Investigation of an In-situ Measurement Method Based on Fluorescence Detection for the Rapid Determination of Microorganisms in Metalworking Fluids

Facing sustainability requirements and efficiency improvements in machining, the maintenance and monitoring of water-miscible metalworking fluids is becoming increasingly important. A major challenge in the use of metalworking fluids is ageing, which has a decisive impact on service life. In industrial operating conditions, metalworking fluids are used over a period of several months or even over a year. Various factors can negatively affect the performance of metalworking fluids. In the specific case of water-miscible metalworking fluids, microbial contamination is a significant factor. Microbial populations develop and spread during use, thereby contributing to progressive degradation over time. Current methods to monitor microbial contamination, such as dip slides and laboratory analysis using microbiological culture, are time-consuming and inefficient, as the results are often only available after several days. Due to this time-delay, it is impossible to accurately determine the current status of the metalworking fluid, since the ageing process continues to change during the long growth and evaluation phase of these measurement methods. Furthermore, preventive measures to extend the service life can only be taken after a time-delay. Testing and use of a measuring system based on fluorescence detection of microbial enzymes enables real-time monitoring of ageing by measuring microbial activity directly at the machine tool. Initial validation tests show promising results with regard to its application for monitoring the ageing status of water-miscible metalworking fluids.