Microstructure and Process Based Topology Optimization for Direct Metal Deposition

Vibhas Mishra (PhD candidate) and Matthijs Langelaar (supervisor)

The Aim2XL research programme focusses on exploring the capabilities of new metal based Additive Manufacturing (AM) technology called Direct Metal Deposition (DMD). DMD is a process in which the metal is simultaneously melted and deposited along predefined deposition paths and order. DMD has advantages such as high deposition rate, simultaneous deposition of the different metals and freedom to choose deposition paths and order, over other AM methods. Large scale structures such as ship propellers, aircraft structures and bridges with dimensions in order of few meters can be produced in few days through DMD. The Aim2XL program has three research lines namely, (i) optimization, (ii) microstructure prediction and control and (iii) microstructure – mechanical property relationship. Our research activities fall in the optimization research line.

Objective

The objective of the optimization research line is to generate optimized designs specific to the DMD process and generate the optimized deposition patterns on the design such that produced parts have the required microstructure and consequently the required mechanical performance.

Methods

Topology Optimization (TO) is used as the design methodology to generate the optimized designs specific to the DMD process and deposition patterns on it. The restrictions posed by the DMD process are identified and captured in mathematical formulations, that can be integrated in TO as constraints

Results

One of the restrictions of the DMD process is that the intersecting features are problematic to manufacture as these lead to extra material deposition at the intersecting location. This gives non-homogeneous deposition heights in the structure as shown in Figure 1. Therefore, intersecting features should be avoided in a design. A stress-based parameter was develop to identify the intersecting features in a design during TO. Furthermore, a mathematical cost function was developed such that minimizing it results into minimizing the intersecting features in a design. Figure 2a shows an optimized design obtained from TO. This design is problematic to manufacture through DMD as there are many intersecting features, considering an out-of-plane printing direction. Using the DMD constraint developed in this project, the number of intersecting features has been reduced significantly and the updated design is shown in Figure 2b. Since intersecting features have been minimized, it is much better producible through the DMD process.

Figure 1. Intersecting Feature with non-homogeneous deposition height
Figure 2. In (a), Design obtained through compliance minimization (baseline design). In (b), Design obtained through minimization of the intersecting features in the design (Updated Design). Updated design is suitable for DMD.
(a)(b)

 Partners involved

  • Partner Universities Delft University of Technology, Eindhoven University of Technology, University of Groningen and University of Twente.
  • Managing Partners M2i and RAMLAB
  • Industrial Partners Air Liquide B.V., Allseas, Autodesk, Damen, Element Materials Technology, Fokker Technologies Holding B.V., Heerema Fabrication Group, Huisman, Jungle, Lincoln Electric B.V., Lloyd’s Register EMEA, MX3D, OCAS NV, Shell, Trumpf Nederland B.V., Valk Welding B.V. and VandeGrijp International Gear Suppliers B.V.

 

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