Multiple Activity Study

MULTIPLE ACTIVITY and MATERIAL HANDLING STUDIES Rodger Koppa, P.E., Ph.D. Industrial and Systems Engineering

Multiple Activity Study

Definition Multiple Activity Study is the creation of a description that brings together the contributions of more than one operator and/or equipment to complete a task, often linked by a common timeline.

Multiple Activity Chart A chart on which the activities of more than one subject (worker, machine, or item of equipment) are each recorded on a common time scale to show their interrelationship. Introduction to Work Study (4th Ed) G. Kanawaty (Ed) International Labour Office, Geneva, Switzerland 1992

Comments on Multiple Activity Charting  Can have both workers and equipment on same timeline  Use shading or crosshatching to discriminate “productive” from “unproductive” time  Times are observed from video recordings, actual observation (time each component separately during cycle)  SWAG for preliminary analysis

Task Description vs Task Analysis  Task description is systematic identification or recording of operations (including times) at a level adequate for purpose at hand  Task Analysis fulfills the purpose of:     

Job description Task improvement Workplace layout Training Standards for cost and/or wage setting

Microtask Description  Two-handed Process Chart  Activities of worker’s hands or limbs recorded in their relationship to each other  Use same symbols as in macro charts:  Operation

O

 Temporary Storage

D

 Transport

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 Hold (“storage”)

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Example of Microtask Description

Comments on 2-handed Process Charts Leave space for sketch/photo of layout Chart one hand at a time Video recording almost a must unless you can have worker repeat many times Record actions on same line only when the occur at same time

Operational Sequence Diagraming • Multiple workers and/or equipment • Uses standard process chart symbols • Can be written along vertical timeline (sequence and approximate time period)

Pictorial Variant • Operational Sequence Diagrams may use pictorial elements • Purpose may be to present ideas to higher management not familiar with process chart conventions • Works well for tasks that cover a lot of territory with multiple people and equipment

Material Handling (Travel) Studies

Worker/Material Handling 

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Movement of workers and/or materials around the work area Two approaches  

String Diagram Travel Chart

String Diagram  

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Scaled layout of work area Each worker or piece of material gets its own diagram or color thread (3 or less) Pins and threads (or computer analog) Multiple cycles or other specified period of operation Each translation from one station to

Example of String Diagram Study

Comments on String Diagrams  

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Compelling graphic Complicated operations can make the diagram a rat’s nest Time-consuming to construct Use Travel Charting when many movements and complex paths are encountered

Travel Charting  A tabular record for presenting quantitative data about movement of workers, material, and equipment between stations over a given period of time  Matrix is always square, FROM along top and TO along side  Each column and row is assigned to a station – 6 stations would require 6 x 6 matrix  Accompanied by layout sketch showing spatial relationship of stations

Travel Chart Procedure  Use data sheet to record movements  Square for each from-to movement  Tallies for each time that movement happens

 Fill in chart with √ or just l for each movement  Get marginal totals  Compare FROM and TO marginal totals

Travel Chart Analysis  Rank order stations from busiest to least busy  High-ranked stations should be close to each other to minimize travel times  On example, 2,5,9 highest frequency FROM or TO  Busiest route 5-2-9  cell frequencies (5-2) = 5; (2-9)=6

Weighted Travel Chart  

Same concept as plain travel chart Translations weighted by  

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weight or volume carried (quantity) Total recorded in cells of chart

Rank order by marginal quantity High loads between stations mean short distances, conveyor belts, crane, etc.

Resources Resources for this lecture include: Kanawaty, G. (Ed) Inroduction to Work Study (4th Ed.) Geneva: International Labour Office 1992 Groover, M.P. Work Systems and the Methods, measurement, and Management of Work PearsonPrentice Hall 2007