Work measurement II

文章目录

  • Work measurement II
    • Outline
    • learned so far
    • How work measurement techniques correspond to different levels in the general hierarchy
    • Questions
    • Basic motion elements
    • Micromotion analysis
    • Example: picking up pegs and inserting them holes (board)
    • eg continued
    • Predetermined motion time system (database)
    • PMTS Procedure: applied to a task
    • Methods-Time Measuremnt
    • MTM-1
    • MTM-1 Time to reach (R)
    • MTM-1 Time to grasp (G)
    • MTM-1 Time to move (M)
    • P
    • Release,
    • Time to apply pressure, eye travel, and eye focus
    • Other motion time measurement systems
    • Example: motion time measurment MTM
    • Micro motion analysis
    • MTM Example- basic time calculation right hand
    • TMU Calculaor
    • Other MTM Systems
    • Advantages of Predeternmined time standards
    • SDS Database (used for highly revenue, repetitive, and it is worthwhile to build a good characterization of the system)
    • When a starndard data system
    • Standard data systems and predtermined motion time systems
      • PMTS
      • SDS
    • Advantages and disadvantages
    • Work sampling
    • Work sampling defined
    • When work sampling appropriate?
    • Typical work sampling applications
    • Steps in a work sampling study
    • Determine the required accuracy and required confidence limits
    • Example: How work sampling works
    • How accurate is this?
    • Statistical absis of work sampling
    • statical baiss of work sampling
    • Confidence interval
    • Standard normal table
    • Z score: How to use the standard normal table
    • Confidence interval
    • Number of observation required
    • Advantages of work sampling
    • disadvantages and limitations
    • Summary
    • Outline of 3P5

Outline

  • Pre determined motion time
  • Standard data system

learned so far

  • work study

    • method study

      • methods analysis

        • observation
        • charting
        • Questioning
      • method design
        • motion economy
        • ergonomics
        • Lean
    • work measurement
      • time study
      • pmts
        • Pre determined motion time
      • standard data system
      • work sampling

How work measurement techniques correspond to different levels in the general hierarchy

  • job level

    • performance app
  • task level
  • work element level
  • basic motion element level

Questions

  • how can we develop a time standard without doing doing a direct time study?

    • direct time study cons

      • expensive
      • not adaptive to changes
      • not accurate
  • how can we estimate the time spent by workers/ machines on different tasks?

Basic motion elements

  • 17 Therbligs

    • Physical basic motion elements

      • effective

        • transport empty
        • grasp
        • transport loaded
        • release load
        • use
        • assemble
        • Disassemble
      • in effective
        • hold
        • Preposition
    • physical and mental absic motion elements
      • effective
      • ineffective
        • position
        • search
        • Select
    • mental basic element
      • effective

        • Inspect
      • ineffective
        • Plan
    • delay elements
      • effective

        • Rest
      • Ineffective
        • unavoidable delays
        • avoidable delay

Micromotion analysis

  • apply to any task
  • analysis of therbligs that make up a repetitive task
  • objectives
    • eliminate ineffective therbligs if possible
    • avoid holding objects with hand
      • use work holder
    • Combine therbligs
      • perform high-hand and left-hand motions simultaneously
    • simply

Example: picking up pegs and inserting them holes (board)

  • left
  • time right
  • cumulative time

eg continued

  • sequence
  • Left hand
  • therbligs
  • right hand
  • cumulative time

Predetermined motion time system (database)

  • a database
  • motion elements
  • basic normal time values
  • procedures
  • analyse manual tasks
  • establish standard times for the tasks

PMTS Procedure: applied to a task

  • synthesize

    • described in terms of basic motion elements
  • retrieve
    • sum the element times to determine the task basic time
  • evaluate
    • eliminate motions
    • reduce distances
    • introduce specifal tools
  • applu allowances

Methods-Time Measuremnt

  • procedure
  • analyze any manual operation
  • basic motions
  • assigns to each motion a
  • predetermined time standard
  • determined by the nature of the motion
  • Time Units
    • TMUS
  • 1 TMUs
    • 0.00001 hr
    • 0.0006 min
    • 0.036 s
  • 1 sec
    • 27.8 TMU
  • TMU.ORG

MTM-1

  • reach
  • grasp
  • move
  • position
  • release
  • disengage

MTM-1 Time to reach ®

  • Distance

    • cm
    • Inches
  • tie in TMU
    • a
    • b
    • c or d
    • e
  • Hand in motion
    • a
    • b
  • case and description
    • A reach Objects in other hand
    • b vary from cycle
    • c jumped
    • d
    • e

MTM-1 Time to grasp (G)

  • type of grasp

    • pickup
    • regrasp
    • transfer
    • select
    • Contact
  • case
    • 1a
    • 1b
    • 1c1
    • 1c2
    • 1c3
  • time, tu
    • 2.0
    • 3.5
    • 7.3
    • 8.7
    • 10.8
  • description and object dimensions

MTM-1 Time to move (M)

  • distance
  • time in tmu

P

  • clas
  • Description of fit
  • symmetry
  • ease to handle
  • difficult to handle

Release,

Time to apply pressure, eye travel, and eye focus

Other motion time measurement systems

Example: motion time measurment MTM

  • sharpening a penciule
  • start and finish with the pencil
  • sharpener
  • lying on the table
  • five turns of 120 degrees are used while sharpening

Micro motion analysis

left hand right time
reach reach

MTM Example- basic time calculation right hand

activity mtm symbol tmu
Reach r12b 12.9
Grasp G1B

TMU Calculaor

Other MTM Systems

  • Get
  • Put

Advantages of Predeternmined time standards

  • produce a more detailed descripton of the work than other method
  • can be readily compared using time as a criterion
  • before producton operations start!!!
    • the most important thing for us to evaluate the
  • do not require the assessment of rate of working
  • stop watch
  • objective and consistent
    • in different countries
    • can be put in the other places in branches
    • how objective can they be?
      • Where did they get
      • they have been tested in the worldwide
      • Observe and get their

SDS Database (used for highly revenue, repetitive, and it is worthwhile to build a good characterization of the system)

  • various format be used for SDS

    • Charts
    • tables
    • mathematical formulas
    • worksheets
    • computerized database and retrieval system
  • Under certain conditions work avriables

When a starndard data system

  • similiarity in tasks

    • many similar tasks
  • large number of standards to be set
    • more productive than direct time study
  • need to set standards before production
    • direct time study requires obserbayion of actual task to set standard, SDS does not

Standard data systems and predtermined motion time systems

PMTS

  • Predetermined motion time system
  • normal time
  • standard time

SDS

  • predetermiend motion time system
  • standard data system
  • normal time
  • standard time

Advantages and disadvantages

  • PMTS

    • increased productivity
    • build up the capability
    • consistency in the standard

Work sampling

  • Categories and subjects

  • ? when to use

Work sampling defined

  • statical techniques

When work sampling appropriate?

  • multiple subjects

    • study activities of multiple subjects (workers and machines)
    • rather than one
  • long cycle times
    • for the jobs covered by the study
  • sufficient time is available to perform the study
    • several weeks usually required for a work sampling study
  • non repetive work cycles
    • jobs consist of various tasks rather than a signle repetitive task

Typical work sampling applications

  • machine utilization

    • time spent by machines in various categories of activities
  • worker utilization
    • how workers spend their time
  • alowances for time standards
    • assessment of delay components in allowance
  • average unit time
    • determining the average time on each work unit
  • time standards
    • limited statistical accuracy when stadards set by work sampling
    • useful to set proportions, but not to set standards

Steps in a work sampling study

  • define the problem

    • deinition of subjects, activity categories

  • Determine the required accuracy and required confidence limits

  • make a prelimary estimate of the occurrence of the desired activity
  • design the main study
    • find number of obserbations required
    • design sampling plan
  • carry out study according to above plan
    • summarising the data at the end of each shift

Example: How work sampling works

  • a total 500 obserbations
  • one week period (40 hours)
  • 10 machine
  • categories
    • being set up
    • running production
    • machine idle
  • No of obserbations
    • 75
    • 300
    • 125
  • How many hours per week did an average machine spend in each category?

How accurate is this?

  • activity sampling is essentially drawing a sample

Statistical absis of work sampling

  • bionomial distributions, in which parameter
  • multiple activity categories, so we have p1,p2… pk proportiytion for K different activity actegories
  • for computional convenience, the binomial distribution is often approximated by the normal distribution
  • n= number of observations is greater than 30

statical baiss of work sampling

  • p = prportion of the total number of observations
  • p is our estimate of the true value of the population porportion p
  • confidence interval for the

Confidence interval

  • probability of p lies between Pr ()=1-a

Pr(<p<)=1−αPr(<p<)=1-\alpha Pr(<p<)=1−α

α=0.05\alpha=0.05 α=0.05

Standard normal table

  • single tail

Z score: How to use the standard normal table

  • step 1

  • [(1−0.95)/2=0.025][(1-0.95)/2=0.025] [(1−0.95)/2=0.025]

  • step 2

  • 1−0.025=0.9751-0.025=0.975 1−0.025=0.975

  • look at the table

Confidence interval

  • calculate he 95% confidence interval for the proportion of running time for the machines in the previous examples

Number of observation required

  • decide two parametors

Advantages of work sampling

  • measure activities
  • multiple subjects
  • less time and lower cost
  • less training requirement than DTS or PMTS
  • Less tiresome and tedious and observer than continuous observation
  • being a subject in work sampking is less demanding

disadvantages and limitations

  • not as accurate for setting time standards as others
  • not practical to study a single subject
  • provides less detailed information about work elements
  • Individual differences will be missed
  • workers may be suspicious because they might not understand the statistical basis of working sampling
  • behavior of subjects may be influenced by the act of observing them

Summary

  • pretermined motion time systems
  • standard datasystems
  • work sampling is used

Outline of 3P5

  • factory layout and planning

    • what is the best layout for the purposes for the activities
    • bash
    • continuous processes
    • line processes
    • when and in which situations should
  • 1-7 can be done so far

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