# Comparison of CAD Software for Designing Cellular Structures for Additive Manufacturing
## 2 Materials and Methods  
To narrow down the selection of suitable software for the design of lattice structures, the first eight different CAD systems were short-listed. The reason for the selection of these software tools was, on the one hand, their already proven use in the field of AM at the university of applied sciences and, on the other hand, the short-term availability on the market due to trial versions for research for students as well as faculty. In terms of origin, all except one software tool is being developed in the USA. Considering functionality, most of the short-listed software tools offer an integrated module for the generation of lattice structures, although more stand-alone solutions are entering the market. For the eight CAD systems, seven different significant criteria including lattice toolbox functionality, repair functionality, AM process integration, visualization and rendering options, materials database, meshing tools, and additional tools available were defined in order to be able to preselect five CAD systems by means of a weighted point evaluation. The distributed point values ranged from 1 (very poor) to 10 (very good) and were assigned to the respective properties of the CAD software tools. All assigned point values were weighted and summed up to identify the most suitable software tools taken into consideration in the next phase of this research project. The weight of each criterion was determined based on its significance. The importance of a well-designed lattice toolbox was considered a key factor and was therefore given a weight of 25%. Similarly, the integration of the respective CAD data output into the AM process chain was given a weight of 20%. This includes the integration of standardized output file types such as STL, AMF, or 3 MF, as well as integration into the next process step, such as slicing or support structure generation. The significance of additional tools such as EFA, GD, or TO in the development process of the lattice structures was given a weight of 15%. The remaining criteria were each given a weight of 10% as they were considered less significant. The evaluation showed that five software tools including Rhino7 (Messhopper(r), 2016), nTopology nTop (Messhopper(r), Altair(r)  
The second geometry is of a more complex character, featuring freeform surfaces and thin-walled structures. This model of a road bike seat, the \"specialized power saddle\" by [PERSON], was downloaded from the GrabCAD Community homepage and used as a reference geometry for use with all the preselected software tools [51]. The original design was modified to limit the use of lattice structures in a given design space, sandwiched between an outer and an inner solid volume (Figure 4). The inner volume incorporates a cutout to help relieve stress and pressure onto the pelvic floor during riding. The purpose of selecting this type of model was to evaluate the capabilities of the preselected software tools in performing complex lattice operations such as progressivity (constant or gradient) and conformity (conformal or non-conformal). When using non-conformal constant lattice structures, the algorithms face an additional challenge because of the presence of freeform surfaces during Boolean or trimming operations. The outer and inner volumes help to protect the otherwise open ends of the lattice structure and add rigidity to the overall design. The software tools' capabilities were tested by evaluating these two geometries. If the respective tools were able to generate these geometries, there should be no obstacle to using more complex ones in the future. In order to sample the chosen software tools and present a comprehensive benchmark of the respective capabilities, computing times and file sizes for specified lattice structure types and sizes were evaluated. The following hardware was used to compute the calculation times and resulting file sizes:  
* Processor: Intel(r) Core(tm) i9-9880H CPU @ 2.30 GHz. * RAM: 32.0 GB (31.7 GB usable). * Graphics: Nvidia Quadro T2000, 5 GB RAM @ 1575 MHz.