Produktionsplanering

1. Produktionsplanering

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

3. Planning is deciding what activities should take place in the operation when they should take place what resources should be allocated to them Control is 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. Significance of planning or control Long-term Planning and Control Uses aggregated demand forecasts Determines resources in aggregated form Objectives set in largely financial terms Months/years PLANNING Medium-term Planning and Control Uses partially disaggregated demand forecasts Determines resources and contingencies Objectives set in both financial and operations terms Time horizon Days/weeks/months 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 CONTROL Hours/days

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

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

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

8. Resource to order Make to order Make to stock Dependent 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 Independent demand

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

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

11. Loading / beläggning

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

13. Finite and infinite loading Load in std. hours Load in std. hours 140 140 Capacity Capacity 120 120 100 100 80 80 60 60 40 40 20 20 0 0 1 2 3 4 5 6 1 2 3 4 5 6 Work centres Work centres Omöjligt, onödigt eller mkt kostsamt att begränsa beläggningen Möjligt, nödvändigt eller begr kostnader för att begränsa beläggningen

14. Sequencing

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. Scheduling

17. Mon 5 Tue6 Wed 7 Thur 8 Fri 9 Mon 12 Tue 13 JOB Table Shelves Kitchen units Bed Scheduled activity time V Time now V Actual progress

18. Mon 5 Tue6 Wed 7 Thur 8 Fri 9 Mon 12 Tue 13 JOB Wood preparation S K T Assembly S B S T S Finishing K T B Paint K S B T V Scheduled activity time Non-productive time Time now V Actual progress

19. Walter Claire Marie Peter Jo Jo 04:00 08:00 12:00 16:00 20:00 Shift pattern (24 hour clock) Mon Tue Wed Thu Fri Sat Sun Number of staff required 3 5 5 5 3 2 2 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 X Full day O Day off

20. Monitoring and control

21. The control feedback loop Input Output Operation Intervention Monitor Plans Compare / replan

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

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. 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. 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. 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. 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. The drum, buffer, rope, concept Bufferof inventory Activity A Activity B Activity C Activity D Activity E Bottleneck drum sets the beat Communicationropecontrols prior activities

30. Kapacitetsplanering

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

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

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

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

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

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

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

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

40. Ways of reconciling capacity and demand Demand Demand Demand C apacity Capacity Capacity Level capacity Chase demand D emand management

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

42. Costs 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…... Revenue Working Capital Service Level

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. Only 5% chance of demand being higher than this Distribution of demand DEMAND DEMAND Only 5% chance of demand being lower than this TIME TIME When demand uncertainty is high the risks to service level of underprovision of capacity are high.

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

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

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

47. Adjust output to match demand Hire Fire Layoff Temporary Labour Overtime Short time Subcontract 3rd party work

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

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