6. Water Jet Machining

Water jet drilling, in spite of its advantages of no tool wear and thermal damage, often creates delamination in composite laminate at bottom. An analytical approach to study the delamination during drilling by water jet piercing is presented. This model predicts an optimal water jet pressure for no delamination as a function of hole depth and material parameters.

Moreover, the kerf formation of a ceramic plate cut by an abrasive waterjet is discussed. The mechanism and the effectiveness of material removal are studied. The kerf is slightly tapered with wider entry due to decreased cutting energy with kerf depth. A high-power input per unit length produces a small taper but a wide slot.

Abrasive waterjet is adequate for machining of composite materials thanks to minimum thermal or mechanical stresses induced. The feasibility of milling of composite materials by abrasive waterjet is discussed. The basic mechanisms of chip formation, single-pass milling, double-pass milling followed by the repeatable surface generation by multiple-pass milling are studied. High volume removal rates as well as a neat surface are desired. Based on the results of single-pass milling tests, this chapter discusses the double-pass milling considering the effect of lateral feed increments. The study then extends to six-pass milling. The obtained surface roughness from the six-pass milling is expressed as a function of the width-to-depth ratio and the lateral increment. With the knowledge of the volume removal rate and the surface roughness as well as the effects of the major process parameters, one can proceed to design a milling operation by abrasive waterjet.