# A Comparative Study of the Application of Different Commercial Software for Topology Optimization
## 7 Discussion  
The goal of this paper was two-fold--first, to develop a novel library of the most applied open source and commercial TO software, and secondly, to focus on the practical implementation of TO via a comparative study of three commercial software platforms using three well-known CAD models as case studies. The results of this research work provide CAD designers with a better understanding of TO and advise them through recommendations to avoid common pitfalls. On the one hand, the developed TO library consists of 70 software platforms, 22 open source and 48 commercial, that encompass TO in their modules. This novel library could be considered an updated version of the library developed by Reddy K, Ferguson, Frecker, Simpson, and Dickman [30]. However, its content is broader, including more software packages and additional information. The identified software platforms were investigated and categorized based on their capabilities in a table together with their name, company, availability, and optimization types and methods, as well as the objective functions and constraints that they provide. In addition, a column in the table contains all the available designer inputs categorized into four clusters--design constraints, supports and connections, loads, and geometric restrictions due to manufacturing constraints. Furthermore, information about the presentation of the TO results in the software interface, as well as representative literature, was included. Moreover, it was the authors' intention to create an updated online database of TO software. Thus, the library can be accessed online where interested readers can both read and edit its contents, contributing in this way to the creation of an updated library of the available TO software. This database could be a practical manual for CAD designers interested in TO and can conserve valuable time in their pursuit of the ideal software that can support their optimization case. Comparing the developed TO library in this paper with the relevant identified TO studies conducted in 2002 [29], 2006 [30], and 2016 [31], it seems that new objective functions and design constraints have been introduced in the TO software over the last years, with a particular focus on the manufacturing constraints. The authors observed that there are continuous introductions of new manufacturing constraints in the commercial software. The software companies try to provide adequate manufacturing constraints that can support the manufacturability of the topologically optimized designs from both CPM and AM. However, the derived design solutions cannot be directly manufactured. There is still a need for manual interpretation of them by the CAD designers, as also stated by Reddy K, Ferguson, Frecker, Simpson, and Dickman [31] in 2016. In the comparison study conducted by the authors, all case studies, including a bell crank lever, a pillow bracket, and a small bridge, were oriented to AM. In this way, the redesign of the optimized solutions demanded by the CPM, in order to mitigate the created organic shapes by TO, could be omitted. However, manual checks and repairs of the faceted geometries were inevitable in order to address the mesh discontinuities in the validation studies. On the other hand, three different commercial software platforms, SolidWorks, ABAQUS, and ANSYS, were used in the comparative study in order to compare their user interfaces and TO outputs. Despite the fact that each of the aforementioned CAD models was optimized in the above software using the same TO method, mesh quality, as well as designer inputs and constraints, the derived optimized designs were not identical. SolidWorks and ABAQUS resulted in a similar optimized bell crank lever and pillow bracket, but their design solutions in the small bridge displayed differences. Furthermore, tetrahedral finite elements of the same size were used in all simulations; however, the number of the discretized finite elements differentiated among the software packages.