By comparing the range in Table 3, we can get the order of influence of six factors on the entrance diameter of holes as C > F > A > E > D > B; the order of influence on the exit diameter of holes as C > D > E > A > B > F. In the following, the influence of each factor on the hole size is specifically analyzed and reorganized using the integrated equilibrium method to select a new optimal combination.
(1) Factor A. The effect of factor A on the entrance diameter is ranked third and the effect on the exit diameter is fourth. When factor A is taken as the second level, the entrance and exit diameters of 400 µm are − 32.629 and − 8.11, while the fourth level is taken, the values are + 0.047 and + 59.336. So factor A is taken as the second level.
(2) Factor B. The effect of factor B on the entrance diameter is ranked sixth and the effect on the exit diameter is ranked fifth. When factor B is taken as the second level, the entrance and exit diameters of 400 µm are − 1.23 and + 56.522, respectively, while when the fifth level is taken, the values are + 14.082 and + 17.528, respectively. So factor B is taken as the fifth level.
(3) Factor C. The effect of factor C on both entrance and exit diameters is ranked first. When factor C is taken as the third level, the entrance and exit diameters of 400 µm are − 29.944 and + 44.601, respectively, while when the second level is taken, the values are − 65.651 and + 37.801, respectively. So factor C is taken as the third level.
(4) Factor D. The effect of factor D on the entrance diameter is ranked third, and the effect on the exit diameter is ranked fourth. The optimal combination of factor D on the entrance and exit diameters is adopted as the second level. So factor D is taken as the second level.
(5) Factor E. The effect of factor E on the entrance diameter is ranked fourth and the effect on the exit diameter is ranked third. When factor E is taken as the third level, the entrance and exit diameters distance of 400 µm is -5.4 and − 22.01 respectively, while when the fourth level is taken, the value is -1.87 and + 63.234 respectively. So factor E is taken as the third level.
(6) Factor F. The effect of factor F on the entrance diameter is ranked second and the effect on the exit diameter is ranked sixth. When factor F is taken as the fourth level, the the entrance and exit diameters distance of 400 µm is -5.4 and − 22.01 respectively, distances of 400 µm are + 5.745 and + 15.43, respectively, while the values are − 0.411 and + 56.072 when the first level is taken. So factor F is taken as the fourth level.
The optimal solution for a 400 µm through-hole is A2 B5 C3 D2 E3 F4, which corresponds to power 7.84 W, overlap 99%, defocus 0 mm, pressure 0.25 MPa, feed 0.020 mm, and end + 0.2 mm. And for the order of taper influence is C > D > E > B > F > A, the preferred solution is A1 B5 C5 D2 E3 F4.
The new optimized combination of through-hole optimal solution and taper optimal solution is A2 B5 C5 D2 E3 F4, which corresponds to power 7.84 W, overlap 99%, defocus + 0.4 mm, pressure 0.25 MPa, feed 0.020 mm, and end + 0.2 mm, this parameter is the optimized parameter for machining a 400 µm through-hole.