[互联网]chapter3 aggragate planning.ppt
《[互联网]chapter3 aggragate planning.ppt》由会员分享,可在线阅读,更多相关《[互联网]chapter3 aggragate planning.ppt(40页珍藏版)》请在三一办公上搜索。
1、Production Planning and Control:Aggregate planning,Contents,IntroductionAggregate Units of Production;Costs in Aggregate Planning;A Prototype Problem;Solution of Aggregate Planning Problem by LP;,Introduction(1),Aggregate planning,also called macro planning,addresses problem of deciding how many emp
2、loyees the firm should retain and,for a manufacturing firm,the quantity and the mix of products to be produced.The aggregate planning methodology here assume that demand is deterministic,or known in advance.Traditional Philosophy for most manufacturers-retain primary production in house;Some compone
3、nts may be purchased from outside suppliers;The primary products are traditionally produced by the firmFord even has a plant of rubber tree for tiresNew one in dynamic environment-manufacturing is outsourced;Sun Microsystems is a successful example;Focus on product innovation and design rather than
4、manufacturing;,Introduction(2),Aggregate planning involves competing objectives.Make frequent and large changes in size of labor force-a chase strategy to react quickly to anticipated changes in demand-cost effective,but a poor long-term strategy;Retain a stable workforce-results in larger buildups
5、of inventory during period of low demand;Develop a production plan for a firm to maximize profit over the planning horizon subject to constraints on capacity.Aggregate planning methodology is designed to translate demand forecast into blueprint for planning staffing and production level for a firm o
6、ver a predetermined planning horizon;,Aggregate Units of Production,Describe aggregate units in the following situations:In terms of“average item-when the items produced are similar;In terms of weights(tons of steel),volume(gallons of gasoline),amount of work required(worker-years of programming tim
7、e,and dollar value(value of inventory in dollars)-when many kinds of items are produced;Appropriate aggregating schema are determined by context of the particular planning problem and the level of the aggregation require.,Aggregate Units of Production,Example 3.1:Decide on aggregating schema for the
8、 manager of a plant that produces six models of washing machines to determine the workforce and production levels.,Aggregate Units of Production,One possibility is to define aggregate unit as one dollar of output-Unfortunately,it is impossible since the selling prices of the various models are not c
9、onsistent with the number of worker-hours required to produce them.Since the percentages of the total number of sales for these six models have been fairly constant(32%,21%,17%,14%,10%and 6%for six models respectively),he decide to define the aggregate unit of production as a fictitious washing mach
10、ine requiring.324.2+.21 4.9+.17 5.1+.14 5.2+.10 5.4+.06 5.8=4.856 hrs of labor time.,Aggregate Units of Production,Defining an aggregate unit of production at higher level of the firm is more difficult;In cases where the firm produces a large of products,a natural aggregate unit is sales dollars;Agg
11、regate planning is closely related to hierarchical production planning(HPP).HPP considers workforce sizes and production rates at different levels of the firm.The recommended hierarchy is as follows:Items-correspond to individual models of washing machines;Families-a group of items,e.g.all washing m
12、achines;Types-groups of families,e.g.large house appliances;,Costs in Aggregate Planning,(1)Smoothing cost-Occurs as result of changing the production level from one period to the next.Cost for changing size of workforce-advertise positions;interview prospective employees,and training new hires;Assu
13、med to be linear;,Fig 3-2 Cost of Changing the Size of the Workforce,Aggregate Units of Production,(2)Holding costs-Occurs as a result of having capital tied up in inventory.Always assumed to be linear in the number of units being held at a particular point in time;For aggregate planning,it is expre
14、ssed in terms of dollars per unit held per planning period;It is charged against the inventory remaining on hand at the end of the planning period;,Aggregate Units of Production,(3)Shortage costs-Shortage occurs when demands are higher than anticipated;For aggregate planning,it is assumed that exces
15、s demand is backlogged and filled in a future period;In a highly competitive situation,the excess demand may be lost-lost sales;It is generally considered to be linear.,Aggregate Units of Production,(4)Regular time costs-Involve the cost of producing one unit of output during regular working hours;A
16、ctual payroll cost of regular employees working on regular time;Direct and indirect costs of materials;Other manufacturing expense;,(5)Overtime and subcontracting costs-costs of production units not produced on regular time;Overtime-production by regular-time employees beyond work day;Subtracting-th
17、e production of items by an outside supplier;Assumed to be linear;,(6)Idle time costs-underutilization of workforce;In most contexts,the idle time cost is zero;Idle time may have other consequences for the firm,e.g.if the aggregate units are input to another process,idle time on the line could resul
18、t in higher costs to subsequent processes.,A Prototype Problem,Example 3.2Densepack 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
19、 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,How to incorporate the starting and ending in
20、ventory constraints into formulation?-the simplest way is to modify the values of the predicated demand;Define:the net predicated demand in period 1=the predicated demand-initial inventory;If there is ending inventory constraint,this amount should be added to the demand in period T;,A Prototype Prob
21、lem,How to handle minimum buffer inventories?-By modifying the predicted demand.If there is a minimum buffer inventory in every period,this amount should be added to the first periods demand;,A Prototype Problem,How to handle minimum buffer inventories?-By modifying the predicted demand.(Cont.)If th
22、ere is a minimum buffer inventory in only one period,this amount should be added to the that periods demand,and subtracted from the next periods demand;,A Prototype Problem,A Prototype Problem,If the shortage is not permitted,the cumulative production must be at least as great as cumulative net dema
23、nd each period-Feasible AP,Fig.3-4 A Feasible Aggregate Plan for Densepack,A Prototype Problem,How to make cost trade-offs of various production plans?Only consider three costs:CH=Cost of hiring one worker=$500;CF=Cost of firing one worker=$1,000;CI=Cost of holding one unit of inventory for one mont
24、h=$80,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 a
25、t 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 orde
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 互联网 互联网chapter3 aggragate planning chapter3
链接地址:https://www.31ppt.com/p-4602285.html