I would love to see new hardware but there's soooo much that's in the software and settings too. If you can get it semi-not-terrible by tweaking with that, then you'll definitely be able to make it totally not terrible with better hardware, lol. keep at it please! really want to see the outcome of this. 

Yes, I will do so. Maybe I need more heat for better melting or so...

I removed the resistor plate from the circuit to get a wider rang for power/heat intensity adjustment with the phase-fired controller. So everything should now be a matter of settings.

Would you consider trying solder wire at first so you can run it at a much lower power/temperature? Probably have more options for finer filaments there too?

I tested it, but it seems like the printer is not really suitable for solder wire. The solder wire don't heats up and melts like the welding wire. Maybe it's too much or to less conductive.

At the moment I use a plastic filament spool sized 5kg spool of 0.6mm copper coated steel welding wire. I think stainless steel and flux core wire can also be used. Maybe aluminum and copper too but I don't know because of their higher conductivity.

Wow, this looks stunning! Also it seems that with good settings bridges are possible. Here they were almost accidental. That's stunning results!

Thank you very much :) Will later test a phase-fired controller for controlling the heating intensity and if it works the heating can be controlled by the part cooling fan parameter of the slicer software.

After that all parameters are controllable like on a normal FDM 3D printer - besides heated bed and part cooling, which could later be added if the print quality would benefit from them. Then the machine should be ready for working with it.

I also added 4 more resistors today what prevent the resistor plate from overheating if the printer controller would freeze while printing and the nozzle get stuck in the printed part or buildplate. So in theory the printer should be safe even if it's for short time unattended.

If I may suggest - this looks like you have too slow movement speed. I would try to go 2x faster (with wire feeding appropriately faster too) and/or decrease height by 1/2.

Yes, I will test it, but before that I want to add the missing parts to get homing and pwm intensity control working, upload the stl files and maybe write a B.O.M.

I have no experience in welding or metallurgy, so finding the right settings for printing metal could be a bit challanging. I noticed on the last test I did, by decreasing the intensity it was easier to print the lines next to each other, but the result didn't bond together very well. Maybe it was due to too low temperature or oxidation. The strongest part until now I could print with 2mm layer high. It was the skirt-line / ring and it was impossible to rip it apart by hand and with pliers it was also like cutting a M4 screw.

Will continue testing...

Plastic heats and cools much slower than metal, because it has low thermal conductivity. Your first test looked like metal melted and already started to cool before you moved printhead away. That big plate underneath works as a rather big thermal mass comparing to your melt zone and due to fast heat transfer cools almost instantly. When you move too slow, top part of material which you want to lay is already solidified, that's why you have those accidental bridges, you can see it at 16s in your video. Melted material is still yellow, but it's already solid enough to move melt zone upper, so you have solid material higher than your plate. You have to move head faster. You may need to increase energy applied, but for me your results look entirely like material stops flowing too soon. Plastics are soft for longer but metals can solidify very nonlinearly with temperature, like one milisecond it's soft, next milisecond it's already solid.

Yes, I think you are right. Maybe some sort of high temperature heated bed could help.

Ordered a silicone heatpad which should be able to heat the build plate up to around 150°C.

Heated bed only helps with warping and adhesion. If it heated up to about 400*C, MAYBE it would help with cooling too fast. Otherwise, don't bother.

Ok, it's more like - it's easy to integrate and maybe it helps so why not. Thought it could be a good thing to keep the buildplate as warm as possible. 

Ordered a ZVS driver today for experimenting with induction heating for the buildplate. If it works out the machine would be a resistance heating based metal 3D printer with an induction heated buildplate, what I think would sound very cool :)

Nice! It could print a frying pan with custom patterns and then also fry some burgers! Joking aside, that induction heated bed is a very good idea!

Thank you, I'm currently testing whether I can reach higher temperatures than with pcb or silicone pad heaters, which voltage I should use and which cables I could use for the induction coil. Measuring the temperature is also a bit challanging...