Chapter coverage Basic layout types Selecting a layout type Detailed design of a layout
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: Fixed position layout Process layout Cell layout Product layout
Fixed position layout In a fixed position layout, the transformed resource does not move between its transforming resources. Equipment, machinery, plant and people who do the processing move as necessary because the product or customer is either: Too large Too delicate or Objects being moved
Process layout In a process layout, similar processes or processes with similar needs are located together because: It is convenient to group them together or The utilization of the transforming resource is improved Different products of customer have different requirements therefore they may take different routes within the process. The flow in a process layout can be very complex.
Loan books in subject order On-line and CD-ROM access room Study desks To journal sack Company reports Current journals Enquiries Reference section Reserve collection Store room Counter staff Copying area Entrance Exit An example of a process layout in a library showing the path of just one customer
Cell layout In a cell layout, the transformed resources entering the operation move into a cell in which all the transforming resources it requires in located. 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. Each cell may be arranged in either a process or product layout. The cell type layout attempts to bring order to the complex flow seen in a process layout.
Books and videos Sports shop Menswear Footwear Entrance Perfume & jewellery Elevators Confectionery, newspaper, magazines and stationery Women’s clothes Luggage and gifts Entrance The ground floor plan of a department store showing the sports goods shop-within-a-shop retail ‘cell’
Product layout In a product layout, the transformed resource flow a long a line of processes that has been prearranged. Flow is clear, predictable and easy to control.
An army induction centre with uses product layout Waiting area Waiting area Lecture theatre Blood test Doctor Doctor Record personal history and medical details X-ray Uniform issuing area Blood test Doctor Doctor X-ray Blood test Doctor Doctor Uniform store X-ray
Line layout cafeteria Cell layout buffet Fixed-position layout service restaurant Desert buffet Starter buffet Main course buffet Service line Preparation Oven Process layout kitchen Cool room Freezer Grill Vegetable prep A restaurant complex with all four basic layout types
Low High Flow is intermittent Volume Fixed-position layout High Process layout Regular flow more feasible Cell layout Variety Product layout Flow becomes continuous Low Regular flow more important Volume-variety relationship
Volume and variety Project process Jobbing process Batch process Mass process Continuous process Professional services Service shops Mass services Decision 1 Process type Strategic performance objectives Fixed position layout Process layout Cell layout Product layout Decision 2 Basic layout type Decision 3 The physical position of all transforming resources Detailed design of layout The flow of the operation’s transformed resources Layout selection steps
1) The nature of the basic layout types Manufacturing B asic layout Service process types types process types Fixed Project processes Project processes Professional position layout services Jobbing processes Process layout Service shops Batch pro cesses Cell layout Mass services Mass processes Product layout Continuous processes
2) Advantages and disadvantages Fixed Process Cell Product - Very high mix and product flexibility - High mix and product flexibility - Good compromise between cost and flexibility position Lo- w unit costs for high volume layout layout layout layout - Gives Opportunities for specialization of equipment - Product/customer not moved or disturbed. - Relatively robust if in the case of disruptions - Fast throughput. - Group work can result in good motivation Advantages - Easy supervision of equipment of plant - Gives Opportunities for specialization of equipment - High variety of tasks for staff Low utilization of resources. Can be costly to rearrange existing layout Can have low mix and flexibility - Very high unit cost. Can have very high WIP Not very robust to disruption Can need more plant and equipment Disadvantages - Scheduling space and activities can be difficult. Complex flow. Work can be very repetitive.
(a) (b) Fixed-position Costs Costs Process Cell Product ? ? ? ? Use cell Use process Use product Use fixed-position Volume Volume Use product Use cell or product Use process or cell or product Use process or cell Use process Use fixed-position or process Use fixed-position (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 3) Consider total cost
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.
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
(a) LOADS/DAY Collecting information in process layout (b) LOADS/DAY If direction is not important, collapses to
A 30 B - 30 60 C - 20 - 30 D 80 40 E Collecting information in process layout (c) LOADS/DAY (d) LOADS/DAY Or alternatively
UNIT COST/DISTANCE TRAVELLED Collecting information in process layout (e) (f) LOADS/DAY If cost of flow differs between work centers, combine with
Collecting information in process layout (g) DAILY COST/DISTANCE TRAVELLED To give
Collecting information in process layout (h) (i) DAILY COST/DISTANCE TRAVELLED DAILY COST/DISTANCE TRAVELLED If direction is not important, collapses to
DEPARTMENT Metrology E Electronic testing A I O Analysis U X I U X Ultrasonic testing O U I U Fatigue testing O E Impact testing A relationship chart
Cell layout design Cells in an operation can be created based on two interrelated decisions: 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 7.28 Which resources to allocate to which cell using: Cluster analysis – which process group naturally together Parts and family coding – based on similar characteristics of parts of products OR Production Flow Analysis (PFA) Examines both product requirement and process grouping (See Fig. 7.31)
Amount of indirect resources included in the cell High e.g. e.g. Plant-within-a-plant manufacturing operation Maternity unit in a hospital Specialist process manufacturing cell Internal audit group in a bank Proportion of the resources needed to complete the transformation included in the cell Low High e.g. Complete component manufacturing cell Lunch and snack produce area in supermarket e.g. Small multi-machine manufacturing cell Joint reference and copying room in a library Low Types of cell
(a) and (b) Using production flow analysis to allocate machines to cells (a) (b) Product Product Cell A Machines Machines Cell B Cell C
Product layout design Product type layout is designed based on a technique called line balancing. The technique consist of the following steps: Calculating the required cycle time. Calculating the number of stages. Producing a precedence diagram. Finally allocating activities to the stages.
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 160 1 product every 15 minutes
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.
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: The circles which represent the elements are drawn as far to the left as possible. None of the arrows which shows the precedence of the elements should be vertical. 0.17 mins e 0.25 mins 0.30 mins 0.05 mins 0.25 mins a b c d f g i 0.12 mins 0.36 mins 0.10 mins h 0.08 mins
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: Choose the largest that will fit into the time remaining at the stage Choose the element with the most ‘followers’.
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
But if work is not equally allocated the cycle time will increase and ‘balancing losses’ will occur An ideal ‘balance’ where work is allocated equally between the stages Cycle time = 3.0 mins Cycle time = 2.5 mins 3.0 2.5 2.2 2.3 Load Load Stage Stage Calculating balancing loss: Idle time every cycle =(3.0 - 2.3) + (3.0 - 2.5) + (3.0 - 2.2) = 2.0 mins Balancing loss = 2 4 x 3.0 = 0.1667 = 16.67% Work allocated to stage Idle time Balancing loss is that proportion of the time invested in processing the product or service which is not used productively
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
Element - -De-tin and trim 0.12 mins a Element - Reshape with off-cuts 0.30 mins b c Element - Clad in almond fondant 0.36 mins 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 0.17 mins e 0.25 mins 0.30 mins 0.05 mins 0.25 mins a b c d f g i 0.12 mins 0.36 mins 0.10 mins 0.08 mins h Element listing and precedence diagram for Karlstad Kates
0.17 mins e Stage 1 Stage 2 Stage 3 Stage 4 0.25 mins 0.30 mins 0.05 mins 0.25 mins a b c d f g i 0.12 mins 0.36 mins 0.10 mins h 0.08 mins Cycle time = 0.48 mins Idle time every cycle= (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42)= 0.24 mins Proportion of idle time per cycle = 0.24 = 12.5% 4 x 0.48 Allocation of elements to stages and balancing loss for Karlstad Kates