This is a nice first step and all, but there are a number of challenges here. The irregular sparking and popping noises imply that the metal laid down will also be irregular. This uses a regular MIG welder as the print head, and MIG welding only allows you to lay so fine of a bead. Large welds tend to be brittle due to internal stresses, voids, and the like.
The more successful commercial metal 3D printers build parts a thin layer at a time. A fine metal powder is sintered on each layer using a laser. This technique is called Direct Metal Laser Sintering (DMLS).
That's a pretty glaring omission. I imagine the prints look pretty awful, but it a neat idea. In the normal use a wire feed welder the arc (bright sparky part) would be uniform to create a bead. From what I saw in the videos they are using a "bad" welding technique that would build up the instead of penetrate the metal. They will need to replace/control the wire feeder and the voltage of the welder in order to better results.
There's a few different ways to do 3D printed metal, but this looks different then them.
Prometal, for example, has a process that's very similar to SLA or SLS, but with a stainless steel powder instead of resin. They then infuse it with bronze, using capillary action to do the work. You end up with pretty solid parts.
There's only a vague resemblance between model and part. No way could you use that sprocket. Not only are the edges rough, it has voids. You could grind or machine down down rough edges, but voids make the process worthless even for making blanks.
That's about what you'd expect with MIG welding. Welding just isn't a good way to make smooth surfaces.
The low-end 3D printer people tend to obsess on the problems of building a 3-axis motion system (a completely solved problem in CNC machines) and gloss over the problems of what's happening at the weld point. The common extruder-type printers are trying to weld a hot thing to a cold thing, which never works very well. (In soldering, that creates cold solder joints. In welding, it creates bad welds.) Heating the bed plate helps a little, but once the thing being built is more than a few cm high, the build plate isn't accomplishing much. That's why most taller objects made with low-end 3D printers fail.
There's a plastic welding technique that's been in use since the 1950s that works reliably. (http://www.professionalplastics.com/WELDER). Not only is the welding rod heated, the target area is heated with hot air. This produces a solid, reliable weld.
I've suggested doing something similar for extruder-type 3D printers, using small lasers (2-5 watts) to preheat the target area just ahead of the extruder. So far nobody has done that.
Heating things with a laser is not quite as easy as you might think. Different materials will absorb different wavelengths of light at different rates. So for example a 1um laser might not heat white polyethylene enough while it would melt black ABS. Hot air has the advantage that it is always a consistent temperature regardless of the material.
Use a laser diode pulsed with pulse width modulation, at perhaps 1KHz, duty cycle < 80%. During the off period, view the hot area with two photodiodes behind different-wavelength IR filters. The ratio between the outputs gives you the temperature. Go closed loop on temperature.
Because perhaps it's just me, but the printed part is the most interesting part of a new 3D material. Just a glance at it lets me know the possibilities for the device, in initial printing resolution and finish quality. So not including it seems like they're hiding it for some reason.
Thanks to jeffmcjunkin above for linking to an image of a printed part. It certainly looks better than I anticipated.
Comments
Sadly I can't find any images or videos of the product of the device. The site has a couple of videos showing it throwing sparks, but that's about it.
This page has a photo of a sprocket from the machine: http://motherboard.vice.com/blog/you-can-now-3d-print-with-m...
This is a nice first step and all, but there are a number of challenges here. The irregular sparking and popping noises imply that the metal laid down will also be irregular. This uses a regular MIG welder as the print head, and MIG welding only allows you to lay so fine of a bead. Large welds tend to be brittle due to internal stresses, voids, and the like.
The more successful commercial metal 3D printers build parts a thin layer at a time. A fine metal powder is sintered on each layer using a laser. This technique is called Direct Metal Laser Sintering (DMLS).
The hackaday article [1] has an image of a printed piece, which helps give an idea of the resolution
[1] http://hackaday.com/2013/12/07/a-rostock-welding-3d-printer/
That's a pretty glaring omission. I imagine the prints look pretty awful, but it a neat idea. In the normal use a wire feed welder the arc (bright sparky part) would be uniform to create a bead. From what I saw in the videos they are using a "bad" welding technique that would build up the instead of penetrate the metal. They will need to replace/control the wire feeder and the voltage of the welder in order to better results.
There's a few different ways to do 3D printed metal, but this looks different then them.
Prometal, for example, has a process that's very similar to SLA or SLS, but with a stainless steel powder instead of resin. They then infuse it with bronze, using capillary action to do the work. You end up with pretty solid parts.
Agreed -- the fact that they don't show a single finished item tells me that the quality of the printed part must be extremely bad.
It is extremely bad. See the actual paper, where they show one part and its CAD model.
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6678...
There's only a vague resemblance between model and part. No way could you use that sprocket. Not only are the edges rough, it has voids. You could grind or machine down down rough edges, but voids make the process worthless even for making blanks. That's about what you'd expect with MIG welding. Welding just isn't a good way to make smooth surfaces.
The low-end 3D printer people tend to obsess on the problems of building a 3-axis motion system (a completely solved problem in CNC machines) and gloss over the problems of what's happening at the weld point. The common extruder-type printers are trying to weld a hot thing to a cold thing, which never works very well. (In soldering, that creates cold solder joints. In welding, it creates bad welds.) Heating the bed plate helps a little, but once the thing being built is more than a few cm high, the build plate isn't accomplishing much. That's why most taller objects made with low-end 3D printers fail.
There's a plastic welding technique that's been in use since the 1950s that works reliably. (http://www.professionalplastics.com/WELDER). Not only is the welding rod heated, the target area is heated with hot air. This produces a solid, reliable weld. I've suggested doing something similar for extruder-type 3D printers, using small lasers (2-5 watts) to preheat the target area just ahead of the extruder. So far nobody has done that.
Heating things with a laser is not quite as easy as you might think. Different materials will absorb different wavelengths of light at different rates. So for example a 1um laser might not heat white polyethylene enough while it would melt black ABS. Hot air has the advantage that it is always a consistent temperature regardless of the material.
Use a laser diode pulsed with pulse width modulation, at perhaps 1KHz, duty cycle < 80%. During the off period, view the hot area with two photodiodes behind different-wavelength IR filters. The ratio between the outputs gives you the temperature. Go closed loop on temperature.
Why you assume that? Is not like they are trying to sell it to you..
Otherwise seems like a very interesting project.
Because perhaps it's just me, but the printed part is the most interesting part of a new 3D material. Just a glance at it lets me know the possibilities for the device, in initial printing resolution and finish quality. So not including it seems like they're hiding it for some reason.
Thanks to jeffmcjunkin above for linking to an image of a printed part. It certainly looks better than I anticipated.
https://www.academia.edu/5327317/A_Low-Cost_Open-Source_Meta...