An assembly operation has a 90 percent learning curve. The line has just begun work on a new item; the initial unit required 28 hours. Estimate the time that will be needed to complete:
a. The first five units.
b. Units 20 through 25.
Use the total time factor in the 90 percent column of Table 7S.1 .
a. Table value: 4.339.
Estimated time for five units: 28(4.339) = 121.49 hours.
b. The total time for units 20 through 25 can be determined by subtraction:
TABLE 7S.1 Learning curve coefficients
70% | 75% | 80% | 85% | 90% | ||||||
Unit Number |
Unit Time |
Total Time |
Unit Time |
Total Time |
Unit Time |
Total Time |
Unit Time |
Total Time |
Unit Time |
Total Time |
1 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 |
2 | .700 | 1.700 | .750 | 1.750 | .800 | 1.800 | .850 | 1.850 | .900 | 1.900 |
3 | .568 | 2.268 | .634 | 2.384 | .702 | 2.502 | .773 | 2.623 | .846 | 2.746 |
4 | .490 | 2.758 | .562 | 2.946 | .640 | 3.142 | .723 | 3.345 | .810 | 3.556 |
5 | .437 | 3.195 | .513 | 3.459 | .596 | 3.738 | .686 | 4.031 | .783 | 4.339 |
6 | .398 | 3.593 | .475 | 3.934 | .561 | 4.299 | .657 | 4.688 | .762 | 5.101 |
7 | .367 | 3.960 | .446 | 4.380 | .534 | 4.834 | .634 | 5.322 | .744 | 5.845 |
8 | .343 | 4.303 | .422 | 4.802 | .512 | 5.346 | .614 | 5.936 | .729 | 6.574 |
9 | .323 | 4.626 | .402 | 5.204 | .493 | 5.839 | .597 | 6.533 | .716 | 7.290 |
10 | .306 | 4.932 | .385 | 5.589 | .477 | 6.315 | .583 | 7.116 | .705 | 7.994 |
11 | .291 | 5.223 | .370 | 5.958 | .462 | 6.777 | .570 | 7.686 | .695 | 8.689 |
12 | .278 | 5.501 | .357 | 6.315 | .449 | 7.227 | .558 | 8.244 | .685 | 9.374 |
13 | .267 | 5.769 | .345 | 6.660 | .438 | 7.665 | .548 | 8.792 | .677 | 10.052 |
14 | .257 | 6.026 | .334 | 6.994 | .428 | 8.092 | .539 | 9.331 | .670 | 10.721 |
15 | .248 | 6.274 | .325 | 7.319 | .418 | 8.511 | .530 | 9.861 | .663 | 11.384 |
16 | .240 | 6.514 | .316 | 7.635 | .410 | 8.920 | .522 | 10.383 | .656 | 12.040 |
17 | .233 | 6.747 | .309 | 7.944 | .402 | 9.322 | .515 | 10.898 | .650 | 12.690 |
18 | .226 | 6.973 | .301 | 8.245 | .394 | 9.716 | .508 | 11.405 | .644 | 13.334 |
19 | .220 | 7.192 | .295 | 8.540 | .388 | 10.104 | .501 | 11.907 | .639 | 13.974 |
20 | .214 | 7.407 | .288 | 8.828 | .381 | 10.485 | .495 | 12.402 | .634 | 14.608 |
21 | .209 | 7.615 | .283 | 9.111 | .375 | 10.860 | .490 | 12.892 | .630 | 15.237 |
22 | .204 | 7.819 | .277 | 9.388 | .370 | 11.230 | .484 | 13.376 | .625 | 15.862 |
23 | .199 | 8.018 | .272 | 9.660 | .364 | 11.594 | .479 | 13.856 | .621 | 16.483 |
24 | .195 | 8.213 | .267 | 9.928 | .359 | 11.954 | .475 | 14.331 | .617 | 17.100 |
25 | .191 | 8.404 | .263 | 10.191 | .355 | 12.309 | .470 | 14.801 | .613 | 17.713 |
26 | .187 | 8.591 | .259 | 10.449 | .350 | 12.659 | .466 | 15.267 | .609 | 18.323 |
27 | .183 | 8.774 | .255 | 10.704 | .346 | 13.005 | .462 | 15.728 | .606 | 18.929 |
28 | .180 | 8.954 | .251 | 10.955 | .342 | 13.347 | .458 | 16.186 | .603 | 19.531 |
29 | .177 | 9.131 | .247 | 11.202 | .338 | 13.685 | .454 | 16.640 | .599 | 20.131 |
30 | .174 | 9.305 | .244 | 11.446 | .335 | 14.020 | .450 | 17.091 | .596 | 20.727 |
Hours | |
Total time for 25 units: | 28(17.713) = 495.96 |
\underline{\text{–Total time for 19 units:}\ \ \ \ \ \ } | 28(13.974) = 391.27 |
Total time for units 20 through 25 | 104.69 |