The Study On Anti-Stick-Slip Phenonmenon And Reducing Friction Of Sliding Machine Tool Guideways Based On Laser Composite Micro Textures

With the rapid development of industrial technology,high-precision,high-efficiency and high-flexibility have become the developing features of the manufacturing industry.Machine tool is the core component of the equipment manufacturing industry,the requirements of the performance,precision and lifetime for the machine tool have increased.However,under certain conditions such as low speed and high load,the stick-slip phenomenon will appear in machine feed system.Stationarity of the machine tool will be affected,the positional accuracy and the sensitivity will reduce,thus,the processing quality and processing precision will reduce too.So it is of great theoretical and practical significance to put forward a surface treatment method in order to restrain the stick-slip phenomenon and reduce the friction and wear.In this paper,the surface of the machine tool guideways were studied and the theoretical and experimental research about laser surface composite textures were carried out.Firstly,the technological tests about laser surface composite textures were conducted,micro textures were processed on the GCr15 bearing steel samples with the SPI pulsed fiber laser.The effects of some laser parameters such as laser power,pulse width,repetition times to the morphology of the textures were researched in order to explore the formation mechanisms of different morphologies for the micro-textures.Secondly,a simplified physical model was built and the mathematical model of the critical speed for the machine tool guideways were studied.Meanwhile,the geometrical model of the machine feed system was built with the ADAMS so that the influence of the difference value for the static and akinetic friction coefficient to the vibration circumstances.Besides,the pin-on-disc friction and wear tests were carried out with the RTEC friction and wear tester under the actual contact form of the machine tool guideways and the actual initial working conditions of the machine tool.The effects of different micro surface textures to the inhibiting stick-slip phenomenon influence were studied.On this basis,the effects of the bulge textures to some surface properties such as metallographic structure,hardness and residual stress were researched.What's more,the effects of the bulge textures with different texture densities to the friction and wear performance wear also investigated with the RTEC friction and wear tester.Lastly,the solid lubricant additives composite with the micro-textured surface were explored in order to improve the lubricanting state of the machine tool guideways.The tests were conducted with the pin-on-block reciprocating friction tests using the RTEC friction and wear tester.The main results are as followed:?1?Using the SPI pulsed fiber laser,at single laser action,the bulge textures can be processed when pulse width is small?1000?s?with the different power,when pulse width increases to certain value,the bulge morphology is slowly fading out and the pit morphology appears.When the laser power and pulse width are certain,the complete pit morphology will appear if the repetition times increase within certain limits.However,large amounts of slags will accumulate because of the thermal effect if repeat too much times.?2?The mathematical model of the critical speed for the stick-slip phenomenon of the machine feed system was deduced,it can be concluded that the critical speed for the stick-slip phenomenon is affected by some elements like the difference value of the static and akinetic friction coefficient,the system stiffness,the system damping and the table quality.Among those influence factors,the difference value of the static and akinetic friction coefficient has the largest impact.?3?It can be concluded that different kinds of surface textures can restrain the stick-slip phenomenon effectively.The stick-slip inhibiting effect of bulge textures is better than that of pit textures and overlapping curve textures,and the pit textures with slags around the pits are better than the polished pit textures when comparing the anti stick-slip ability.The amount of lubricating oil has effect to the anti stick-slip ability of pit textures and overlapping curve textures,but it does not work when the textures have the features of bulge.Too large or too small densities of the bulge textures do no benefit to the stick-slip inhibiting effect,28.2%is the most suitable texture density.?4?Laser texturing has the effect of grain refinement to the melt condensation area.The maximum hardnes of the textured area is almost four times than the substrate region.The textured area shows a certain value of residual tensile stress.The friction coefficients of textured samples with different texture densities are lower than that of the untextured sample in oil medium,and the friction coefficient decrease with the increase of texture density.The bulge textured samples show excellent anti-wear performance,under the same condition,the wear depth of textured samples are much less than the untextured sample.?5?Adding a certain amount of solid lubricant additves can reduce the fricon whatever for smooth surface or textured surface,the friction reduction effect of solid lubricant additives with nano MoS₂ is better than the nano Gr additives.Nano solid lubricant additives composite with micro textured surface has excellent lubricating and anti-wear effect.Under a constant load,with the increase of reciprocating frequency,the friction reduction effect is more significant if combing micro textured surface with nano solid lubricant additives;Under a constant reciprocating frequency,with the increase of load,the friction coefficient relatively smaller if combing micro textured surface with nano solid lubricant additives.