3D Printing Comes to Titanium Wheel Production
The HRE3D+ wheel produced by HRE Performance Wheels and GE Additive (ge.com/additive/) is billed as the first 3D-printed titanium wheel. It has an airy, intricate, spokes-through-spokes structure: Imagine for a moment the cost and complexity of cutting such a design out of expensive titanium plate using subtractive machining technologies.
And assuming it could be done at all, given the intricate design, you could expect the finished wheel to be made up of only 20 percent of the titanium you started with—the other 80 percent would end up as chips—very expensive chips.
Beam It Up—and Around
The HRE3D+ wheel was 3D-printed using electron beam melting (EBM). With EBM, as with more-common laser-based additive systems, a component is built up from a bed of powdered metal—titanium, in this case—joined by the heat of a beam. Instead of a laser, EBM systems deploy a concentrated beam of superheated electrons to completely melt—rather than sinter—the powdered metal. The high-energy beam is created when a tungsten filament is superheated in a “gun” (a containment device with an opening), which creates a cloud of electrons that accelerate to approximately one-half the speed of light. A magnetic field focuses the beam of electrons to the desired diameter while a second magnetic field directs the beam to the desired spot on the print bed. The beam itself can reach temperatures of 3,632° F.
This all takes place in a vacuum chamber to ensure that oxidation won’t compromise the highly reactive titanium. Vacuum production also prevents electrons from colliding with gas molecules.
Once a component has been printed, the build envelope is removed and the build platform and attached object are removed from the loose powder. Powder clinging to the object or remaining in internal cavities is blown or blasted away.
The HRE3D+ wheel was produced in five separate sections on two Arcam EBM machines, then combined with a center section and bolted to a carbon fiber rim using titanium fasteners.
That’s 40 times less metal than the amount removed if the wheel had been made entirely with machining.
It is worth noting that this isn’t all additive: The sections were finished using CNC machining, which results in the removal of about 5 percent of the titanium used in the build. According to HRE, that’s 40 times less metal than the amount necessarily removed if the wheel had been made entirely with machining. Assuming that could be done.
General Motors is working with Autodesk on utilizing advanced design software and 3D printing capabilities to develop parts that are not only lighter than those otherwise developed, but which combine what would otherwise be separate parts, thereby reducing manufacturing complexity.
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