# Function-Oriented Applicability Evaluation of Technical Folding Based on Expert Knowledge
## 6 Testing of the EvalTech Method
### Initial Testing of the EvalTech Method  
The main functions and their sub-functions of the large-scale covering for industrial welding form the starting point for testing the applicability of technical folding using the  
Figure 10: Visualisation of the similarity calculation. EvalTech method implemented in the software application. The _EvalTech Questionnaire_ is qualitatively validated by the product developers by applying it to the concept development of the covering and three successfully realised technical folding systems: the modular origami robot [12], the stent [7], and the origami folding for 3D optics [6]. Answering the _EvalTech Questionnaire_ is user-friendly, and the subsequent automated calculation of the initial match \(sim_{\text{case 1}}\) can be calculated successfully: the comparison of the main functions and sub-functions with the functions of _case base 1_ yields a fit of 0.7026 (=70.26%) for the concept of the covering. The comparison of the functions of the three successfully realised technical folding systems yields a high fit as expected: 0.635 for the robot, 0.693 for the stent, and 0.755 for the origami folding for 3D optics. The _EvalTech Questionnaire_ provides the best results if the functions match literally. Functions that are described with synonymous words or contain grammatical errors or errors in their spelling cannot be considered in the similarity calculation. Functions that correspond in meaning to the functions of the _EvalTech Questionnaire_ can also be selected, but this choice depends on the user's subjective interpretation of the functions of the new technical problem. In the subsequent process step, _specify features_, the specific function structure is efficiently worked out with the help of the HFSB. The function catalogue stored here facilitates the development of the function structure and recommends useful functions for the function structure. Own functions can be added as desired and used for the development of the function structure. For better visualisation, the designed function structure of the covering is shown as a block definition diagram in the following Figure 11.  
Using a deliberate development of non-standardised function structures, it was also possible to validate that the integrated test for checking the quality of the function structure (adherence to the subject-verb method, use of only one main function, connection of at least two sub-functions to a superordinate function) works. In the subsequent process _select_, the automatic calculation of the similarity equations \(sim_{\text{case 2.1}}\) and \(sim_{\text{case 2.2}}\) can be performed successfully with the help of the MATLAB(r) function, _Function Structure Analysis_. The function structure of the covering most closely matches the function structure of the self-deployable stent. The higher the result of the similarity analysis 2.1 and 2.2, the more similar the functions or function structures of the application are to those of an already successfully used folding mechanism. With high values, the application is promising for technical folding. The general functional similarity \(sim_{\text{case 2.1}}\) is 0.2571 (=25.71%) and the structural similarity \(sim_{\text{case 2.2}}\) is 0.5556 (=55.56%). The solution concept of the self-deployable stent is based on the folding scheme _Chickenwire_ and allows a cylindrical movement in radial and axial directions. In addition to the matching with this solution concept, the matches with other solution concepts can be visualised. Based on the result of the calculated match and the visualisation of further solution concepts, the hurdle for the development of a covering based on the solution principle of technical folding has been taken. The solution concept for a foldable covering successfully developed within the research project E\({}^{2}\)F is based on a folding scheme similar to the self-deployable stent, the so-called _Chickenwire_ folding scheme, which enables a cylindrical opening and closing of the covering.