In conventional machine tools, the cooling medium - oil or water - is tempered centrally by the cooling unit and then stored in an intermediate tank. From there, it is distributed to the individual components via a conveyor system. The allocation is purely heuristic, using different hose line cross-sections: small cross-sections for low cooling requirements, large cross-sections for higher cooling requirements. The actual heat loss generated by the individual motors is not taken into account, which means that the cooling unit operates at the same output throughout the process. This leads to unnecessarily high power consumption, as up to 80 % of the electrical power consumed during a machining process is used by the cooling unit and only 20 % by the electric drives.
A more efficient solution would be to allocate coolant according to demand and orientate it to the actual machining process. This would not only reduce energy, time and costs, but would also bring the machines up to operating temperature more quickly. The “Demand Based Cooling” project is therefore developing a general procedure for creating a thermal model. Together with an intelligent controller, the cooling system is then to be dynamically controlled so that cooling is only activated when actually required.
At the start of the project, the actual condition of a 5-axis machining centre from the IFW machine park is analysed. The actual electrical and mechanical performance of the individual motors during the machining process is precisely recorded using a specially designed measurement method. By measuring the return temperatures and volume flows, it is ensured that the interactions between the individual drives are correctly taken into account. Based on the thermal model developed from this, control algorithms are developed for the targeted control of the flow in the cooling circuits.
An industrial PC (IPC) will analyse the data in parallel with the process and control the valves and feed pumps accordingly. In addition to the temperature-controlled cooling medium, the return flow to the machine will also be used for temperature control in order to further reduce the time required to reach a thermally stable state.
Contact:
We look forward to developing innovative solutions for the manufacturing industry with you. For further information, please contact Dominic Fröhlich, Institute of Production Engineering and Machine Tools at Leibniz Universität Hannover, on +49 511 762 4839 or by e-mail at d.froehlich@ifw.uni-hannover.de.
