Solid-state additive manufacturing (SSAM) technologies have been growing in usage because they allow for relatively fast maintenance and sustainment of critical and costly metal components. Cold spray is a solid-state coating deposition method in which powdered metals are accelerated through a nozzle to velocities sufficient to cause plastic deformation and bonding. In this way, layers of new metal can be added to worn surfaces, which can refurbish components subject to corrosion or impact damage and build-up dimensions lost to other degradation processes. Cold spray is a particularly useful method for repairing components that don’t respond well to the use of high heat.
An ongoing CTMA project has been advancing the understanding of cold spray processes for the repair and modification of aerospace and ground vehicle systems for both commercial and DOD applications. This multi-disciplinary initiative involves research conducted by the University of Massachusetts, Amherst, and Mississippi State University, as well as design and fabrication services provided by VRC Metal Systems. The overall objective is to expand cold spray capabilities, incorporating a broader set of metal powders into the cold spray process to allow the repair method to be used on a wider range of materials, and develop the hardware needed to apply those materials.
Among these objectives is the development of a mobile cold spray system that can be utilized for maintenance in a military depot. Unlike conventional cold spray stationary systems, which require a dedicated facility in which to perform the repair, this new unit provides a fully capable cold spray repair system mounted on a platform that can be brought to different locations within the facility to perform repair activities.
VRC Metal Systems has developed the mobile cold spray system comprising two 20-foot modules. The first includes a 7.5’ x 9.0’ spray booth and robotic delivery system; a hoist that provides a means to move into the module any especially heavy parts needing repair; a high-pressure cold spray system; a dust-collection unit; and outdoor hand spray capability. The second module is an optional utility cell with an on-board diesel power generator to power the cold spray module for locations that don’t have the capability to provide the extensive power needed to operate the system; a compressor capable of delivering compressed air at 4,500 psi for use as process gas; and a small lab area with oven for powder prep and nozzle drying.
Another new development in the mobile cold spray unit is the ability for the robotic delivery system to use collaborative path planning as an approach to pre-programming. The operator can safely “teach” the robot where it needs to go by physically positioning it at the correct place and angle at various points along its journey and recording those points. The robot can then follow the pre-programmed path, which allows the operator to avoid hand-entering program parameters into the robot pendant.
“This system can save a lot of time because the maintainer doesn’t have to pull out a part and ship it to a far-away location that has cold-spray capabilities,” says Kris Klus, Lead Project Engineer for VRC Metal Systems. “With hand-spray capability on-site, they can even save on disassembly time, because sometimes a part can be fixed without even removing it from the vehicle.”
Klus says the mobile cold spray unit is nearing completion, and they will begin testing it later this fall. The full project is due to be completed with an on-site demo early next year.