Mechanical Engineering 101

Transcription

1 Mechanical Engineering 101 University of alifornia, Berkeley Lecture #16 1

2 Today s lecture MRP scheduling LFL EOQ/EMQ POQ apacity planning 2

3 Formulae I it max{ 0, I i t 1 SR GR, it it } NR it max 0, GR it I i, t SR 1 it POR it NR i,t i 3

4 MRP LFL Example Filling in the table from last class 4

5 EOQ example Find EOQ for part Z given gross requirements as below setup cost $100 holding cost $.10 per part per period Z: lead time = 1 period GR SR 215 I 13 NR POR 5

6 EOQ example Estimating demand Series

7 EOQ example Find EOQ for part Z given: estimate demand as average Z = setup cost $100 holding cost $.10 per part per period 1. 0< EOQ <= < EOQ <= < EOQ <= < EOQ <= < EOQ <= < EOQ <= < EOQ <= < EOQ <= < EOQ 8

8 .EOQ example Release at start of period 1 Z: lead time = 1 period GR SR 215 I NR POR 10

9 .Periodic Order Quantity regular, cyclic production schedule Use EOQ to set cyclical ordering period find expected time between orders w/ EOQ e.g. EOQ=467, D=109.2 need to produce every 467/109=4.3 periods order production every n=4 periods set actual production = expected NR next n periods order amount in period 1 = NR for periods 2-5 order amount in period 5 = NR for periods

10 . POQ example POR=sum of expected NR Z: lead time = 1 period GR SR 215 I NR POR 16

11 yclical advantages predictability the large production lot won t change periods find optimal sequencing of changeovers e.g. A->B->->A may be much faster than A->->B->A 19

12 When to use LFL? Lot-for-lot make to order setup cost < carrying cost for 1 period of demand otherwise, look to EOQ(EMQ)/POQ 20

13 Announcements Reminder: project update for Thursday 1 per group, turn in to me HW6 due today late deadline will be 4pm Friday! So all can be graded and returned next Tuesday 21

14 Announcements Midterm next Thursday 10/25 HW 1-6, movies, lecture material through end of week Samples posted Review section Monday or Tuesday pm: vote Bring: 3x5 inch card of notes, handwritten, one side only alculator 1. I have an approved calculator 2. I have arranged to borrow an approved calculator 3. I need to follow that link on the website! 22

15 Today s lecture MRP scheduling Materials Requirements Planning: MRP apacity planning Manufacturing Resources Planning : MRP II 23

16 Lot for lot MPS plan from last time X period POR MPS for B? B: lead time = 1 period GR SR I NR POR B X 1 each A 1 ea 1 ea 1 ea 24

17 Manufacturing Resources Planning Standard MRP scheduling ignores workstation capacity assumes infinite! apacity planning Rough cut capacity planning (RP) apacity requirements planning (RP) 25

18 Rough cut capacity planning resource profile graphically shows precedence, lead times annotated with work center (W), time per unit purchased F Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit Week Askin fig

19 RP period (week) POR(A) Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit Week 27

20 Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit W 300 example, week 3 capacity req s: resource profiles for the relevant weeks Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit

21 25* Op# hr/unit E 25* Op#2 D 0.20 hr/unit A W hr/unit W 300 example 50* Op# hr/unit E 50* Op#2 D 0.20 hr/unit A W hr/unit 200* Op# hr/unit E 200* Op#2 D 0.20 hr/unit A W hr/unit Q A3 =25 Q A4 =50 Q A5 =

22 RP r ijk = resources (time) per unit of end item i in work center j in k th period before i completed r A,100,0 =? hrs none of the above Op# hr/unit E Week Op#2 D 0.20 hr/unit A W hr/unit 30

23 RP r ijk = resources (time) per unit of end item i in work center j in k th period before i completed r A,200,2 =? hrs none of the above Op# hr/unit E Week Op#2 D 0.20 hr/unit A W hr/unit 32

24 Resource profile r A,j,k is for single end item A work-content/work-center/period for A period work center Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit Week 34

25 RP period (week) POR(A) period work center Op# hr/unit E Op#2 D 0.20 hr/unit A W hr/unit Week 35

26 Work center load r ijk = resources (time) per unit of end item i in work center j in k th period before i completed Q it = production quantity end item i in period t from MPS 36

27 Work center load r ijk = resources (time) per unit of end item i in work center j in k th period before i completed Q it = production quantity end item i in period t from MPS w jt = load (time) on work center j in period t make sure it s w/in capacity limits! n T w jt ri, j, k t i 1 k t Q ik 37

28 .Work center load W 300 Example period POR(A) ra period work center k=3: r A,300,3-3 = 0.0, Q A3 = 25 k=4: r A,300,4-3 =.15, Q A4 = 50 k=5: r A,300,5-3 =.15, Q A5 = 200 k=6: r A,300,6-3 = 0.0, Q A6 = 0 n T w jt ri, j, k t i 1 k t w 300,3... Q ik 38

29 25* Op# hr/unit E 25* Op#2 D 0.20 hr/unit A W hr/unit. W 300 Example 50* Op# hr/unit E 50* Op#2 D 0.20 hr/unit A W hr/unit 200* Op# hr/unit E 200* Op#2 D 0.20 hr/unit A W hr/unit Q A3 =25 Q A4 =50 Q A5 =

30 Work center load period POR(A) ra period work center <=w 200,2 <5 2. 5<=w 200,2 < <=w 200,2 < <=w 200,2 < <=w 200,2 <25 w 6. 25<=w 200,2 < <=w 200,2 < <=w 200,2 < <=w 200,2 < <=w 200,2 n T w jt ri, j, k t i 1 k t 200,2...? Q ik 42

31 75* Op# hr/unit E 75* Op#2 D 0.20 hr/unit A W hr/unit. W 200 Example 25* Op# hr/unit E 25* Op#2 D 0.20 hr/unit A W hr/unit 50* Op# hr/unit E 50* Op#2 D 0.20 hr/unit A W hr/unit Q A2 = 75 Q A3 =25 Q A4 =50 44

32 apacity Requirements Planning What does RP ignore? inventory setup times larger batch production of components w/ POQ RP looks at detailed production plans add capacity resources in MRP explosion as additional components inventory = stored capacity not flexible capacity, though! 46

33 Work center load report available capacity available capacity Hours Hours Late Time period Time period planned order releases open shop orders 47

34 MRP II links additional modules to traditional MRP scheduling: capacity planning BOM processor EO management customer order entry financial planning forecasting inventory & warehouse management purchasing 2-way communication between modules 48

35 Enterprise Resources Planning (ERP) beyond individual company whole supplier-producer-customer network use electronic data interchange (EDI) 49

36 MRP assumptions known, constant lead times dependent demand adequate capacity accurate BOM good demand forecasts predictable scrap rates accurate inventory records 50

37 Ensuring accurate inventory data Why off? scrap not recorded correctly parts cannibalized just plain lost One solution: hire cycle counter given list of part numbers to count find and count on shop floor, in storage update electronic record 51

38 EOs Engineering hange Orders lag existing inventory implementation of process change vendor qualification coordination purchasing manufacturing engineering: testing, analyzing 52