Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Flow and Batch Processing Sections: 1.Sequential Operations and Work Flow 2.Batch Processing 3.Defects in Sequential Operations and Batch Processing 4.Work Cells Chapter 3

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Some Definitions  Sequential operations – series of separate processing steps that are performed on each work unit  Work flow – physical movement of work units through the sequence of unit operations  Batch processing – processing of work units in finite quantities or amounts

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Sequential Operations in Industry  Manufacturing  Assembly  Construction  Mortgage applications  Medical services  Education  Transportation

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Flow Patterns  Pure sequential – all work units follow the same exact sequence of operations and workstations  Work flow is identical for all work units  Mixed sequential – different work units are processed through different operations  Different work flows for different types of work units

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Flow Patterns Network diagrams representing (a) pure sequential work flow and (b) mixed sequential work flow

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Moves in Sequential Work Flow  In-sequence move – forward transport to operation immediately downstream  Bypassing move – forward transport to an operation beyond the neighboring station  Backflow – transport in a backward direction  Repeat operation – operation is repeated at the same workstation

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Four Types of Work Movement

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. From-To Chart  Indicates any of several possible quantitative relationships among operations in a multi- station work system  Possible variables in a from-to chart:  Quantities moving between operations  Flow rates of materials  Distances between work stations

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. From-To Chart

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Network Diagram Network diagram showing same data as in previous From-To Chart

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Bottlenecks in Sequential Operations  Bottleneck = slowest operation in the sequence  The bottleneck operation limits the production rate for the entire sequence  Terminology:  Blocking – production rate(s) of one or more upstream operations are limited by the rate of a downstream operation  Starving - production rate(s) of one or more downstream operations are limited by the rate of a upstream operation

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Batch Processing  Batch processing - processing of work units in finite quantities or amounts  Work units can be materials, products, information, or people  Batch processing is common in production, logistics, and service operations

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Examples of Batch Processing Batch production in manufacturing Passenger air travel Cargo transport Book publishing Entertainment Payroll checks Class action lawsuits Laundry Grading of student papers

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Types of Batch Processing  Sequential batch processing – members of the batch are processed one after the other  Simultaneous batch processing – members of the batch are all processed at the same time

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Examples of Batch Processing Sequential Production machining Batch assembly Book printing Payroll checks Grading of student papers Simultaneous Chemical batch processes Heat treating of multiple parts Passenger air travel Cargo transport Laundry

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Batch Production Alternating cycles of setup and production run experienced by a work system engaged in batch production

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Why Batch Processing is Important  Work unit differences – different types of work units must be processed separately  Learning curve effect – cycle time per work unit decreases as batch quantity Q increases (apples only to sequential batch production)  Equipment limitations – limits on the quantities that can be processed  Material limitations – the material must be processed as a unit (e.g., processing of integrated circuits on a silicon wafer)

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Disadvantages of Batch Processing  Changeovers between batches represent lost productive time  Setup changeovers in batch production  Airplanes at a terminal unloading and loading passengers  Work-in-process – multiple batches competing for the same equipment  Queues of work units form in front of each workstation, resulting in large inventories of partially processed units

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Economic Order Quantity Model Inventory level over time in a typical make-to- stock situation

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Economic Order Quantity Model Total annual inventory cost TIC where C h = inventory carrying cost, Q = batch quantity, C su = setup or ordering cost, and D a = annual demand

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Economic Order Quantity Model  From the total inventory cost equation can be derived the batch size that minimizes the sum of inventory carrying costs and setup costs

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Defects in Unit Operations  Input/output relationship for a unit operation in batch processing Q = Q o (1 – q) where Q = quantity produced, pc; Q o = original starting quantity, pc; q = fraction defect rate D = Q o q where D = number of defects

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Defects in Unit Operations Processing of Q o starting units to yield Q good products and D defects

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Defects in Sequential Operations and Batch Processing  Input/output relationship in a sequence of n unit operations Q f = Q o (1 – q 1 )(1 – q 2 ).. (1 – q n ) where Q f = final quantity at the conclusion of the sequence  Defects D f = Q o – Q f  Yield for the sequence Y =

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Sequential Operations Compounding effect of fraction defect rate at each unit operation in a sequence of operations

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Cells Work cell - a group of workstations dedicated to the processing of a range of work units within a given type  Part family – the range of work units that are processed  Members of the part family are similar but not identical  Mixed sequential work flow system  Work cells and part families are associated with group technology

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Group Technology An approach to manufacturing in which similar parts are identified and grouped together to take advantage of their similarities in design and production  Work units are processed individually and continuously, without the need for time- consuming changeovers between part types  Avoids disadvantages of batch processing

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Cell Layouts  In-line – straight line flow of work units  U-shaped – shape of work flow is “U”  Similar to in-line except for shape  Better communication among workers  Loop – continuous flow of work units around a loop layout  Rectangular - similar to loop layout

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. In-Line Work Cell

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. U-Shaped with Manual Handling

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. U-Shaped with Mechanized Handling

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Cell with Loop Layout

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Work Cell with Rectangular Layout

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Worker Teams  Group of workers who work as a team to achieve common objectives:  Meet the production or service schedule  Achieve high quality in the goods and services provided by the cell  Make the operation of the cell as efficient as possible

Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN ©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Success Factors for Worker Teams  Teamwork – the collective skills and efforts of the team members exceed the sum of their individual skills and efforts  Cross-training – workers become trained in more than one job in the cell  Allows for job rotations to increase work variety and job satisfaction  Mitigate problems of absences