[Psychology] Mechanical Assemblies Phần 10 docx

502 18 ECONOMIC ANALYSIS OF ASSEMBLY SYSTEMS 1 2 3 4 5 6 7 S 9 10 11 77- 13 14 15 16 T7~ 18 T9— 2U 21 22 23 24 25 -26— 27 -28— 29 "SC- SI 32 33 34 •35- •35- 37 •38" A | B | C | D | E | F 7 fEAR 0 1 2 3 4 5 6 7 8 /EAR 0 1 2 3 4 4 Nb 1 PHEStNT VALUE CASH FLOW ANALYSIS YEARS ECONOMIC LIFE EXPENSE FORECAST RATIO 100.00% INCOME ($400) $100 $181 $198 $150 $83 SALVAGE VALUE N YEAR 4 3ROSS INCOME slET INCOME ; $713 $313 TAX RATE 34.00% DEPRECIATION $38 $65 $47 $33 $0 $183 $183 0% DEPRECIABLE 66.67% G | H SALVAGE VALUE % OF COST AT END OF ECONOMIC LIFE INCOME FORECAST SAVINGS $100 $181 $198 $150 TOTAL INVESTMENT DEPRECIABLE INVESTMENT INTERNAL RATE OF RETURN PRO FORMA CASH FLOW TAXES ($45) $21 $39 $51 $40 $0 $152 $106 CREDITS $0 $0 $0 $0 $0 $0 $0 $0 DEPRECIATION 14.29% 24.49% 17.49% 12.49% 8.92% 8.92% 8.92% 4.46% $400 $267 18.41% GOAL SEEK ON CELL G38 = 0 NET ($355) $79 $142 $147 $110 $83 $561 $206 TAX RATE 34.00% 34.00% 34.00% 34.00% 34.00% CREDIT SUM OF UNUSED YRS DEPR= 31 .22% USED FOR SALVAGE VALUI I OF REMAINING DEPRECIABLE INVESTMEN RESULT OF DISC NET ($355) $67 $101 $88 $56 $42 $355 ($0) TAX CREDIT IN YR 0 ON UNDEPRECIATED INVESTMEN FIGURE 18-11. Spreadsheet for Performing Net Present Value Calculation. This sheet is set up to find the IRoR that yields zero net present value. It does so using the Goal Seek feature, seeking the rate of return in cell F21 that drives the discounted return in cell G38 to zero. TABLE 18-3. Explanation of Terms in Pro-Forma Cash Flow in Figure 18-11 Term Ratio Depreciable Savings Depreciation (difference between A and B) Tax rate Net income NI (difference between A and B) Disc net Gross income Net income How much of the investment occurs in year 0 What fraction of the investment is depreciated over several years; the rest is taken as an expense in year 0. The ratio of total cost to depreciable cost is called p. Undepreciable expenses include engineering and installation of the system. They generate a tax credit in year 0. The difference between (revenues minus costs) of alternatives A and B during each time period The amount of the depreciable part of the investment that is deducted each year. The pattern is mandated by U.S. tax laws. If the horizon of the investment is less than the eight years shown, the investment is assumed to have a salvage value equal to the sum of the unused depreciation. This is approximately 34% by U.S. tax law. Taxes are paid on income (savings) less depreciation. NI, = (1 — T,)S t + T,D t , where S, = savings, D, = depreciation, r t — tax rate in period t Net income discounted to year 0 using the IRoR shown in cell F21 Sum of rows 28-32 Sum of rows 27-32 Meaning (a) (b) 1 2 3 4 -5- b / B 9 10 •11 12 -re- 14 15 -T6- T7~ IF" ~W 2U 21 22 23 24 25 26 27 28 '&) 30 31 32 ay 34 3b 3b 3/ 38 A 7 Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 B Years Econo C | D | E Net Present Value Cash Flow Analysis mic Life ExpenseForecast Ratio 100.00% Tax Rate 34.00% 0% Depreciable 25.00% F Salvage Value % Of Cost At E 1 IncomeForecast Savings 0 0 0 $400 $600 $800 $800 $800 $1,000 $1 ,000 $1,000 $1,500 $1 .son $1 r 500 $1.500 $1 ,500 $1.500 $1,750 $2,100 $2,100 $2,100 $2,400 $2,400 $3,000 $3,000 Total In vestment Depreciablelnvestment Depreciation 14.29% 24.49% 17.49% 12.49% 8.92% 8.92% 8.92% 4.46% 0 0 ($10,500) ($2,625) Internal Rate Of Return \ 11.33% (Goal Seek bnCellG71=0 G H nd Of Economic Life Tax Rate 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% 50.00% Credit I Tax Credit In YrO On Undepreciated Investment 39 40 41 42 43 44 4b 46 47 48 49 bO 51 b'2 b3 b4 bb 56 b/ by by 50 61 b2 63 64 65 66 b/ 68 69 i 70 71 Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 a ross Income Met Income Income ($3,500) -3500 -2500 -1000 $400 $600 $800 $800 $800 $1 ,000 $1 ,000 $1 ,000 $1,500 $1 ,500 $1 ,500 $1,500 $1 ,500 $1 ,500 $1 ,750 $2,100 $2,100 $2,100 $2,400 $2,400 $3,000 $3,000 $34,250 $23,750 Pro Forma Cash Flow Depreciation ($375) ($643) ($459) ($328) ($234) ($234) ($234) ($117) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($2,624) ($2,624) Taxes ($3,937.50) ($1,562.44) ($928.57) ($270.44) $363.93 $417.08 $517.08 $517.08 $458.54 $500.00 $500.00 $500.00 $750.00 $750.00 $750.00 $750.00 $750.00 $750.00 $875.00 $1 ,050.00 $1 ,050.00 $1 ,050.00 $1 ,200.00 $1,200.00 $1 ,500.00 $1,500.00 $14.937 $1 1 ,000 Credits $0 $0 $0 $0 $0 $0 $0 $0 Net Income $438 ($1,938) ($1,571) ($730) $36 $183 $283 $283 $341 $500 $500 $500 $750 $750 $750 $750 $750 $750 $875 $1 ,050 $1 ,050 $1 ,050 $1 ,200 $1,200 $1 ,500 $1 ,500 $12,313 $12,750 Disc Net $438 ($1 ,740) ($1 ,268) ($529) $23 $107 $283 $133 $145 $190 $171 $154 $207 $186 $167 $150 $135 $121 $127 $137 $123 $110 $113 $102 $114 $103 $0 $0 Sum Of Undisc Net Inc $438 ($1 ,500) ($3,071) ($3,801^ ($3,765) ($3,582) ($3,299) ($3,016) ($2,675) ($2,175) ($1 ,675) ($1,175) ($425) $325 $1 ,075 $1 ,825 $2,575 $3,325 $4,200 $5,250 $6,300 $7,350 $8,550 $9,750 $11,250 $12,750 $438 ($1,303) ($2,571) ($3,099) ($3,076) ($2,969) ($2,686) ($2,553) ($2,408) ($2,218) ($2,047) ($1 ,893) ($1,686) ($1 ,500) ($1,333) ($1,184) ($1 ,049) ($928) ($801) ($664) ($542) ($431) ($318) ($217) ($103) $0 FIGURE 18-12. Example Net Present Value Calculation for a Large Passenger Aircraft, (a) Net present value cash flow analysis, (b) Pro-forma cash flow. 503 504 18 ECONOMIC ANALYSIS OF ASSEMBLY SYSTEMS FIGURE 18-13. NPV for Large Passenger Aircraft. NPV is positive for interest rates less than 11.33%, not a very attractive investment on economic grounds alone. 18.G.7. Remarks The pattern of cash flows shown in Figure 18-4, in which there is one large negative flow at the beginning fol- lowed by numerous smaller positive and negative flows thereafter, is typical in the kinds of problems studied here. This kind of cash flow pattern gives rise to the pattern of PV versus discount rate behavior shown in Figure 18-13. The methods of comparing investments discussed above are valid when the pattern of PV ver- sus discount rate looks like this but may give the wrong answer if it does not. The NPV method has its critics and there are many ways to interpret the results. Note that the goal of a com- pany is to make money, not to earn a particular rate of interest. Suppose the company has $100 million to invest and has two choices: to invest $90 million for an IRoR of 15% or to invest $15 million for an IRoR of 20%. One in- vestment earns a higher rate of return but the other makes much more money. Thus the results of the calculations must be judged carefully and a decision rule should not be followed blindly. Another criticism of the NPV method is that it favors short term results and tends not to select projects that will mature over a longer period. While this is true, there are other reasons why a short term view is often taken, even if they are not always good reasons. Capital costs money, and that cost is certain. Profits are in the future and they are uncertain. Discounting is the main way to compensate for the differences in uncertainty. Another way to take uncertainty into account is to imag- ine different scenarios for future cash flows. Perhaps one can assign a most likely value, a most optimistic value, and a most pessimistic value. Then it is possible to calcu- late the mean and standard deviation of the IRoR and PV. Investments with a larger mean and smaller standard devi- ation might be more attractive. In practice, the mean and standard deviation of returns are usually correlated, and one will not find the lowest standard deviation together with the highest mean. 18.H. CHAPTER SUMMARY This chapter and the two before it comprise a way of look- ing at assembly (or other manufacturing) systems in a combined economic-technical way. This process begins with the requirement to produce a product or family of products at a certain rate for a certain period of time using some mix of resources. Investments and ongoing costs are involved. A simplified diagram of this process appears in Figure 18-14. It shows that product design (including de- sign simplification), assembly sequence, alternate assem- bly technologies, and macro- and microeconomic factors all must be considered. 18.J. FURTHER READING 505 FIGURE 18-14. Logic Diagram for the Cre- ation of Economically-Technically Effective Systems. Most of the factors discussed in earlier chapters are involved in this diagram. "General economic conditions" affect many blocks in the chart, so this block is not linked by arrows to other blocks in the interest of simplicity. 18.1. PROBLEMS AND THOUGHT QUESTIONS 1. Prove that the payback period method of annualizing fixed costs is equivalent to the annual recovery method with r = 0. Note that this cannot be proven by substituting r = 0 in Equa- tion (18-4). Instead, L'Hopital's Rule must be used. 2. In Figure 18-6 and Figure 18-8 the unit cost versus production volume plot falls and then rises suddenly, then repeats this pattern several times. However, in Figure 18-7 no such behavior can be seen. Explain why the sudden rises happen in two of the figures but not in the third. 3. Discuss the various terms in Equation (18-10). In particular, discuss possible tradeoffs between robot speed, represented by T, robot cost, represented by S$, and tool cost, represented by T$. For example, a more costly robot could be afforded if some of the cost were devoted to versatility that required fewer tools. 4. The NPV analysis of large passenger aircraft in Fig- ure 18-13 utilizes a tax rate of 50%, appropriate for Europe. If 34% is used, appropriate for the United States, one finds that the NPV is considerably smaller. Explain why this is so. 18.J. FURTHER READING [Cooper and Kaplan] Cooper, R., and Kaplan, R. S., "Measure Costs Right: Make the Right Decisions," Harvard Business Review, September-October, pp. 96-103, 1988. [Lynch] Lynch, P. M., "Economic-Technological Modeling and Design Criteria for Programmable Assembly Machines," Ph.D. thesis, MIT Mechanical Engineering Department, June 1976. [Mishina] Mishina, K., "Beyond Flexibility: Toyota's Robust Process-Flow Architecture," in Coping with Variety: Flexible Productive Systems for Product Variety in the Auto Industry, Lung, Y., Chanaron, J J., Fujimoto, T., and Raff, D., editors, Aldershot, UK: Ashgate Publishing, Ltd., 1999. [Nevins and Whitney] Nevins, J. L., and Whitney, D. E., Concur- rent Design of Products and Processes, New York: McGraw- Hill, 1989. [Peschard and Whitney] Peschard, G., and Whitney, D. E., "Cost and Efficiency Performance of Automobile Engine Plants," available at http://web.mit.edu/ctpid/wwwAVhitney/ papers.html. [Thuesen and Fabrycky] Thuesen, G. J., and Fabrycky, W J., Engineering Economy, Upper Saddle River, NJ: Prentice- Hall, 2001. This page has been reformatted by Knovel to provide easier navigation. INDEX Index Terms Links A Accommodation method 257 Activities in a simulation 447 Activity-based-costing 490 Activity cycle diagram 448 Acyclic graph 215 Additive processes 134 Adept Technology 478 Adhesive bonding 167 Adhesives 318 338 384 401 Adjustment 167 168 318 328 388 396 428 of an assembly 23 of a sewing machine 9 Airbus 365 461 Airbus A380 365 461 501 Airbus A380 wing product architecture example 367 Aircraft assembly 213 Aircraft engines 400 Aircraft fuselage DFC example 240 Aircraft product family example 365 Aircraft structures 70 105 Aircraft wing 344 346 349 Aircraft wing subassembly 251 Aladdin 351 American National Standards Institute 114 AND/OR tree 188 194 This page has been reformatted by Knovel to provide easier navigation. Index Terms Links Angular error 152 198 255 256 265 266 269 influence on wedging 271 Angular stiffness 267 Angular velocity vector 80 Annual recovery method 494 ANSI Y 14.5-M 114 APOS vibratory part feeding system 472 481 Archimedes system 194 Architectural flow 367 Architecture 348 attributes 345 desktop stapler 3 of fixed automation assembly machine 429 product 3 8 of product family 10 of products and companies 345 Architectures for automobile bodies 346 Array product structure 392 Artificial constraints 259 ASDP 457 Assembleability 380 Assembleability problems 86 Assemblies improperly constrained 64 overconstrained 86 perform many functions 2 properly constrained 64 86 as systems 16 348 types 34 underconstrained 86 Assembly definition of 64 design process 1 feature 3 6 This page has been reformatted by Knovel to provide easier navigation. Index Terms Links Assembly (cont) high volume 11 history 12 importance 1 integrative nature 1 317 329 low volume 11 main activities 11 nominal 19 supports business processes 2 6 time available 421 467 479 484 time required 421 467 479 Assembly approach direction 44 Assembly cost 190 396 479 increased by rework 437 Assembly cost analysis 382 489 Assembly cycle times short 443 Assembly design intent 1 21 34 211 215 221 Assembly difficulty 328 389 396 422 Assembly efficiency 382 395 low-cost staple gun example 414 related to assembly reliability 401 rugged staple gun example 413 Assembly errors 254 263 479 Assembly feature 34 42 44 62 112 141 142 213 214 245 342 384 chosen to achieve KCs 217 constructed from basic surface contacts 89 in a DFC 216 Screw Theory model of 78 toolkit of 78 90 107 Assembly fitup 243 Assembly fixtures 65 77 407 410 Assembly forces 253 Assembly instructions 425 Assembly interface 354 This page has been reformatted by Knovel to provide easier navigation. Index Terms Links Assembly in the large 2 253 317 379 influenced by product architecture 341 steps in 321 Assembly in the small 2 253 379 steps in 329 Assembly line 13 388 432 443 499 Assembly method 396 426 465 Assembly mistakes 329 390 424 432 445 467 468 six kinds 436 Assembly model 34 213 including product variety 362 Assembly modeling in CAD systems 213 Assembly motion 253 Assembly operations 420 Assembly process capability 152 244 Assembly processes 383 Assembly process requirements 323 Assembly requirements 468 Assembly resource 422 470 Assembly resource choice 13 423 449 465 470 479 Assembly robots 13 431 Assembly sequence 2 180 221 246 330 393 396 420 431 436 449 457 465 499 algorithms 181 of automobile alternator 195 of automobile transmission 229 counting how many 202 criteria 180 189 197 205 disassembly questions 184 feasible 182 187 190 igniter 484 infeasible 183 influence on assembly system design 423 of juicer 55 199 This page has been reformatted by Knovel to provide easier navigation. Index Terms Links Assembly sequence (Cont.) KCs and DFC of 232 Linear 183 190 of missile seeker head 53 of rear axle assembly 201 official 330 precedence relations 188 questions 183 184 187 191 199 related to decoupling point 358 related to delayed commitment 360 relation to DFC 214 to remove KC conflict 236 241 of sheet metal parts 167 state 189 202 203 transitions 189 205 two-handed 194 Assembly sequence analysis 211 Assembly sequence design 183 186 Assembly sequence editing 186 189 Assembly sequence method Bourjault 184 190 207 cut set 184 192 exploded view 182 onion skin 184 subset rule 186 superset rule 186 Assembly sequence software Archimedes (Sandia) 194 Draper/MIT 194 Assembly simulation software 188 Assembly success 265 389 Assembly system 253 Assembly system capacity 426 Assembly system design 317 327 420 465 basic factors 420 This page has been reformatted by Knovel to provide easier navigation. Index Terms Links Assembly system design methods 425 heuristic design method 449 systematic 426 454 Assembly system performance 447 Assembly task network 454 Assembly technology. See Assembly resource Assembly time 497 Actual 395 ideal minimum 395 Assembly time and cost 420 Assembly time available 426 Assembly time estimate low-cost staple gun example 414 rugged staple gun example 413 Assembly time required 427 449 451 454 Assembly tree(s) 205 Assembly workstation 253 design methods 477 Assembly workstation design 317 327 420 465 Assembly-driven manufacturing 364 AT&T Bell Laboratories 338 Automatic assembly 55 198 322 332 370 380 383 396 436 Igniter 484 Automatic assembly machines 13 Automatic guided vehicles 469 Automatic screw insertion machines 401 Automatic transmission 72 cellular assembly 434 truck 472 See also Automobile transmission Automobile air-fuel intake systems product architecture example 370 Automobile alternators 396 robot assembly 195 [...]... 317 382 Design for disassembly 327 Design for manufacturing (DFM) 379 396 Design improvements 324 327 Designing quality in 435 Design of assembly 324 Design procedure for assemblies 245 Design simplification 15 380 Desktop copier 68 105 Desktop stapler 2 212 417 415 assembly features 44 degrees of freedom and constraint 63 KC delivery chain 5 matrix transform model 36 variations 329 123 DFx 379 DFx in... provide easier navigation Index Terms Links Fixture (Cont.) for mounting car doors 238 needed for Type 2 assemblies 211 part of transport system 424 powered 186 to provide missing constraint 221 providing constraint for sheet metal parts 167 for sheet metal part assembly 165 sources of variation in Type 2 assemblies 224 Fixturing features 112 232 Fixturing surface 328 329 15 322 341 343 423 449 497 Flash... delivery chain automobile engine 116 design steps for 117 DFC role as 211 including fixtures 155 length of 156 KC flowdown 23 113 141 KC priority 25 224 243 KC proliferation 26 Kinematically constrained assemblies 102 114 Kinematic assembly 62 68 achieved by datum hierarchy in GD&T 74 120 Kinematic design 388 Kinematic realignment 143 Kinematics 247 Kits for part presentation 469 472 This page has been reformatted... Ordo gear mating patent 281 Outer panel of car door 28 113 235 This page has been reformatted by Knovel to provide easier navigation Index Terms Links Outsourcing 2 8 10 324 342 345 481 347 of assembly system design 422 percent by cost 10 Outsourcing strategy 324 Overconstraint 197 426 inside a feature 348 490 492 433 458 478 89 prevented by self-aligning bearings 222 226 Overdimensioning 152 Overhead... method for finding assembly sequences 182 Exploratory phase of an industry 344 F Fabrication 423 features 43 operations 420 of parts at assembly station 476 Fabrication-driven manufacturing 364 Facets 102 Facility constraints 323 Factory performance 323 Factory’s defect fraction 402 Failure rate of different part presentation methods 44 473 423 Fan motor DFC example Fastener 226 182 193 194 318 324... DFA during 391 Concept generation 320 Concurrent engineering 253 Cone point screws 279 Connective assembly model 42 including fixtures 155 of nominal assembly 48 nominal assembly examples 48 of varied assemblies 48 varied assembly examples 152 with variation, for compound features 144 with variation, for simple features 142 Connector pins manufacturing method 474 Connectors electrical 263 Constant Force... 454 Hole and slot compound feature 49 Hollow core molding 395 Holmes-Cooprider method for assembly system design 454 Honda 169 423 143 237 237 Hub and spokes airline architecture 365 liaison diagram 210 Human performance 465 HVAC 35 Hybrid mate-contact 239 Hydraulic actuator system 362 240 I IBM 356 Igniter 484 Impedance matching 349 Independent rear axle for automobiles 455 Indirect cost 490 Industry... 287 Insertion force experiments 274 Insertion operations statistics 393 Inspecting 12 Inspection 465 Instability in force feedback 255 Instructions assembly 469 Instrument cluster 358 Instrument panel assemblies 445 Integral and modular compared 346 Integral architecture 341 Intel 323 Interactions intended and unintended 353 Interchangeable modules 348 305 345 354 This page has been reformatted by Knovel... Index Terms Links Contacts (Cont.) in Cuisinart 231 in sheet metal example 219 Continuous improvement 443 Conveyor 424 Conveyor belts 353 Cooprider, Curt 454 Coordinate frame 36 445 447 469 62 79 142 47 107 of basic surfaces 87 for calculating twist 80 for calculating twist intersection 87 for calculating wrench 82 in a chain of frames 41 on desktop stapler 36 element of connective model 57 expressed... algorithm 258 Mass production 68 114 Material handling 423 424 Materials 318 327 329 336 344 348 400 492 cost component 382 490 knowledge needed for DFA 397 polymer 395 relation to recycling 403 212 217 102 141 Mates 5 73 in aircraft assembly 231 defined using Screw Theory 219 between parts and fixtures 222 in sheet metal example 219 in wheel-axle example 217 incoming 223 251 36 75 215 239 in Cuisinart . ,500 $1.500 $1,750 $2 ,100 $2 ,100 $2 ,100 $2,400 $2,400 $3,000 $3,000 Total In vestment Depreciablelnvestment Depreciation 14.29% 24.49% 17.49% 12.49% 8.92% 8.92% 8.92% 4.46% 0 0 ( $10, 500) ($2,625) Internal. ,500 $12,313 $12,750 Disc Net $438 ($1 ,740) ($1 ,268) ($529) $23 $107 $283 $133 $145 $190 $171 $154 $207 $186 $167 $150 $135 $121 $127 $137 $123 $ 110 $113 $102 $114 $103 $0 $0 Sum Of Undisc Net Inc $438 ($1 . Income Income ($3,500) -3500 -2500 -100 0 $400 $600 $800 $800 $800 $1 ,000 $1 ,000 $1 ,000 $1,500 $1 ,500 $1 ,500 $1,500 $1 ,500 $1 ,500 $1 ,750 $2 ,100 $2 ,100 $2 ,100 $2,400 $2,400 $3,000 $3,000 $34,250 $23,750 Pro Forma Cash Flow Depreciation ($375) ($643) ($459) ($328) ($234) ($234) ($234) ($117) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($2,624) ($2,624) Taxes ($3,937.50) ($1,562.44) ($928.57) ($270.44) $363.93 $417.08 $517.08 $517.08 $458.54 $500.00 $500.00 $500.00 $750.00 $750.00 $750.00 $750.00 $750.00 $750.00 $875.00 $1