Extending the possibilities of cryogenic assisted grinding

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In grinding operations, metal working fluids (MWF) are used to minimize the heat-associated problems such as surface cracks, burning, and tensile residual stresses. Filtration, recycling, and disposal of MWFs are additional cost factors. All these factors have led to intensify the research to minimize or eliminate the MWF from the manufacturing process. In response to these requirements, methods such as minimum quantity lubrication (MQL) and application of cryogenic fluids as MWF were developed. In the majority of the cases, cryogenic fluids are applied, similar as conventional MWF, continuously throughout the process. The inert nature and immediate evaporation of cryogenic from working environment makes benefit in terms of filtering, recycling and disposal costs. Drawbacks are the additional cost of the cryogenic delivery system and safety requirements. At this juncture, our collaborator (Brazilian research group) has developed a method of dry grinding with precooled parts. In this method, the parts to be finished will be cooled in a cryogenic medium, and then subjected to grinding operation without any MWF supply. However, the performance of the precooled parts in dry grinding depends on the shape, size, and dimensions of the part. Hence, in this collaborative project, investigations will be carried out to determine the advantages and disadvantages of the precooled parts in the dry grinding mode with a wide range of variables (different grinding processes, various workpiece dimensions), which were not given an attention so far. Two types of grinding process will be considered. The German research group will focus on surface grinding, whereas the Brazilian research group will focus on cylindrical plunge grinding. To investigate the cooling method, selection criteria and heat transfer simulations will be done together based on the part geometry, wheel and workpiece thermal properties to classify the suitable workpiece dimensions for a precooling method and in-situ partial precooling method. In the in-situ partial precooling method, only a portion of the part is precooled. Based on simulation results, workpieces will be classified as large (not suitable for precooling method) and short (suitable for any cooling method) type, and accordingly, possible cooling methods will be applied. During this project, responses related to process (e.g., forces, temperature, power, wheel wear, G-ratio) and ground surface (e.g., microstructural changes, micro hardness, surface roughness) will be examined and discussed. By comparing the benefits and limitations of each cooling method, a comprehensive knowledge on the capabilities of cryogenic application in grinding can be achieved. Ultimately, unrestricted exchange of the research results will lead to strengthen the relationship of this binational research group.