One of the benefits of additive manufacturing is the potential to eliminate the need for stored inventory. From end products to replacement parts to tools, 3D printing could make it possible to print what we need,
when and where we need it, with the mythical batch size of one and completely
custom made with very low lead time.
Heavy-duty Cummins cylinder heads wear out
after a million miles on the road. Ordinarily, these cast iron parts would have
to be replaced with new castings, a costly process in terms of time, energy,
and money. Instead, the team ‘scoops out’ the worn section, and uses additive
techniques to deposit a high-performance alloy in its place, like a heavy-duty
dental filling.
New Process Prints Metal Directly onto Machined Surface
Niyanth Sridharan is an ORNL Post-Doctorate
Research Associate working on the project with colleagues Brian Jordan and Ryan
Dehoff. Niyanth told me the details of the process:
First, Cummins receives damaged cylinder
heads that are out of service, with damage near the site of the fuel injector.
Cummins uses conventional milling to machine out the damaged area, and sends it
to ORNL.
The researchers then draw a CAD file of the
machined section, and preprogram their printer using G-code, so that the filler
metal can be deposited directly onto the part, without the need for any other
substrate or fabrication.
The G-Code is loaded onto a DM3D direct energy deposition system, a
laser powder blown machine, which uses a laser mounted on a 5-axis CNC head.
The nozzle sprays a cloud of atomized metal powder right on the area which
needs to be repaired and the laser melts the powder to build fully dense parts
layer by layer. The advantage of this process is that it can be used to build onto
existing parts making the process applicable for repair and hard facing
coatings. DM3D is a small business based in Detroit, Michigan.
Oak Ridge has modified DM3D’s device, adding
infrared sensors to monitor temperature, and heaters to avoid cracking of the
cast iron during the repair/rebuilding process.
Challenges and Next Steps for Engine Repair 3D Printing
Cast iron is extremely difficult to repair,
due to its tendency to crack. The researchers are using a
high-nickel-containing alloy to avoid cracking and increase thermal efficiency
of the part. The deposited alloy bonds to the existing cast iron during the
additive process. Microscopic analysis of the bonds shows good adhesion, but
the repaired parts have yet to be tested on the road.
Niyanth says next steps for the project
include testing how strong the bonds and interfaces are. After that, the team
will try out slightly different alloys proposed by Cummins. In-service testing
will be the true test, putting the repair through the intense heating/cooling
cycles of engine use.
This intriguing research shows the
potential of 3D printing: not only replacing parts, but repairing and even
upgrading existing parts.
The automotive industry would see obvious
benefits from this ability. A dealership or even a third-party repair shop
could print the parts needed for a repair instantly, not only eliminating the
need for inventories of parts, but also reducing shipping costs and lead times
of ordering replacement parts.
Instead of seeing “parts and labor” on your
mechanic’s invoice, you may soon see “raw materials and labor.”
Read more about applications of metal additive
manufacturing here.