Chapter 6 Process Selection and Facility Layout

Chapter 6 Process Selection and Facility Layout

Introduction n Process selection n n Deciding on the way production of goods or services will be organized Major implications n n Capacity planning Layout of facilities Equipment Design of work systems

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

Process Selection Batch n Variety n n Flexibility n n How much Job Shop What degree Volume n Repetitive Expected output Continuous

Types of Operations Project/ Job Shop Unit or Batch Mass/ Continuous Assembly INCREASED VOLUME

Process Design n n Project Processes (Fixed Position) Intermittent Flow Processes (Batch Shops) Continuous Flow Processes (Flow Shops) Processing Industries (Continuous)

Job Shop (Fixed Position) n n People and material move Have limited duration Small scale Examples n n Housing Ship building Dam Appliance Repair

Intermittent Flow Processes (Batch Shops) n n No pattern exists between process of different products Appropriate to service organizations Moderate volume Example: n n Machine Shops Auto Repair Shops Commercial Bakery Classroom Lecture

Continuous Flow Processes (Flow Shops) n n n Sequences are the same (Standard Routes) High volumes of standardized goods or services Examples: n n Assembly Lines Car Wash

Processing Industries (Continuous Flow) n n n One primary input (gas, wheat, etc) is converted to multiple outputs Very high volumes of non-discrete goods Example: n n n Petroleum Chemicals Food Industries

Process Characteristics Project Intermittent Continuous PRODUCT Order Type Single Unit Batch Continuous or large batch Flow of Product None Jumbled Sequence Product Variety Very High Low Market type Unique Custom Mass Volume Single Unit Medium High

Process Characteristics Project Intermittent Continuous CAPITAL Inventory Medium High Low Equipment General Purpose Special Purpose LABOR Skills Task Type High Low Non-routine Repetitive

Process Characteristics Project Intermittent Continuous CONTROL Production Difficult Easy Quality Difficult Easy Inventory Difficult Easy EQUIPMENT General Purpose Special Purpose

Automation n Automation: Machinery that has sensing and control devices that enables it to operate n n Fixed automation Programmable automation

Automation • Computer-aided design and manufacturing systems (CAD/CAM) • Numerically controlled (NC) machines • Robot • Manufacturing cell • Flexible manufacturing systems(FMS) • Computer-integrated manufacturing (CIM)

Functional Areas Being Linked to Manage the Flow of Information n n Design Handling of Materials Storage and Retrieval of Information Control of Machine Tools

Design n CAD n n n No longer limited to the top, side and front views Can observe the rotation of the part about any axis on the screen Generally, improves productivity in the drafting room by a factor of 3 or more At GM, the redesign of a single auto model requires 14 months instead of 24 months The time needed to design custom values reduced from six months to one

Handling of Materials n Data processing technology can be applied to the control of 3 general kids of machines in the factory: n n n Machines that store, retrieve, or transport materials Machines that process the materials Robots

Handling of Materials n Automatic storage and retrieval systems transfer pallets of material into or out of storage rack up to 100 feet high n Mini Loaders n n Hold drawers of small parts Automatic Warehouse n Automatic shuttle takes the place of the fork-lift truck and its human operations

Storage and Retrieval of Information n GT n n The formation of part families based on design or manufacturing similarities (or both) Classification of parts speed up the design of similar parts in the company Only 20% of the parts actually need new design. 40% could be built from an existing design and the other 40% could be created by modifying an existing design. Automatic guided vehicle

Control of Machine Tools n NC n n Machine tools run by programs DNC n n Direct numerically controlled machine tools Several computerized, NC machine tools are linked by a hierarchy of computers

Control of Machine Tools n n n FMS Flexible Manufacturing System It consists of an integrated collection of: n Automated Production Processes n n n NC Robots A material transport system n n An automated transfer line Robots

Control of Robots n n Main features: n n n A programmable machine capable of moving materials and performing repetitive tasks. They are flexible They eliminate the need for operators Applications n n Loading and unloading of machine tools Jobs that are dirty, hazardous, unpleasant, or monotonous

The Operating Capabilities of the Factory of the Future n n n Economic order quantity approaches 1 Variety has no cost penalty (economy of slope) Rapid response to changes in product design, market demand, and production mix Unmanned and continuous operation is standard Consistent high levels of quality and accuracy and repeatability introduce higher levels of certainty into the production planning and control activity

Facilities Layout n Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system

Importance of Layout Decisions n n n Requires substantial investments of money and effort Involves long-term commitments Has significant impact on cost and efficiency of short-term operations

Basic Layout Types n Product layout n n Process layout n n Layout that uses standardized processing operations to achieve smooth, rapid, highvolume flow Layout that can handle varied processing requirements Fixed Position layout n Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Product Layout Raw materials or customer Material and/or labor Station 1 Material and/or labor Station 2 Material and/or labor Station 3 Station 4 Finished item Material and/or labor Used for Repetitive or Continuous Processing

Advantages of Product Layout n n n n High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routing accounting and purchasing

Disadvantages of Product Layout n n n Creates dull, repetitive jobs Poorly skilled workers may not maintain equipment or quality of output Fairly inflexible to changes in volume Highly susceptible to shutdowns Needs preventive maintenance Individual incentive plans are impractical

Assembly Line Balancing n Cycle time n n The time required to produce one part is called the cycle time, or the maximum time allowed at any one work station Assembly Line Balancing n Given a cycle time, find the minimum number of work stations or minimize the cycle time for a given number of work stations

Assembly Line Balancing - Example Task Time (min) Immediate Predecessors A B 0. 2 0. 3 ----A C D E F 0. 25 0. 15 0. 3 A A B, C D, E Total 1. 4

Assembly Line Balancing

Assembly Line Balancing CYCLE TIME. 30 £ C £ 1. 40 C = productive time/output rate C = (8 hr x 60 min) =. 5 min 960 Number of work stations, N = total time/C N = 140 = 2. 8 =3. 5

Solution to Assembly Line Balancing Problem Station Time 1 2 3 Tasks Assigned Total Task Time Idle A, B C, D E, F TOTAL 0. 5 0. 45 1. 4 0 0. 05 0. 1

Line Balancing Rules Some Heuristic (intuitive) Rules: n Assign tasks in order of most following tasks. n n Count the number of tasks that follow Assign tasks in order of greatest positional weight. n Positional weight is the sum of each task’s time and the times of all following tasks.

Assembly Line Balancing Solution n Line Efficiency = Total Work Content Cx. N Efficiency = 1. 40 =. 93 or 93%. 5 x 3 Balance Delay = 1 – efficiency = 1 -. 93 = 7%

Example 2 0. 3 a b e 0. 8 0. 6 c d f g h 1. 0 0. 4 0. 3

Solution to Example 2 Station 1 a b Station 2 Station 3 e f c Station 4 d g h

A U-Shaped Production Line In 1 2 3 4 5 Workers 6 Out 10 9 8 7

Process Layout (functional) n Assume we have the following departments: n n n Accounting (A) Production Planning (P) Customer Service (C) Sales (S) What arrangement would be better?

Used for Intermittent processing Job Shop or Batch A P C S S C A P

Intermittent Process n Criteria n n n Desirability ranking Volume of interaction Cost of interaction n n Distance Time Safety Facility Limitations

Advantages of Process Layouts n n Can handle a variety of processing requirements Not particularly vulnerable to equipment failures Equipment used is less costly Possible to use individual incentive plans

Disadvantages of Process Layouts n n n n In-process inventory costs can be high Challenging routing and scheduling Equipment utilization rates are low Material handling slow and inefficient Complexities often reduce span of supervision Special attention for each product or customer Accounting and purchasing are more involved

Cellular Layouts n Cellular Production n n Layout in which machines are grouped into a cell that can process items that have similar processing requirements Group Technology n The grouping into part families of items with similar design or manufacturing characteristics

Process Layout - Example Milling Assembly & Test Grinding Drilling Plating Process Layout - work travels to dedicated process centers

Functional Layout 22 2 Grind 3333 Assembly 3 44 44 Heat treat 111 4 3 3 33 333 Lathes 33 11112222 3 33 111 333 Drill 22 Mill 222 33 3 444 222 111 444 33 222 Gear cutting 111 444

Cellular Manufacturing Layout – Group Technology Lathe Mill Drill 22222 Mill 33333 Lathe Mill 4444444 Drill Mill Heat treat Gear -1111 cut Heat treat Grind - 2222 Heat treat Grind - 3333 Drill Gear - 4444 cut Assembly -1111