# Optimization of Brake Calipers Using Topology Optimization for Additive Manufacturing
## 5 Results  
The CAD designs and the bill of materials (BOM) of the caliper design concepts, developed at the first level of the optimization process, are depicted in Figure 9. Both calipers were dual-piston fixed calipers, and the size and number of their components were decreased, resulting in lighter design solutions. At this level, the weights of the front and rear caliper, except the housings, were 29.4% and 26.2% lighter than their commercial counterparts. On the other hand, the design space of their housings increased approximately five times comparing to the ISR housings, utilizing the maximum available space between the wheel, brake disc and surrounding suspension components. Hence, there was enough material for the TO conducted at the third optimization level. However, this increased the optimization time dramatically. The TO resulted in 42% and 64.7% weight reduction of the housings of the front and the rear caliper. The optimized geometry of the housings that was reconstructed in SolidWorks, resulted in a weight increase of 2.1% and 12.5%, respectively. This is something that was expected since both the partial redesign and the 3D printing preparation altered the initial geometries of the optimized results. However, the total weight of the front caliper was reduced to 36.9%, while the rear caliper was 48.5% lighter. The optimized 3D models of the housings are presented in Figure 10.  
Figure 10: The optimized housings in SolidWorks: (**a**) Front, (**b**) Rear. Figure 9: The assemblies of the caliper design concepts after the first optimization level in SolidWorks: (**a**) Front, (**b**) Rear. The stress and displacement distribution at both housings and their assemblies, found by the validation studies, are depicted in Figures 11 and 12. The validation studies of both housings and calipers showed that the optimized housings were topologically optimized without sacrificing their stiffness. The validation studies of the assemblies were also utilized as a connectivity checking tool between the housings and the other components. On the one hand, the maximum stresses of the housings of the front and the rear caliper were 5.9% and 3.9% smaller than the ISR. Moreover, their maximum displacements were reduced by 59.3% and 17.1%, respectively. On the other hand, the optimized housings fit correctly to the calipers' assemblies. Furthermore, the  
Figure 11: The results of the validation studies in ABAQUS for the front caliper: (**a**) Stress plot of the front housing, (**b**) Stress plot of the front caliper, (**c**) Total displacement of the front housing, (**d**) Total displacement of the front caliper. Figure 12: The results of the validation studies in ABAQUS for the rear caliper: (**a**) Stress plot of the rear housing, (**b**) Stress plot of the rear caliper, (**c**) Total displacement of the rear housing, and (**d**) Total displacement of the rear caliper. front caliper had a 400 MPa maximum stress while the rear caliper 447 MPa. Moreover, the displacements of both calipers were reduced. Specifically, the assemblies of the front and the rear caliper had a 50% and 17.5% reduction of their maximum displacement in y-direction compared to the ISR calipers. The optimized housings were 3D printed at an EOS Lasertec 30 Dual SLM 3D printer in Ti6 Al4V. Figure 13 depicts the 3D-printed parts on the building plate after the post-treatment. More components were printed for backup. A weight deviation of both 3D printed housings was observed. In particular, the housing of the front caliper was 0.9% heavier than its 3D model, while the housing of the rear caliper was 6% heavier. Possible reasons for these differences could be the used tolerances of the STL files, especially on all part interacting surfaces, the insufficient removal of the support material, as well as remaining powder inside the 3D printed parts.