Computational and experimental investigations of supersonic micro nozzles for laser processing applications

Abstract

Recently there has been an explosion of interest in applications, which require miniaturisation of micro mechanical components. These components are produced in many ways, but the majority relies on some form of etching, lithography or electro-forming. The reliance on these processes severely limits the choice of material and design available to the micro engineer at the concept stage, and adds months to new product lead-time. This paper investigates the design, development and performance characteristics of supersonic micro nozzles, that will enable the downscaling of many macro laser materials processing techniques, including cutting and machining.The initial nozzle design was developed using the method of characteristics. These profiles were then tested using a compressible computational fluid dynamics (CFD) code. The use of CFD code, gives the ability, to adjust the nozzle profile allowing speedy assessment of the suitability of the flow field for the particular process in question. The authors were particularly interested in developing, shock free, supersonic flow with maximum free jet length and maximum mass flow rate of process gas. Final prototype nozzles were manufactured using stereolithography and subsequently tested experimentally using pressure mapping techniques and Shadowgraph imaging. The effect of the position of the nozzle on its performance in the kerf was then examined using CFD to investigate the performance of these nozzles in industrial applications.Recently there has been an explosion of interest in applications, which require miniaturisation of micro mechanical components. These components are produced in many ways, but the majority relies on some form of etching, lithography or electro-forming. The reliance on these processes severely limits the choice of material and design available to the micro engineer at the concept stage, and adds months to new product lead-time. This paper investigates the design, development and performance characteristics of supersonic micro nozzles, that will enable the downscaling of many macro laser materials processing techniques, including cutting and machining.The initial nozzle design was developed using the method of characteristics. These profiles were then tested using a compressible computational fluid dynamics (CFD) code. The use of CFD code, gives the ability, to adjust the nozzle profile allowing speedy assessment of the suitability of the flow field for the particular process in question. The authors were p...