ILAS 2019: LASER SURFACE TEXTURING


MINIMISING FRICTION USING LASER SURFACE TEXTURING


Dr Daniel Arnaldo del Cerro, laser applications engineer at Oxford Lasers, describes how global energy consumption could be cut back through laser surface texturing to minimise the friction of moving mechanical components


F


riction between sliding surfaces has a significant impact on our everyday life. It is the reason you can steer the wheels of your car to keep it on the road, why you


can walk on a pavement without slipping, and why you can warm your hands by rubbing them together. Conversely, lack of friction is the reason why your car slides when driving on an icy or wet surface. Perhaps less evident, but no less significant,


is that a proportion of the fuel costs for your car can be attributed to friction. Te relative movement of the pistons inside the cylinder liners of your car engine produces friction. Tis friction reduces the efficiency of the engine through energy loss, and also contributes to the gradual deterioration of these moving parts. Engines, pumps and compressors are just a


few examples of where friction between sliding surfaces has a detrimental impact on performance. Tis has a huge impact in key sectors such as transportation, power generation and manufacturing, not just because of reductions in efficiency, but also because wear can cause the catastrophic failure of key components, which can be difficult to predict, contributes to additional machine downtime, and results in significant cost to the industries concerned. According to a recent study by Holmberg and Erdemir (2017)1


, up to 20 per cent of the


world’s energy consumption is wasted overcoming friction, with an additional 3 per


cent then being used to replace damaged parts due to wear – these are astonishing numbers! Terefore, engineers are faced with the challenge of improving designs in an effort to reduce friction and the resulting dramatic energy losses. Laser surface texturing is a manufacturing


process with fine surface etch control that can provide a solution. Te surface finish of sliding parts plays a key


the world’s energy consumption is wasted overcoming friction


Up to 20 per cent of


role in controlling the friction they experience. It has been shown that well-controlled surface micro-cavities of varying geometry – for example dimples or rectangular pockets – with lateral dimensions ranging between 10 to 100µm, and shallow depth profiles of up to a few tens of micrometres, can dramatically decrease coefficients of friction. Te range of desirable


feature sizes makes laser surface texturing an ideal tool for producing them, as the laser beam trajectory and


other processing parameters – power, spot size, pulse frequency and scan speed – can be adjusted while scanning across the workpiece, enabling a variety of surface textures to be produced with sufficient accuracy, down to the single-unit micrometre level. Tis ability to adjust parameters during scanning is particularly relevant in friction reduction, as the optimal surface texture for reducing friction changes with the relative speed of a moving part. A piston, for example, accelerates and decelerates rapidly as it moves between two points, reaching its highest speed mid-stroke2


, therefore different surface


textures are needed along the piston’s trajectory to ensure optimal friction reduction is achieved. Laser surface texturing on piston rings has previously been demonstrated to reduce the fuel consumption of an engine by up to 4 per cent3


. Tere is, however, a severe geometrical Figure 1: a laser surface texture for friction


reduction on a cylindrical segment (left), and a close up of the generated dimples (right)


22 LASER SYSTEMS EUROPE ISSUE 42 • SPRING 2019


constraint: as the film thickness of the lubricant being used between two sliding


@lasersystemsmag | www.lasersystemseurope.com


Arnaldo del Cerro et. al


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36