Question 4.6: Figure 4.88 shows a fixture setup for the milling operation ...
Figure 4.88 shows a fixture setup for the milling operation on the part for a slot feature. The fixturing system is implemented by using the 3–2 principle. The primary plane makes the contacts to the bottom surface of the part. The movements along x-axis and y-axis are constrained by one and two locators, respectively. The position of locator A can be placed at L_{1} = 25, 75, and 125 mm; the position of locator B can be placed at L_{2} = 175, 225, and 275 mm; and the position of locator C can be placed at H =25, 75, 125, and 175 mm. The clamping forces along x-axis and y-axis are – 2 kN and -0.5 kN, respectively, and the cutting forces are (F_{t\_ x} , F_{t\_y} ) = (-4kN, -2kN). Determine the positions of the locators to optimize the dimensional accuracy of the part.
Based on the provided information, the workpiece and fixture elements are modeled, and an FEA model for static analysis is further defined in the Solidworks Simulation. The model for static analysis is shown in Fig. 4.89a, and an example of the workpiece deformation from the simulation is illustrated in Fig. 4.89b. To optimize the layout of three locators, a design study in Fig. 4.89c is defined for three variables (i.e., L_{1} , L_{2} , and H) to evaluate the displacement of workpiece. The design study finds that the optimized positions of three locators are L_{1} = 75 mm, L_{2} = 175 mm, and H = 175 mm, and the minimized displacement is 2.89 microns.
