Manufacturing the Future 2012 Part 12

Tham khảo tài liệu 'manufacturing the future 2012 part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Concurrent Process Tolerancing Based on Manufacturing Cost and Quality Loss 541 20 X3 9 X4 12 X5 X6 12 X7 unit mm . Two critical dimensions yi and y2 . y1 is the critical axial gap between bush 7 and frame 9. y2 is another critical axial gap between nut 8 and frame 9. It is not difficult to formulate the assembly functional equations using the method presented by Huang et al. 2001 . y1 - x1 - x2 - x3 x5 y2 -X4 - x5 - x6 x7 Figure 5. Wheel assembly According to Equation 13 the deviation equations of critical dimensions are w1 y1 - y1 -Ax1 - Ax2 - Ax3 Ax5 w2 y2 - y2 -Ax4 - Ax5 - Ax6 Ax7 With Equation 14 the functional tolerance inequalities by worst-case model are ty1 tx1 tx2 tx3 tx5 ty2 tx4 tx5 tx6 tx7 Provided that the manufacturing process takes place under stable conditions each process dimension will be of normal distribution. For simplicity assume that the distribution center of each process dimension is just equal to its nominal value. Each critical dimension variance can be expressed as the function of its design tolerance 542 Manufacturing the Future Concepts Technologies Visions var w 1 txf tx2 x x 36 1 2 3 5 var w2 tx2 x tx2 tx2 36 4 5 6 Similarly the covariance of the two correlated critical dimensions can be expressed as the function of the pertinent design tolerances cov w1 w2 1 x 36 The critical tolerance ranges of y1 and y2 in Figure 5 are determined both by performance satisfaction and manufacturing cost of this assembly. To finally determine the optimum tolerance of these two critical dimensions and then allocate them to the related process dimensions quality loss and manufacturing cost must be determined first. Provided that when critical dimension y1 and y2 deviate from their target nominal vector with values w 1 W1 1 0 T 0 T w 2 0 W2 2 T 0 T or w 3 W1 3 W2 3 T Twill result in product failure and cause a quality loss of 300. The constant matrix K can thus be decided by Equation 22 ku

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