In-situ measurement of electrochemical jet machining using low coherence interferometry

The ability to provide surface texturing at the micrometre to millimetre scale is of growing interest in many high-value manufacturing applications, for example, improving a components ability for heat transfer, chemical sensing, wettability and bio-mimicking. Electrochemical Jet Machining (EJM) has shown promise for performing surface structuring, providing material removal via electrochemical dissolution. This gives benefits of being able to machine without introducing stress hardening or thermally affected regions and for processing shear resistant materials. Current quality control processes for EJM involve an offline approach to verify adherence to design tolerances. This requires removal of the part from the machining setup and cleaning which is time consuming and error prone if re-machining is required. Offline approaches do not allow for adaptive control feedback to be implemented during the machining process, which requires an in-situ measurement system. . However, Low Coherence Interferometry (LCI) is a measurement technique that has shown promise for operating in non-ideal environments through its use in biological imaging. Additionally, LCI benefits from easy integration into fibre optic systems allowing for small sensor footprints and has been demonstrated to effectively work in a range of operating mediums. The work presented here investigates the feasibility of applying a fully fibre enclosed common-path LCI sensor within EJM.