Đang chuẩn bị liên kết để tải về tài liệu:
Micromachining Techniques for Fabrication of Micro and Nano Structures Part 9

Tham khảo tài liệu 'micromachining techniques for fabrication of micro and nano structures part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Micro Eletro Discharge Milling for Microfabrication 149 3.2.1 Desirability function approach In the analysis the objective function D Yi called the desirability function reflects the desirable ranges for each response Yi x where i Ra Ry TWR MRR . For each response a desirability function di Yi assigns numbers between 0 and 1 to the possible values of Yi. di Yi 0 representing a completely undesirable value of Yi and di Yi 1 representing a completely desirable or ideal response value. The individual desirabilities are then combined using the geometric mean which gives the overall desirability D 1 D - n d1 X d2 X X dn - d1 X d2 X X dn n 3.5 where n is the number of responses in the measure. From the equation 4.5 it can be noticed that if any response Yi is completely undesirable di Yi 0 then the overall desirability is zero. In this case the geometric mean of overall desirability is as follows 1 D - dRa X dR X dTWR X dMRR 3 a y 3.6 Depending on whether a particular response Yi is to be maximized minimized or assigned a target value different desirability functions di Yi can be used. In this case Ra Ry and TWR are needed to be minimized while MRR are needed to maximized. Following are the two desirability functions di Yi Yi x Li Li Yi x Ti Yi x T 1.0 i. ifY if Yi x Ti di Yi I Y r Ui I if Ti Yi x Ui I T - Ui J 0 if Yi x Ui 3.7 3.8 where Li Lower limit values Ui Upper limit values Ti Target values s weight define the shape of desirability functions Feed rate pm s Capacitance nF Voltage volts Ra pm Ry pm TWR MRR mg min Desirability 4.79 0.10 80.00 0.04 0.34 0.044 0.08 88.06 Table 3.3. Values of process parameters for the optimization of Ra Ry TWR and MRR 150 Micromachining Techniques for Fabrication of Micro and Nano Structures Equation 3.7 is used when the goal is to maximize while to minimize Equation 3.8 is needed. The value of s 1 is chosen so that the desirability function increases linearly towards Tị. Table 3.3 shows the process parameters obtained after multiple .