Title:

Recirculating Water System for Water Droplet Machining Process

The goal of this project is to analyze, design, and construct a water recirculation system for the existing water droplet machining (WDM) device located at UNH’s John Olson Advanced Manufacturing Center. Water droplet machining is a new manufacturing process where a series high-velocity of water droplet impacts are used to erode and cut-through metal workpieces. The process is conducted within a sub-atmospheric pressure environment, i.e., vacuum chamber, to inhibit aerodynamic drag and atomization of the waterjet and droplet stream. This preserves droplet momentum and enables a more efficient transfer of kinetic energy to fracture energy at the workpiece surface than in traditional pure waterjet cutting. Prior to the work of this senior design project, the cutting water accumulated at the bottom of the chamber floor preventing continuous and steady-state operation of the WDM device. Therefore, this project aims to solve this problem by implementing a novel vacuum-rated drainage procedure. Additionally, as a proof-of-concept, the drain water is filtered to a high purification so that the WDM machine can recycle it’s cutting fluid, rendering the flow of water “closed-loop.” This is advantageous for manufacturing in remote areas such as in outer-space, where resources are limited. As the WDM machine is a metal plate cutting process that uses only water droplets rather than water mixed with expensive cutting filament, i.e., garnet abrasive, like most water machining devices jets. The main application of the WDM device is in space manufacturing, and one of the main concerns with space manufacturing is the cost of getting materials into space. The recirculation system developed allows for the same water to be constantly used instead of using new water for every cut. The system is a closed loop system designed to filter the water with metal particles after cutting to meet the water quality requirements of the high-pressure water jet of the WDM device before being reused by the system. The filtration system used is a standard reverse osmosis sink filter, a rough filter, a fine filter, and a 60-psi water pump to force the water through the reverse osmosis membrane. Iterations of testing were done to ensure the total dissolved solids of the water after filtration fall within in the range of 50-100 TDS regardless of initial water total dissolved solid level and to determine the filtration speed of the system. Two tables made from 80/20 extrusion were also developed to contain the filtration system and support weight of the drainage tank welded to the vacuum chamber.

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