Cost Modeling and Design Tools for Additive Manufacturing with Laser Powder Bed Fusion

Open Access
Author:
Barclift, Michael W
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 06, 2018
Committee Members:
  • Timothy Simpson, Thesis Advisor
Keywords:
  • Additive Manufacturing
  • 3D Printing
  • Metal
  • Laser
  • Powder Bed Fusion
  • CAD
  • Design Tools
  • DFAM
  • Cost Modeling
  • Powder Reuse
  • API
  • Depreciation
  • Powder Recycling
  • Cost Estimation
  • Support Structures
  • Optimization
  • Powder Feedstock
  • LPBF
  • AM
Abstract:
Additive Manufacturing (AM) is a novel process that uses 3D model data to create complex geometry and functional structures by joining materials layer-by-layer. Despite growing interest, industry’s adoption of AM has been limited due to challenges in cost-effectiveness, lack of subject matter expertise, and disparities amongst commercial software programs that capture the full breadth of design inputs and process considerations for AM. Designers have limited tools within the 3D modeling (e.g., CAD) environment that inform them on critical design parameters and tradeoffs that can impact the overall cost and feasibility of producing a part in AM. In this thesis, cost modeling and design tools are examined for Laser-Powder Bed Fusion (LPBF). Traditional cost models have estimated that the material cost can range up to 46% of the total cost; however, these models have not accounted for the reuse (i.e., recycling) of the un-melted powder feedstock in LPBF. To capture susceptibilities to chemical contamination, diminished powder size distributions, and inconsistent mechanical performance, financial depreciation models using Sum-of-the-Years digits and Straight Line are implemented to define the value of a powder feedstock as function of each build cycle reuse in LPBF. A case-study is presented for an automotive upright designed for production and analyzed using a generic LPBF activity-based cost model. Sensitivity analysis revealed that traditional cost models assuming infinite material reuse undervalued the cost of build jobs with virgin powder by 3-11% or 13-75% depending on the material, feedstock price, and maximum permitted reuses in LPBF. Cost modeling is iterative and estimates will vary as updates are made to the 3D model. To aid in informing designers on costs of their parts, a software plug-in is presented using the SolidWorks Application Programming Interface (API) that integrates the proposed LPBF cost model within the 3D CAD environment. The tool enables designers to generate support structures and distinguish from internal and external supports on their part. In addition to querying volume and surface data from the 3D model, the manipulation of the part’s build orientation allows designers to concurrently estimate build time, feedstock requirements, and optimize parts for AM production while they are being designed in CAD. A case study is presented for an automotive upright where results found that varying the support angle by 15 degrees, underpredicted support structure volume by 34% and build time by 20%. Furthermore, poor packing of geometries on the build platform led to powder depreciation costs being nearly twice the material costs. Based on this two-part study, recommendations are made for additional research on LPBF cost modeling, post-processing cost modeling, powder feedstock reusability metrics, and CAD-integrated design tools with greater inputs, support structure libraries, and considerations for AM processes.