Process Selection and Facility Layout Lecture 5

Forecasting Product and Service Design Technological Change Capacity Planning Process Selection Facilities and Equipment Layout Work Design Process Selection and System Design

Introduction  Process selection Deciding on the way production of goods or services will be organized  Major implications Capacity planning Layout of facilities Equipment Design of work systems  New product and service, technological changes, and competitive pressures

 Variety of products and services How much  Flexibility of the process; volume, technology and design What type and degree  Volume Expected output Questions Before Selecting a Process Process Selection and System Design

Job ShopBatchMassContinuous Job varietyVery HighModerateLowVery low Process flexibility Very HighModerateLowVery low Unit costVery HighModerateLowVery low Volume of output Very lowLowHighVery high Product – Process Matrix Process Selection and System Design

Product Variety vs. Production Quantity Process Selection and System Design Three quantity ranges: 1.Low production – 1 to 100 units 2.Medium production – 100 to 10,000 units 3.High production – 10,000 to millions of units

Batch Production Mass Production Job shop Quantity Automation Specialization Variety Material Handling Complexity Skills Process Selection and System Design

Facility layout refers to the arrangement of machines, departments, workstations, storage areas, aisles, and common areas within an existing or proposed facility. Layout decisions significantly affect: How efficiently workers can do their jobs, How fast goods can be produced, How difficult it is to automate a system, Facility layout

The basic objective of the layout decision is to ensure a smooth flow of work, material, people, and information through the system. Effective layouts also: Minimize material handling costs; Utilize space efficiently; Utilize labor efficiently; Eliminate bottlenecks; Reduce manufacturing cycle time and customer service time; Incorporate safety and security measures; Provide flexibility to adapt to changing conditions. Facility layout

Three basic types of layout: 1. Fixed-Position Layout 2. Process Layout 3. Product Layout Three hybrid layouts: 1. Cellular Layout 2. Flexible Manufacturing Systems 3. Mixed-model Assembly Lines Facility layout

Large projects too big to move Equipment and parts moved in and out of work area Highly skilled workers Fixed-Position Layout The product or project remains stationary, and workers, materials, and equipment are moved as needed.

Examples: Ship and aircraft buiding Fixed-Position Layout

Process Layout For small, discrete-parts manufacturing. Machines are grouped into departments according to type of operation. Advantages: work schedule more flexible Disadvantages: cost in inventory and storage space, high material handling cost, highest skill level required from operators.

Manufacturing Process Layout L L L L L L L L L L M M M M D D D D D D D D G G G G G G A AA Receiving and Shipping Assembly Painting Department Lathe Department Milling Department Drilling Department Grinding Department P P Process Layout

Arrange activities in sequence of operation Line set up for one product Specialised machines Suitable for mass production Line flow – avoid bottlenecks Not flexible Efficient IN OUT Product Layout

Advantages: minimized material handling, easy to automate material handling, less WIP, easier to control. Disadvantages: inefficient to alter the sequence of operations, breakdown on one machine can stop the entire line Product Layout

 Workers  Inventory  Storage space  Material handling  Aisles  Scheduling  Layout decision  Goal  Advantage  Workers  Inventory  Storage space  Material handling  Aisles  Scheduling  Layout decision  Goal  Advantage l Limited skills l Low in-process, high finished goods l Small l Fixed path (conveyor) l Narrow l Line balancing (Easier) l In-line, U-type l Equalize work at each station l Efficiency Process Comparison of Product and Process Layouts l High skills l High in-process, low finished goods l Large l Variable path (forklift) l Wide l Dynamic (More difficult) l Functional l Minimize material handling cost l Flexibility Product

Try to mix flexibility of process layout with efficiency of product layout Several different types of machines are grouped together to form a cell - each cell is designed to produce a family of parts. Suitable for small to mid-volume production of parts Advantages: setup time is reduced, lead time is reduced, finished inventory is reduced. Disadvantages: layout is less flexible than process layout, higher skill level required from operators. Hybrid Layout

Group Technology (CELL) Layouts One of the most popular hybrid layouts uses Group Technology (GT) and a cellular layout GT has the advantage of bringing the efficiencies of a product layout to a process layout environment

Process Flows before the Use of GT Cells

Process Flows after the Use of GT Cells

Original Process Layout CABRaw materials Assembly

Revised Cellular Layout Assembly A C B Raw materials Cell 1 Cell 2 Cell 3

Production systems correlate to the necessary type of layout. LowMediumHigh Low Medium High Product Variety Production Volume Fixed Location Layout Group Technology Layout Product Layout Process Layout

LOGO Operations Management by R. Dan Reid & Nada R. Sanders 3 rd Edition © Wiley 2007

Product Layout  Processes/work stations arranged in sequence of activities required to produce the product/service (Assembly Line). Use for high volume, standardized products and services WIP and handling of materials/customers is minimized Equipment is specialized, capital intensive Output is dependent on the slowest work station The “line” must be balanced for effectiveness.

Product Layouts  Specialized equipment  High capital intensity & wide use of automation  Processing rates are faster  Material handling costs are lower  Less space required for inventories  Less volume or design flexibility

Product Layout Product A Product B Product C Step 1 Step 2 Step 3 Step

Designing Product Layouts  Step 1: Identify tasks & immediate predecessors  Step 2: Determine the desired output rate  Step 3: Calculate the cycle time  Step 4: Compute the theoretical minimum number of workstations  Step 5: Assign tasks to workstations (balance the line)  Step 6: Compute efficiency, idle time & balance delay

Assembly Line Balancing 1.Precedence diagram: circles=tasks, arrows show the required sequence. 2.Determine cycle time: 3.Determine required workstations (theoretical minimum) 4.Set rules for assigning tasks (number of following tasks, longest task time)

Assembly Line Balancing 5.Assign tasks to first workstation, using rules and staying within cycle time. Repeat for following workstations until all tasks are assigned. 6.Evaluate line efficiency: 7.Rebalance if efficiency is not satisfactory.

Step 1: Identify Tasks & Immediate Predecessors

Layout Calculations  Step 2: Determine output rate Vicki needs to produce 60 pizzas per hour  Step 3: Determine cycle time The amount of time each workstation is allowed to complete its tasks Limited by the bottleneck task (the longest task in a process):

Layout Calculations (continued)  Step 4: Compute the theoretical minimum number of stations TM = number of stations needed to achieve 100% efficiency (every second is used) Always round up (no partial workstations) Serves as a lower bound for our analysis

Layout Calculations (continued)  Step 5: Assign tasks to workstations Start at the first station & choose the longest eligible task following precedence relationships Continue adding the longest eligible task that fits without going over the desired cycle time When no additional tasks can be added within the desired cycle time, begin assigning tasks to the next workstation until finished

Last Layout Calculation  Step 6: Compute efficiency and balance delay Efficiency (%) is the ratio of total productive time divided by total time Balance delay (%) is the amount by which the line falls short of 100%

Other Product Layout Considerations  Shape of the line (S, U, O, L): Share resources, enhance communication & visibility, impact location of loading & unloading  Paced versus un-paced lines Paced lines use an automatically enforced cycle time  Number of products produced Single Mixed-model lines

Comparison of Product vs. Product Layouts Process Layouts Product Layouts Products: large #, different small # efficiently Resources: general purpose specialized Facilities: more labor intensive more capital intensive Flexibility: greater relative to market lower relative to market Processing slower faster Rates: Handling costs: high low Space requirements: higher lower

Hybrid Layouts  Combine elements of both product & process layouts Maintain some of the efficiencies of product layouts Maintain some of the flexibility of process layouts  Examples: Group technology & manufacturing cells Grocery stores

Hybrid Layouts  Cellular Layout Cross between product/process layout group a number of machines into a cell to produce a family of parts requiring similar processing (group technology). Often arranged into U- or C-shaped line flows  Modular Layout achieves layout flexibility so that layouts can be changed, expanded, or reduced without much difficulty.