chapter  5
Energy Fields inWaterjet Machining
Pages 32

It can be said that the harnessing and management of concentrated energy elds are behind the progress of mankind. Throughout history, we have been searching for and developing new tools to survive and prosper. The use of a sharp rock as a tool to hunt and cut was probably man’s rst innovation to focus energy for useful purposes. The energy of waterfalls and rivers has been known since creation. This energy-kinetic energy-is what alerted man to using water as a cutting tool. In ancient Egypt, river branches were diverted to wash out soil in search of gold and other

5.1 Introduction .......................................................................................................................... 141 5.2 Waterjet Tools and Processes ............................................................................................... 142 5.3 Waterjet Energy Fields.......................................................................................................... 143

5.3.1 Pressure Generation .................................................................................................. 143 5.3.1.1 Waterjet Pumps .......................................................................................... 143

5.3.2 Energy Transport: Plumbing..................................................................................... 145 5.3.3 Pressure Release: On/Off Valve ............................................................................... 145 5.3.4 Jet Formation ............................................................................................................ 146

5.3.4.1 Waterjet ...................................................................................................... 146 5.3.4.2 Abrasive Waterjet Formation ..................................................................... 149 5.3.4.3 Air and Abrasive Entrainment ................................................................... 151 5.3.4.4 Slurry Jet Formation .................................................................................. 152 5.3.4.5 Pulsed Waterjets ........................................................................................ 152 5.3.4.6 Cryogenic Jets (CJs) ................................................................................... 154

5.3.5 Material Removal ..................................................................................................... 154 5.3.5.1 Cutting ....................................................................................................... 154 5.3.5.2 Cutting Attributes ...................................................................................... 155 5.3.5.3 Small-Hole Drilling ................................................................................... 160 5.3.5.4 Controlled-Depth Milling .......................................................................... 163 5.3.5.5 Turning ....................................................................................................... 164 5.3.5.6 Multi-Process Machining .......................................................................... 165 5.3.5.7 Hybrid Processes and Systems .................................................................. 165

5.3.6 Energy Dissipation .................................................................................................... 167 5.4 Final Remarks ....................................................................................................................... 168 Questions ........................................................................................................................................ 168 About the Contributing Author ...................................................................................................... 169 References ...................................................................................................................................... 169

minerals. This was possible because this excavation did not require high energy dense ows. Harder formations, such as coal, required the directing of river ow through pipes to focus the energy for washing out and carrying the ore. Early in this century, pumps were developed to obtain more energetic jets for protable mining practices. The increase in pump pressures (>2 MPa) over time has been critical to modern waterjet cutting. Today, waterjets operate at 600 MPa and their energies are as dense as 100 kW/mm2, which make them capable of cutting rocks and a wide range of nonmetals. Adding abrasives to waterjets provides another means of focusing the kinetic energy. In this case, the water kinetic energy is transferred to the abrasives, whose sharp tips do the cutting action, similar to man’s rst invention mentioned above. This has enabled the cutting of metals, brittle materials, composites, and hard rocks.