3-D Printing with Metal

[Chris_Ely]

John,
This might be of interest to your students as they continue their design:
Scientists Build a Low-Cost, Open-Source 3D Metal Printer

I submitted the survey. I am very interested in what your students come up with.

[techhelpbb]

3D printing (really material addition) with a MIG/GMAW welder is not actually a new idea.
The issue with those welders is the spatter and properly slicing the model to insure the welds laid down are consistent over the travels.

You can't really do like a 3D plastic extruder does. A 3D plastic extruder is basically pushing into a state of partial stall on the extruder stepper. That's part of the reason the extruder steppers tend to get hot. Once we get an arc going the spool in a MIG does not take much effort to push too much and takes some skill not to push too little.

So while I can see putting a MIG torch suitable for CNC operation on a Prusa I3 frame in the same way I can so doing it with a CNC plasma cutter. What I don't see is how you control the quality of the weld consistently over different objects. With a plasma cutter the goal is really to cut and sever so as long as you are in the ball park it's good enough considering what it's doing.

To put this in perspective we've had robotic arms do MIG/GMAW for decades now.
There's a process to dial them in to achieve the right results on a consistent flow of similar parts that start at room temperature.
In trying that with 3D printing you are laying down metal that will cool and the size and shape of the target will change as you reheat the welds changing various aspects as the thermal mass changes.

http://hackaday.com/2014/11/07/print...-a-mig-welder/

So in the video they make a simple 'wall'.

Didn't really need a Prusa printer frame for this purpose.
A cheap school robotic arm could manage the same with basic motion control it just wouldn't be Cartesian.
So maybe you start the travel and you exit after the straight line to let it cool or force air to cool it.

However if you look the layers are more inconsistent than 3D plastic printing.
So the 'slicing' or making of layers would become much more difficult for complex layer travels.

I wouldn't aspire to making plates of metal as a 3D printing goal.
At that point I'd rather have a robotic arm welder to weld properly prepared plates for more consistent results.
Maybe more robotic arms to grasp the assembly in progress of assembly.
The inverse kinematics of the robot arm welder and work holders are equally an interesting motion control problem.
That's a problem where the feedback of actually maneuvering the arms manually could be really helpful in training the robot.

[asid61]

Best of luck! I would like to see something that's not a welder, as my school banned us from having one on the grounds that it was "unsafe".
Meanwhile, the milling machine, bandsaw, and various power tools are A-OK.

[JesseK]

Originally Posted by asid61

Best of luck! I would like to see something that's not a welder, as my school banned us from having one on the grounds that it was "unsafe".
Meanwhile, the milling machine, bandsaw, and various power tools are A-OK.

Welding requires proper ventilation as the aluminum additives heat and off-gas. I don't know your shop, but welding is considered unsafe without the ventilation.

In other news, metal 3D printing is so last year:
http://arstechnica.com/science/2015/...tead-of-hours/