Chapter 6 Process Selection and Facility Layout

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

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

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

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

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

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

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

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

Processing Industries (Continuous Flow) One primary input (gas, wheat, etc) is converted to multiple outputs Very high volumes of non-discrete goods Example: 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 High Low Market type Unique Custom Mass Volume Medium

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

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

Automation Automation: Machinery that has sensing and control devices that enables it to operate 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 Design Handling of Materials Storage and Retrieval of Information Control of Machine Tools

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

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

Storage and Retrieval of Information GT 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 NC Machine tools run by programs DNC Direct numerically controlled machine tools Several computerized, NC machine tools are linked by a hierarchy of computers

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

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

The Operating Capabilities of the Factory of the Future 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 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 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 Product layout Process layout Fixed Position layout Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow Process layout Layout that can handle varied processing requirements Fixed Position layout Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

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

Advantages of Product Layout 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 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 Cycle time 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 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 0.2 ----- B 0.3 C D 0.25 E 0.15 B,C F D,E Total 1.4

Assembly Line Balancing

Assembly Line Balancing CYCLE TIME .30 £ C £ 1.40 C = productive time/output rate C = (8hr x 60min) =.5 min 960 Number of work stations, N = total time/C N = 140 = 2.8 =3 .5

Solution to Assembly Line Balancing Problem Station Tasks Assigned Total Task Time Idle Time 1 A, B 0.5 0 2 C, D 0.45 0.05 3 E, F 0.45 0.05 TOTAL 1.4 0.1

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

Assembly Line Balancing Solution Line Efficiency = Total Work Content C x N Efficiency = 1.40 = .93 or 93% .5 x 3 Balance Delay = 1 – efficiency = 1-.93 = 7%

Example 2 0.2 0.2 0.3 a b e 0.8 0.6 c d f g h 1.0 0.4 0.3

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

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

Process Layout (functional) Assume we have the following departments: 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 Criteria Desirability ranking Volume of interaction Cost of interaction Distance Time Safety Facility Limitations

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

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

Functional Layout Gear cutting Mill Drill Lathes Grind Heat treat Assembly 111 333 222 444 1111 2222 3333 333333333 44444 333333 22222

Cellular Manufacturing Layout – Group Technology -1111 222222222 - 2222 Assembly 3333333333 - 3333 44444444444444 - 4444 Lathe Mill Drill Heat treat Gear cut Grind