Antti Salonen KPP227 KPP227 1

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1 KPP227 KPP227 1

2 What is Aggregate Planning? Aggregate (or intermediate-term) planning is the process of determining a company s aggregate plan = production plan. The aggregate plan specifies how the company will use their existing facilities and equipment most efficiently to reach their goals and satisfy demand. Capacity expansion is normally achieved though the use of overtime, subcontracting or adding work shifts. KPP227 2

3 Sales and Operations Plan Operations planning and scheduling is the process of making sure that demand and supply plans are in balance at all levels! KPP227 3

4 Concept of Aggregation Marketplace and demand Product decisions Research and technology Process planning and capacity decisions Workforce Demand forecasts, orders Aggregate plan for production Inventory on hand Raw materials available Master production schedule and MRP systems External capacity (subcontractors) Detailed work schedules KPP227 4

5 Concept of Aggregation Business or annual plan Production or staffing plan MPS or workforce schedule KPP227 5

6 Concept of Aggregation Instead of planning for individual products, similar products are put together in groups. In aggregate planning, one group of products is treated as one unit. A group of products or services that have similar demand requirements and common processing, labor and material requirements is called a product family. KPP227 6

7 Concept of Aggregation Product family Product type Item KPP227 7

8 Concept of Aggregation If demand was absolutely certain, aggregate planning would not be needed. Company could develop a production process and a workforce level that would produce exactly the amount of product needed every month in a repeating cycle while maintaining almost no inventories. However, in real life demand is uncertain, but so is capacity (e.g. workforce level), materials prices etc. Aggregate Planning is a dynamic process that requires constant updating! KPP227 8

9 The Process of Aggregation Determine requirements for planning horizon Identify alternatives, constraints and costs Prepare prospective plan for planning horizon No Is the plan acceptable? Yes Move ahead to next planning session Implement and uppdate the plan KPP227 9

10 The Process of Aggregation Step 1: New planning horizon! Update files with actual sales, production, inventory, costs, and constraints. Step 2: Participate in the forecasting and demand planning to create the authorized demand forecasts, e.g. staff requirements. Step 3: Update the sales and operations planning spreadsheet for each family, recognizing relevant constraints and costs including e.g. availability of materials from suppliers, machine capacities, or limited storage space. KPP227 10

11 The Process of Aggregation Step 4: Have one or more consensus meetings with the stakeholders on how best to balance supply with demand. Step 5: Present recommendations by product family at the executive S&OP meeting,. Step 6: Update the spreadsheets to reflect the authorized plan, and communicate the plans to the important stakeholders for implementation. KPP227 11

12 Inventory Control Systems Independent demand Items for which demand is influenced by market conditions and is not related to the inventory decisions for any other item held in stock or produced. Dependent demand Items required as components or inputs to a service or product. Dependent demand exhibits a pattern very different from that of independent demand and must be managed with different techniques. (will be covered in upcoming lectures) KPP227 12

13 Options and strategies Supply options Anticipation inventory Workforce adjustment Workforce utilization Part-time workers Subcontractors Vacation schedules Planning strategies Chase strategy Level strategy Mixed strategy KPP227 13

14 Approaches to Aggregate Planning Two simple trial and error approaches Chase strategy Involves hiring and laying off employees to match the demand forecast over the planning horizon. Varying the workforce s regular-time capacity to equate supply to demand requires no inventory investment, overtime, or undertime. Level Involves keeping the workforce constant (except possibly at the beginning of the planning horizon). Utilization is varied to match the demand forecast via overtime, undertime (paid or unpaid), and vacation planning (i.e. paid vacations when demand is low). KPP227 14

15 Definitions Backlog Accumulation of customer orders that have been promised for delivery at some future date. Backorder An order that a customer is (reluctantly) prepared to wait a limited time for. Stockout The customer is not ready to wait and hence, the order is lost. KPP227 15

16 EXAMPLE 1 Chase vs. Level strategy KPP227 16

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18 SOLUTION a. Chase Strategy This strategy simply involves adjusting the workforce as needed to meet demand, as shown in Figure Rows in the spreadsheet that do not apply (such as inventory and vacations) are hidden. The workforce level row is identical to the forecasted demand row. A large number of hirings and layoffs begin with laying off 4 part-time employees immediately because the current staff is 10 and the staff level required in period 1 is only 6. However, many employees, such as college students, prefer part-time work. The total cost is $173,500, and most of the cost increase comes from frequent hiring and layoffs, which add $17,500 to the cost of utilized regular-time costs. KPP227 18

19 a. Chase Strategy Start with 10 workers KPP227 19

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21 Peak! b. Level Strategy KPP227 21

22 EXAMPLE 2 Chase and Level strategy KPP227 22

23 A General Motors Buick plant manufactures several Buick models. The company has forecast its quarterly demands during the next four quarters, which is listed below. The plant can produce approximately 25 autos per quarter for each worker on staff. Workers receive an average of $15,000 per quarter in wages and benefits, and it costs $7,000 to hire and train a new worker and $10,000 to lay off a worker. Workers can be hired or laid off at the beginning of any quarter. GM expects to have 480 workers on staff and 2000 autos in inventory at the end of the current quarter. Any auto held in inventory at the end of a quarter incurs a holding cost of $1,000. Construct an aggregate plan for the next four quarters using the chase and level strategies and compute their total costs. Quarter Aggregate demand 1 10, , , ,000 KPP227 23

24 Chase strategy: Quarter Aggregate demand 1 10, , , ,000 Quarter Aggregate demand (units) Planned output (units) 1. Determine the number of workers needed to meet the demand in each quarter (in this example: 25 autos per worker and quarter). 2. Then, adjust the workforce accordingly. 1 2 Workers on staff Workers hired Workers laid off Inventory (units) ,000 8, ,000 12, ,000 9, ,000 11, Total (quarters 1-4) Salaries: 1600 workers x $15,000/Q = $ 24,000,000 Hiring cost: 240 workers x $ 7,000 = $ 1,680,000 Layoff cost: 280 workers x $ 10,000 = $ 2,800,000 Inventory cost: 0 units x $ 1,000 / unit = $ 0 Total cost: = $ ,000 KPP227 24

25 1 Level strategy: Q Net CumulaJve Requirements Workers needed to make CumulaJve Requirements 1 8, , , , Quarter Aggregate demand (units) Planned output (units) 1. Determine the maximum number of workers needed to meet the Cumulative Requirements. 2. Set the workforce to the maximum number required. Workers on staff Workers hired Workers laid off Inventory (units) ,000 10, ,000 10, ,000 10, ,000 10, Total (quarters 1-4) Salaries: 1600 workers x $15,000/Q = $ 24,000,000 Hiring cost: 0 workers x $ 7,000 = $ 0 Layoff cost: 80 workers x $ 10,000 = $ 800,000 Inventory cost: 3000 units x $ 1,000 / unit = $ 3,000,000 Total cost: = $ 27,800,000 KPP227 25

26 EXAMPLE 3 Mixed strategy KPP227 26

27 A company makes several models of DVD-players, which form a product type at its faciclity. The predicted sales for these products for the next six months are shown in the table. Each unit of product requires approximately 1.5 person-hours of labor to make. Workers work an eigh-hour day, and they recieve an average of 2000 per month in wages and benefits. It costs approximately 2500 to lay off an employee and approximately 3000 to recruit and train a new employee. DVDs produced in one month can be held in inventory and shipped in subsequent months, but it costs 10 per month to hold the item in inventory. For simplicity we assume that at the beginning of each month a decision to hire/dismiss workers is made. Then production occurs during the month and all shipments are made at the end of the month. Any item on hand at the end of the month that is not shipped incurs the 10 holding cost. The decisions facing the company are to select the number of employees to have on staff each of the next six months (and the number to hire and dismiss). The number of DVDs to produce each month, and then indirectly how many to have in inventory at the end of each month. The company expects to have 1850 production workers on staff during september, and it expects to end september with 5000 units of inventory available for use. In addition, the company wants to complete March with between 1800 and 1900 production workers on staff and with between 2000 and 2150 units of product in inventory. Month Sales Work days Oct Nov Dec Jan Feb Mar KPP227 27

28 Chase Strategy The company s net requirements for October are (in inventory) = The net requirements for later months equal the demand except for March, which requires an additional 2000 units for ending inventory. The number of units that can be produced by an employee each month equals (8h/ day x number of work days/month) / (1.5 person-hour/unit) assuming that all workers produce the maximum number of units each month. A B Month Sales Work days Oct Nov Dec Jan Month A: Net requirements B: Prod./ employee Oct Nov Dec Jan Feb Mar C = A/B Employees C Feb Mar Note that the required number of employees is rounde up to the next integer. KPP227 28

29 Aggregate plan Chase Strategy Month No. Of workers No. Hired No. Dismissed Net Requirements Production Sep Oct Nov Dec Jan Feb Mar Apr Total: (Oct-Mar) Ending inventory Total cost for this strategy: Wages: x 2000= Hiring: 1471 x 3000 = Dismissal: 1427 x 2500 = Inventory: 3200 x 10 = Total cost: KPP227 29

30 Aggregate plan Since this number exceeds the Month No. Of No. No. Dismissed Net capacity Production of one worker, Ending the workers Hired Requirements number of workers can inventory be adjusted downwards. Sep Oct Nov Dec Jan Feb Mar Apr Total: (Oct-Mar) Chase Strategy Total cost for this strategy: Wages: x 2000= Hiring: 1471 x 3000 = Dismissal: 1427 x 2500 = Inventory: 3200 x 10 = Total cost: KPP227 30

31 Aggregate plan Chase Strategy Month No. Of workers No. Hired No. Dismissed Net Requirements Production Sep Oct Nov Dec Jan Feb Mar Apr Total: (Oct-Mar) Ending inventory Also this is adjusted downwards. Total cost for this strategy: Wages: x 2000= Hiring: 1470 x 3000 = Dismissal: 1428 x 2500 = Inventory: 2304 x 10 = Total cost: KPP227 31

32 Mixed Level/Chase Strategy A simple way to construct an aggregate plan that keeps personnel adjustments to a minimum is to first compute the net cumulative requirements for each period; the net requirements summed for all periods in the planning horizon up to that period. Then, for each month we compute the minimum stable workforce that would be required to produce the net cumulative requirements up to that point. Last, we identify the Peak requirements of employees for handling the cumulative production requirements. Month A: Net cumulative requirements B: Cumulative Prod./employee Oct Nov C = A/B Employees Dec Jan Peak Feb Mar KPP227 32

33 Aggregate plan Mixed Level/Chase Strategy Month No. Of workers No. Hired No. Dismissed Net Requirements Production Sep Ending inventory Oct Nov Dec Jan Feb Mar Apr Total: (Oct-Mar) Total cost for this strategy: Wages: x 2000= Hiring: 438 x 3000 = Dismissal: 396 x 2500 = Inventory: x 10 = Total cost: KPP227 33

34 Scheduling Scheduling will be covered in a comming lecture KPP227 34

35 Relevant book chapters Chapter: Planning and scheduling operations : Operations planning and scheduling across the organization Stages in operations planning and scheduling Managing demand Sales and operations plans KPP227 35

36 Questions? Next lecture on Thursday Inventory management KPP227 36