Grinding Machine Tool Research Articles

Special Issue on Advanced Material Driven Design of Machine Tools

Special Issue on Advanced Material Driven Design of Machine Tools

Volumetric error analysis and modelling of CNC internal and external cylindrical grinding machine tool

In order to improve grinding accuracy, it is necessary to analyze and study geometric and thermal errors of NC machine tools. Based on the method of coordinate transformation of multi-body system theory, the error matrix of cutting points is established in workpiece and tool kinematic chains. The coupling relationship between thermal error and geometric error is analyzed, and the comprehensive mathematical model of geometric error and thermal error of CNC internal and external grinder is deduced. The precise machining constraint equation of grinder is established, which lays a theoretical foundation for subsequent error compensation.

Constructive ensuring the accuracy of processing of the spherical ends of the bearing rollers

The article focuses on ensuring the accuracy of the ends of the rollers of tapered bearings when machining on sphere grinding machines. Reviewed of the design the spherical grinding machine tools, with the periphery of the wheel profiled by a given radius have been given. The use of a corrected radius for profiling a circle is proposed, for which the design of the device for the basing and moving the rollers has been developed. Experimental studies of the use of the device are held. The results showed that the proposed constructive solution ensures the accuracy of processing the sphere of the end face of the tapered bearing roller.

Influence of drag finishing parameters on the cutting edge radius of solid carbide mills

Paper deals with the cutting-edge preparation of milling tools by drag finishing. The aim of the experiment was to determine the optimal parameters of the process on a prototype device for edge preparation. The prototype device was based on a 3-axis milling centre and the drag finishing media used was Al2O3 granulating. Tools for the experiment were manufactured on a tool grinding machine Reinecker WZS 60 from the cemented carbide rod with chemical composition WC+Co (10%). After that, the tools were drag finished. Then, cutting edges radii were measured on a Zeiss SURFCOM 5000 surface and form measuring machine. The effect of process parameters such as spindle rotation speed, feed rate and time of the drag finishing on the size of the cutting-edge radius and shape was examined. The experiment design was described as well as measurement and evaluation of the output values. Purpose of the experiment and multi-criteria analysis described in this article was to determine the influence of process parameters on the cutting-edge radius sizes when drag finishing the cemented carbide mills.

Using multi-criteria analysis to evaluate the impact of drag-finishing technological parameters on the carbide tool radius

Abstract Article describes the usage of multi-criteria analysis of drag finishing in order to determine the optimal parameters of the process on a prototype device for edge preparation. The prototype device was based on a 3-axis milling center and the drag finishing media used was Al2O3 granulate. Tools for the experiment were manufactured on a tool grinding machine Reinecker WZS 60 from the cemented carbide rod. After that, the tools were drag finished. Then, cutting edges radii were measured on a Zeiss SURFCOM 5000 surface and form measuring machine. The effect of process parameters such as spindle rotation speed, feed rate and time of the drag finishing on the size of the cutting edge radius and shape was examined. The experiment design was described as well as measurement and evaluation of the output values through multi-criteria analysis in the Minitab software. The results of the multi-criteria optimization were summarized and compared. Purpose of the experiment and multi-criteria analysis described in this article was to determine the influence of process parameters on the cutting edge radius sizes when drag finishing the carbide tools – special carbide milling tools

Experimental study of double-sided face grinding machine tool

The work considers the methodology of experimental studies of double-sided face grinding machines on the criterion of heat stability. The proposed methodology includes: procedure of grinding process simulation; procedure of temperature measurement; procedure of determining the mutual angular position of the grinding wheels due to thermal deformations; procedure of machining error measurement. The described techniques allow you to fine-tune the machine under production conditions. Preliminary full-scale test of a double-sided face grinding machine showed that excess temperatures were distributed nonuniform over the elements of the load-bearing structure of the machine tool when grinding an industrial batch of cylindrical rollers. When idling the end face of the spindle headstocks and bed had the highest excess temperature. When grinding the surface of the machine units, located in the immediate vicinity of the grinding zone, had the highest temperature. The experiments carried out confirmed the coordination of the nature of the change in excess temperatures at characteristic points and cutting coolant when simulating the grinding process on a machine with the corresponding experimental data obtained on a working machine.

Crucial geometric error compensation towards gear grinding accuracy enhancement based on simplified actual inverse kinematic model

The geometric error, which will significantly affect grinding accuracy of the gear form grinding machine tool, should be compensated. This paper proposes a crucial geometric error compensation method towards gear grinding accuracy enhancement, and it can directly obtain simplified explicit analytical expressions of compensated motion commands for more efficient and effective compensation. Firstly, an actual forward kinematic model is established by rapid reconstruction of the geometric error modules of motion axes. Next, the conventional actual inverse kinematic model (IKM) directing at tool posture error compensation is developed to calculate analytical expressions of compensated motion commands. Then, the material removal mechanism of gear form grinding process is considered to construct the geometric error- tooth surface posture error model, which directly reveals the mapping rules between the geometric error and the tooth surface errors. On this basis, the crucial error elements regarding tooth profile and helix deviations are identified based on global sensitivity analysis, and the compensated expressions obtained by the actual IKM are further simplified and modified directly towards gear accuracy enhancement. Finally, the crucial error identification and compensation process was verified by both numerical analysis and machining tests. The results show that tooth profile deviations will reduce by more than 80% theoretically but only by 43.27% in fact due to other errors, and it proves the feasibility and effectiveness of the proposed method.

Grinding Deviation Analysis of Offset Face Gear Based on Involute Disc Wheel

Offset face gear drive has shown many unique advantages in the area of crossed-axes transmission. In this paper, deviation analysis of an offset face gear using a involute disc wheel as a cutting tool has been discussed to achieve precised machining.Firstly, equations of involute disc wheel and offset face gear are derived based on meshing theory.Then, a grinding machine tool is designed and equations of offset face gear containing machining deviation are derived.At last,figures of deviation cloud of face gear surface are created with MATLAB and importance of different machining deviation is discussed.The results show that the deviation Az along the axis of grinding wheel is the most influential deviation,while Ay along the axis of face gear is the least one.

Modeling of Precision Machining for Crankshaft Follow-up Grinder

In this paper, follow-up grinding of crankshaft is studied and the mathematical model of follow-up grinding motion is established. Taking the double grinding wheel crankshaft follow-up grinder as the research object, the motion errors of the machine tool are obtained by analyzing the motion relations among the moving bodies. Based on the kinematics theory of multi-body system, the kinematics model of the whole machine tool is established. The position matrix of any cutting point is described according to the kinematic chain of “bed-workpiece” and “bed-tool”, and the precise machining model of double grinding wheel follow-up grinding machine tool is established by using the coincidence principle of tool actual trajectory and tool path. The coordinate system of each moving body is established, the transformation matrix between moving bodies is obtained, and the precision machining model of double grinding wheel follow-up crankshaft CNC grinding machine is solved, which lays a foundation for error compensation of the machine.

Motion control analysis of hybrid grinding and polishing machine tool for blade finishing

Blade is the key component in the energy power equipment of turbine, aircraft engines and so on. Research on the process and equipment for blade finishing becomes one of important and difficult points. The motion control of hybrid grinding and polishing machine tool is different from that of traditional machine tool, and there exists motion coupling phenomenon when it moves as a whole. In order to control precisely motion of machine tool, the inverse and forward kinematics solution considering motion coupling of parallel mechanism was solved based on designed hybrid grinding and polishing machine tool for blade finishing in this paper. Firstly, the coupling factor of parallel mechanism was taken into account in the new model, and the inverse kinematics solution was modified to improve the solution accuracy. Then, the forward kinematics solution of machine tool based on inverse kinematics solution was solved. Finally, the motion simulation was made to verify the inverse and forward kinematics algorithm based on kinematic coupling factor of parallel mechanism by simulation software ADAMS. The simulation result shows that the inverse and forward kinematics solution deduced is correct, which provides theoretical basis for the motion control scheme of machine tool calibration and inspection control system.

Influence of Grinding Conditions and Tilting the Spindle on the Spindle Load when a 5-Axis Grinder is Used

This article deals with the influence of grinding conditions and tilting the spindle on changes in the spindle load when grinding tool steel on a 5-axis tool grinding machine. The experiment was designed to investigate any changes in cutting speed, feed rate or tilting of the spindle. The size of the load is very important, because the load can influence the tool life, the life of the machine components, quality of the surfaces and dimensional accuracy of the components. A medical femoral knee replacement was selected as the semi-finished component for the experiment, as its surface is a good representative of a complex-shaped surface. This article is limited only to the grinding of maraging steel MS1 with a CBN grinding wheel. The second part of this article is focused on the experiment where the spindle load is evaluated and the results of the experiments are compared.

An identification method for crucial geometric errors of gear form grinding machine tools based on tooth surface posture error model

The identification for crucial geometric errors of gear form grinding machine tools is essential for the later error accurate compensation, but complicated and difficult. To reveal the mapping rules between geometric errors and machining errors, the tool posture error model (TPEM) was first constructed but it failed to consider the effects of grinding process. Hence, the tooth surface posture error model (TSPEM) was established based on the discretization of the grinding trajectory and the calculation of the grinding contact lines. Then the improved Sobol method was performed to analyze the error sensitivity and identify the crucial errors and sensitive components by considering the stochastic and intercoupling characteristics of geometric errors. To validate the effectiveness of the proposed method, the identified results were compared with that of the Morris method and the modification experiment of crucial errors was conducted. It shows that the tooth surface errors in the δy-direction are reduced by 68.75% for the TSPEM and 43.36% for the TPEM and that the TSPEM is more effective for the identification of crucial geometric errors.

Experimental Analysis of Force/Temperature with Time for Cutter Grinding Machine Tool Operation

Experimental Analysis of Force/Temperature with Time for Cutter Grinding Machine Tool Operation

Error identification and verification of cycloid gear profile surfaces in precision forming grinding

ABSTRACT This paper presents an error identification method for directly related geometric errors of 4-axis forming grinding machine tool and some processing-induced errors from actual teeth profiles of a machined cycloid gear. Based on the developed 4-axis geometric error model, we build up an overall error model of cycloid gear-tooth profiles by forming grinding, which includes some directly related geometric errors of the machine tool and processing-induced errors. Error separation or identification methods are developed in correspondence with the form grinding process and are verified by some non-cutting identification or measurement techniques, including multi-lateration laser measurement technique and a laser rotary axis calibrator. The experiment results demonstrate that the separated geometric errors based on the machining test approach reach a better accuracy. In order to further improve the machining accuracy of the cycloid gear, two identified geometric errors and tooth-shaped error can be utilised for error compensation in the future.

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.

Reliability Modeling and Evaluation Method of CNC Grinding Machine Tool

How to determine subsystem’s reliability and evaluate the whole machine’s reliability of the CNC (computer numerical control) grinding machine tool is important for reliability design and promotion. Each subsystem was modeled by a different distribution based on collected data and the models were optimized by the modified gray correlation degree, which was called the similar slope and close median gray correlation method. Methods of generating random data were proposed for different models. The reliability evaluation algorithm based on Monte Carlo simulation was studied and the whole machine’s reliability of the CNC grinder was evaluated by the algorithm. The evaluation result by the Monte Carlo algorithm was compared using the observed value and the evaluation value by the whole fitting method. The results show that the point estimation value evaluated by the algorithm based on Monte Carlo has high accuracy. The interval estimation by the Monte Carlo method was 20.2% and 38.1% by the observed value and the whole fitting value, respectively, which has more practical engineering significance. The reliability evaluation method can be used to assess the whole CNC grinding machine’s reliability in reliability design, and is also one reference for reliability evaluation of other electromechanical equipment.

Ultra-precision grinding machine design and application in grinding the thin-walled complex component with small ball-end diamond wheel

Complex structural components with small concave surfaces are widely needed in aerospace, optics, and electronic industry. On account of the interference between grinding wheel and workpiece and small concave surfaces, traditional grinding machine cannot realize the grinding process; hence, a specialized grinding machine tool with on-machine electric discharge truing function is needed. After analyzing the structural characteristics and processing requirements of the component, the kinematic chain and configuration were designed. The structure of the machine tool was divided into four function modules, and each module was designed, analyzed, and optimized, respectively. Then the finite element analysis (FEA) of the whole machine tool was conducted including static, modal, and harmonic response analysis to verify the performance of the machine and identify the weak links of the structure loop. The error model was established by screw theory to study the quantitative relationship between the static deformations and processing accuracy. Both finite element analysis and error model can provide guidance for further optimization. Finally, the performance of the machine tool was evaluated by the grinding and on-machine truing experiments, achieving the profile accuracy (PV) of 0.339 μm, surface roughness (Ra) of 50.2 nm, and the grinding wheel surface with diamonds distributing homogeneously. The results indicate that the developed machine tool can well satisfy the processing requirements of the component.

Thermal characteristic analysis of Z-axis guideway based on thermal contact resistance

The Z-axis feeding system of large computer numerical control (CNC) gear grinding machine tools generates lots of heat during processing, which leads to tilt and pitch deformation of the Z-axis guideway and reduces the machining accuracy. In view of this situation, a three-dimensional finite element analysis method is proposed to conduct transient thermal-structural coupling analysis of the Z-axis guideway and feeding system. Considering the microscopic contact state on machine tool joint surfaces and using the root mean square measurement method, the fractal parameter is identified and the thermal contact resistance at the joints is calculated. The friction heat on the guideway is calculated and the thermal value of the motor is obtained. Then, the heat generation rate of the bearing and the screw nut is calculated according to the friction torque. The convective heat transfer coefficient is determined according to the Reynolds number and the Nusselt number. The finite element model is established to obtain the finite element simulation results of thermal error. Finally, the experimental platform for measuring the temperature and thermal deformation of the large computer numerical control gear grinding machine tool is set up, and the accuracy and reliability of the method is verified.

Dynamic design of grinding and polishing machine tool for blisk finishing

A virtual prototype was built in the dynamic design process of grinding and polishing machine tool for blisk. Through the analysis of multi-body dynamic of main structures changed to be flexible, column and beam had been found to be the weak link of the whole machine tool. Column and beam were optimized by changing the layout of plate to improve the low order natural frequency. The multi-objective optimization solutions of column were obtained through the genetic optimization algorithm in the FEA software. The sensitivity analysis was used to correct a set of optimized solution for the engineering. According to the optimization result, a new beam structure with inclined reinforcement plate is put forward. The first three order natural frequency of the optimized column increased by 11.9%, 18.2% and 2.8% respectively. The first three order natural frequency of the optimized beam increased by 45.3%, 8.23% and 17.8%. Analysis result of the whole machine tool show that the static and dynamic properties had improved significantly after optimization.

Development of a precision grinding machine system for the fabrication of micro V-grooves array

The microstructures arrays are widely used and have good prospects in different applications because of their special and unique engineering functions. Micro V-grooves array is one of the most common micro structures used for optical and biomedical functions. Precision grinding is one of the micro mechanical machining technologies for a wide range of hard non-ferrous materials to fabricate micro structures array. In this paper, a three-axis computer numerical control (CNC) grinding machine tool is designed for the grinding of micro V-grooves array on hard and brittle materials. Material removal and machining strategy are studied for the grinding of V-grooves array. A machining strategy design (MSD) system is established to generate NC program, simulate the tool paths and machining process as well as predict the total machining time for the grinding of V-grooves array in the developed machine tool. Experiments are designed to grind flat surface and micro V-grooves array on optical glass. The experimental results show that the grinding machine tool can produce high quality surface and micro V-grooves array with sub-micrometer form accuracy.