High Performance Grinding Research Articles

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.

Influence of Type of Grinding Stone on Rail Grinding Efficiency

Rail grinding using a grinding stone has long been a regular part of rail maintenance. This paper discusses the development and evaluation of a new type of high-performance grinding stone. Prototype stones were tested on a grinding test bench with rotation speed and pressing load as the bench test conditions. Grinding capacity of the new grinding stone was compared with that of the current grinding stone. Metallographic analyses of the rail specimens after grinding were also conducted. The findings showed that the proposed stone improved grinding capacity. The new stone also improved grinding performance due to its more moderate impact on rails from a metallographic point of view. These findings indicate that the prototype grinding stone should be field tested as a substitute for the current grinding stone.

S1303-2-3 焼き入れ鋼のcBN砥石による研削における砥石への溝入れ効果([S1303-2]先端材料と加工(2))

S1303-2-3 焼き入れ鋼のcBN砥石による研削における砥石への溝入れ効果([S1303-2]先端材料と加工(2))

Virtual high performance grinding with CBN wheels

The development of future products requires designing, manufacturing, and testing components in a virtual environment before hardware parts are actually made. This paper presents a generalized process simulation and multi-constraint optimization strategy for five-axis grinding with cubic boron nitride (CBN) wheels to increase material removal rates while avoiding process problems such as damage to the machined surfaces and premature wheel failure. The wheel–workpiece engagement conditions under five-axis grinding are extracted from a CAM system by geometrically processing the NC program, the wheel geometry and the part geometry. The interpreted geometric contact data are used in combination with empirical grinding models to predict physical process parameters such as forces, power, heat flux, and temperature. These parameters are then used as the decision variables in a multi-constraint optimization to optimize process parameters such as workspeed to reduce cycle time.

High Performance Grinding Zirconia Ceramics by Brazed Monolayered Diamond Wheels

A new segmented grinding wheel of the brazed monolayer diamond was developed with a defined grains pattern on the wheel surface. Results of grinding zirconia using brazed segmented diamond wheel were presented. The experiment results showed that the grinding forces ratio becomes higher with the increasing of the specific material removal rate and the specific energy falls with the increasing of the maximum undeformed chip thickness during grinding zirconia process. In this investigation, brazed diamond wheels with defined distribution patterns was conditioned by touch-dressing method so that grit tips get micro-conditioned and allow the underlying grits to participate and consequently improve the quality of finish. All the ground surfaces of zirconia were generated by the combined removal modes of brittle and ductile.

Laser processing of high performance grinding wheels

High performance grinding is a process that produces engineering components with a desired surface roughness. The grinding efficiency of vitrified grinding wheels deteriorates as the sharp cutting edges become blunt due to the formation of wear flats. Dressing is essentially a sharpening operation designed to generate a specific topography on the working surface of the grinding wheel. The use of high power lasers is being explored as a non-contact cleaning and dressing technique. In the present study, a high power laser was used to clean metal chips from the surface of the grinding wheel and to dress the wheel by causing phase transformations to occur on the surface of vitrified grinding wheel. Experimental results indicated that laser modified grinding wheels are comparable in performance to conventionally cleaned and dressed grinding wheels.

Mechanical design of high performance grinding wheels

High performance grinding processes require grinding wheels that can be dressed with a variety of different methods and that can rotate at exceptionally high speeds without distorting or failing catastrophically. These wheels are usually reinforced and the grinding medium is usually attached to the periphery of the wheel using a strong bonding agent such as epoxy adhesive. This paper uses a set of procedures that were developed for designing grinding wheels for creep feed grinding processes and the more modern process of high efficiency deep grinding. Procedures for safe practice and good mechanical design safety at very high rotational speeds are discussed.

Development of a dressing monitoring system through artificial intelligence and acoustic maps for high performance grinding

High performance grinding implies in reliable monitoring at high speeds. In this paper, the development of a dressing monitoring system based on Artificial Intelligence (AI) is discussed. Different from previous works that adopt AI to classify Acoustic Emission (AE) measurements in grinding operations, the proposed approach is less sensitive to noise. The results point out to increases in production velocity and quality. Simulated tests indicate to the high performance of the monitoring even in noise conditions.

Interaction of process and machine during high-performance grinding: towards a comprehensive simulation concept

Many simulations of grinding processes focus on the penetration of a grinding wheel and a workpiece and neglect displacements of the machine system. This paper presents a modular concept and initial applications for developing a comprehensive simulation of the grinding process and the grinding machine.

Economical aspects of profiling diamond-grinding wheels

This paper presents the results of a recent study on various tools and methods for the profiling and dressing of diamond-grinding wheels. Special focus was placed upon economical implications of the use of diamond-dressing tools. A closed analytical correlation was developed in order to create an evaluation instrument for the optimisation of dressing operations in high performance grinding processes. It was shown that profiling of diamond-grinding wheels with rotating diamond tool is only recommendable with the assistance of a continuous-sharpening process or an ultrasonic vibration.

High-performance grinding—A review

Presented paper deals with the contemporary aspects of grinding with regards to enhanced productivity and precision demands. High-performance grinding is essential to achieve high dimensional accuracy and surface integrity of ground components at optimum cost efficiency. The objectives of this paper refer to a review of state of the art technology of high-performance grinding at increased wheel speeds with highly efficient abrasives. The review relies on notable academic publications and recent conference proceedings.

Optical wear assessment system for grinding tools

The inspection and monitoring of the wear of grinding tools is essential to ensure the quality of the grinding tool surface and the finished product. Most of the current methods for examining a grinding tool surface rely on dismounting the grinding tool. Often, the state of the grinding tool surface is checked indirectly by evaluating the quality of the workpiece. We describe the application of image processing, which offers an effective means for in situ inspection and monitoring. It yields more detailed information about the surface and the kind of wear observed than the common methods. By using multidirectional illumination and image fusion, an image with a high degree of relevant information is generated that is then segmented using the wavelet transform (multiscale analysis) and classified to distinguish grains and cavities on the surface. Results of the application of the algorithms for a high-performance grinding tool with CBN grains embedded in a resin base are presented.

Computer aided design of high-performance grinding tools

This paper considers computer aided design of high-performance cylindrical grinding wheels. The finite element method has been used as the numerical tool to examine the influence of geometric shape and size of abrasive elements on the safe design of high-speed grinding tools. Conventional cylindrical grinding wheels are limited to low peripheral speeds due to the strength of the abrasive body. By replacing the centre section of the wheel with a stronger material and bonding abrasive segments to it, it is shown that a substantial increase in maximum operating speed is possible while maintaining the required margin of safety. Optimization of the number and size of abrasive segments is considered as well as the material used for the reinforcing centre section. A new concept wheel is also presented that is used to increase the maximum operating speed even further.

Studies on refractory bonding systems used in vitrified silicon carbide grinding wheels

The performance of vitrified silicon carbide grinding wheels is dependent on the molten properties of their bonding systems. The erosion of silicon carbide during the manufacture of grinding wheels is enhanced by the action of high glass content vitrified bonding systems that reduces their wear resistance during the grinding process. Replacing the glass content of the bond with a clay that does not vitrify can improve their wear resistance. However, the harmful effects of quartz particles that are found in clay minerals need to be eliminated during the firing process before the grinding wheels are used to grind precision engineering components. A mathematical model describing the dissolution of quartz in refractory bonding systems was compared with experimental data using X-ray diffraction techniques. It was found that when grinding wheels were isothermally heat treated, the residual mass fraction of quartz was found to be a function of time. When compared with experimental data, the model was found to be accurate for short periods of heat treatment that are associated with vitrified silicon carbide firing cycles. The model is of practical use for predicting the complete dissolution of quartz in vitrified bonding systems used for high-performance silicon carbide grinding wheels.

Kinematic Simulation for Analyzing and Predicting High-Performance Grinding Processes

In grinding technology, the application of superabrasives and increasing demands for higher productivity and higher quality require an appropriate selection of optimum set-up parameters. Therefore, the development of analytical or empirical models for reliable prediction of machining performance and work results is a key issue. This paper presents a comprehensive concept for process modeling which provides a software tool for analyzing and designing high performance grinding processes, using the method of kinematic simulation. On the basis of synthetic 3D-models describing the macro- and micro-geometry of the grinding wheel and the workpiece, together with mathematical models describing the relative motions and kinematic engagement conditions, grinding processes can be reproduced as the cumulation of multiple grit engagements. The proposed simulation tool allows the generation of optional grinding wheel topographies and the analysis and prediction of the machining performance and work result for different grinding techniques, taking into account thermo-mechanical and dynamic effects in the contact area.

High-Performance Surface Grinding – The Influence of Coolant on the Abrasive Process

The availability of newly designed grinding machines with high stiffness. high spindle power and wheel speeds, super-abrasive CBN-grinding wheels, adaptive dressing techniques, coolant delivery, coolant filter, and wheel surface cleaning systems enables application of the high-performance grinding method. This grinding technique using CBN-grinding wheels, can be characterized by high cutting speeds, relatively high material removal rates, and good surface finish. This paper presents the consideration of chip thickness and its influence on the grinding process, due to the grinding parameters, such as cutting speed, depth of cut and work speed. Results obtained in practical investigations concerning the impact of the coolant delivery, on the emerged forces and on the power demand at high peripheral wheel speeds are discussed.

特集 最近の高能率研削・重研削技術 超砥粒ホイールによるＮｉ基耐熱合金の高能率研削

特集 最近の高能率研削・重研削技術 超砥粒ホイールによるＮｉ基耐熱合金の高能率研削