Christoph Baumgart
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- Efficient machining of complex-shaped seal slots for turbomachineryItem type: Journal Article
- Optimierung der Kühlschmiermittelzufuhr beim Außenrundschleifen unter Berücksichtigung der LuftströmungItem type: Book Chapter
- Auslegung und Gestaltung der KSS-Zuführung beim AussenrundschleifenItem type: Conference Paper
- Flushing velocity observations and analysis during EDM drillingItem type: Conference Paper
- Investigation of the coolant fluid flow distribution in the grinding gapItem type: Conference Paper
- Grinding BurnItem type: Encyclopedia Entry
- Fluid Supply in Cylindrical GrindingItem type: Doctoral ThesisBaumgart, Christoph (2020)Grinding technology has evolved in the last decades into a process of high efficiency and precision to keep track with increasing demands of the industry. However, the coolant supply has not developed in the same pace. Most grinding machines still use ancient coolant supply nozzles, which prevent them from maxing out their capabilities. The research presented in this thesis concerns the understanding of the coolant flow into the grinding gap during the external cylindrical plunge grinding operation. An optimisation of the active flow rate, which is the coolant flow through the grinding gap and the bulk coolant in contact with the workpiece, can improve cooling and lubrication effects in order to enhance material removal rates, process efficiency and tool wear behaviour. The exit cross-section of the coolant nozzle plays a major role in the distribution of coolant, and furthermore in terms of efficiency of the coolant supply. This aspect is particularly important for wide workpieces and grinding wheels. In this work single-jet coolant nozzle combinations are chosen to establish an uniform coolant supply over the whole width of a 60mm wide workpiece. The effect of the exit velocity of the coolant is taken into account. The general rule that the exit speed of the fluid should correspond to 60-100% of the cutting speed could not be confirmed for all nozzle types, as much lower values show sufficient coolant supply for the single-jet nozzles. It is proposed to adapt these indications to the actual grinding process and the used nozzle type. Grinding tests are conducted using different numbers of single-jet round nozzles with a diameter between 1.5mm and 3.0mm. With the use of an individual coolant jet, the region of influence of the coolant supply could be defined. Suitable methods for an evaluation along the workpiece width are developed for the roughness, the residual stress profile and the grinding wheel cleaning condition. It is clearly shown, that these parameters are maintained in a favourable range in a region along the grinding wheel width of 3-4x the nozzle diameter. The distribution of the coolant above the workpiece-tool contact line and the supply into the grinding gap is broaden, depending on the actual transport capacity of the grinding wheel. A distance between the nozzles of 7mm allowed a uniform and smooth profile of all measured values. To apply the principle of the single-jet nozzles to a wide range of grinding processes, a method is proposed to determine a suitable distance of the nozzles based on few grinding tests. These results are adapted on the used type of coolant, cutting velocity, flow velocity, orientation and used nozzle diameter. An insight in the grinding gap during coolant supply is created by replacing the workpiece with a transparent Plexiglas tube. The flow distribution and filling of the grinding gap is compared for several nozzles and flow rates. In contrast to known indirect measurements, the fluid supply is shown along the grinding wheel width and transferred into the specific volume flow per width. To consider the non-uniform boundary layer airflow of the grinding wheel and uneven coolant nozzles, full 3D CFD multiphase simulations are conducted alongside the grinding experiments. Cooling effects of the bulk flow, which is not passing the grinding gap, are considered equal to the real grinding conditions. Good agreement of the simulated heat distribution below the workpiece surface and the measured residual stress profile are found. The final stress state and the tool wear is primary influenced by the temperature profile along the width of the workpiece. Based on the presented results, the application of single-jet nozzles with large distances is described and justified. The precise and defined supply by individual nozzles can bring advantages in terms of process stability, coolant use and flexibility on the grinding contact geometry. Furthermore, when minimising the amount of coolant, small inhomogeneities of the coolant supply can become crucial and lead to insufficient supply and thermal damage in certain areas. These local faults might not be detected by conventional averaging measurements. However, increasing requirements of the workpiece integrity can take the uniformity of the roughness and residual stress profile with tight tolerances as given.
- Fluid Dynamics in Electrode Flushing Channel and Electrode-Workpiece Gap During EDM DrillingItem type: Conference Paper
- A study of the interaction between coolant jet nozzle flow and the airflow around a grinding wheel in cylindrical grindingItem type: Conference Paper
- Optimierung der Kühlschmiermittelverteilung vor dem Schleifspalt beim AussenrundschleifenItem type: Other Conference ItemBaumgart, Christoph; Callejo Goena, Nicolás; Kuster, Friedrich; et al. (2016)
Publications1 - 10 of 11