Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 1 Kafli 17 í Chase … Verkröðun  Skilgreiningar  Markmið verkröðunar  Helstu reglur við verkröðun  Úthlutun verka, uppsetningartímar  Nokkur heilræði  Vaktaskipulag

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 2 Vinnustöð Skilgreining  Vinnustöð er svæði eða staður í fyrirtæki þar sem aðföng eru skipulögð og verk unnin.  Getur verið vél, hópur véla, hópur manna, FMS-kerfi, …  Verk geta verið pantanir frá viðskiptavinum eða þörf fyrir nýjar framleiðslulotur (endingatími birgða að verða búinn)

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 3 Dæmigerðar ákvarðanir í verkröðun  Ráðstafa pöntunum eða lotum, tækjum og vélum, starfsmönnum, …  Ákvarða forgang verka (pantana, lota)  Ákvarða röð m.t.t. uppsetningatíma (skiptingar, stillingar)  Gangsetning verka  Eftirlit, neyðarákvarðanir

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 4 Markmið verkröðunar  Standa við lofaða skilafresti  Lágmarka afhendingartíma  Lágmarka uppsetningartíma eða -kostnað  Lágmarka birgðir í ferlinu (WIP)  Hámarka nýtingu vinnustöðva

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 5 Helstu reglur við verkröðun 1. Fyrstur kemur, fyrstur fær (FCFS, FIFO) 2. Stysti vinnslutími fyrst (SOT, SPT) 3. Skilafrestir ráða röð (EDD) 4. Byrjunartímar ráða (due date-lead time) 5. Slakar, “Least slack time remaining” (STR)

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 6 Helstu reglur við verkröðun (Framhald) 6. STRO, “Least slack time remaining per operation as opposed to per job” 7. Minnsta “critical ratio” (CR) (due date-current date)/(number of days remaining) 8. Minnsta “queue ratio” (QR) (slack time remaining in schedule)/(planned remaining queue time) 9. Síðastur inn, fyrstur út (LCFS) 10. Hendingar ráða (“random order”)

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 7 Mælikvarðar á árangur verkröðunar  Staðið við skilafresti.  Flæðitími sem minnstur (tíminn sem verk er í ferlinu).  Birgðir í ferlinu (WIP) sem minnstar.  Nýting vinnustöðva, iðjuleysi sem minnst.

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 8 Dæmi 1: FCFS regla Answer: FCFS Schedule Suppose you have the four jobs to the right arrive for processing on one machine. What is the FCFS schedule? Do all the jobs get done on time? No, Jobs B, C, and D are going to be late.

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 9 Dæmi 1: SOT regla Answer: Shortest Operating Time Schedule Suppose you have the four jobs to the right arrive for processing on one machine. What is the SOT schedule? Do all the jobs get done on time? No, Jobs A and B are going to be late.

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 10 Dæmi 1: LCFS regla Answer: Last-Come First-Served Schedule No, Jobs B and A are going to be late. Suppose you have the four jobs to the right arrive for processing on one machine. What is the LCFS schedule? Do all the jobs get done on time?

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 11 Dæmi 1: EDD regla Answer: Earliest Due Date First Suppose you have the four jobs to the right arrive for processing on one machine. What is the earliest due date first schedule? Do all the jobs get done on time? No, Jobs C and B are going to be late.

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 12 Dæmi 1: CR regla Suppose you have the four jobs to the right arrive for processing on one machine. What is the CR schedule? Do all the jobs get done on time? No, but since there is three- way tie, only the first job or two will be on time. In order to do this schedule the CR’s have be calculated for each job. If we let today be Day 1 and allow a total of 15 days to do the work. The resulting CR’s and order schedule are: CR(A)=(5-4)/15=0.06 (Do this job last) CR(B)=(10-7)/15=0.20 (Do this job first, tied with C and D) CR(C)=(6-3)/15=0.20 (Do this job first, tied with B and D) CR(D)=(4-1)/15=0.20 (Do this job first, tied with B and C)

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 13 Dæmi 2: Johnson’s regla (hluti 1) Suppose you have the following five jobs with time requirements in two stages of production. What is the job sequence using Johnson’s Rule? Time in Hours Jobs Stage 1Stage 2 A B C D

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 14 Dæmi 2: Johnson’s regla (hluti 2) First, select the job with the smallest time in either stage. That is Job D with the smallest time in the first stage. Place that job as early as possible in the unfilled job sequence below. Drop D out, select the next smallest time ( Job A), and place it 4th in the job sequence. Drop A out, select the next smallest time. There is a tie in two stages for two different jobs. In this case, place the job with the smallest time in the first stage as early as possible in the unfilled job sequence. Then place the job with the smallest time in the second stage as late as possible in the unfilled sequence. Job Sequence Job AssignedD A B C Time in Hours Jobs Stage 1Stage 2 A B C D

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 15 Úthlutun verka á vinnustöðvar 1. Gefinn tími eða kostnaður við að vinna hvert verk á hverri vinnustöð. 2. Ákvarða hver á að vinna hvert verk þannig að heildartími eða –kostnaður sé lágmarkaður. 3. Úthlutunarlíkanið (Assignment Model), sértilvik af flutningalíkaninu.

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 16 Lágmörkun uppsetningartíma 1. Gefið fylki með uppsetningartímum (skiptitímum) eða -kostnaði milli verka (pantana eða lota) 2. Ákvarða röð verka þannig að heildar uppsetningartími sé lágmarkaður. 3. Hliðstætt “Travelling Salesman Problem” (TSP)

Operations Management For Competitive Advantage © The McGraw-Hill Companies, Inc., 2001 C HASE A QUILANO J ACOBS ninth edition 17 Vaktaskipulag  Skipulagning vakta, frídaga, eða daglegs vinnutíma.  Byggist á greiningu á mönnunarþörfum  Hægt að leysa með Línulegri bestun