# A Trimming Design Method Based on Bio-Inspired Design for System Innovation
## 4 Case Study
### Analysis of the Steel Tape Armoring Machine before Trimming  
The metallic armor illustrated in Figure 8a is an indispensable component of a cable that needs to resist stretching. The armoring machine shown in Figure 8b is a current device used to coat cables with steel tape. However, there are some significant problems in the current system. One of the most significant flaws of the current machine is that the roller vibrates extensively as the rotating speed of the steel tape plate increases, resulting in loud noise and harmful effects on the machine. Therefore, in order to maintain an acceptable level of vibration, a limitation is set on the rotating speed of the steel tape plates, which, in turn, reduces the productivity of the armoring machine. This is a clear opportunity for redesigning the high-speed steel tape armoring machine by eliminating the trade-off that causes the noise. Therefore, the proposed methodology was applied to solve this design problem by following the workflow in Figure 1.  
Step A1: Performing function analysis of the existing steel tape armoring machine. One of the most significant causes of vibration in the analyzed device is that the weights of the steel plates decrease as they wind around the cable during the armoring process. It is difficult to maintain the same rate of weight loss for two plates, and the accumulation of weight differences leads to significant vibration and noise. The rotating speed of steel plates in the armoring machine is an important factor that causes a contradiction: on the one hand, the speed should be high since it is closely related to productivity, and on the other hand, the speed should be low because it is the root cause of vibration. In order to eliminate this fundamental problem, a function analysis of the existing product system is first conducted before formulating the trimming plan. The functional model of the existing product is shown in Figure 9.  
Step A2: Identifying major design problems. Referring to the functional model of the original system, CECA can be performed as shown in Figure 10 to indicate causal relationships between components and the different functional roles that they play. The information in Figure 9 reveals a major harmful  
Figure 8: (**a**) An indispensable component of a cable; (**b**) Illustrations of the cable armoring machine. Figure 9: Functional model of the original steel tape armoring machine. function, i.e., the vibration of the roller. All of the causal relations between the functions and components are represented in Figure 10.  
Step A3: Determining trimming priorities. Based on the CECA result, the function value for each component can be calculated by Formula (1). The results are listed in Table 7, which includes key variables such as \(F_{\text{i}}\), \(L_{\text{i}}\), and \(T_{\text{i}}\) based on the causal relations between functional roles and components. All components in Table 7 are ranked by their function values. The ranked results in Table 7 are used to define trimming priorities. As the steel plate shaft, steel plate and roller have negative function values, they are prioritized for trimming. Figure 10: Function tree of the original model of the steel tape armoring machine based on CECA (partial). The Trimming Analysis of the Steel Tape Armoring Machine and the Analysis of the Device after Trimming  
Step B1: Formulating the trimming plan and trimming the selected components. From the results in Table 1, a trimming plan is formulated to remove all three components that have negative function values. If these components are trimmed, the structure of their connected components will change; therefore, components that are connected to the trimmed components must be assessed to determine whether they need to be redesigned as well. Figure 4 highlights the trimmed area, which is circled by a red dotted line. Step B2: Verifying that the designated components have been trimmed. First, it is confirmed that the three designated components (steel shaft, steel plate and roller) have been trimmed.