Effect of laser-textured micro dimples on inhibition of stick-slip phenomenon of sliding guideway

Purpose This study aims to investigate the efficacy of micro dimple in inhibiting stick-slip phenomenon on the sliding guideway. Design/methodology/approach In this study, micro-dimples were fabricated by laser on surfaces of steel disk and guideway. The disks and guideways were respectively performed pin-on-disk tribological tests and working condition experiments to study differences in lubrication condition and friction stability between textured and untextured surfaces. Findings Micro-dimples help reduce critical sliding speed that allows contact surfaces to enter in hydrodynamic lubrication regime. This increases hydrodynamic lubrication range and narrows speed range where stick-slip phenomenon can occur, enhancing sliding guideway’s adaptability for broader working conditions. Furthermore, friction stability on the textured surface improved, lowering the occurrence possibility of stick-slip phenomenon. Finally, difference between static and kinetic frictions on the textured surface is lower relative to the untextured surface, which decreases the critical velocity when the stick-slip phenomenon occurs. Originality/value The results indicate that laser-textured micro-dimples are significantly conducive to inhibit stick-slip phenomenon, thus providing smoother movement for the guideway and eventually increasing precision of the machine.

Numerical investigation of dimple-texturing on the turning performance of hardened AISI H-13 steel

Forming micro-dimples nearer to the cutting edge on the rack face of the tungsten carbide cutting inserts will positively influence the machinability. However, it is challenging to machine the perfect micro-dimple dimensions by utilizing the available machining techniques. Finite element analysis can be an efficient way to observe the influence of dimple-texture area density, micro-dimple size, and various micro-dimple shapes on cutting inserts' machinability. This paper numerically analyses the impact of micro-dimple-textured cutting inserts in dry machining of AISI H-13 steel using AdvantEdge (virtual machining and finite element analysis software). Micro-dimples are formed on the rack face of tungsten carbide cutting inserts to observe the effect of dimple-textured cutting inserts on machinability compared to non-textured cutting inserts in terms of micro-dimple shape, micro-dimple size, and micro-dimple area density ratio. Their outcomes are analysed in terms of chip-insert contact length, main cutting force, and thrust force. It is observed that micro-dimple textured cutting inserts exhibit minimal main cutting force and thrust force in line with increasing the cutting insert life span. The abrasive wear was reduced in dimple-textured cutting inserts due to minimal contact between the cutting insert and chip developed compared to non-textured cutting inserts.

Influence of piston surface treatment on piston assembly friction in an eco-mileage vehicle engine

This study investigated the effect on piston assembly friction after treating piston surfaces with a fine particle bombarding process, using a friction measurement apparatus with a floating cylinder liner, similar to an eco-mileage vehicle engine. Friction was measured in four conditions: (1) no treatment (standard piston in a commercially-available engine), (2) micro dimple treatment (45 μm ceramic particles were air-blasted onto the piston surface), (3) molybdenum disulfide (MoS2) shot treatment (1 μm MoS2 particles were air-blasted onto the piston surface), and (4) combination of the previous two micro dimple and MoS2 shot treatments (first 45 μm ceramic particles and then 1 μm MoS2 were air-blasted onto the piston surface). Results indicated that friction decreased in the following order: no treatment > micro dimple treatment > MoS2 shot treatment > combination of micro dimple and MoS2 shot treatments.

Investigation on Bidirectional Pulse Electrochemical Micromachining of Micro Dimples

Through-mask electrochemical micromachining (TMEMM) is a promising method to prepare micro dimples on the surface of metallic parts. However, the workpiece is machined one by one in traditional TMEMM. This paper introduced bidirectional pulse to TMEMM to improve the machining efficiency. Two masked workpieces were placed face to face, and connected to the ends of the bidirectional pulse power supply. Along with the change of the pulse direction, the polarities of the two workpieces were interchanged periodically, and micro dimples could be prepared on both workpieces at one time. The simulation and experiment results indicated that with bidirectional pulse mode, micro dimples with same the profile can be prepared on two workpieces at one time, and the dimension of micro dimple was smaller than that with unidirectional pulse mode. In bidirectional pulse current, the pulse frequency and pulse duty cycle played an important role on the preparation of micro dimple. With high pulse frequency and low pulse duty cycle, it is useful to reduce the undercut of micro dimple and improve the machining localization. With the pulse duty cycle of 20% and pulse frequency of 10 kHz, micro dimples with etch factor (EF) of 3 were well prepared on both workpieces surface.