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© Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 7 7.1 Layout and Flow.

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Presentation on theme: "© Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 7 7.1 Layout and Flow."— Presentation transcript:

1 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Layout and Flow

2 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Chapter coverage Basic layout types Selecting a layout type Detailed design of a layout

3 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Layout: The layout of an operation is concerned with the physical location of its transforming resources, that is deciding where to put the facilities, machines, equipment and staff in the operation. Layout types: 1) Fixed position layout 2) Process layout 3) Cell layout 4) Product layout

4 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Fixed position layout 1)In a fixed position layout, the transformed resource does not move between its transforming resources. 2)Equipment, machinery, plant and people who do the processing move as necessary because the product or customer is either: i.Too large ii.Too delicate or iii.Objects being moved

5 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Process layout 1)In a process layout, similar processes or processes with similar needs are located together because: i.It is convenient to group them together or ii.The utilization of the transforming resource is improved 2)Different products of customer have different requirements therefore they may take different routes within the process. 3)The flow in a process layout can be very complex.

6 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter An example of a process layout in a library showing the path of just one customer EntranceExit On-line and CD-ROM access room Loan books in subject order Enquiries Store room Counter staff Copying area Company reports To journal sack Current journals Reserve collection Reference section Study desks

7 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Cell layout 1)In a cell layout, the transformed resources entering the operation move into a cell in which all the transforming resources it requires in located. 2)After being processed in the cell, the transformed resource may move to a different cell in the operation or it may be a finished product or service. 3)Each cell may be arranged in either a process or product layout. 4)The cell type layout attempts to bring order to the complex flow seen in a process layout.

8 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter The ground floor plan of a department store showing the sports goods shop-within-a-shop retail cell Sports shop Menswear Womens clothes Luggage and gifts Confectionery, newspaper, magazines and stationery Books and videos Footwear Perfume & jewellery Elevators Entrance

9 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Product layout 1)In a product layout, the transformed resource flow a long a line of processes that has been prearranged. 2)Flow is clear, predictable and easy to control.

10 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter An army induction centre with uses product layout Lecture theatre Uniform issuing area Uniform store Waiting area Doctor Blood test Blood test Blood test X-ray Record personal history and medical details

11 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter A restaurant complex with all four basic layout types Fixed-position layout service restaurant Cell layout buffet Line layout cafeteria Cool room Freezer Vegetable prep Grill Preparation Oven Process layout kitchen Main course buffet Starter buffet Desert buffet Service line

12 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Fixed-position layout Product layout Cell layout Process layout Volume LowHigh Variety Low High Flow is intermittent Regular flow more important Flow becomes continuous Regular flow more feasible Volume-variety relationship

13 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Project process Jobbing process Batch process Mass process Continuous process Professional services Service shops Mass services Fixed position layout Process layout Cell layout Product layout The physical position of all transforming resources The flow of the operations transformed resources Process type Basic layout type Detailed design of layout Volume and variety Strategic performance objectives Decision 1 Decision 2 Decision 3 Layout selection steps

14 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Selecting a layout type

15 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter ) The nature of the basic layout types Basic layout types Manufacturing process types Service process types Fixed position layout Project processes Process layout Cell layout Product layout Jobbing processes Batch processes Mass processes Continuous processes Professional services Service shops Mass services Project processes

16 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter ) Advantages and disadvantages Fixed position layout Process layout Cell layout Product layout Disadvantages Advantages - Very high mix and product flexibility - Product/customer not moved or disturbed. - Very high unit cost. - Scheduling space and activities can be difficult. - High mix and product flexibility - Relatively robust if in the case of disruptions Low utilization of resources. Can have very high WIP Complex flow. - Good compromise between cost and flexibility - Fast throughput. - Group work can result in good motivation Can be costly to rearrange existing layout Can need more plant and equipment Lo- w unit costs for high volume - Gives Opportunities for specialization of equipment Can have low mix and flexibility Not very robust to disruption Work can be very repetitive. - High variety of tasks for staff - Easy supervision of equipment of plant - Gives Opportunities for specialization of equipment

17 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter (a) The basic layout types have different fixed and variable cost characteristics which seem to determine which one to use. (b) In practice the uncertainty about the exact fixed and variable costs of each layout means the decision can rarely be made on cost alone Use fixed-position Use fixed-position or process Use process Use process or cell Use process or cell or product Use cell or product Use product Volume Costs Fixed-position Process Cell Product Volume Costs Use product Use cell Use process Use fixed- position (a)(b) ???? 3) Consider total cost

18 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Detailed design of a layout

19 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Fixed position layout design: The location of resources for each project is unique and it will be determined on the convenience of transforming resources themselves. Although there are techniques which held to locate resources on fixed position layouts, they are not widely used because this layout can be very complex and planned schedules do change frequently.

20 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Process layout design: When cost of traveling is important: –Collecting information such as: number of loads per day cost per distance traveled When process relationship is important –Relationship chart

21 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Collecting information in process layout If direction is not important, collapses to LOADS/DAY (b)(b) (a)(a)

22 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Collecting information in process layout Or alternatively LOADS/DAY (c)(c) (d)(d) A B C D E

23 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Collecting information in process layout If cost of flow differs between work centers, combine with LOADS/DAYUNIT COST/DISTANCE TRAVELLED (e)(e) (f)(f)

24 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Collecting information in process layout To give DAILY COST/DISTANCE TRAVELLED (g)(g)

25 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Collecting information in process layout If direction is not important, collapses to DAILY COST/DISTANCE TRAVELLED (h)(h) (i)(i)

26 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter A relationship chart Metrology Electronic testing Analysis Ultrasonic testing Fatigue testing E I I I A U O O U X DEPARTMENT Impact testing E O U U X

27 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Cell layout design 1)Cells in an operation can be created based on two interrelated decisions: 1)What is the extent and nature of the cell i.e. the amount of direct and indirect resources the cell has as shown in Fig )Which resources to allocate to which cell using: i.Cluster analysis – which process group naturally together ii.Parts and family coding – based on similar characteristics of parts of products OR 2)Production Flow Analysis (PFA) Examines both product requirement and process grouping (See Fig. 7.31)

28 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Types of cell High Low Complete component manufacturing cell Lunch and snack produce area in supermarket Small multi-machine manufacturing cell Joint reference and copying room in a library Plant-within-a-plant manufacturing operation Maternity unit in a hospital Specialist process manufacturing cell Internal audit group in a bank Amount of indirect resources included in the cell Proportion of the resources needed to complete the transformation included in the cell e.g.

29 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter (a) and (b) Using production flow analysis to allocate machines to cells Product Machines Product Machines Cell A Cell B Cell C (a) (b)

30 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Product layout design 1)Product type layout is designed based on a technique called line balancing. The technique consist of the following steps: 1)Calculating the required cycle time. 2)Calculating the number of stages. 3)Producing a precedence diagram. 4)Finally allocating activities to the stages.

31 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Cycle time: It is the time between completed products emerging from the process. Example: Suppose the regional back-office operation of a large bank is designing an operation which will process its mortgage applications. The number of applications to be processed is 160 per week and the time available to process the applications is 40 hours per week. Cycle time = 40= 1/4 hours= 15 minutes product every 15 minutes

32 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Number of stages Required no. of stages = total work content required cycle time Where the total work content is the total quantity of work involved in producing the product given in time. Example: Suppose that the bank in the previous example calculated that the average total work content of processing a mortgage application is 60 minutes. The number of stages needed to produce a processed application every 15 minutes can be calculated Required no. of stages = 60 minutes= 4 stages 15 minutes If you get a fraction round it up to the higher whole number.

33 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Precedence diagram This is a diagram representing the ordering of the elements which comprise the total work content of the product or service. Two rules when constructing the diagram: 1.The circles which represent the elements are drawn as far to the left as possible. 2.None of the arrows which shows the precedence of the elements should be vertical. abcd e fg h i 0.12 mins 0.30 mins 0.36 mins 0.25 mins 0.05 mins 0.17 mins 0.10 mins 0.08 mins 0.25 mins

34 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Allocating activities to the stages The general approach is to allocate elements from the precedence diagram to the first stage, starting from the left, until the work allocated to the stage is as close to, but less than, the cycle time. When the stage is full of work without exceeding the cycle time, move to the next stage. Two rules help to decide which activities to allocate to a stage: 1.Choose the largest that will fit into the time remaining at the stage 2.Choose the element with the most followers.

35 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Balancing loss The effectiveness of the line balancing activity is measured by the balancing loss. This is the time wasted through the unequal allocation of work as a percentage of the total time invested in processing the product or service. Balancing loss =Total idle time No. of stages x Cycle time

36 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Balancing loss is that proportion of the time invested in processing the product or service which is not used productively Load Stage Cycle time = 2.5 mins Load Stage Cycle time = 3.0 mins An ideal balance where work is allocated equally between the stages But if work is not equally allocated the cycle time will increase and balancing losses will occur Work allocated to stage Idle time Calculating balancing loss: Idle time every cycle =( ) + ( ) + ( ) = 2.0 mins Balancing loss = 2 4 x 3.0 = = 16.67%

37 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Worked Example Consider Karlstad Kakes, a manufacturer of specialty cakes, which has recently obtained contract to supply a major supermarket chain with a specialty cake in the shape of a space rocket. It has been decided that the volumes required by the supermarket warrant a special production line to perform the finishing, decorating and packing of the cake. This line would have to carry out the elements shown in the next slide, which also shows the precedence diagram for the total job. The initial order from the supermarket is for 5000 cakes a week and the number of hours worked by the factory is 40 per week. From this: The required cycle time = 40 hrs x 60 mins = 0.48 mins 5000 The required number of stages = 1.68 mins (total work content) 0.48 mins (required cycle time) = 3.5 stages

38 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Element listing and precedence diagram for Karlstad Kates Element - - De-tin and trim 0.12 mins a Element - Reshape with off-cuts 0.30 mins b Element - Clad in almond fondant 0.36 mins c Element - Clad in white fondant 0.25 mins d Element - Decorate, red icing 0.17 mins e Element - Decorate, green icing 0.05 mins f Element - Decorate, blue icing 0.10 mins g Element - Affix transfers 0.08 mins h Element - Transfer to base and pack 0.25 mins i Total work content = 1.68 mins abcd e fg h i 0.12 mins 0.30 mins 0.36 mins 0.25 mins 0.05 mins 0.17 mins 0.10 mins 0.08 mins 0.25 mins

39 © Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter Allocation of elements to stages and balancing loss for Karlstad Kates abcd e fg h i 0.12 mins 0.30 mins 0.36 mins 0.25 mins 0.05 mins 0.17 mins 0.10 mins 0.08 mins 0.25 mins Stage 1Stage 2Stage 3Stage 4 Cycle time = 0.48 mins Idle time every cycle = ( ) + ( ) + ( ) = 0.24 mins Proportion of idle time per cycle = 0.24 = 12.5% 4 x 0.48


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