上海交通大学：《生产计划与控制 Production Planning and Control》课程教学资源（课件讲稿）chap03 Aggregate Planning ?A Prototype Problem; ?Solution of Aggregate Planning Problem by LP

Production and Operation Managements Chapter 3 Aggregate Planning Dr Na genG Department of Industrial Engineering Management Shanghai Jiao Tong University

Production and Operation Managements Dr Na GENG Department of Industrial Engineering & Management Shanghai Jiao Tong University Chapter 3 Aggregate Planning

图 Chapter 3 Aggregate Planning Contents .Introduction Aggregate Units of Production; .Costs in Aggregate Planning; .A Prototype Problem; .Solution of Aggregate Planning Problem by LP

Chapter 3 Aggregate Planning Contents •Introduction •Aggregate Units of Production; •Costs in Aggregate Planning; •A Prototype Problem; •Solution of Aggregate Planning Problem by LP

A Prototype Problem Example 3.2 Densepack is to plan workforce and production level for six-month period Jan.to June.The firm produces a line of disk drives for mainframe computers.Forecast demand over the next six months for a particular line of drives in a plant are 1,280,640,900,1,200,2,000 and 1,400.There are currently (end of Dec.)300 workers employed in the plant.Ending inventory in Dec.is expected to be 500 units,and the firm would like to have 600 units on hand at the end of June

A Prototype Problem Example 3.2 Densepack is to plan workforce and production level for six-month period Jan. to June. The firm produces a line of disk drives for mainframe computers. Forecast demand over the next six months for a particular line of drives in a plant are 1,280, 640, 900, 1,200, 2,000 and 1,400. There are currently (end of Dec.) 300 workers employed in the plant. Ending inventory in Dec. is expected to be 500 units, and the firm would like to have 600 units on hand at the end of June

A Prototype Problem Month Predicated Net Net Cumulative Demand Predicated Demand Demand Jan. 1,280 780(1280-500) 780 Feb. 640 640 1,420 March 900 900 2,320 April 1,200 1,200 3,520 May 2,000 2,000 5,520 June 1,400 2,000(1400+600) 7,520

A Prototype Problem Month Predicated Demand Net Predicated Demand Net Cumulative Demand Jan. 1,280 780(1280-500 ) 780 Feb. 640 640 1,420 March 900 900 2,320 April 1,200 1,200 3,520 May 2,000 2,000 5,520 June 1,400 2,000(1400+600 ) 7,520

A Prototype Problem If the shortage is not permitted,the cumulative production must be at least as great as cumulative net demand each period-Feasible AP 8 AP:Any curve above the accumulated net demand Feasible 5 production schedule Cumulative net 3 demand 2 Inventory 0 3 4 5 6 Month Fig.3-4 A Feasible Aggregate Plan for Densepack

A Prototype Problem If the shortage is not permitted, the cumulative production must be at least as great as cumulative net demand each period-Feasible AP Fig. 3-4 A Feasible Aggregate Plan for Densepack AP: Any curve above the accumulated net demand

A Prototype Problem How to make cost trade-offs of various production plans? Only consider three costs: CH-Cost of hiring one worker=$500; C-Cost of firing one worker=$1,000; C-Cost of holding one unit of inventory for one month-$80

A Prototype Problem • How to make cost trade-offs of various production plans? Only consider three costs:  C H=Cost of hiring one worker=$500;  C F=Cost of firing one worker=$1,000;  C I=Cost of holding one unit of inventory for one month=$80

A Prototype Problem .Translate aggregate production in units to workforce levels: Use a day as an indivisible unit of measure (since not all month have equal number of working days)and define: K-Number of aggregate units produced by one worker in one day. A known fact:over 22 working days,with the workforce constant at 76 workers,the firm produced 245 disk drives. Average production rate=245/22=11.1364 disk drives per day, One worker produced an average of 11.1364/76=0.14653 drive in one day.K=0.14653

A Prototype Problem •Translate aggregate production in units to workforce levels:  Use a day as an indivisible unit of measure (since not all month have equal number of working days) and define:  K=Number of aggregate units produced by one worker in one day.  A known fact: over 22 working days, with the workforce constant at 76 workers, the firm produced 245 disk drives.  Average production rate=245/22=11.1364 disk drives per day;  One worker produced an average of 11.1364/76=0.14653 drive in one day. K=0.14653

A Prototype Problem Two alternative plans for managing workforce: .Plan 1 is to change workforce each month in order to produce enough units to most closely match the demand pattern-zero inventory plan; .Plan 2 is to maintain the minimum constant workforce necessary to satisfy the net demand-constant workforce plan;

A Prototype Problem Two alternative plans for managing workforce: •Plan 1 is to change workforce each month in order to produce enough units to most closely match the demand pattern-zero inventory plan; •Plan 2 is to maintain the minimum constant workforce necessary to satisfy the net demand-constant workforce plan;

⑧ A Prototype Problem P1:Zero Inventory Plan(Chase Strategy)- minimize inv.level. Table 3-1 Initial Calculation for Zero Inv.Plan for Denspack A B C Month No.of No.of Units Produced Working per Worker(BxK) Days Jan. 20 2.931 Feb. 24 3.517 March 18 2.638 April 26 3.810 May 22 3.224 June 15 2.198

A Prototype Problem P1: Zero Inventory Plan (Chase Strategy) – minimize inv. level. AB C Month No. of Working Days No. of Units Produced per Worker (B K) Jan. 20 2.931 Feb. 24 3.517 March 18 2.638 April 26 3.810 May 22 3.224 June 15 2.198 Table 3-1 Initial Calculation for Zero Inv. Plan for Denspack

⑧ A Prototype Problem P1:Zero Inventory Plan(Chase Strategy)- minimize inv.level. Table 3-1 Initial Calculation for Zero Inv.Plan for Denspack A B C D Month No.of No.of Units Produced Forecast Net Working per Worker(BxK) Demand Days Jan. 20 2.931 780 Feb. 24 3.517 640 March 18 2.638 900 April 26 3.810 1,200 May 22 3.224 2,000 June 15 2.198 2,000

A Prototype Problem P1: Zero Inventory Plan (Chase Strategy) – minimize inv. level. AB C D Month No. of Working Days No. of Units Produced per Worker (B K) Forecast Net Demand Jan. 20 2.931 780 Feb. 24 3.517 640 March 18 2.638 900 April 26 3.810 1,200 May 22 3.224 2,000 June 15 2.198 2,000 Table 3-1 Initial Calculation for Zero Inv. Plan for Denspack