Facility Layout & Design PDF

. Facility Layout & Design 1  Objectives of Facility Layout  A facility layout problem may have many objectives. In the context of manufacturing plants, minimizing material handling costs is the most common one.  Other objectives include efficie...

. Facility Layout & Design 1  Objectives of Facility Layout  A facility layout problem may have many objectives. In the context of manufacturing plants, minimizing material handling costs is the most common one.  Other objectives include efficient utilization of  space  labor  Eliminate  bottlenecks  waste or redundant movement  Objectives of Facility Layout  Facilitate  organization structure  communication and interaction between workers  manufacturing process  visual control  Minimize  manufacturing cycle time or customer flow time  investment  Provide  convenience, safety and comfort of the employees  flexibility to adapt to changing conditions  Requirements for a Good Layout  Understand capacity and space requirements.  Understand information flows.  Understand cost of people and product flows.  Select appropriate material handling equipment.  Consider environment and aesthetics.  Consider safety and regulations.  Systematic Layout Planning Muther (1961) 0 Data gathering 1 Flow 2 Activities Analysis 3 Relationship 4 Space diagram 5 Space requirements available 6 Space relationship diagram Search 7 Reasons to 8 Restrictions modify 9 Layout alternatives Selection 10 Evaluation  Layout Types Product layout Process or Functional layout Project or Fixed-position layout Cellular Manufacturing Group Technology 6  Product Layout Facility organized around product Design minimizes line imbalance  Delay between work stations Types:Fabrication line; assembly line Examples  Autoassembly line  Paper manufacturing. 7  Product Type Layout Lathe Drill Grind Drill W A S a s r t s o Drill e Press Bend e h r a m o g b u se e l y Mill Drill Lathe Lathe Drill  Process Layout + Allows specialization - focus on one skill + Allows economies of scale - worker can watch several machines at once + Design places departments with large flows of material or people together + High level of product flexibility 9  Process Layout Milling Assembly Grinding & Test Drilling Plating Process Layout - work travels to dedicated process centers 10  Project or Fixed-Position Design is for stationary project Workers & equipment come to site Complicating factors  Limitedspace at site  Changing material needs Examples  Shipbuilding  Highway construction 11 Fixed-Position Layout 12  Fixed Position Layout Lathe Press Grind W S a t r o e r h a o g u e s e Weld Paint Assembly Layout Types: Manufacturing - 13  What Is Cellular Manufacturing?  Equipment and workstations arranged in a sequence that supports smooth material flow, with min. transport or delay  A Manufacturing Cell consists of people and machines or workstations required for performing the process steps  For example - if a process for a product requires cutting, followed by drilling and finishing, the cell would arrange equipment in that order  Helps companies achieve High-variety production  Cellular Manufacturing Defined “…The cells are arranged to easily facilitate all operations. Parts are handed off from operation to operation eliminating setups and unnecessary costs between operations.”  Cellular Layout (Work Cells) Every cell contains a group of machines brought together to make a product or machines are dedicated to the production of a family of parts. These layouts are also called as group technology layouts. Example: Assembly line set up to produce 3000 identical parts in a job shop 16  Cellular Manufacturing  Typical objectives of cellular manufacturing:  To shorten manufacturing lead times  To reduce WIP  To improve quality  To simplify production scheduling  To reduce setup times 17  Cellular Layouts Machines Enter Worker 2 Worker Worker 1 3 Exit Key: Product route Worker route  Group Technology/Cellular/Product Family Layout Lathe Drill Grind Assembly W S a t re o Mill Assembly Weld Paint h r o a u g se e Press Lathe Drill Press Assembly Grind Drill Assembly Drill Grind  Advantages of Cellular Layouts Reduced material handling and transit time Reduced setup time Reduced work-in-process inventory Better use of human resources Better scheduling, easier to control and automate  Disadvantages of Cellular Layouts Sometimes cells may not be formed because of inadequate part families. Some cells may have a high volume of production and others very low. This results in poorly balanced cells.  Disadvantages of Cellular Layouts When volume of production changes, number of workers are adjusted and workers are reassigned to various cells. To cope with this type of reassignments, workers must be multi- skilled and cross-trained. Sometimes, machines are duplicated in different cells. This increases capital investment. Group Technology (GT) Defined A manufacturing philosophy in which similar parts are identified and grouped together to take advantage of their similarities in design and production  Similarities among parts permit them to be classified into part families  In each part family, processing steps are similar  The improvement is typically achieved by organizing the production facilities into manufacturing cells that specialize in production of certain part families  Part Family A collection of parts that possess similarities in geometric shape and size, or in the processing steps used in their manufacture  Part families are a central feature of group technology 24 parts shown are different in size, shape, and material, but quite similar in terms of manufacturing All parts are machined from cylindrical stock by turning; some parts require drilling and/or milling Part Families Similar prismatic parts requiring similar milling operations Dissimilar parts requiring similar machining operations (hole drilling, surface milling Identical designed parts requiring completely different manufacturing processes  Ways to Identify Part Families 1. Visual inspection  Using best judgment to group parts into appropriate families, based on the parts or photos of the parts 2. Parts classification and coding  Identifying similarities and differences among parts and relating them by means of a coding scheme 3. Production flow analysis  Using information contained on route sheets to classify parts © 1- Visual Inspection Method  Basic Layout Types Product Volume vs. Product Variety High Product Planning Department Product Layout Medium Product Family Volume Planning Department Fixed Location Layout Process Layout Group Technology Layout Fixed Materials Process Planning Low Location Planning Department Department Low Medium High Variety Flexible Manufacturing System Highly automated GT manufacturing cell, consisting of a group of processing workstations, interconnected by an automated material handling and storage system, and controlled by a distributed computer system What does flexible mean? 1. Can identify and operate different part/product styles 2. Quick changeover of process/operating instructions 3. Quick changeover of physical setup FMS operations: 1. Processing operations 2. Assembly operations  Activity Relationship Chart  A graphical tool used to represent importance of locating pairs of operations near each other.  Letter codes used to describe importance are A- absolutely necessary E- especially important I - important O - ordinarily important U- unimportant X- undesirable Closeness Rating: multiple criteria 45  Legend 5 8 7 A Rating E Rating 10 9 6 I Rating O Rating 4 2 3 U Rating X Rating Fig 6 Activity relationship 1 diagram  Assembly Line Balancing General Procedure 1. Determine cycle time - The time between production of successive units. (May be measured in seconds, minutes, etc.) 2. Calculate the theoretical minimum number of workstations, denoted N. (May not be achievable.) 3. Assign tasks to workstations to “balance” the line. Compute the efficiency. 9-47  Assembly Line Balancing Equations Production time available Cycle time = Production rate Minimum  Task times number of = N = Rounded up work stations Cycle time  Task times Efficiency = (Actual number * (Cycle time) of work stations) 9-48  Assembly Line Balancing Heuristics  Most following tasks.  Choose task with largest number of following tasks.  Longest (or shortest) task time.  Choose task with longest (or shortest) operation time.  Ranked positional weight.  Choose task where the sum of the times for each following task is longest. 9-49 Figure 6.10 Precedence Diagram Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements 0.1 min. 1.0 min. A Simple Precedence a b Diagram c d e 0.7 min. 0.5 min. 0.2 min.  Line Balancing Immediate Task Time Predecessor A 0.2 min. - B 0.6 min. A,C Suppose we want to C 0.5 min. - produce 450 units/day D 0.3 min. - E 1.0 min. B,D and 8 hours are available F 0.2 min. D each day. G 0.9 min. E,F 3.7 min. cycle time  480 minu tes / day 1.0667 minu tes / unit 450 units / day N  3.7 minu tes  3.47... or 4 workstatio ns 1.0667 minu tes