Page 18 - 3D Metal Printing Spring 2017

3D Designing for Additive Manufacturing
Topology Optimization
Topology optimization determines the optimal material distribution in the design space (red) for the objective, while satisfying defined design constraints.
The optimization yields a distribution of variable density.
A threshold density is selected to determine which elements will be removed.
Elements below the threshold are removed, while elements above the threshold are considered fully dense and are remeshed.
Finite-element analysis is applied to the remeshed model to verify that the design constraints have been met.
Fig. 2
allowed to change are designed into the ‘non-design’ space. These elements/ regions (typically interface surfaces/ mandatory component features) may not change shape nor topology with the analy- sis iterations.
Designers use two classes of structur- al-optimization methods—those for con- ceptual design and those for fine-tuning.
When used in conjunction, these process- es provide the best results. The goal of the conceptual analyses: determine the optimal material distribution for several sets of load cases and constraints. The results of this exercise then are used as a starting point for the design, as it defines the general regions where mass must be included to meet the defined constraints.
The shapes and topologies that result from conceptual-design analyses allow design- ers to consider unintuitive, complex regions of the design space. These opti- mum material distributions are not biased by traditional ‘design for manufacturabil- ity’ rules.
Three Conceptual-Design Methods
Topology Optimization—This opti- mization method allows for individual elements to be removed from the set of design elements. In doing so, part shape and topology are allowed to change. This method proves useful in determining the optimal material distribution for structural problems where a large design space is available. The most efficient material lay- out is determined based on user-defined design space, design targets and con- straints of the component.
Topography Optimization—This method finds use when determining the reinforce- ment beads or swages of thin-walled structures. Removal of elements is not optional with this method; rather, the thickness of the elements is varied to gen- erate integrated reinforcements to achieve the objective of the analysis.
Free-Size Optimization—Designers use this method for generating optimal thickness distribution that meets design requirements.
After determining the optimal material distribution, the designer further refines the design by making limited changes to dimensions or model parameters. These methods may be applied to more accu- rately determine the localized features of the component.
Two Fine-Tuning Methods
Shape Optimization—Here we opti- mize the shape variables based on design requirements, to reduce stress concentrations.
Size Optimization—This process refines the model parameters, such as cross-sec- tion dimensions and thicknesses, to fur- ther optimize localized regions.
With the detailed design complete, the engineer turns to manufacturing optimization, evaluating the part within
Load Case 1 Load Case 2
Load Case 3 Load Case 4
Fig. 3
16 | 3D METAL PRINTING • SPRING 2017
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