*4.1. Preparations before the Tests*

Problem description: When there are three influence factors of TPD, ME and LCM at the same time for a certain type of gear, one must research the influence degree of each factor on the TSCS and the interaction between them, and then determine the optimal combination of factor levels, so as to reduce the TSCS as much as possible.

Quality characteristic and ideal function: Take the maximum TSCS as the quality characteristic. The smaller the maximum TSCS is, the better.

Control factors: The above three factors are the control factors of the Taguchi method. For the TPD, it is divided into three levels (grade 2 precision, grade 4 precision and grade 6 precision). For the ME, <*a* is divided into three levels (0.2◦, 0.4◦ and 0.6◦), and <*b* is divided into three levels (−0.04◦, −0.08◦ and −0.12◦). For the LCM, it is divided into three levels (*C* = 3.5 μm, *C* = 7 μm and *C* = 10.5 μm). The control factor levels are shown in Table 9.


**Table 9.** The levels of control factors.

Test design: According to Table 9, the next step is to establish an orthogonal test table to record the test data, and the corresponding FEM simulation model is established according to the orthogonal test table. In this paper, Minitab is used to generate the orthogonal test table. There are two kinds of test tables with four factors and three levels. One has nine groups of tests, and the other has 27 groups of tests. Because we want not only to ge<sup>t</sup> the optimal combination of the factor levels, but also to research the interaction between various factors, 27 groups of tests are selected. The test table is shown in Table 10.


**Table10.** Theorthogonaltesttable.
