Experimental study of parameters in micro-photochemical machining using maskless digital projection on flat surfaces of 100Cr6 steel

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Photochemical machining (PCM) is a chemical etching process, in which a photoresist agent is used to cover parts of the workpiece that need to be protected from etching. In this study, the main goal is to create a groove on the flat surface of a workpiece made of 100Cr6 steel using the PCM process and to investigate different variables on the dimensional and geometrical accuracy of the groove. The experiments were designed using the response surface method with a central composite methodology, involving 20 experiments and three repetitions. In this study, the effects of different variables such as time of etching, the concentration of ferric chloride (FeCl3) in the etchant solution, and the weight ratio of hydrochloric acid (HCl) to FeCl3 in the etchant solution were investigated on dimensional accuracy such as length and width error and also geometrical accuracy such as out of parallelism, out of squareness, and out of straightness. Results indicate that as the etching duration increases, the length, width, out of straightness, out of parallelism, and out of squareness also increase. This error becomes substantial with longer durations. Also, with an increase in FeCl3 concentration in etchant solution, errors in length and width, out of straightness, out of parallelism, and out of squareness reduce. The optimal variables resulting in the least possible errors were an etching duration of 10.72 minutes (10 minutes and 43 seconds), FeCl3 solution concentration of 599.64 g/L, and a weight ratio of HCl to FeCl3 in the etchant solution of 0.1. The following results on the flat surface were obtained: groove length: 3,056 µm, groove width: 625 µm, groove depth: 48 µm, and surface roughness (Ra): 1.285 µm.