*Appl. Sci.* **2020**, *10*, 3935

The comparison should read that the lower the score, the more you need to redesign/reduce the product design. From the comparison of the assessment, it can be concluded that the Boothroyd-Dewhurst method is the most stringent and focused on reducing/simplifying the details of the project components. At the same time, in the case of production which is not qualified for high-volume production, the result of such an assessment may be a product with a small number of components, but in a very complicated form and therefore will have a high cost of processing, quality and others in the field of production organization. However, the new fuzzy method, because it takes into account the treatment and its limitations and the index of production organization in which it directs the result towards small-lot production gives the least result which improves the technological efficiency of this sub-assembly for the assumptions of the model of fuzzy small-lot production.

The result of a single method does not give a picture of effectiveness nor a new fuzzy method. For this purpose, a comparison of a selected transmission fragment of the new method and existing methods was carried out. The selected fragment in the form of a drive shaft assembly and was compared in Table 3 from the overall assessment of the transmission. Comparisons show that for small lot production assessment B&D with 0.3 results, Lucas with 0.24 results, versus fuzzy defined for a small lot with 0.53 results, was a less restrictive approach of Fuzzy method. This was very important as small lot production usually has much less capital available.

The comparison should be read as follows, the lower the score, the more you need to redesign/reduce the product design. From the comparison of the assessment, it can be concluded that the Boothroyd & Dewhurst method was the most stringent and focused on reduce/simplify the components of the project. At the same time, in the case of production not qualified for high-volume production, the result of such assessment may be a product with a small number of components, but a very complicated form and therefore a high cost of processing and quality and other in the field of production organization. The Lucas method in a more balanced way assesses the above project, but the difference from Boothroyd-Dewhurst is not large, which means that it will also work best in mass production.

#### **6. Conclusions and Comments**

In this study, we have focused on the assessment of gearbox using a new developed fuzzy method and compared it to the most known Boothroyd and Lucas DFA methods. The purpose was to assess gearbox development for small lot production, propose design changes and evaluate its design. This was very important as small lot production usually has much less capital available. The method developed is open and other or additional criteria may be considered according to the production conditions of the company concerned.

The fuzzy method was more tuned to this volume level of process and it was an advantage of this method in comparison to other methods that were more suitable for only mass production. The flexibility of this method was one of the aims of creating it.

In standard technology analysis, according to B&D and Lucas DFA, this was associated with a reduction in the number of components that have no significant effect on the product functions which results in an improvement in terms of assembly time and costs. In the traditional arrangement, of the above mentioned the methods, they were oriented towards mass production.

The proposed proprietary method based on the analysis of the obtained values of the parameters of the assessment of the efficiency of the entire process enables:



The presented method is universal. The use of fuzzy logic allows expressing incomplete and uncertain information in natural language, in a simple way for humans based on expert knowledge and empirical data. The method considers the analysis of the production process in a holistic way.

**Author Contributions:** Conceptualization, J.M., T.S. and A.M.; data curation, T.S.; formal analysis, J.M., T.S. and A.M.; funding acquisition, J.M.; methodology, J.M.; resources, J.M., T.S. and A.M.; software, T.S.; validation, A.M.; visualization, A.M.; writing—original draft, J.M., T.S. and A.M.; writing—review and editing, J.M., T.S. and A.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research has received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
