ABSTRACT
Chemical machining has a considerable value in the solution of machining problems that are
constantly arising due to the requirement for high surface finish of difficult to machine materials
such as stainless steel which has a widespread application in industry in annealed and cold worked
forms. The present work is aimed at utilizing of robust experimental design Taguchi method for
optimization of chemical machining parameters. The influence of machining temperature, machining
time, and previous cold working on surface finish of chemically machined stainless steel-420
samples. Taguchi experimental design concept, L 16 (3×4) mixed orthogonal array is used to
determine the S/N ratio, analysis of variance, F- test to indicate the significant parameters affecting
the surface finish, and to optimize the process parameters. Basing on the analyses of multiple
regression method, mathematical predictive model had been designed and validated to select an
optimum combination of the studied parameters. To achieve the objectives of the present work
Datafit ver9, and Mtb14 softwares had been employed.
Alloy samples of (44.5×44.5×3mm) dimensions with (0, 20, 40, and 60%) cold rolled alloy
samples were chemically machined at machining temperatures of (45, 50, 55, and 58oC) for a
machining times of (2, 4, 6, and 8min.). The results show that previous cold working is the most
significant parameter for the surface performance. Cold worked stainless steel 420 can be
chemically machined in [H2O + HCl + HNO3 + HF + HCOOH] etchants in optimum conditions of
60% cold working at 45?C for 2 min. Conformation tests verify the effectiveness of results of the
designed predictive model with an error ranging between (4-12%).