Thermal Management Approaches for Distortion Control in Metal Additive Manufacturing

Khare, Vivek Kumar and S, Suryakumar (2018) Thermal Management Approaches for Distortion Control in Metal Additive Manufacturing. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Additive manufacturing has proved to be effective compared to conventional processes in terms of manufacturing of complex parts with good surface integrity in less lead time and cost. Among the various AM processes, weld based AM is a technique in which weld beads are deposited in layer by layer trend to fabricate the final product. In this process, the melting of consumable electrode wire deposits the material to realize the part. Weld based deposition process is ideally suited for manufacturing of large-scale components compared to other AM processes. Gas Metal Arc welding (GMAW) based weld deposition process gives leverage over other powder deposition processes, due to high metal deposition rate, good mechanical properties, time and cost-effective components. However, the high heat involved and the non-uniform heat distribution resulting in the Residual Stress (RS) and Distortion may a�ect the geometrical accuracy of the fabricated part. Different factors or parameters are identified based on the literature survey, which is responsible for Residual Stress and Distortion. The experiments are conducted in two stages. The first stage of experiments is performed by the different combination and variation of the selected process parameters to study their effect on RS and Distortion. The chosen parameters are current, torch speed, geometry, continuous or delay in the deposition and cooling arrangement. The experimental result suggests that torch speed, geometry, and current, torch speed, continuous or delay in the deposition are solely responsible for residual stress and distortion respectively. The hardness analysis of the samples proposes that hardness is nearly constant along the width, but varies along the height. The Buy to Fly ratio (BTF) and SurfaceWaviness (SW) analysis of the samples proposes that continuous deposition gives better surface integrity. In the second stage, six di�erent set of experiments and FEA simulations are conducted by three of them by providing insulation at the bottom of the base plate and rest three to study the e�ect of sti�ness of the base plate on distortion. The analysis of results proposes that heating the base plate minimizes the RS and distortion in comparison to change in current across height and with the normal insulation condition. However, the hardness, BTF, and SW are nearly uniform for all the three cases. The experimental results for the change in the sti�ness of the base plate indicate that reducing the sti�ness results in more distortion. A comprehensive comparison between the �rst and second stage work suggest that the BTF, SW, Residual stress and Distortion are minimal with continuous deposition and heating the base plate.

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