Acoustic emissions in the glass polishing process: a possible approach for process monitoring

Abstract

Acoustic emissions (AEs) are elastic stress waves in solids. They occur when irreversible changes take place in the internal structure (e. g. the formation of cracks) of a solid (material). The benefits of the measurement of AEs are well known, and their application has already been described for various use cases. They are, for example, used for monitoring bridges to detect rope cracks. We want to investigate the possibilities of using AEs in the polishing process of glass, a complicated manufacturing process with several overlapping, chemical and mechanical influences. We will present the results of preliminary studies which shall answer the following questions: • Is it possible to measure acoustic emission signals, even if an unhindered access to the place of origin under manufacturing situations can not be guaranteed? • How is the development of the signal during the polishing process? • How can acoustic emissions be used in the future to improve optics manufacturing? • Is the opportunity of an endpoint detection existing? Answering these questions will demonstrate the abilities AEs can offer for evaluating and monitoring manufacturing processes. In the future it should be possible to create a cyber-physical system (CPS). In such a system, AE signals can be merged with other sensor signals (e. g. power of the machine, pH value, · · ·).