Designing for Metal Additive Manufacturing: Design Challenges with Three Industry Relevant Components

Open Access
Author:
KANTAREDDY, SAI NITHIN REDDY
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 27, 2016
Committee Members:
  • Timothy William Simpson, Thesis Advisor
  • Mary Frecker, Committee Member
  • Karen Ann Thole, Committee Member
Keywords:
  • Laser-based powder bed fusion
  • Additive Manufacturing
  • Design for Additive Manufacturing
  • Topology Optimization
  • Lightweighting
  • Lattice Structures
  • Design Workflow
Abstract:
Additive manufacturing (AM) offers unprecedented design freedom to produce complex designs in a single step. Laser-based powder bed fusion, in particular, is a promising metal AM process to fabricate complex metal parts that are otherwise difficult, costly, or impossible to manufacture using traditional means. Many techniques for lightweighting designs and improving part performance such as topology optimization, lattice structures, and part consolidation, often result in designs with complex features that can only be made with AM. Although AM is not necessarily constrained by this geometric complexity, it does require unsupported/overhanging features in the design to be structurally supported by additional structures that can be later removed by post-processing using various techniques such as hand tools, machining, wire EDM (Electrical Discharge Machining), etc. Depending on the complexity of the part, support structures can often be substantial, difficult to access, and complex in shape; therefore, removing the support structures may be very difficult and require multiple post-processing steps. As a result, overall manufacturing cost, material consumption, and manufacturing time may unnecessarily increase, making AM less economical than initially conceived. Additionally, the thermo-mechanical nature of the metal AM process induces residual stresses and distortions in the built parts. In-process distortions can lead to build failures, part curling and warping, and material waste. Therefore, many designs cannot be easily manufactured using AM or may actually cost more to produce with AM. Design for Additive Manufacturing (DfAM) can remedy these limitations. DfAM encompass a set of principles or guidelines based on theory and experience to help design parts to be manufactured easily with AM. Effective implementation of DfAM during the design phase can result in parts suitable for AM, which can be affordable to make and easier to produce. However, the strategies to implement DfAM principles are not generalized and vary from part to part, process to process, and material to material. These part-specific requirements may require modifications in the existing design workflow, and a single workflow may not be suitable for all the design cases. To understand some of these differences, this thesis focuses on investigating the design process for leveraging metal AM capabilities at different levels of design complexities by redesigning three industry relevant components for additive manufacturing. In each case, the design conceptualization, workflow, design tools, DfAM principles, and improvement in product performance are compared and contrasted. Based on these three cases, recommendations are made for improving the design tools, and ultimately for improving the design workflow to reduce the computation time and improve the information flow across the software platforms.