Work Flow and Batch Processing
Chapter 3
Sections:
1. Sequential Operations and Work Flow
2. Batch Processing
3. Defects in Sequential Operations and
Batch Processing
4. Work Cells
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
Sequential Operations in Industry

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




Manufacturing
Assembly
Construction
Mortgage applications
Medical services
Education
Transportation
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 multistation 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 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
From-To Chart
To operation j
1
From operation i
1
2
-
40
3
-
30
3
10
-
5
5
15
2
4
4
20
25
50
-
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
Economic Order Quantity Model
Inventory level over time in a typical make-tostock situation
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
Economic Order Quantity Model
Total annual inventory cost TIC
ChQ Csu Da
TIC =
+
2
Q
where Ch = inventory carrying cost, Q = batch
quantity, Csu = setup or ordering cost, and Da =
annual demand
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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
Q = EOQ =
2 Da C su
Ch
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 = Qo(1 – q)
where Q = quantity produced, pc; Qo = original
starting quantity, pc; q = fraction defect rate
D = Q oq
where D = number of defects
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
Defects in Unit Operations
Processing of Qo 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 0-13-140650-7.
©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
Qf = Qo(1 – q1)(1 – q2) . . (1 – qn)
where Qf = final quantity at the conclusion of
the sequence
 Defects Df = Qo – Qf
Q
f
 Yield for the sequence Y = Q
o
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 timeconsuming changeovers between part types
 Avoids disadvantages of batch processing
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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 0-13-140650-7.
©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
Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover, ISBN 0-13-140650-7.
©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.