The effect of nozzle design on laser micro-machining of M2 tool steels

This paper shows how computational techniques have been used to develop axi-symmetric, straight, sonic-line, minimum length micro nozzles that are suitable for laser micro-machining applications. Gas jets are used during laser micro-machining processing applications to shield the interaction zone between laser and workpiece material, and they determine the machining efficiency of such applications. The paper discusses the nature of laser-material interactions and the importance of using computational fluid dynamics to model pressure distributions in short nozzles that are used to deliver gas to the laser-material interaction zone. Experimental results are presented that highlight unique problems associated with laser micro machining using gas jets.

On the selective removal of steel by laser-assisted vortex machining

Of all laser-based processes, laser machining has received little attention compared with others such as cutting, welding, heat treatment and cleaning. The reasons for this are unclear, although much can be gained from the development of an effcient laser machining process capable of processing diffcult materials such as high-performance steels and aerospace alloys. Existing laser machining processes selectively remove material by melt shearing and evaporation. Removing material by melting and evaporation leads to very low wall plug effciencies, and the process has difficulty competing with conventional mechanical removal methods. Adopting a laser machining solution for some materials offers the best prospects of effcient manufacturing operations. This paper presents a new laser machining process that relies on melt shear removal provided by a vertical high-speed gas vortex. Experimental and theoretical studies of a simple machining geometry have identifed a stable vortex regime that can be used to remove laser-generated melt effectively. The resultant combination of laser and vortex is employed in machining trials on 43A carbon steel. Results have shown that laser slot machining can be performed in a stable regime at speeds up to 150mm/min with slot depths of 4mm at an incident CO2 laser power level of 600 W. Slot forming mechanisms and process variables are discussed for the case of steel. Methods of bulk machining through multislot machining strategies are also presented.