Water jet guided laser as an alternative to EDM for micro-drilling of fuel injector nozzles: A comparison of machined surfaces

• Published in: Journal of manufacturing processes Vol. 15; no. 4; pp. 524 - 532
• Main Authors: Rashed, C.A.A., Romoli, L., Tantussi, F., Fuso, F., Burgener, M., Cusanelli, G., Allegrini, M., Dini, G.
• Format: Journal Article
• Language: English
• Published: Dearborn Elsevier Ltd 01-10-2013; SME
• Subjects: Drilling; EDM; Laser Micro-Jet; Lasers; Manufacturing; Micro-drilling; Microscopy; Shear Force Microscopy; Studies; Surface quality; Topography; Micro-drilling; Surface quality; Laser Micro-Jet; Shear Force Microscopy; EDM
• ISSN: 1526-6125; 2212-4616
• DOI: 10.1016/j.jmapro.2013.08.002

•The surface of drilled holes obtained by EDM and water jet guided laser drilling is analyzed by Shear Force Microscope.•The surface texture is characterized by (i) maximum peak-to-valley distance and (ii) periodicity.•Total excursion up to 1.7μm and 800nm is generated by micro-EDM and Laser Micro-Jet (LMJ), respectively.•EDM generates averaged Rq of about 450nm compared to the 150nm of the LMJ drilling.•LMJ has proved to be a reliable alternative to micro-EDM to facilitate the atomization of the fuel jet.
To characterize the inner surface of the fuel injector nozzle holes drilled by EDM and water jet guided laser drilling (Laser Micro-Jet) a specifically conceived scanning probe microscopy technique with true non-contact operating mode was used. A difference in morphology of the drilled surfaces is evident from the acquired surface topography along the hole axis for the two compared drilling techniques. Results showed that the surface texture can be characterized by (i) maximum peak-to-valley distance and (ii) periodicity. Acquired maps confirm that electro-eroded surfaces are an envelope of craters randomly distributed with total excursion up to 1.7μm with a crater size of 15μm. While, the efficient melt expulsion and immediate cooling of water jet guided laser generates a peak to valley distance of 800nm with a periodicity of 18μm. Average Rq derived from the measured cylindrical surfaces was 450nm and 150nm for EDM and Laser Micro-Jet, respectively. Water jet guided laser drilling has proved to be a reliable alternative to EDM from the point of view of repeatability of the results and surface quality to facilitate the atomization of the fuel jet.