But since there's plastic as well you don't get the nice properties like conductivity.
If you just want some of the properties then electrolysis might be the better choice of technology.
If you want robust parts then as far as I know the traditional methods are the best as the metals properties are constant or controlled.
Something like cnc welding layers on layers wouldn't make sense in terms of cost and predictability I would think. You'd need too much heat and it's unlikely to be as strong as traditional metal forming. It has been used for a long time to spot weld, but not build up layers as far as I know.