CNC Grinding Research Articles

An experimental investigation on effective friction coefficient in elliptical ultrasonic assisted grinding of monocrystal sapphire

In this study, in order to investigate the effective friction coefficient in elliptical ultrasonic assisted grinding (EUAG) of sapphire, the single abrasive grain scratching experiments are performed to simulate the grinding process by setting up the elliptical ultrasonic vibrator attached with the sapphire substrate on a multi-axis CNC grinder. The single grain diamond tool slides on the elliptically vibrated surface at a serial of pressures, and the grinding forces are measured. The friction coefficients under different pressure and vibration amplitude are obtained by calculating the ratio of tangential grinding force to normal grinding force, i.e., Ft/ Fn. Comparing friction coefficients in both scratching with and without vibration, there is a critical pressure Fpc at a range of pressure. As the pressure is less than Fpc, the friction coefficient in EUAG is smaller than that in conventional grinding (CG), and once the increasing pressure is more than Fpc, that is much higher than that in CG. When the pressure is slight, ploughing occurs and no chips are generated, and actually at low pressure, the ratio Ft/ Fn can be close to the effective friction coefficient in EUAG. Thus, the experimental results at low pressure indicate that the effective friction coefficient in EUAG is less than that in CG, and is decreasing with the increasing vibration amplitude.

The Study of Contact Pressure Analyses and Prediction of Dynamic Fatigue Life for Linear Guideways System

The application of the linear guideways is very extensive, such as automation equipment, heavy-duty carry equipment, heavy-cut machining tool, CNC grinding machine, large-scale planning machine and machining center with the demand of high rigidity and heavy load. By means of the study of contact behavior between the roller/guideway and roller/slider, roller type linear guideways can improve the machining accuracy. The goal of this paper is to construct the fatigue life model of the linear guideway, with the help of the contact mechanics of rollers. In beginning, the analyses of the rigidity of a single roller compressed between guideway and slider was conducted. Then, the normal contact pressure of linear guideways was obtained by using the superposition method, and verified by the FEM software (ANSYS workbench). Finally, the bearing life theory proposed by Lundberg and Palmgren was used to describe the contact fatigue life.

The Design of CNC Grinding Processing for Glass-Ceramic Convex

This article describes the process design of machining of CNC carved glass-ceramic, which overcomes the question that the traditional process is difficult to process glass-ceramic. Process includes the choice of cutting tools, grinding wheel, coolant, tooling design and roughing finishing etc. It has a certain reference value for glass-ceramic processing technology.

Soft Compensation for CNC Crankshaft Grinding Machine Tool

Wear and deformation CNC grinding machine tool, will be aggravated over time ofwhich will influence the manufacturing precision. To reduce the effect, the soft compensation method by modifying NC instruction was put forward to maintain the manufacturing precision of CNC crankshaft grinding machine tool. The error sources were analyzed, the errors caused by grinding force were calculated, and the precise grinding kinematics model was deduced by the multibody kinematics. Numerical simulation and manufacturing experiment were carried out and the rank tests were taken for the manufactured crankshafts. Experiments show that the manufacturer precision of the crank can be enhanced by 63.69%, 52.06%, 42.27%, and 30.96% by soft compensation of 10 years of service life and 10 μm grinding depth, 4 years of service life and 10 μm grinding depth, 10 years ofservice life and 6 μm grinding depth, and 4 years of service life and 6 μm grinding depth, respectively. Soft compensation can be applied to the machine tool in which the manufacturer precision has declined and the NC instruction with compensation should be updated periodically.

Intelligent dimensional error pre-compensation in CNC grinding using iterative learning approach

This paper focuses on the problem of intelligent compensation of nonlinearly appeared dimensional error in the computer numerical control grinding process. An intelligent error pre-compensation scheme is proposed with intelligent controller, automatic dimensional error measurement, and feedback information. Iterative learning approach is applied to infer the error compensation of the next workpiece machining by using the historical data. The simulation results and the real system input and output responses show that the proposed intelligent error compensation scheme and the iterative learning approach have significant superiority.

Research on Reliability of CNC Grinding Machine Based on Function Structure Tree

Based on the function structure tree ,the spot failure data of CNC grinding machine were analyzed and found out that of the all failure positions in the subsystem of the CNC machine was High-frequency Motor Built-in Spindle an high failure frequent and main criticality failure position . By further in detail analysis found out that the main failure cause of the CNC grinding machine was burning out of components. It was defined the main direction to improve the reliability of this CNC grinding machine and put forward the corresponding improvement measures. It can offer a theory basis for the reliability design and analysis of CNC machine tool .

A practical optimization design of helical geometry drill point and its grinding process

Drill with helical geometry drill point was developed to avoid the disadvantages of planar drill. For the visualization design and optimization of helical drill, a numerical modeling and simulation CAD system has been developed based on the mathematical models of helical drill. The characteristics of helical drill, such as lip clearance angle along cutting lip, heel clearance angle along flank surface, cutting edge inclination angle, rake angle, and so on, are described. Therefore, drill geometric parameters are modified reasonably according to different drilling requirements by the aid of the developed CAD simulation system. Besides, grinding parameters are obtained to guide the flank grinding process of helical drill. A case has been given to demonstrate the function of the system. And the calculated grinding parameters in the above case have been applied on a five-axis CNC grinding machine RollomΛtic 620XS with an assistant fixture to accomplish the flank grinding process. Drill geometry of ground drill shows good agreement with the simulative one, which validates the accuracy of proposed model method and relative CAD system.

Determination of the relative position between grinding wheel and a cylindrical workpiece on a 7 axis grinding machine by acoustic emission

The contact between grinding wheel and workpiece in the grinding process is recognized by acoustic emission (AE). Two acoustic emission monitoring systems (MS) were integrated into a 3 axis CNC grinding machine. A laptop allows the signal acquisition and visualization. The acquired AERMS signals from the contact between tool and workpiece are analyzed permitting to establish the most suitable AE monitoring system to recognize the contact in a particular grinding machine. In a second experimental setup the selected MS was installed on a 7 axis tool grinding machine at an industrial partner. At this partner, the relative position between grinding wheel and workpiece was previously determined manually. This procedure has a direct influence on the results depending on the technical skills of the operator. The automation of this activity supported by acoustic emission has led to satisfactory results regarding the relative position between grinding wheel and workpiece and contributed to the setup time reduction.

The Research of CNC Grinder System with Online Detection

Analyses the main methods of on-line detection technology in CNC system, and puts forward a method based on eddy current sensor. Because of the grinder’s special structure that different from the lathe’s, fixed the detection device on the Z axis with the cutter, which was proved available. Designed a new sensor structure and using impedance to analyze the signal and process, the experiments show that it has a high precision relatively. Programmed PC software in VB, through G code compiler, the PC can detect and control the system synchronously in the form of motion control card.

A Time-Domain Surface Grinding Model for Dynamic Simulation

The quality of a workpiece resulting from a grinding process is strongly influenced by the static and dynamic behavior of the mechanical system, composed by machine tool, wheel, fixture and workpiece. In particular, the dynamic compliance may cause vibrations leading to poor surface quality. In order to evaluate in advance the process performance in terms of surface quality, a simulation model for surface grinding has been developed, based on workpiece discretization by means of a z-buffer approach. The volume engaged by the wheel is associated to the grinding force by means of a variable specific energy that is a function of the equivalent chip thickness. The model is able to provide static and dynamic grinding force components taking into account the following aspects: nonlinearity of the grinding force with respect to cutting parameters, grinding damping effect, contact stiffness, machine-workpiece dynamics in all the relevant degrees of freedom (radial and tangential both for wheel and workpiece). The implementation in Matlab/Simulink™ environment allows an easy connection with any given mechatronic models of the grinding machine. Stable surface grinding tests with force measurements have been performed on a commercial CNC grinding machine for identifying the model parameters; then, the validation was extended to the dynamic case by introducing an artificial wheel unbalance.

The Static and Dynamic Characteristics Analysis of a CNC Grinding Machine Bed Made from Artificial Granite

The machine tool bed is an important fundamental unit of the Machine tool, and its static and dynamic characteristics directly influence the precision of the Machine tool’s process. The precise composite B2-K3000 CNC grinding machine bed is made from artificial granite. Through entity modeling, adding the boundary conditions and stress conditions to the bed, this article analyses the static stiffness, natural frequency, vibration mode and harmonic response of the grinding machine bed, and masters the natural characteristics and preponderant natural frequency.On the basic of the bed’s structure characteristics and stiffness requirements, the original bed’s structure gets partial improvements. By increasing the number of ribs and using the cross-shaped ribs, the improved result indicates that the bed’s static stiffness can be enhanced obviously and the bed’s static and dynamic characteristics can be more excellent.

Accuracy Analysis of Grinding Indexable Inserts Related to the Centrifugal Force of High Speed Abrasive Wheel

When grinding the carbide insert with the abrasive wheel at high rotating speed, the accuracy of inserts is impacted by the changed size of abrasive wheel by the centrifugal force. This paper proposes a computing model of grinding location for insert, and giving an analysis of dynamic simulation of the abrasive wheel at high rotating speed. The analysis showed which the diameter of wheel is enlarged, and its axial size is indented. According to the result, some geometrical parameters offsets were afforded to realize to grind inserts accurately in the CNC grinding machine tool.

A Path Planning Approach for Wedge/Aspheric Lens Element Grinding Based on Space Coordinate Transformation

Wedge/aspheric lens element is a combination of wedge prism and aspheric lens as a single piece component forming a decentred lens, which plays an important role in the fields of liquid crystal projection display, laser fusion, high-energy laser, satellite optical system and large astronomical telescope, etc. Wedge/aspheric lens element are primarily manufactured by CNC machining, especially 3-axis CNC grinding. This paper presents a facile tool path generation approach based on space coordinate transformation. The proposed method can be used to improve and automate three-axis Wedge/aspheric lens element machining for CAD/CAM systems. As part of the validation process, the tool paths generated are analyzed to compare with the desired part.

Failure Mode, Effect and Criticality Analysis of CNC Grinder

CNC grinder is considered as the key equipment of camshaft production line. Its reliability directly influences the quality of the products. This article takes an analysis of fault record of 15 sets of CNC grinders of production line, gets failure positions analysis, and then reaches data of failure modes, fault reason of CNC grinder. Comprehensive analyses of criticality for the machine are done through establishing models. Therefore, this analysis provides technical basis for repair, maintenance and update of CNC grinder of camshaft production line.

Static and Dynamic Characteristics Analysis of Precise Composite CNC Grinding Machine

The parameters of joint parts must be included in the finite element model of a whole grinding machine. The subject investigated in this paper is B2-K3000 high-precision composite flexible grinding machine. Through finite element modeling, the joint part parameters are integrated into the whole grinding machine model to establish a dynamic model and then analyze its static and dynamic characteristics. The result shows that the whole grinding machine possesses good features, but it still needs to be improved. This paper gives suggestions for its structure development and application.

A Quick-Test Method to Determine the Grinding Wheel Topography Based on Acoustic Emission

A quick-test method for the determination of the topographic characteristics of a CBN grinding wheel is developed based on acoustic emission technology. For implementing the strategy, an acoustic emission (AE) monitoring system was integrated into a 3 axis CNC grinding machine. A computer with specific software allows the signal acquisition and visualization of the AERMSsignals, which are originated through interferences between the grinding wheel and dressing tool in a range of a few micrometers. The acquired AERMSsignals from these interferences are used in order to establish an on-line map from the grinding wheel periphery, indicating the active cutting grains during the contact amid grinding wheel and dressing tool. The implementation of such activity supported by AE has led to satisfactory results regarding the required time to evaluate the strategy as well as the verified correlation with different grinding topographies caused by changes in the dressing parameters.

Study on Machining and Measurement for Borosilicate Glass Conical Ellipsoid

Surfaces formed by rotating quadratic curve are widely applied in engineering practice. After having studied machining methods and machines, the CNC grinding method based on macro program B for borosilicate glass elliptical cone surface machine with high precision is proposed. Within the allowable error, the coordinates are calculated according to the equation of axial section curve and the surface is formed with tools moving on axial section curve. Through setting parameters of the lathe, the new canned cycle can be defined to process all different kinds of the elliptical cone surface of same type. With surface triangle adaptive measurement method, machined elliptical cone surface can be detected on coordinate-measuring machine and compared with the theoretical curve. The tolerance resulted from analysis is within 0.025mm. Except ellipsoidal surface all solids of rotation and their deformation, in which their axial sections are represented with equation, can be processed and measured with this method.

Dispersed grinding wheel profiles for accurate freeform surfaces

Dispersed grinding wheel profiles are proposed to replace its ideal ones for planning 3D tool paths in CNC grinding. Its advantage is to register irregular and discontinuous grinding wheel profiles and directly eliminate their form-truing error for the accurate freeform surfaces of a large-size workpiece. First, the actually form-trued grinding wheel profiles were dispersed to be a tool point cloud by rotating the measured 2D wheel-section profile points; then a discrete-form algorithm was constructed to plan 3D tool paths on the base of a mutual-tangency between tool point cloud and workpiece point cloud; finally, the effects of discrete-form variables such as wheel spacing angle, lattice grid size and searching interval were investigated on discrete-form accuracy and efficiency. It is shown that the discrete-form algorithm may improve the form accuracy of ground freeform surface by about 37% compared with a normal-form algorithm. In discrete-form algorithm, the discrete-form accuracy increases and the discrete-form efficiency greatly decreases with decreasing wheel spacing angle, lattice grid size or searching interval, but the discrete-form error may converge to the wheel-section profile error. It is confirmed that the lattice grid size in 0.5 mm and a large searching interval may be employed to enhance the discrete-form accuracy and efficiency simultaneously.

The Section Line of the Cutting Edges of the Rotary Burs after CNC Controlled Grinding

A study is made of the forming theories and the computer aided design of the rotary cutting burs, for the purpose of finding the movement of the machining system and the corresponding sectional curvature of the groove conveniently. The equation of the cutting edges on the tool surface is deduced in this paper. The contact condition between the cutting edge of the tooth of the cutter and the grinding wheel is found, and the equation of the contact condition is deduced as well. Then the section line of the cutting edges of the rotary burs after CNC controlled machining is calculated. The research is useful for the programming of the CNC grinding on the CNC controlled machine tool.

Development of CAD/CAM system and profile measuring device for CNC grinding machine to obtain an optimal grinding speed

Cam mechanics is one of the most popular devices for generating irregular motions and is widely used in automatic equipment, such as textile machines, internal combustion engines, and other automatic devices. In order to obtain a positive motion from the follower using a rotating cam, its shape should be correctly designed and manufactured. The development of an adequate CAD/CAM system for a cam profile CNC grinding machine is necessary to manufacture high-precision cams. The purpose of this study is the development of a CAD/CAM system and profile measuring device for a CNC grinding machine to obtain an optimal grinding speed with a constant surface roughness. Three types of disk cams were manufactured using the proposed algorithm and procedures to verify effectiveness of the developed CAD/CAM system.