The objective of this effort is to demonstrate an environmentally sound abrasive waterjet technology that can replace conventional means of grinding and honing pressure vessels.

Abrasive waterjet machining can be used for both cutting through and controlled milling of virtually any material: metals, composites, plastics, glass, etc. In both cases, material is removed by abrasive garnet particles carried by a high-speed jet of water. This process eliminates the need for hazardous lubricants associated with conventional material removal techniques including cutting, milling, grinding, and honing. This project will avoid the use of metal working fluids (MWF) and hard tooling while recycling up to 100 percent of the water and abrasive used in this process.

Although waterjets are commonly used to cut completely through materials, this effort will focus on using a waterjet in a more controlled way, analogous to grinding and honing. This controlled process is called waterjet milling, to distinguish it from through cutting.

Waterjet milling relies on two operations:

(1) sweeping the waterjet across the material in a controlled fashion to remove a small but predictable amount of it with each pass.

(2) accurately measuring the geometric profile of the surface after each pass (or number of passes). These measurements are used to gage progress, calibrate operational parameters, and achieve in process inspection.

This effort will also develop roller burnishing technology to be adapted to the waterjet head. Thus, if waterjet milling alone cannot achieve the required surface finish, a hybrid machine with roller burnishing technology can easily finish the job without the need for post processing.

As stated above, waterjet milling can be used to machine almost any material, including those that have proven extremely difficult to machine by conventional means. Hence, waterjet milling is an enabling technology that allows the use of new chromium-free pressure vessel coatings and liners that would otherwise be impractical due to machining limitations. Thus, it supports the Army’s thrust to eliminate toxic hexavalent chromium and its associated exposure issues.

Waterjet milling would reduce life cycle costs associated with purchasing, handling, and disposing of toxic hexavalent chromium solutions and MWF. It would also reduce the costs of purchasing conventional honing and grinding tooling. Overall, it is estimated the total life cycle costs may be reduced by 80 percent, as compared to current process technologies, while vastly increasing production and readiness. (Anticipated Project Completion - 2026)