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1 Produktionsplanering. 2 What is planning and control? Supply of products and services Planning and control Demand for products and services The operation’s.

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En presentation över ämnet: "1 Produktionsplanering. 2 What is planning and control? Supply of products and services Planning and control Demand for products and services The operation’s."— Presentationens avskrift:

1 1 Produktionsplanering

2 2 What is planning and control? Supply of products and services Planning and control Demand for products and services The operation’s resources The activities which reconcile supply and demand The operation’s customers

3 3 Planning is deciding Control is what activities should take place in the operation when they should take place what resources should be allocated to them understanding what is actually happening in the the operation deciding whether there is a significant deviation from what should be happening (if there is deviation) changing resources in order to affect the operation’s activities

4 4 Significance of planning or control Time horizon Hours/days Days/ weeks/ months Months/years Medium-term Planning and Control Uses partially disaggregated demand forecasts Determines resources and contingencies Objectives set in both financial and operations terms Long-term Planning and Control Uses aggregated demand forecasts Determines resources in aggregated form Objectives set in largely financial terms Short-term Planning and Control Uses totally disaggregated forecasts or actual demand Makes interventions to resources to correct deviations from plans Ad hoc consideration of operations objectives PLANNING CONTROL

5 5 Planning and control needs…. Information on Demand levels Information on Resources

6 6 The nature of supply and demand PurchaseMakeDeliver D P PurchaseMakeDeliver PurchaseMakeDeliver D P Make to stock Make to order Resource to order P D P=total genomloppstid D=leveranstid (dvs den tid kunden måste vänta)

7 7 Dependent and independent demand Dependent demand e.g. input tyre store in car plant Demand for tyres is governed by the number of cars planned to be made Demand for tyres is largely governed by random factors ACE TYRES Inependent demand e.g. tyre fitting service

8 8 Resource to orderMake to orderMake to stock Dependent demand Independent demand Each product or service large compared with total capacity of the operation Each product or service small compared with total capacity of the operation

9 9 Pull and push philosophies of planning and control CENTRAL OPS. PLANNING AND CONTROL SYSTEM Work centre DEMAND Work centre Instruction on what to make and where to send it FORECAST OR PUSH CONTROL Work centre DEMAND Request Delivery PULL CONTROL

10 10 Scheduling Loading Sequencing Monitoring and control When to do things? In what order to do things? How much to do? Are activities going to plan? The activities of planning and control

11 11 Loading / beläggning

12 12 Quality losses Slow running equipment Equipment “idling” “Breakdown” failure Set-up and changeovers Not worked (unplanned) Valuable operating time Maximum available time Not worked (planned) Tillgängligheten i en maskin

13 Load in std. hours Capacity Load in std. hours Capacity Work centres Finite and infinite loading Omöjligt, onödigt eller mkt kostsamt att begränsa beläggningen Möjligt, nödvändigt eller begr kostnader för att begränsa beläggningen

14 14 Sequencing

15 15 Except for in situations with physical constraints, various sequencing rules are used in operations: -customer priority; - due date; -LIFO - last in, first out; -FIFO - first in, first out; longest operation time first; -shortest operation time first. -

16 16 Scheduling

17 17 JOB Mon 5 Tue 6 Wed 7 Thur 8 Fri 9 Mon 12 Tue 13 Table Shelves Kitchen units Bed Scheduled activity time Actual progress V V Time now

18 18

19 19 Claire Walter Peter Jo Marie Jo 04:0008:0012:0016:0020:00 Shift pattern (24 hour clock) Peter X X X X O O X Marie X X X X X O O Claire X X X X O O X Walter O X X X X X O Jo O X X X X X O Number of staff required X Full dayO Day off Mon Tue Wed Thu Fri Sat Sun

20 20 Monitoring and control

21 21 Operation Intervention Plans Compare / replan Monitor InputOutput The control feedback loop

22 22 Beläggningsplanering Beläggning = inplanerade operationer under en viss tidsperiod på viss/vissa resurser Beläggningsplanering = balansering av beordrad produktion mot statistiskt beräknad nettokapacitet Kö - uppstår när kapaciteten understiger tillgänglig beläggning

23 23 Kö Nackdelar... - extra kostnader - högre genomloppstider - ökad kapitalbindning - kräver fysiskt lagringsutrymmer - irritationsmoment - kräver särskild administration och ger upphov till särskilt planeringsarbete

24 24 Kö...men också fördelar - möjligheter till smart omplanering (samkörning med artiklar med likartat ställarbete) - kompetensanpassning - högre arbetstempo - gardering mot störningar - fullt kapacitetsutnyttjande Optimering av kapacitetsutnyttjande kontra kapitalbindning

25 25 Kö - tumregler Trånga/viktiga resurser (styrande maskiner) beläggs med 100% genom ökad nettokapacitet och buffertar Överkapacitet i billiga resurser där dyra o/e genomloppstidsmässigt viktiga artiklar tillverkas (kompletterande maskiner) Utbilda arbetsstyrkan mot ökad flexibilitet – flödesgrupper

26 26 Volymvärdeanalys En operation kan inte starta utan material Fullt plock = alla artiklar som krävs för en operation finns tillgängliga vid start Svårt att garantera fullt plock utan betydande kapitalbindning i mellanlager Volymvärdeanalys – rangordning av artiklar med avseende på kapitalbindning Artiklar med hög kapitalbindning (A) planeras och följs upp mkt noga, just-in-time-lev eftersträvas Artiklar med låg kapitalbindning (C) köps in/produceras i god tid i väl tilltagna kvantiteter

27 27 Flaskhalsar Genomloppstiden styr av flaskhalsens kapacitet Balansera materialflöde snarare än att utnyttja alla resurser fullt ut PIA accumuleras vid flaskhalsen Minskning i flaskhalsens output, sänker systemets hela output Ökning av output i en “icke-flaskahls” ökar inte output i systemet som helhet

28 28 OPT Optimized Production Technology (Goldratt & Cox, 1986) –Balansera flöde, inte kapacitet –Utnyttjandet i en “icke-flaskhals” bestäms av andra begränsningar i systemet, ej av sin egen kapacitet –En förlorad timme i en flaskhals är en förlorad timme för systemet –En vunnen timme i en “icke-flaskhals” är en illusion –Flaskhalsar styr genomloppstid och PIA i systemet –Transportvolymen behöver inte, och skall ibland inte, vara lika stor som processvolymen –Processvolymen skall vara variabel, inte statisk –Ledtid beror på planeringen och kan inte bestämmas på förhand –Planering skall skapas genom att se till alla begränsingar samtidigt

29 29 Activity AActivity BActivity CActivity DActivity E Buffer of inventory Bottleneck drum sets the beat Communication rope controls prior activities The drum, buffer, rope, concept

30 30 Kapacitetsplanering

31 31 Construction materials Beverages (beer, cola) Foods (ice-cream, Christmas cake) Clothing (swimwear, shoes) Gardening items (seeds, fertilizer) Fireworks Travel services Holidays Tax processing Doctors (influenza epidemic) Sports services Education services BehaviouralPolitical Financial SocialFestiveClimatic Causes of seasonality

32 32 Not worked (unplanned) Quality losses Slow running equipment Equipment “idling” Breakdown failure Set-up and change- overs Loading time Total operating time Net operating time Valuable operating time Speed losses Quality losses Availability rate = a = total operating time / loading time Performance rate = p = net operating time/total operating time Quality rate = q = valuable operating time / net operating time Availability losses

33 33 How capacity and demand are measured Design capacity 168 hours per week Effective capacity 109 hours per week Planned loss of 59 hours Actual output - 51 hours per week Avoidable loss - 58 hours per week Actual output Effective capacity Efficiency = Actual output Design capacity Utilisation =

34 34 Time Low variability - narrow distribution of process times High variability - wide distribution of process times Simple queuing system

35 35 Outcome Actual demand and actual capacity Decision How much capacity next period? Outcome Actual demand and actual capacity? Decision How much capacity next period? Shortages Queues Inventory Capacity level Shortages Queues Inventory Current capacity estimates Updated forecasts Current capacity estimates Updated forecasts Costs Revenues Working capital Customer satisfaction etc Costs Revenues Working capital Customer satisfaction etc Period t - 1 Period t Period t + 1

36 36 Lay off staffDelay any action Overtime Hire temporary staff Short-time Idle time Do nothing Overtime Hire temporary staff Make for inventory Short-time Hire and make for inventory Start to recruit Hire staff POOR Outlook < 1 NORMAL Outlook = 1 GOOD Outlook > 1 POOR Outlook < 1 NORMAL Outlook = 1 GOOD Outlook > 1 Short-term outlook Long-term outlook Outlook = Forecast demand Forecast capacity

37 37 The nature of aggregate capacity Aggregate capacity of a hotel: -rooms per night; -ignores the numbers of guests in each room. Aggregate capacity of an aluminium producer: -tonnes per month; -ignores types of alloy, gauge and batch variations.

38 38 Long-, medium- and short-term capacity planning Macro operation with a given set of resources might produce 6 tables or 12 chairs or some combination

39 39 Objectives of capacity planning and control Step 1 -Measure aggregate capacity and demand. Step 2 -Identify the alternative capacity plans. Step 3 -Choose the most appropriate capacity plan. Time Estimate of current capacity Forecast demand Aggregated output

40 40 Ways of reconciling capacity and demand Level capacity Capacity Demand Chase demand Demand Capacity Demand management Demand Capacity

41 41 Cumulative representations Cumulative demand Cumulative capacity Time Building stock Unable to meet orders Capacity and demand

42 42 OBJECTIVE To provide an “appropriate” amount of capacity at any point in time. The “appropriateness” of capacity planning in any part of the operation can be judged by its effect on…... Costs Revenue Working Capital Service Level

43 43 Good forecasts are essential for effective capacity planning. But so is an understanding of demand uncertainty because it allows you to judge the risks to service level. When demand uncertainty is high the risks to service level of underprovision of capacity are high. DEMAND TIME Distribution of demand DEMAND TIME Only 5% chance of demand being higher than this Only 5% chance of demand being lower than this

44 44 It is useful to know not only the average capability of resources but also their variation in capability FREQUENCY TIME TO PROCESS ONE UNIT OF DEMAND Average processing time

45 45 How do you cope with fluctuations in demand? Absorb demand Adjust output to match demand Change demand

46 46 Absorb demand Keep output level Make to stock Make customer wait Part finished, Finished Goods, or Customer Inventory Queues Backlogs Have excess capacity

47 47 Adjust output to match demand HireFire Temporary Labour Lay off Overtime Subcontract Short time 3rd party work

48 48 Change demand Change pattern of demand Develop alternative products and/or services

49 49 Actual Demand Actual Demand Forecast Demand Forecast Demand Replan Capacity Replan Capacity Actual Capacity Actual Capacity Allocate Capacity Allocate Capacity Refine Forecast Refine Forecast Key question - “How often do you change capacity in response to deviations from demand forecasts?”


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