Work measurement II

文章目錄

• 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 handright time

reach	reach

MTM Example- basic time calculation right hand

activitymtm symboltmu

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

$$Pr(<p<)=1?\alpha$$

$$\alpha =0.05$$

Standard normal table

• single tail

Z score: How to use the standard normal table

• step 1

• $$[(1?0.95)/2=0.025]$$

• step 2

• $$1?0.025=0.975$$

• 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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