The effect of pressure fluctuation on the cutting ability of pure waterjet

The Waterjet and Abrasive Waterjet technology is the object of a concentrated research. This research area is oriented to understand the material removal mechanisms and to optimise the process parameters (fluid dynamical and technological) of various applications. The optimisation of the process parameters is especially difficult because of their instability during the process. Many authors have inquired into the physical-mechanical aspects of the interaction between the jet and the mechanical properties of the material and they developed models and different interpretations. However, the existing models, mostly, try to describe the cutting mechanism only for AWJ technology. The interpretation of the mechanism of striation formation in AWJ cutting does not explain the striation formation in the pure WJ process. In fact, whereas in the cutting surface realised by pure WJ cutting along the whole surfaces there are irregularities (striations), the surface generated by AWJ cutting is characterized by a streaked morphology in the bottom zone of the cutting surface.Previous studies have demonstrated that the cutting surface realised by WJ has not influenced either the pressure fluctuations or the pressure signal form but depends strongly on the exogenous and endogenous vibrations. In fact, a considerable reduction of these vibrations allows obtaining remarkable improvements on the surface quality, especially as regards the striation morphology. Although the pressure fluctuation does not have a substantial effects on the WJ surface quality, it should have influence on the depth of cut.In this work, the effect of the pressure fluctuation on the depth of cut, in no-passing WJ cuts, has been analysed. In order to do this, the thrust trend of the water jet on a plane surface has been analyzed. The aim of this experimentation has been to analyze the penetration ability trend of the jet at the exit of a passing cut; afterwards, the correlation between the thrust signal and the bottom profile generated by a no-passing cut on polycarbonate slabs has been analyzed.