Grinding Wheel Spindle Research Articles

Research on the grinding rounding mechanism and law of the cylindrical grinding system supported all by hydrostatic spindles

The maximum achievable journal roundness accuracy range by the conventional “Rolling bearing supported spindle and fixed center clamping” grinding solution is about 0.2–0.5 μm, which barricades the grinding roundness improvement. To further improve the grinding roundness, this study proposes a novel “Fully hydrostatic supported spindle and movable center clamping” grinding solution, which adopts hydrostatic supported grinding wheel spindle, and hydrostatic supported movable clamping centers. Firstly, based on the interaction between wheel and workpiece, a coupling material removal deformation compatibility model is built, and the rounding process of external cylindrical grinding is quantitatively simulated. Secondly, a fully hydrostatic supported grinding system is developed and tested. The optimal roundness error in the experiment reached 0.12 μm, the maximum relative error between the simulated results and the measured average results is 18.5 %, which validates the proposed solution and the algorithm. Thirdly, from the perspective of grinding parameters, the grinding rounding law of the system is studied. Finally, the proposed grinding solution is compared with the conventional grinding solution, the novel grinding solution has better grinding efficiency and grinding roundness. The proposed grinding solution may provide a new path for grinding accuracy improvement.

Design and Development of a High-Speed Precision Internal Grinding Machine and the Associated Grinding Processes

In order to meet the P2-grade bearing grinding requirements, we designed a high-speed internal grinding machine to be used for grinding bearing raceways and inner circles. The machine has a T-type layout and a four-axis numerical control linkage. It is supported by hydrostatic pressure and driven directly by a torque motor. In addition, it is equipped with a high-speed hydrostatic grinding wheel spindle. Our design includes a hydrostatic workpiece shaft and hydrostatic turntable, and the process has a good engineering application value. Finally, the designed precision grinding machine was used to grind a P2-grade bearing raceway.

Transient oscillatory processes at the balancing device operation of abrasive wheel grinder

In conditions of the practice development of building new production facilities following the concept of Industry 4.0 and the intensification and complication of production processes, the need for a general reduction in costs arises. One of these problems is the lengthening the life of supports of abrasive wheel grinding machines based on the balancing process automation without stopping the machines for maintenance work. This paper proposes a method for numerical calculation of the motion path of the grinding wheel spindle axis during the balancing process. Based on the proposed method, a numerical calculation was carried out and the motion path of the grinding wheel centre was built. As a result of the work, a transient balancing oscillatory process of a damping mode was built. This process does not lead to the forcing of the system in the eigenmode range, which creates prospects for the introduction of this balancing method in the grinding process and reducing production costs.

A novel double rotor coupling model for inner bore grinding process

Hydrostatic bearings are the supporting parts of hydrostatic spindles. Hence, the bearing inner bore roundness may affect the spindle shaft equilibrium position and rotation accuracy. Although many scholars have established various models to simulate the internal and external grinding process, the existing models cannot provide precise calculations for choosing an efficient grinding strategy, and the final bore roundness predictions are also insufficient. To achieve precise prediction for grinding process and final bore roundness, the coupling interaction between the grinding wheel spindle system and the workpiece-spindle system during the inner bore grinding process is considered, and then a novel inner bore grinding double rotor model is established. The model adopts iterative algorithm to calculate material removal and the bore roundness forming process. Based on the model, different inner bore grinding strategies are quantitatively simulated for a given grinding system. The material removal and inner bore forming process under different grinding conditions are compared. The final bore roundness roughly matches the experiment results. The proposed double rotor system model and the simulation algorithm could be a new path for further studies of the grinding transition process.

Configuration design and accuracy analysis of special grinding machine for thin-walled small concave surfaces

In this work, a special grinding machine tool using a small ball-end grinding wheel is designed to achieve ultra-precision grinding of complex components with small concave surfaces. A comprehensive error propagation model is established, considering kinematic errors, setup errors and structure parameters. Sensitivity analysis is performed by the Sobol' method to quantify the relationship between the errors, structure parameters and geometric accuracy of the machine tool. On this basis, error allocation is carried out, and the inclination angle of the grinding wheel spindle and the working range of the C-axis are optimized to reduce the influence of the setup errors on machining accuracy. Then, the predicted geometric accuracy of the machine is 0.3 μm, contributing only to half of the profile accuracy requirement for peak-to-valley PV < 0.6 μm. The developed machine is tested by grinding ψ-shaped components to achieve an average profile accuracy of 0.589 μm and a surface roughness of 40.2 nm, which means that the machine tool developed by the error model and sensitivity analysis meets the design requirements. By compensating the setup errors and linear errors based on the error propagation model, the profile accuracy of the ground component reaches 0.34 μm, indicating that the error propagation model can accurately represent the geometric accuracy of the machine tool.

A high-efficient precision grinding for fabricating moderately thick plane mirror (MTPM)

Plane mirrors have been widely used in various optical systems. The performance of optical systems relies heavily on the surface quality and flatness of plane mirror which are achieved by grinding or lapping followed by polishing or figuring. It is widely acknowledged that grinding is a high efficient method to machine plane mirrors with appropriate dimensional accuracy before polishing. However, the deformation of mirror induced by the mounting or clamping force will influence the final surface shape accuracy especially for the plane mirror with a feature of moderate thickness. In this paper, a new method is proposed for machining a moderately thick plane mirror (MTPM) employing the rotational grinding technique and the deformation compensation method. An accurate plane mirror can be machined efficiently relying on measuring the elastic deformation of the mirror in the clamping process and the mathematic relationship between the posture angles of grinding wheel spindle and surface profile of the plane mirror. A Φ100 mm × 6 mm silicon mirror (Si mirror) is machined based on the proposed method. The experiment results show that the Si mirror is totally removed 15 μm in thickness with feed rate of 15 μm/min and the peak and valley (PV) value of the Si mirror surface is reduced from 4.80 to 1.32 μm. The average value of the surface roughness Ra 9.6 nm is measured by means of the atom force microscope (AFM). The research indicates that the proposed method is excellent in machining MTPM with high quality and flatness.

An experimental study of the effects of dressing parameters on the topography of grinding wheels during roller dressing

Vitreous-bonded grinding wheels are widely used for machining features on aerospace components achieving high material removal rates under high pressure coolant. Dressing is a vital stage in the grinding process to ensure a consistent wheel topography and performance. However, the effects of roller dressing on functional performance of vitreous grinding wheels as well as its influence on different abrasive grit morphologies have not been fully characterised. This paper studies the influence of dressing parameters on the topography, morphology and characteristics of the surface of different vitrified abrasive wheels in order to better understand the process and therefore optimise the preparation of grinding wheels for industrial machining. Alumina grinding wheels with conventional and engineered grit shapes were dressed at two different infeed rates over a range of seven different speed ratios (from −0.8 to +1). An experimental methodology has been developed incorporating a range of known techniques to define the abrasive wheel condition including measured power consumption and ground graphite coupons as well as using optical microscopes to measure grain fracture flats, peak density and abrasive grain shape. It has been found that power consumption of the grinding wheel spindle increases at higher infeed rates and speed ratios. This leads to increased fracturing of the grains and whole-grain pull out. According to the results the infeed rate has a more substantial effect on wheel topography than speed ratio and the response of engineered grit morphologies to dressing is dependent on grit orientation.

Effects of kinematic parameters on electric discharge truing of small ball-end diamond wheels for small concave surfaces grinding

To meet the strict requirements for processing quality, the metal-bonded small ball-end diamond wheel (SBDW) has become a promising choice to process the hard and brittle materials with small concave surface. Unlike conventional diamond wheels, the profile accuracy of SBDW would so greatly affect the form accuracy of ground small concave surfaces that a truing system must be adopted to insure the accuracy of SBDW. Hence, the effects of kinematic parameters of the truing system on the on-machine electric discharge truing (EDT) of SBDW are investigated. The effects of the errors from kinematics, electrode geometry and relative position on truing are analyzed by establishing the mathematical model through screw theory. In the experiments, the effects of spindle speeds of SBDW and tool electrode on truing are investigated and the complex component with small concave surfaces is ground by the optimally trued SBDW. The results indicate that there are more factors affecting the dimension accuracy than profile accuracy of the trued SBDW. Each factor affects dimension accuracy equally, while the radial run-out error of grinding wheel spindle influences profile accuracy more significantly than others. The spindle speed of SBDW affects the profile accuracy more remarkably than that of tool electrode, and the relative speed between them affects the truing efficiency and surface quality of SBDW. The final profile error (PV) and surface roughness (Ra) of the practically ground component are 0.328μm and 50.2nm, respectively.

Development and Experimental Study of the Online Dynamic Balance System for Grinding Machine

The vibration of grinding wheel spindle will significantly reduce the machining quality and machining accuracy of precision grinding. In order to suppress the grinding wheel rotor vibration effectively, the Spray-Typed online dynamic balance system for specific grinding wheel spindle was designed composed of terminal balance, hydraulic system and control system. To achieve the amount of spindle unbalance accurate extraction and liquid volume control, using hydraulic system to achieve the balance of the terminal of the liquid loading and using high-performance DSP chip as a control method. A segmented spindle online dynamic balance method , combining the advantages of influence coefficient method and coordinate rotation optimization method was proposed. The method can fast approaching the goal of balancing and meet the local precise adjustment of the balance weight. At last, the online dynamic balance experiment of grinding wheel spindle is carried out in the industrial field, the grinding spindle vibration displacement amplitude decreased from 17.8 to 7.7 before and after balance, fall by as much as 55%, which verifies the validity and feasibility of the system.

Effects of Relative Velocity on Grinding Performances under Si Wafer Rotary Grinding

For the backgrinding of semiconductor devices, a rotary grinding process is indispensable for achieving the required wafer thickness. The relative velocity between the grinding wheel and the wafer is maximum at the periphery of the wafer and minimum at the center of wafer. Generally, the grinding performances are discussed in terms of the ratio of the rotational speeds of the grinding wheel and the wafer. However, it is not possible to use this ratio to determine the grinding conditions for different wafer sizes grinding as this ratio does not show the difference in relative velocity. Therefore, a new relative velocity ratio was defined in this study. Then, the Si wafer grinding was performed to investigate the effect of the surface roughness and the power consumption of the grinding wheel spindle on the relative velocity ratio.

Effect of grinding wheel spindle vibration on surface roughness and subsurface damage in brittle material grinding

The external interference and vibration can seriously affect the machining errors in brittle materials grinding process. This paper proposes a new model to analyze the relationship between surface roughness (SR) and subsurface damage (SSD) depth on the basis of grinding kinematics analysis and indentation fracture mechanics of brittle materials taking the wheel spindle vibration into account. The basic equations, for example, equations of grain trajectory and penetration depth are derived in new forms. Based on the basic equations above, the existing SR and SSD formulae are modified for further study. The effects of grinding and vibration parameters on SR and SSD are respectively analyzed in detail. Results show that both SR and SSD increase with the increase of table speed and vibration amplitude resulting in bad surface and subsurface quality. On the other hand, both the increasing grinding speed and decreasing vibration frequency can improve the quality of ground surface and subsurface with small SR and SSD. In addition, the increase of initial grinding depth and vibration initial phase increase the depth of SSD but have little effect on SR. The penetration depth and distance between grain's tip and finished surface are the two main factors considered to cause the different effect laws on SR and SSD among these parameters. Experiment is carried out to validate the rationality of proposed model. The effect trends of various grinding parameters on SR obtained by our model consist with measured experimental data. The typical subsurface crack system is clearly revealed through the experimental observation on SSD using SEM. Finally, the relationship between the two is fitted utilizing quadratic polynomial. Results show that the SSD depth is nonlinear monotone increasing with SR and the fitting accuracy is more or less affected by both grinding and vibration parameters.

A novel method for grooving and re-grooving aluminum oxide grinding wheels

In this paper, a new grinding wheel grooving system is proposed that is able to both groove as well as re-groove a grinding wheel using a single-point diamond dressing tool. The re-grooving capability of the new system is achieved by synchronizing the grinding wheel angular position with the dressing tool translational position. This position synchronization enables the diamond dressing tip to repeatedly engage the grinding wheel at the same angular position around the wheel and then proceed to trace the existing groove pattern along the wheel surface to, for example, refresh a worn groove geometry. Furthermore, the proposed system can be mounted on either a non-CNC or a CNC conventional grinding machine and can groove and re-groove the grinding wheel without the need to remove it from the grinding wheel spindle. The novel wheel grooving system was experimentally validated by creating helically shaped circumferential grooves on the grinding wheel surface. The resulting maximum differences in groove width and depth were found to be 0.015 and 0.013 mm, respectively, for ten consecutively cut grooves. These small discrepancies are believed to be primarily due to the brittle fracture mechanism of the abrasive grits. Furthermore, the new wheel grooving system was shown to be able to create a wide range of different groove patterns on the wheel surface. A wear study was then carried out to compare the performance of both grooved and non-grooved grinding wheels. For the conditions used in this research, the results of this wear study showed that a grooved wheel not only exhibits less wear than a non-grooved wheel but also can remove approximately twice as much workpiece material before failure occurs.

C004 Characteristics of thermal displacement of cylindrical grinding machines with rotation of wheel spindle : Influence of thermal displacement of wheel spindle and wheel spindle head

Measurement devices are proposed for the relative thermal displacement between the grinding wheel and the workpiece, and for the thermal displacement of the wheel spindle itself during rotation of the wheel spindle. Then by separating the thermal deformation of the wheel spindle and the wheel spindle head from the relative thermal deformation between the wheel spindle and workpiece, the thermal deformation of the grinding machine is evaluated in detail. The following results are obtained. (1) The grinding wheel spindle and the wheel spindle head cause the thermal displacement in various directions. (2) A percentage of the influence of the wheel spindle and the wheel spindle head in the relative thermal deformation is different depending upon the direction of the thermal displacement.

Research on Dynamic Balance of Grinding Wheel Spindle

In this paper, grinding wheel spindle of high precision CNC is researched. Mathematics - mechanical mode of dynamic balance of grinding wheel is established on the principle of rotor dynamic balance. New method of critical speed of grinding wheel is proposed, and verified by testing the reasonableness. And, dynamic unbalance of grinding wheel spindle of high precision CNC is studied on quality surface. These studies provide theoretical direction for balance speed range and the accurate level.

Investigation of Hydrodynamic Pressure in High-speed Precision Grinding

The conventional method of delivering grinding fluid that floods delivery with high supply fluid pressure and nozzle fluid rare to achieve high performance grinding. However, the hydrodynamic fluid pressure can be generated ahead of the contact zone due to the wedge effect between the wheel's peripheral surface and the work surface. Indeed, this reduces the depth of cutting and increases grinding wheel spindle deformation and overall grinding resistance, thereby affecting machining accuracy. In this paper, a theoretical hydrodynamic pressure modeling is presented for the flow of coolant through the grinding zone during high-speed precision grinding. The simulated results show that the hydrodynamic pressure was proportional to the velocity of the grinding wheel and inverse proportional to the minimum gap between the wheel and the workpiece. Furthermore, the hydrodynamic pressure peak value was only generated in the minimum clearance region where a higher fluid pressure gradient was observed. It can also be deduced that the hydrodynamic pressure distribution was uniform in the direction of the width of the wheel. However, due to side leakage, the edge of the wheel was an exception to this rule.

Fault diagnosis of cylindrical grinding machine

Based on experiment modal analysis (EMA) and operation modal analysis (OMA), the dynamic characteristics of cylindrical grinding machine were measured and provided a basis for further failure analysis. The influences of grinding parameters on dynamic characteristics were studied by analyzing the diagnostic signals extracted from racing and grinding experiments. The significant frequency of 38 Hz related to grinding wheel spindle speed of 2 307 r/min showed that the wheel spindle system was in a state of imbalance. And wheel rotating frequency of 38.45 Hz in grinding process was close to the first natural frequency of 38 Hz, which resulted in resonance. Moreover, the main excitation at 147 Hz in grinding process together with resonance led to the deterioration of workpiece. Roundness measurement of workpiece shows good agreement with the vibration responses obtained from dynamic experiments. The fault diagnosis method was also applicable to similar machining systems.

Study on the Ultrahigh Speed Grinding of Superhard Materials with Squeeze Film Damping Technology

In order to further improve machining quality of superhard materials, it was presented that adds a squeeze film damper on the wheel spindle of ultrahigh speed grinder as a assistant elastic sustain to attenuate the vibration of the wheel spindle. Work principle of squeeze film damper was analyzed; the squeeze film pressure distribution was researched through simulation and damper parameters effect on damping coefficient was studied. Base on the theory research the damper was designed and experiments was done. Experimental result shows the amplitude of the grinding wheel spindle can be reduced 20% and machining quality of superhard materials can be improved 10%～20%. Research works provides a new method for superhard materials machining.

Study on the Dynamic Characteristics of Ultrahigh Speed Grinding Spindle Based on Squeeze Film Damping Technology

For improving grinding quality of ultrahigh speed grinding a new design method for ultrahigh speed grinding spindle is put forwarded based on squeeze film damping technology. Working principle of squeeze film damper of ultrahigh speed grinding spindle is study and differential equations of motion of the ultrahigh speed grinding wheel spindle with a squeeze film damper are set up according to d'Alembert principle. Effects of design parameters of the damper on the motion section of the spindle are studied by the way of simulation based on it. Research works show that the dynamic characteristic of ultrahigh speed grinding spindle can be improved well through adding a squeeze film damper. Research works provides a new technology for the design of the ultrahigh speed grinding spindle system.

Research of Ultrahigh Speed Grinding Spindle System Based on Squeeze Film Damping Technology

Ultrahigh speed grinding is a kind of high efficient metal cutting method. In order to improve ability of ultrahigh greed grinding wheel spindle to resist vibration and grinding quality, an ultrahigh speed grinding spindle system with a squeeze film damper (SFD) was designed based on the theory of squeeze film damping technology. Pressure distribution and squeeze film stiffness characteristic of SFD was study by the method of simulation. Based on theory study an ultrahigh speed spindle system with a SFD was designed and experiments were done. The study results show that application of SFD technology can effectively restrain vibration which is caused by the imbalance quality when the grinding wheel spindle turning at ultrahigh speed. And the speed of the grinding spindle is higher and the effect of attenuation of SFD to grinding spindle is better. Research works provides a new technology for the design of the ultrahigh speed grinding spindle system.

Experimental Study of the Ultrahigh Speed Grinding Spindle System with a Squeeze Film Damper

In order to improve the attenuation ability of grinding wheel spindle and manufacturing quality of workpiece, an ultrahigh speed grinding spindle system with a SFD was designed based on the theory of squeeze film damping, and a series of experiments were done. The study results show that the application of SFD technology can effectively restrain vibration which is caused by the imbalance quality when the grinding wheel spindle turning at ultrahigh speed. And the speed of the grinding spindle is higher and the effect of attenuation of SFD to grinding spindle is better. Research works provides a new technology for the design of the ultrahigh speed grinding spindle system.