A thermodynamics coupled modeling approach for analysis and improvement of high-speed motorized spindle system

The performance of high-speed motorized spindle system is greatly affected by spindle’s thermal and dynamic behavior. So, it is very important to predict these properties in design stage of spindle system. However, the thermal and dynamic behaviour reacts upon each other for the high rotational speed and complex structure of the spindle system. To control and optimize the dynamic behaviour and the temperature rise of spindle, this paper developed a dynamic and thermal coupled model of the spindle system by using the finite element method (FEM). The shaft and rotor were modeled as Timoshenko’s beam, the rational interference fit between shaft and rotor was treated as mass-spring combinations, the bearings were modeled as nonlinear spring element. The thermal analysis procedure contained the calculation of heat generation and confirmation of boundary condition. The accuracy of this coupled model was validated by corresponding experiments. With this coupled model, the thermal and dynamic performance of the spindle system was studied. The effects of rotational speed, axial preload and material of bearing and the diameter of shaft on thermal and dynamic behavior were analyzed. The spindle system was optimized with the result of analyses above. After optimization, the temperature rise of spindle system falls significantly to 24.5°C, which was 30.2°C before, while the dynamic stiffness at working speed increases from 156 to 197 N/μm

Effect of grinding wheel on the dynamic performance of high-speed spindle system with an improved FE model

The grinding wheel is a key factor which should be considered in the process of predicting the dynamic performance of the high-speed spindle system. Currently, most research is mainly focuses on shaft and bearing using Timoshenko’s beam and Jones’ bearing model. In this research, considering the effect of grinding wheel on the dynamic behavior of the high-speed motorized spindle system, a dynamic model of spindle system has been established by utilizing the finite element method (FEM). The model is improved by optimizing the relevant parameters of spindle system and validated by measuring FRF using impact hammer test. The reported results are well matched (maximum error is 5 %). Using the improved model, the effect of grinding wheel on the critical speeds, mode shapes, centrifugal force and gyroscopic effects of spindle system are analyzed. In addition, the impact of different diameters, materials and fixed methods of grinding wheel on the dynamic property of spindle system are also carried out. The result shows the affect of grinding wheel and design guideline of the spindle and grinding wheel

Study of experimental modal analysis method of machine tool spindle system

Dynamic properties of the machine tools especially the spindle systems contribute greatly to the reliability of the machine tools. The increasing use of modal analysis as a standard tool to estimate the dynamic modal parameters means that both experienced and inexperienced analysts are faced with new challenges: uncertainty about the accuracy of results. Therefore, the key requirement for experimental modal analysis is a reliable, efficient and accurate experimental method in spindle system analysis. Several processes, such as reference and response selection in modal test however would make the system identification process for structural dynamics inaccurate. To investigate the results accuracy when applying experimental modal analysis on machine tool spindle, this work hence further studied the experimental setup itself based on the reference and response selection. The reference selection and reference optimization method is developed for the accuracy and efficiency improving purpose. First, by comparing results from different reference quantity and direction test, the method to select reference points is studied. Then the modal parameters are verified by the complex mode indicator functions and finite element analysis to study the influence of the reference on the modal analysis accuracy. Next, improved algorithm of response points optimization is developed based on the MAC matrix to minimize the number and location of measuring response points. Lastly, the general standard and method to select the reference and response points are put forward. The approach setting-up the experimental impact test provides reliable and accurate results and can reduce the testing time at the same time

Dynamic Characteristics Analysis of a Micro Grinding Machine Tool

Developing miniaturizedultraprecision machine tools (MUMTs) is a rational approach to manufacture micro/mesoscale mechanical components. The dynamic characteristics of MUMTs can be different from that of conventional machine tools, because of its miniaturized structure, downsized components and more flexible assembly. Their dynamics behaviorneeds to be studied. In this paper, the dynamic characteristics of a verticalultraprecisionmicro grinding machine tool were analyzed. An analysis model was established based on finite element method(FEM). Modal analysis was then conducted to obtain vibration mode characteristics of the machine tool, and then the harmonic response analysis was applied to machine tool for verifying its mechanical behaviour. This work helps MUMT developers make a better product at the early design stage with lower cost and development tim

Dynamic Characteristics Analysis of a Micro Grinding Machine Tool

Developing miniaturizedultraprecision machine tools (MUMTs) is a rational approach to manufacture micro/mesoscale mechanical components. The dynamic characteristics of MUMTs can be different from that of conventional machine tools, because of its miniaturized structure, downsized components and more flexible assembly. Their dynamics behaviorneeds to be studied. In this paper, the dynamic characteristics of a verticalultraprecisionmicro grinding machine tool were analyzed. An analysis model was established based on finite element method(FEM). Modal analysis was then conducted to obtain vibration mode characteristics of the machine tool, and then the harmonic response analysis was applied to machine tool for verifying its mechanical behaviour. This work helps MUMT developers make a better product at the early design stage with lower cost and development tim

Residual Stresses Distributions in Grinding of 3J33 Maraging Steel with Miniature Electroplated CBN Wheel

It is well known that the residual stresses on the ground surface and the subsurface can influence the service quality of a component, such as fatigue life, tribological properties, and distortion. In this paper, an experimental investigation was conducted to determine the effects of grinding force, temperature and grinding conditions, such as grinding speed, workpiece speed and grinding depth, on the surface and in-depth residual stresses distributions induced by grinding of 3J33 maraging steel with the miniature electroplated CBN Wheels. The results show that a ‘hook’ shaped residual stress profile is generated with the maximum compressive stresses occur at the depth of 3-14 ?m below the ground surface. There is a good correlation between residual stress and cutting force, but the trend related to grinding temperature is not obvious. The main grinding parameters affecting the residual stresses distributions is grinding speed, while the workpiece speed and grinding depth have the least effect

Residual Stresses Distributions in Grinding of 3J33 Maraging Steel with Miniature Electroplated CBN Wheel

It is well known that the residual stresses on the ground surface and the subsurface can influence the service quality of a component, such as fatigue life, tribological properties, and distortion. In this paper, an experimental investigation was conducted to determine the effects of grinding force, temperature and grinding conditions, such as grinding speed, workpiece speed and grinding depth, on the surface and in-depth residual stresses distributions induced by grinding of 3J33 maraging steel with the miniature electroplated CBN Wheels. The results show that a ‘hook’ shaped residual stress profile is generated with the maximum compressive stresses occur at the depth of 3-14 ?m below the ground surface. There is a good correlation between residual stress and cutting force, but the trend related to grinding temperature is not obvious. The main grinding parameters affecting the residual stresses distributions is grinding speed, while the workpiece speed and grinding depth have the least effect

Atomistic insights on the nanoscale single grain scratching mechanism of silicon carbide ceramic based on molecular dynamics simulation

The precision and crack-free surface of brittle silicon carbide (SiC) ceramic was achieved in the nanoscale ductile grinding. However, the nanoscale scratching mechanism and the root causes of SiC ductile response, especially in the atomistic aspects, have not been fully understood yet. In this study, the SiC atomistic scale scratching mechanism was investigated by single diamond grain scratching simulation based on molecular dynamics. The results indicated that the ductile scratching process of SiC could be achieved in the nanoscale depth of cut through the phase transition to an amorphous structure with few hexagonal diamond structure. Furthermore, the silicon atoms in SiC could penetrate into diamond grain which may cause wear of diamond grain. It was further found out that the chip material in the front of grain flowed along the grain side surface to form the groove protrusion as the scratching speed increases. The higher scratching speed promoted more atoms to transfer into the amorphous structure and reduced the hexagonal diamond and dislocation atoms number, which resulted in higher temperature, smaller scratching force, smaller normal stress, and thinner subsurface damage thickness, due to larger speed impaction causing more bonds broken which makes the SiC more ductile