16
2/28: More CPM: Crashing • Roll call / return exams / return homework • Review: Critical Path Management – Creating the CPM diagram – Calculating the critical path – Calculating the ES & EF, the LS & LF – Calculating the slack • Crashing: When you’re willing to spend money to get the project done sooner. • Small Group Exercise • Homework for the week

2/28: More CPM: Crashing

  • Upload
    haven

  • View
    53

  • Download
    0

Embed Size (px)

DESCRIPTION

2/28: More CPM: Crashing. Roll call / return exams / return homework Review: Critical Path Management Creating the CPM diagram Calculating the critical path Calculating the ES & EF, the LS & LF Calculating the slack - PowerPoint PPT Presentation

Citation preview

Page 1: 2/28: More CPM: Crashing

2/28: More CPM: Crashing• Roll call / return exams / return homework

• Review: Critical Path Management– Creating the CPM diagram– Calculating the critical path– Calculating the ES & EF, the LS & LF– Calculating the slack

• Crashing: When you’re willing to spend money to get the project done sooner.

• Small Group Exercise

• Homework for the week

Page 2: 2/28: More CPM: Crashing

Exam Scores• Maximum: 100% (four people)

• Minimum: 63%

• Mean & Median: 88%

• Correct exams are available at:http://www.adbook.net/teach022/305/m.htm

Page 3: 2/28: More CPM: Crashing

CPM: Creating the Diagram

Act. Dur. Follows

A 4 -

B 5 -

C 2 A

D 4 C

E 7 C

F 5 D

G 1 B

start

A4

B5

C2

E7

D4 F

5

G1

finish

Page 4: 2/28: More CPM: Crashing

CPM: Calculating the Critical Path

start

A4

B5

C2

E7

D4 F

5

G1

finish

Possible paths from start to finish:A-C-D-F A-C-EB-G

4+2+4+5 = 154+2+7 = 135+1 = 6

Page 5: 2/28: More CPM: Crashing

CPM: Calculating the ES & EF

start

A | 0 4 4 |

B | 0 55 |

C | 4 62 |

E | 6 137 |

D | 6 104 | F | 10 15

5 |

G | 5 61 |

finish

Early start: how soon it can startEarly finish: ES + Duration

Page 6: 2/28: More CPM: Crashing

CPM: Calculating the LS & LF

start

A | 0 4 4 | 0 4

B | 0 55 | 9 14

C | 4 62 | 4 6

E | 6 137 | 8 15

D | 6 104 | 6 10 F | 10 15

5 | 10 15

G | 5 61 | 14 15

finish

Late finish: the last possible time it must be done to not affect the overall project time.Late start: LF - Duration

Page 7: 2/28: More CPM: Crashing

CPM: Calculating the slack

start

A | 0 4 4 | 0 4

B | 0 55 | 9 14

C | 4 62 | 4 6

E | 6 137 | 8 15

D | 6 104 | 6 10 F | 10 15

5 | 10 15

G | 5 61 | 14 15

finish

Slack: how much “wiggle room” you have for an activitySlack = LS – ES = LF - EF

S=0 S=0

S=0S=0

S=9

S=2

S=9

Page 8: 2/28: More CPM: Crashing

Crashing: Buying Time• Sometimes you can buy a quicker time for an

activity – Paying overtime– Paying for another worker to help– Paying for guaranteed quicker delivery (EX: FedEx)

• But is it worth it?

Page 9: 2/28: More CPM: Crashing

Crashing Activity Times• Things to consider:

– Is the activity on the critical path?– How much will it cost to crash the activity?– Are there other activities that are more cost-effective

to crash?– How much do you need to crash the project time?

Page 10: 2/28: More CPM: Crashing

Crashing Activity Times: ExampleShorten project by 2 days while minimizing costs.Activity Duration Follows Normal

Cost ($)Crashed Cost ($)

Max. Time Reduction

A 4 - $600 $800 2

B 5 - $1300 $2000 2

C 2 A $400 $700 1

D 4 C $1000 $1200 3

E 7 C $1200 $1500 4

F 5 D $300 $200 2

G 1 B $400 - -

Page 11: 2/28: More CPM: Crashing

Crashing Activity Times: ExampleShorten project by 2 days while minimizing costs.

First, calculate the cost/day to crash each activity.Act Dur Foll Norm

Cost Crash Cost

Max Red.

Cost / day to crash

A 4 - 600 800 2 (800-600)/2

B 5 - 1300 2000 2

C 2 A 400 700 1

D 4 C 1000 1200 3

E 7 C 1200 1500 4

F 5 D 300 200 2

G 1 B 400 - -

Page 12: 2/28: More CPM: Crashing

Crashing Activity Times: ExampleShorten project by 2 days while minimizing costs.

Next, see what’s on the critical path.Act Dur Foll Norm

Cost Crash Cost

Max Red.

Cost / day to crash

CP?

A 4 - 600 800 2 100 Yes

B 5 - 1300 2000 2 450 No

C 2 A 400 700 1 300 Yes

D 4 C 1000 1200 3 66.66 Yes

E 7 C 1200 1500 4 75 No

F 5 D 300 200 2 50 Yes

G 1 B 400 - - - (irrelevant)

Page 13: 2/28: More CPM: Crashing

Crashing Activity Times: ExampleShorten project by 2 days while minimizing costs.

Finally, see what the cheapest way to reduce is.Act Dur Foll Norm

Cost Crash Cost

Max Red.

Cost / day to crash

CP?

A 4 - 600 800 2 100 Yes

B 5 - 1300 2000 2 450 No

C 2 A 400 700 1 300 Yes

D 4 C 1000 1200 3 66.66 Yes

E 7 C 1200 1500 4 75 No

F 5 D 300 200 2 50 Yes

G 1 B 400 - - - (irrelevant)

Page 14: 2/28: More CPM: Crashing

Crashing Activities: Watch Out• If we had to crash the project by more than two

days, we would have had to look again – the critical path may change.

start

A4

B5

C2

E7

D4 F

5

G1

finish

A-C-D-F A-C-EB-G

4+2+4+5 = 154+2+7 = 135+1 = 6

Page 15: 2/28: More CPM: Crashing

Small Group ExerciseCrash the project by 3 days while minimizing costs.

Act Dur Foll Norm Cost

Crash Cost

Max Red.

Cost / day to crash

CP?

A 6 - 600 900 2

B 4 A 500 700 2

C 5 A 1000 1200 1

D 6 B 1300 1600 4

E 7 C 800 1000 3

F 5 E 400 550 2

G 3 B 500 800 2

H 2 F 1100 1500 3

Page 16: 2/28: More CPM: Crashing

Homework: Do it on PAPER• Ch. 10 #21 a & b

• Ch. 10 #22 b & c

• Ch. 10 #24 a, c, d (use 26 weeks), & f