Work Meas Overview

WORK MEASUREMENT Overview Rodger Koppa, P.E., Ph.D. Industrial and Systems Engineering

Uses of Work Measurement Compare efficiency of alternative methods Balance work among team members Optimize number of machines per operator (e.g., in a work cell) Establish basis for

1.

2. 3.

4. • • • •

Production planning and control Layout Process planning JIT

More Uses 1. 2.

3.

Pricing estimation Standards for labor performance and machine use for 1-5 and for incentives Information for labor cost control – enable standard costs to be fixed and maintained

Basic Six Pack   



 

SELECT what to study RECORD that activity or operation EXAMINE the recorded data and modify procedures/task allocation/layout using Work Study to get the best method MEASURE quantity of work with respect to time with the best method or ESTIMATE using predetermined time data COMPILE a standard time for activity, including allowances DEFINE activity and standard time

Work Measurement Techniques 1. 2. 3. 4.

Work Sampling Structured Estimation Time Study Predetermined Motion Time Standards (PMTS) 5. Standard Data Systems (SDS)

Technique 1: Work Sampling

Definition—Work Sampling 



Work sampling is a method of finding the percentage occurrence of a given activity by statistical sampling and random observations Also known as:     

Activity sampling Ratio-delay study Random observation Snap-reading method Observation ratio study

When to Use Work Sampling  

 

Lots of time available (weeks) More than one worker and/or machine Long cycle times Non-repetitive work cycles (but must be distinct number of categories)

Setting How Often 





How much confidence you need determines how many times you must observe and go through the six-pack Sometimes the target operation will be going on, sometimes not Spend a period of hours or visit 5 times or more to estimate % time activity happens

For Each Observation  

Record what is happening to level of detail required: Machine working?   



Cutting Boring Grinding

Machine Idle?   

Maintenance Waiting for materials Worker in restroom

Work Sampling: So What? 

 





Simple technique usable in plants, service operations, offices Low cost Avoids controversial aspects of time study Management gets good idea of where inefficiencies may lie Can trigger method studies, travel studies

Work Measurement Techniques o o o o

Work Sampling Structured Estimation Time Study Predetermined Motion Time Standards (PMTS) o Standard Data Systems (SDS)

Str uctur ed Est imati on  Most widely used and oldest approach  Based on past experience with same/similar operations  Very cheap to apply, but you get what you pay for  Much used for jobs/operations not yet implemented

An al ytical A ppr oac h t o Str uctur ed Est imati on  Estimator should have experience in type of job being considered and in work study techniques (tall order)  Alternatively the estimator derives times/rates of production from experienced workers by debriefing

An al ytical A ppr oac h  Break job into elements than can estimated for time  Apply available estimates (experience, Dodge Manual, other labor statistics)  Time similar task elements or use mockup/simulated workplaces  SWAG

Work Measurement Techniques o o o o

Work Sampling Structured Estimation Time Study Predetermined Motion Time Standards (PMTS) o Standard Data Systems (SDS)

What is a “Time Study?” “Time study is a work measurement technique for recording the times of performing a certain specific job or its elements carried out under specified conditions, and for analyzing the data so as to obtain the time necessary for an operator to carry it out at a defined rate of performance” Introduction to Work Study 4th Ed G. Kanawaty (Ed.) International Labor Office, Geneva Switzerland 1992

Basic Time Study Approach  Except for a Q&D study, don’t bother with a stop

watch  

Heisenberg principle Requires practice and multiple runs

 Acquire and use a video camera  Digital video camera best and getting cheaper every year  Many digital (still) cameras have “movie” mode that suffices for short cycles (5 min or less)  “Movie Maker” software to analyze

When to Do a Time Study  Don’t bother with time study until Method

Study is done and as much inefficiency is wrung out as possible  Must optimize method before setting a standard!  Aim for what a “qualified” worker can do without “undue” fatigue (engineering judgment)

Caution  Don’t try to do covert observations either with

stopwatch or with camera  Invasion of personal privacy  May or may not meet criterion of “motivated” worker  Duck image of “efficiency expert”

8 Basic Steps Identify background, operator, environmental factors that pertain to work 2. Do a Task Description down to “element” level of detail 3. Do a Methods Study and optimize the task 4. Time each task element from video data or by direct observation with a stopwatch 1.

8 Basic Steps (Cont’d) n n n n

Assess observed pace vs expected pace (IF past experience/standard times exist) Extend observed times to Basic Times Determine Allowances Establish Standard Times

4. Perform Time Study How many repetitions to time or video? 2 Approaches: 3. Statistical estimation of sample size 4. Industrial practice (preferred) Industrial Practice (source: General Electric)  The shorter the cycle time, the larger the sample size (Number of reps)  Vary from 0.10 min = 200 reps to 40 or more min = 3 reps

Timing Each Element  Video Recording:  Record as many cycle reps as needed for sample  Use time scale in software  Stopwatch (ugh):  Cumulative timing: note start time of cycle and then note time at end of each element  Flyback timing: watch reset (but not stopped) at end of each element and time noted  Digital watch MUCH easier than analog  Will have to go through cycle as many times as needed for sample size and repeat for each concurrent element

Time Study Rating  Very subjective and full of pitfalls  Helps if observation is as unobtrusive as

possible without being covert  Helps if enough reps done so worker forgets you are observing him AND if the worker is “qualified”

Rating Actual Performance  100 scale actually 10 scale  Ordinal scale of measurement  Rater must be experienced and very familiar

with operation

Intervening Variables  Variation in quality of materials or

subassemblies  Changes in efficiency of tools and machines  Method changes  Worker attention and motivation  Working environment  Speed/accuracy tradeoff

0 – 100 Rating Rating Performance Walking 50 Very slow, clumsy 2 mph fumbling, unmotivated 75 Steady, deliberate, unhurried 100 Brisk, businesslike piece work pace 125 Very fast, assured, dexterous coordinated 150 Exceptionally fast, intense concentration, hard to keep up pace

3 4 5 6

Deriving Standard Times for Elements  Convert observed times to Basic Times

BT = Observed Time x Observed Rating Standard Rating (100)  Derive “representative” BT

Mean (but consider outliers)  Median or mode 

Variable Elements  Compute SD as well as Mean  Continue to observe until SD stabilizes  Use mean as best estimate of time

Work Measurement Techniques o o o o

Work Sampling Structured Estimation Time Study Predetermined Motion Time Standards (PMTS) o Standard Data Systems (SDS)

Predetermined Motion Time Standards “ An organized body of information, procedures, techniques, and motion times employed in the study and evaluation of manual work elements. The system is expressed in terms of the motions used, their general and specific nature, the conditions under which they occur, and their previously determined performance times” --ANSI Standard Z94.11- 1989

Basic PMTS Approach 1. 2. 3.

4. 5.

Do task description in terms of basic motions in a defined workspace just as in Time Study Perform work studies to improve task (unless task is in planning stage) Retrieve from data base the basic times associated with each motion as modified by task conditions and work variables Sum all of these times to form the basic time for the task (ratings automatically included) Apply allowances (to be discussed) to arrive at standard time for the task

PMTS Levels Level 1: Very elemental motions like Therbligs, suitable for short cycles Level 2: Some motions combined, e.g., reach and grasp become get Level 3: May only be 3 or 4 elements, e.g., handle, transport, step/foot motions, bend/rise

A Few PMTS Variants     



Work-Factor (1930’s) WF Methods-Time Measurement (MTM-1, MTM-2, MTM-3, others) Basic Motion Time Study (BMTS) based on MTM-1 and Therbligs Master Standard Data (MSD) based on MTM-1 Maynard Operation Sequence Technique (MOST) emphasizes production and material handling at Level 1 and 2 Modular Arrangement of Predetermined Time Standards (MODAPTS) based on MTM’s and MSD; finger motion is basic element

Basic MTM Postulates:  A given motion has a fundamental time to accomplish that motion  Each motion is independent of any other with respect to time  Simple chaining can provide a consistent and accurate prediction of the basic time of a given operation

Time Units Vary from system to system  Most common: Time Measurement Unit (tmu) = 0.00001 hour 0.0006 min 0.036 sec 

MTM-2 Most widely used MTM Technique  15 basic motions  Modify times by distance moved and weight  Not as complicated as it looks but requires practice 

Motions in MTM-2 Refer to handout, MTM-2 Basics GET– reach, grab, release GA –No grasp needed GB – grasp, close hand GC – thumb, finger only GW – grasp and move mass

Motions in MTM-2 PUT – Move object from a to b PA – ballistic motion PB – Controlled motion PC – Complex motion, obvious correcting PW –Moving significant mass

Motions in MTM-2 REGRASP (P) –change mode of grasp APPLY PRESSURE (A) –Isometric application of force EYE ACTION (E) – Examine object, search FOOT MOTION (F) – Shift foot position less than 30 cm STEP (S) –Displace trunk, leg motion more than 30 cm BEND & ARISE (B) – Lowering trunk, reach at/below knees, return CRANK (C) – Circular motion of handle

MTM -3 Bare-bones “quick and dirty” analysis  Only 4 work elements: 

 Handle

(HA and HB)  Transport (TA and TB)  Step and foot motions (SF)  Bend and rise (B) 

A and B for H and T refer to “light” and “heavy” loads

MOST Maynard Operation Sequence Technique  Basic MOST 

 Motion

aggregates concerned with material handling and moving objects General move-object is freely moved through space  Controlled move-object is slid or manipulated  Tool use-hand tool operations 

Basic MOST General Move  A – Action Distance: hand translation loaded or unloaded, feet translation  B –Body motion sit/stand  G –Gain control (same as grasp)  P –Placement: position, orient, lay aside object

Basic MOST Controlled Move Object being moved is constrained (e.g., a contrtol lever)  A, B, G as in General Move  M –Move, controlled: object is moved over a certain path  X –Process time associated with machine  I –Align: motions at end of movement to ready object for next operation

Basic MOST Tool Use  A,B,G,P as in General and Controlled Move  Additional subtype is the specific use of the tool:  Fasten,

Loosen

 Cut  Surface

treat  Measure  Record  Think

Other MOSTs MaxiMOST – for long, complex cycles, e.g., heavy assembly, machine setup  MiniMOST – Very short cycle, highly repetitive work (1.6 min or less)  Clerical MOST – For office operations 

MOST for Windows  

Basic, Maxi, or MiniMOST 2 Modules:  Quick

MOST – Select work methods given application, canned procedures and times edited by user as needed. Similar to using standard data systems  Direct MOST – User provides data on industry and work situation, program generates possible work method. Method refined by user (intelligent system)

Work Measurement Techniques o o o o

Work Sampling Structured Estimation Time Study Predetermined Motion Time Standards (PMTS) o Standard Data Systems (SDS)

Standard Data Systems  Industry

or company specific data base  Common elements from different tasks are grouped and summarized  Industry sources may have data that can be applied to make a good-enough estimate of cycle/operation times  MOST for Windows is such a data base  Semi-quantified experience

Data Base Development   

Decide what to cover, what to omit (otherwise data base will be too large) Break jobs into elements that are common enough to group together Derive times from standard data handbooks, previous time or PMTS studies on similar operations, or very limited observations (video tape if possible) of representative elements in each group  

May need to use mockups or “air guitar” to get a feel for the times Estimates from workers familiar with the tasks can be very helpful, but NOT sufficient

Elements to Include  Setup

and Production  Constant and variable  Worker-paced and machine-paced  Regular and irregular

From Basic Time to Standard Time • Once you have basic times from any

of the 5 approaches for each element of interest you’re not finished yet! • To derive a standard time for planning, costing, and payroll, allowances must be made • Then basic time is adjusted by allowances to arrive at standard time

Allowances Individual (e.g., disabilities) 2. Work Factors 3. Environmental Factors Cycle time is adjusted (longer) by allowances to obtain Standard Time for cycle or activity Rest periods may also be built into a shift or the time prorated over cycles as allowances 1.

PFD Allowance Personal, fatigue, and delay allowance  Personal: 5% or more if stressful environment  Fatigue: 5% up to 20% or more for heavy labor (negotiated or use formulas)  Delay: (unintentional, caused by breakdown or inefficiencies) depends on company experience 

Other Allowances Contingency: Unscheduled maintenance, breakdowns, out of tolerance products, should NOT exceed 5%  Policy: machine part of cycle, training, OJT  Special: Industry specific such as exposure to toxic materials, radioactivity 

Machine Allowance 



A “Policy allowance” negotiated between Tstd = Tnt (1 + Apfd ) + Tm (1 + Am ) management and labor Where T = worker time during cycle Pertains to wage T = machine time during cycle A = PFD allowance incentive program A = Machine allowance Machine time (automatic) “significant” part of cycle time nt

m

pfd



m

Allowance Example Assembly of a framus  Cycle basic time is 10 min  PFD allowance is 10% (no definite breaks, worker is free to go to restroom, water cooler)  Contingency allowance is 10% (junky equipment up the line)  Machine allowance is 0 (hand and pneumatic tools only in this operation)  Training allowance is 5% (high turnover) Standard time = 10 x 1.25 = 12.5 min

Resources Beside the WEB, consider these publications: 1. Groover, M.P. Work Systems and the Methods, Measurement, and Management of Work Pearson Prentice Hall, 2007 2. Kanawaty, G. (Ed) Introduction to Work Study (4th Ed) International Labour Office, Geneva, Switzerland, 1992 3. Mundell, M.E. and Danner, D.L. Motion and Time Study: Improving Productivity (7th Ed) Prentice Hall 1994