Method of grinding a workpiece having a cylindrical bearing surface and method for determining processing parameters

The present disclosure relates in general to a method of grinding a workpiece by means of a grinding wheel, the workpiece comprising a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall. The present disclosure also relates to a method for determining processing parameters of such a grinding method

On geometry and kinematics of abrasive processes: The theory of aggressiveness

Due to the stochastic nature of the abrasive-tool topography, abrasive processes are difficult to model and quantify. In contrast, their macro geometry and kinematics are usually well defined and straightforwardly controlled on machine tools. To reconcile this seeming contradiction, a novel unifying modelling framework is defined through the theory of aggressiveness. It encompasses the arbitrary geometry and kinematics of a workpiece moving relative to an abrasive surface. The key parameter is the point-aggressiveness, which is a dimensionless scalar quantity based on the vector field of relative velocity and the vector field of abrasive-surface normals. This fundamental process parameter relates directly to typical process outputs such as specific energy, abrasive-tool wear and surface roughness. The theory of aggressiveness is experimentally validated by its application to a diverse array of abrasive processes, including grinding, diamond truing and dressing, where the aggressiveness number is correlated with the aforementioned measured process outputs

Optimierung von Schleif- und Abrichtprozessen mit Hilfe der Theorie der Aggressivit\ue4t: Fallstudien aus der Praxis

In den ersten sechzig Jahren der Schleifforschung (1914-1974) wurden verschiedene dimensionslose Parameter eingef\ufchrt, um die grundlegende Mechanik eines Schleifkontakts zu beschreiben. Sp\ue4ter wurden diese Parameter durch verschiedene Spandickenmodelle ersetzt, die eine schwierige und oft uneindeutige Quantifizierung der Schleifscheibentopographie erforderten. Der Ansatz der Grundprinzipien ist vor kurzem durch die gro fe vereinheitlichende Theorie der Aggressivit\ue4t und die praktische Aggressivit\ue4tszahl wieder aufgetaucht. Diese ist ein dimensionsloser Parameter, der sich bei der Optimierung jedes beliebigen Schleifprozesses, einschlie flich Schleifen und Abrichten, als leistungsf\ue4hig erwiesen hat. Die Aggressivit\ue4tszahl erfreut sich inzwischen einer gr\uf6 feren Beliebtheit und wird verwendet, da sie die grundlegende Prozessgeometrie und -kinematik erfasst und gleichzeitig eine Quantifizierung der Schleifscheibentopographie \ufcberfl\ufcssig macht. In diesem Beitrag wird die Verwendung der dimensionslosen Aggressivit\ue4tszahl in mehreren Fallstudien aus der realen Produktion untersucht. Dabei wird gezeigt, wie das Konzept zur Optimierung industrieller Prozesse eingesetzt werden kann, z. B. beim Schleifen von Nocken- und Kurbelwellen, S\ue4gespitzenschleifen, Nutenschleifen, Doppelseitenschleifen und Abrichten von Diamantscheiben

Method of grinding a workpiece and method for determining processing parameters

The present disclosure relates to a grinding method for grinding of non-circular workpieces with an improved productivity and quality of the resulting workpiece. The method comprises a first and a second stage. The rotational speed profile of the workpiece in the first stage is controlled with the purpose of maintaining a pre-selected maximum surface temperature of the workpiece during said first stage, and grinding of the workpiece in said second stage is performed while controlling an aggressiveness number of said second stage so as to achieve an intended final surface quality. The present disclosure also relates to a method for determining the processing parameters of such a grinding method wherein the first and the second stage of the grinding method are iterated to thereby determine the processing parameters leading to a high productivity and desired quality of the workpiece after grinding

Truing of diamond wheels - Geometry, kinematics and removal mechanisms

An investigation is made into traverse truing of diamond grinding wheels using various truing grit types, grit sizes and truing parameters. Geometry and kinematics of the truing contact are modeled. Specific energies are found to depend on truing-grit size but not on truing parameters, indicating little to no size effect. Removal mechanisms are analyzed via SEM examination of diamond- and truing-wheel swarf. A fundamental relationship is established relating the truing compliance number to the truing efficiency, which encompasses truing parameters and truing- and diamond-grit sizes. Recommendations are made for optimum conditions to minimize force-constrained truing time

High-performance industrial grinding: recent advances and case studies from the automotive engine production

The development of new high-performance industrial grinding technologies for engine production in the automotive industry is presented. The grinding fundamentals are revisited in view of modeling and simulation to examine the effects of process design on grinding temperatures. The advantages associated with utilization of newly developed temperature-controlled grinding processes are explained via the analysis of process-control strategies. Two research-and-development projects from Scania\ub4s engine-production plant are discussed to illustrate industrial challenges and achieved impacts. Two case studies are presented for (1) cam-lobe grinding and (2) crankpin grinding, demonstrating optimized grinding processes for achieving shorter cycle times and higher quality. Both patent-pending technologies are experimentally validated in actual production and are implemented in existing production lines

A Novel and More Efficient Way to Grind Punching Tools

A simulation model of punch grinding has been developed which calculates the instantaneous material-removal rate, arc length of contact and temperature based on the kinematic relationships between wheel and workiece and determines the optimum machine parameters to reduce cycle time and achieve a constant-temperature no-burn situation. Two basic outputs of the simulation model include arc length of contact and specific material-removal rate. A thermal model is included in the simulation to calculate maximum grinding zone temperature rise. A novel method is developed to constrain this temperature rise in the simulation. The thermal model inputs a constant value of specific grinding energy and the energy partition, which represents the fraction of the grinding energy conducted as heat to the workpiece. The simulation-based optimization can lead to a drastic reduction of grinding cycle time. Moreover, the limitation of maximum grinding zone temperature rise below the transitional temperature can help to avoid generation of workpiece thermal damage, which includes thermal softening, residual tensile stress, and rehardening burn. The grindability of high speed steel (HSS) is also discussed in terms of power consumption, specific grinding energy and undeformed chip thickness.QC 20110913EUREKA E!4957-PUNCH-GRIN

Assessment of low-fidelity fluid–structure interaction model for flexible propeller blades

Low-fidelity fluid–structure interaction model of flexible propeller blades is assessed by means of comparison with high-fidelity aeroelastic results. The low-fidelity model is based on a coupled extended blade-element momentum model and non-linear beam theory which were both implemented in Matlab. High-fidelity fluid–structure interaction analysis is based on coupling commercial computational fluid dynamics and computational structural dynamics codes. For this purpose, Ansys CFX® and Ansys Mechanical® were used. Three different flexible propeller blade geometries are considered in this study: straight, backward swept, and forward swept. The specific backward and forward swept blades are chosen due to their aeroelastic response and its influence on the propulsive performance of the blade while a straight blade was selected in order to serve as a reference. First, the high-fidelity method is validated against experimental data available for the selected blade geometries. Then the high- and low-fidelity methods are compared in terms of integral thrust and breaking power as well as their respective distributions along the blades are compared for different advancing ratios. In a structural sense, the comparison is performed by analyzing the blade bending and torsional deformation. Based on the obtained results, given the simplicity of the low-fidelity method, it can be concluded that the agreement between the two methods is reasonably good. Moreover, an important result of the comparison study is an observation that the advance ratio is no longer a valid measure of similarity in the case of flexible propeller blades and the behavior of such blades can change significantly with changing operating conditions while keeping the advance ratio constant. This observation is supported by both high- and low-fidelity methods.Aerospace Structures & Computational Mechanic