EXPERIMENTAL INVESTIGATION INTO FINISHING OF FREEFORM SURFACE BY ABRASIVE FLOW MACHINING

Abstract

Freeform complex surfaces have become an important part of many devices to perform necessary functions. In the applications of these surfaces, surface roughness is required at nano level or micron-level to perform the desired function efficiently. In the present work, freeform surfaces, especially hip joint, was designed and manufactured using the Selective Laser Sintering (SLS) technique. Surface finish of SLS printed parts is not good and Abrasive Flow Machining (AFM) can be used to finish these surfaces. In this process, a semi-solid abrasive media is used that can finish the complex geometry and inaccessible areas of parts. Surface finish obtained from the AFM process rely upon various workpiece-based, media-based, and machine-based parameters. In this study, extrusion pressure, media flow speed (machine based), and abrasive mesh size (media-based) parameters at three different levels are taken during the finishing. The design of experimentation was done using the Taguchi L9 orthogonal array method, and an assessment of Material Removal (MR) and surface roughness percentage change (% ∆Ra) at the surfaces was done with help of signal-to-noise ratio (S/N ratio), and analysis of variance (ANOVA). Minitab 18 software was used to optimize the output of the process responses. Experimentally, a maximum value of MR 69 mg and maximum improvement in surface roughness of 25.19% were obtained in this study. Every material, product, and production process have ecological impact. In order, to find out the impact on the environment or ecological impact a life cycle assessment study has been done on the finishing of polylactic acid parts using both hydrogel-based and polymer-based abrasive media. The PLA parts, fabricated using Fused Deposition Modeling (FDM) process, have been finished through AFM. Then, Life Cycle Assessment (LCA) analysis has been performed using SimaPro (version 9.1.0.8) software. The energy consumed during media preparation, printing of workpiece, and AFM, media constituents, and work material were considered as inventory for LCA analysis. The ReCiPe 2016 V 1.04 midpoint(E) and endpoint(E) module available was used for impact assessment. The LCA results showed that hydrogel-based AFM process has less adverse effect on environment than polymer-based AFM process. Also, power consumed at different stages was found to be a significant contributor to the impact on environment. The results of this LCA analysis provides a base for sustainability assessment in AFM process.