Aplicação do projeto de experimentos no processo anodização em empresa do segmento de produtos para a saúde: um estudo de caso

Abstract

Anodizing is a technique used in order to increase protection against corrosion and osseointegration of orthopedic implants. Potentiostatic anodization is a process of forming oxides of a metal alloy in order to provide finish and colorimetric characteristics of metal parts with complex geometries. From a theoretical point of view, this electrochemical technique is based on the anodic deposition of metal oxides on the implant (anode) through an applied voltage in between the anode and cathode (counter electrode), and high current density which flows through the electrolytic solution by the displacement of electroactive metallic ions. It is a complex process which requires deep knowledge and control of its many variables, in which productivity, performance and quality are determined by the specifications of electrochemically machined products. Problems related to the lack of knowledge in critical process variables, or the use of non-optimized operating conditions result in heterogeneity in the oxide layer deposited on the anodized implants, non-optimized cycle time, rework or non- conformities of the anodized parts. Based on this context, it is necessary to develop a research project using the Lean Six Sigma, specifically, the DMADV cycle. This tool will be used to deepen the knowledge in the process and propose technically viable solutions which will likely bring a positive impact in quality and productivity of the process. Each of the phases of the DMADV cycle has specific objectives, that is, it begins with the definition of the problem and its outlined situations, followed by the assessment of the status quo of the process, then the assessment and identification of problems and their root causes, application of Design of Experiments (DOE) for identification and optimization of critical variables to the process, and at last the validation of the proposed project by generating data statistically validated. Initial results and optimization of anodizing process parameters were analyzed in Minitab software. As a result, there was an 85% reduction in the number of non-conformities related to the color uniformity of anodized parts, exceeding the initial expectations of the project. It is concluded that the improvements implemented throughout the project, combined with the use of the Taguchi Technique, contributed decisively to obtaining uniformity of the anodized batches.