C. Heinzel

Friction, Cooling and Lubrication in Grinding

Abstract It is generally considered that the heat produced during the grinding process is critical in terms of workpiece quality. Relatively high friction effects in abrasive machining cause heat generation which can lead to thermal damage in the surface layer of a machined part; cooling and lubrication therefore play a decisive role during grinding. The keynote paper shows the effect of coolant type, coolant composition and coolant supply on grinding processes and process results. Further investigations in the fields of fluid dynamic processes in supply nozzles and in the grinding zone are the key to optimization of cooling and lubrication during grinding, thus offering the chance to minimize the amount of coolant in circulation, leading to a reduction of adverse environmental effects and cost.

Modelling and optimization of grinding processes

The paper describes different methods for modelling and optimization of grinding processes. First the process and product quality characterizing quantities have to be measured. Afterwards different model types, e.g. physical–empirical basic grinding models as well as empirical process models based on neural networks, fuzzy set theory and standard multiple regression methods, are discussed for an off-line process conceptualization and optimization using a genetic algorithm. The assessment of grinding process results, which build the individuals in the genetic algorithms population, is carried out using a target tree method. The methods presented are integrated into an existing grinding information system, which is part of a three control loop system for quality assurance.

Assessment of Grinding Fluid Effectiveness in Continuous-Dress Creep Feed Grinding

Abstract Creep feed grinding is a high-productivity abrasive removal process that is often limited by thermal damage and high wheel wear. A review of current industrial practices in the area of fluid supply optimisation in grinding shows that very little knowledge of the pressure, flowrate and method of application exists in industry. This paper presents an experimental procedure to evaluate fluid supply conditions in grinding on a continuous-dress creep feed grinder. Using tapered workpieces, the authors have evaluated the influence of wheel speed and material removal rate on grinding fluid effectiveness, based on the material removal rate at the position of the wheel along the ramp when burn starts to occur and the corresponding spindle power surge. Correlations are investigated between visible discoloration, metallurgical examinations and change in spindle power, in order to establish the onset of grinding burn. This procedure serves to determine the upper limit of material removal rate or - respectively - the lower limit of fluid flow rate for given grinding systems consisting of specified wheel type, material type, fluid type and fluid supply nozzle. The advantage of the presented method is its easy and time saving application in industry, but it is also of help to researchers who need to optimise fluid supply conditions prior to their grinding tests.

Experimental and numerical identification of process parameters of grind-hardening and resulting part distortions

Using the heat input into the workpiece during grinding to simultaneously realize surface hardening is the innovative approach of the grind-hardening process. Due to the complex physical phenomena within this process, the layout requires extensive experimental analysis to handle the surface hardening and the process-related part distortions. This paper presents a method supporting the layout by means of the finite element analysis (FEA). Besides the hardening depth distributions and the resulting distortions, the research results comprise the numerical identification of the range of the grind-hardening process regarding the analyzed parameter sets. Therewith, the FEA provides the possibility to meet the characteristics of the grind-hardening and to support the layout of the process efficiently.

Development and application of a wheel based process monitoring system in grinding

As an advantage to conventional monitoring systems sensor equipped grinding wheels offer the possibility to gain information on the process status from direct measurements of physical quantities in the contact zone. This can be realized by the integration of small temperature and force sensors into segmented grinding wheels. A new thermocouple sensor concept was developed whose novelty is the continuous contacting of the thermocouple by the grinding wheel wear. Further tests where conducted using a piezoelectric sensor integrated into the grinding wheel. By this set-up, forces in grinding as well as in dressing processes were obtained. After assessing the systems capability for monitoring grinding and dressing processes tests in an industrial environment showed the reliability of the monitoring system which therefore may become the basis for a novel kind of process control in the future.

Current Approaches in Design and Supply of Metalworking Fluids

Metalworking fluids play a significant role in machining operations and have a substantial impact on tool life, shop productivity, and the quality of the workpiece. The results presented in this article show the influence of the properties of the metalworking fluids and the supply system on the workpiece quality in cutting and grinding processes. Chemical, physical, and tribological aspects have an impact on the properties of the generated surface. For the assessment of cooling effectiveness, a special test rig for the investigation of the coolant supply system in a grinding process is presented. Another approach to investigate the effectiveness and efficiency of the cooling and lubrication system during grinding is to monitor the temperatures and forces by a wheel-based measurement using telemetric data transmission. A further important aspect of water-soluble metalworking fluids is the influence of microbial effects on working results in machining. Microbial degradation leads to drastic changes in the physical and chemical properties of the metalworking fluid during service life. Besides the demands on the efficiency and economy of cutting processes, their environmental friendliness becomes a crucial issue itself. Therefore, an example for a holistic view on the environmental impacts of machining processes and the application of metalworking fluids is given.

Experimental and numerical analysis of transient behavior during grind-hardening of AISI 52100

The grind-hardening process is an innovative approach to substitute conventional heat treatment processes. Due to the complex physical interrelationships and the lack of understanding regarding the process behavior and layout, extensive test series are required to assure reproducible hardening results. Therefore, methods for modeling and simulation are developed and used to analyze the thermo-metallurgical and thermo-mechanical effects during grind-hardening considering aspects like characteristics of process forces and tool wear. The objective of this paper is to predict the hardening depth distribution depending on the grinding path during grind-hardening in surface grinding by using finite-element-based simulations. Input data for the simulation are grinding forces, which are calculated by using regression analysis with respect to process parameters, e.g. specific removal rate

Dressing of Coarse-Grained Diamond Wheels for Ductile Machining of Brittle Materials

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