Quality Waterjet Newsletter – 10/10/2006 Abrasive Contamination on AWJ Cut Surfaces AWJ cutting produces a sand-blasted-like surface. Abrasive contamination becomes a concern in some applications, especially in aerospace industry. Patel and Chen* conducted an experimental study on this issue, trying to quantify it and provide a solution as well. It is a great effort in their study and the results are interesting. But some of the writings are a bit confusing. The main points are highlighted here. Aluminum samples of 20 mm in thickness were cut at 345 MPa (50 kpsi) and 2 mm/s as well as at 380 MPa (55 kpsi) and 3 mm/s. The cutting was done with two different ways: “straight cut” (constant speed) and “oscillation cut” (nozzle wiggling in the cutting direction at 3 Hz and 2.5° as well as 4 Hz and 3.5°). Scanning electronic microscopy (SEM) and advanced image processing technique were used to conduct quantitative microstructure analysis on the cut surfaces. Along the cutting depth, 5 SEM images (each 1.2 x 1.4 mm) were taken, summing up to a total of 120 SEM images for this study. The photos above show the particle counts for “straight cut” (Left) and “oscillation cut” (Right). The chart gives a quantitative comparison. Their conclusion is that oscillation cut can reduce abrasive contamination by ten times, but it will not completely eliminate it. * Patel, K. & Chen, F. (2003) Quantitative study of abrasive contamination in a ductile material during abrasive aqua jet machining (AAJM), in Proceedings of the 2003 WJTA American Waterjet Conference, Houston, Texas, August 17-19, paper 2-D.

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