According to the article on Engineering.com Italian aerospace company Avio (a part of GE Aviation) is using an electron gun 10 times more powerful than the laser beams currently used for printing metal parts to fabricate blades for jet engine turbines.
The material used is called titanium aluminide (TiAl) which is 50 percent lighter than the nickel-based alloys typically used for low pressure turbine blades. But titanium aluminide is also notoriously hard to work with. Companies normally use lost-wax casting or spin casting to make TiAl parts. However, the material has a very high contraction ratio and can become fragile and prone to cracks as it cools.
The electron beam melting or EBM technology created by Avio together with Sweden's Arcam solves these problems.
(Score: 0, Funny) by Anonymous Coward on Thursday August 21 2014, @03:39PM
So now we need sharks with frickin' electron guns mounted on their heads?
(Score: 4, Interesting) by jcross on Thursday August 21 2014, @03:43PM
EBM is hardly new technology. There was a working machine in the Industrial Engineering department at my university at least 10 years ago. Now, the fact that they're using it for relatively large-run commercial aerospace parts might well be news. The main issue with the process as I understand it is that when you melt a little spot of powder with the beam, it's hard to keep the heat from spreading to areas outside the part, especially since it's all under vacuum and the only other way to get rid of heat is by radiation. So you wind up with a pretty rough surface finish, which can be improved somewhat by shot peening or vibratory polishing, or made really good with some CNC work, which of course mitigates some of the advantages you got from 3D printing the part.
(Score: 2) by JeanCroix on Thursday August 21 2014, @03:58PM
(Score: 2) by LoRdTAW on Thursday August 21 2014, @04:22PM
The system at your Uni, was it the Sciaky system?
(Score: 2) by jcross on Friday August 22 2014, @01:36PM
No, I think it was made by Arcam. One of the IE professors was Swedish so that may have had something to do with the deal. This is N.C. State University, and according to their website they bought the very first machine sold in 2003.
(Score: 2) by kaszz on Thursday August 21 2014, @04:46PM
A vacuum pumped compartment has a magnetically steered electron gun at 3 kW that fires electrons towards a bed of TIA powder that is gradually built up?
(sounds like a super powered TV tube ;))
Side question.. how do they contain the heat from one spot to the next?
(Score: 2) by opinionated_science on Thursday August 21 2014, @05:48PM
I don't know, but in electron microscopy that would the low end of power...
of course, we use just electrons and they are using chunk ions...
(Score: 2) by kaszz on Friday August 22 2014, @12:36AM
That gun uses ions, not electrons?
(Score: 2) by opinionated_science on Friday August 22 2014, @03:00PM
yes, just relating what I have experience with...different target...!
(Score: 2) by Blackmoore on Thursday August 21 2014, @06:29PM
Would this be a viable technology for building items while in space? certainly would be able to dump the heat faster.
(Score: 5, Informative) by LoRdTAW on Thursday August 21 2014, @07:10PM
Electron beam welding is done the same way and has been for decades. Depending on feed rates, 3kW can do a lot of smaller welding. Our machines are rated to 7.5kW (50mA @ 150kV). At maximum power they can penetrate stainless steel to depths of about 50mm. The largest EB machines are 100kW and over. Those are serious machines designed for very specific jobs, usually deep welds in very heat conductive metals like aluminum and copper.
Every EB machine has deflection coils but they normally only offer a few mm of movement on an X-Y plane. They are mostly used for gun alignment correction and also in conjunction with a simple deflection generator to create a circle or line for dressing the weld (it's for aesthetics).
EB drilling machines have a deflection coil like that of a CRT in a TV or monitor. The deflection action is like a laser galvo head which is CNC controlled. A big application is the ability to drill thousands or millions of small holes (~1mm) in cylindrical tubes. As the tube is rotated about its axis, the beam is scanned linearly and rapidly switched on and off to punch small holes. The beam can be both focused and scanned for a 3D X-Y-Z placement of the beams focal point. The beam can usually be moved many cm compared to normal deflection.
Other uses for electron beam in materials processing is EB melting for vacuum metallurgy.
As for your side question: The heat will propagate through the part and build up over time. In a vacuum there is no convection cooling so heat buildup is a concern. When printing the heat load would have to be factored in and beam power and feed rate be adjusted so there is no excess heat added. Aluminum and copper are good heat sinks so cracking is another concern as molten metal cools so fast that the metal cracks instead of shrinking. In some cases heat treating to relieve stress from shrinking is necessary afterward. Perhaps a water or oil cooled table might be necessary to remove heat from the part as it is being printed.