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Time Study

Time Study. Procedure for the determination of time required to perform a task involving either human or machine under certain standard conditions of measurement. Direct time study Predetermined time system Standard time data Work sampling. Techniques. Predetermined Time System.

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Time Study

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  1. Time Study Procedure for the determination of time required to perform a task involving either human or machine under certain standard conditions of measurement • Direct time study • Predetermined time system • Standard time data • Work sampling Techniques

  2. Predetermined Time System • Systematic procedure that divides an operation into motions or work elements, with a set of time data assigned to each elements • Allowance excluded • Various available systems, for examples • Work - Factor System • Method - Time Measurement (MTM)

  3. Work - Factor System • Developed from 4-year implementation of Micromotion study • Employed in 1938 • Four techniques: • Detailed • Ready • Brief • Mento-Factor

  4. What Factors? Time Unit: 1/10,000 min • Body Members Finger, Hand, Arm, Body, Leg , Foot, etc. • Distance by Inch • Weight & Resistance • Manual Control Basic, Definite stop, Directional control, Care, Change of direction

  5. T, FT, L, HT F, H, A, FS 0 = Basic 1, D = Definite stop 2, S = Directional control 3, P = Care 4, U = Change of direction การวิเคราะห์งาน และบันทึกเวลาด้วย Work Factor • Body Members • Distance by Inch • Weight & Resistance • Manual Control

  6. Examples A10 Description of job: ….. Time Required: …... A30WS Description of job: ….. Time Required: …..

  7. Method -Time Measurement • More Focus on Basic elements • First developed for Drill Press Work • Time Unit: 1/ 100,000 hr (TMU, 0.0006 min) • A family of MTM

  8. Standard Elements of Work • Transport (Reach & Move) • Grasp • Pre-Position • Assemble • Use (Manual, Process or Machine) • Disassemble • Mental Process • Release

  9. Basic Elements & Its Variables (1) • Reach • Class of Reach: A - E • Distance measured in Inch • Motion of hand • Example: R8C, Time Unit= 11.5 • Equivalent to …… Min.

  10. Basic Elements & Its Variables (2) • Move • Class of Move: …….. • Load measured in ……. • Motion of hand ?? • Example: mM10C, Time Unit= …... • Equivalent to …… Min.

  11. PROs • Trial time study, Based on work instruction & work station layout • Verify time data, Compared to Direct time study • Applicable to most of jobs • No Rating Factor • Facilitate Motion-Minded training • Tools & equipment Design / Setup • Estimate processing time required for cost estimation

  12. CONs ???? • Selection of Various Systems • Well trained analyst

  13. Standard Time Calculation

  14. Work Sampling Concept: To find out the proportions of total time devoted to various activities that constitute a job, by taking a large number of observations at random times. Applications 1) Determine machine utilization / downtime 2) Determine allowances 3) Establish time standards

  15. Distribution of a proportion: at 95%CI and +/- 5% relative accuracy, Z = 1.96 • Mean, proportion of working time = p • Standard Deviation = pq n Work Sampling • Basic idea • Random sampling over a long period of working hour • Binomial distribution: p,q ratio out of n observations, which approaches Normal distribution when n is large

  16. Study Plan 0) Obtain cooperation from all concerns 1) Trial observations or a past record 2) Determine the number of obs. needed: Alignment chart 3) Design data collection procedure a. Observer: number of person, position b. Period of the study c. Time table for daily random observation d. Observation sheet 4) Assure 95% CI and +/- 5% relative accuracy 5) Calculate utilization ratio or standard time

  17. Daily Random Observation Table of Random Numbers Daily working hours Frequency of daily obs. Routes of observation Observation sheet Observe At First sight Data Summary and control Recheck CI and accuracy level

  18. p, daily UCL = p + 3sigma mean LCL = p - 3sigma day Actual readings Control Chart (P chart) is to make sure every reading is in normal condition mean = expected value of relevant proportion, p sigma = standard deviation of p 3 sigma = 99.7% of population should fall within the range

  19. Out of the control lines P chart: To detect unusual situation during the study Within chart values Out of chart values Reasons of the unusual daily p a) accident b) lack of proper production flow c) a change in expected value of p reconstruct the p chart, using the new information

  20. The Right "p" • 95% CI & +/- 5% relative accuracy • Alignment chart orTable for determining the number of obs. given degree of accuracy, value of p at 95% CI • Table for determining the degree of accuracy given number of obs., value of p at 95% CI

  21. Rep. Time = (total time spent) (proportion) total output during total time Standard Time Normal Time = Rep. Time (Performance Index) Std. Time = Normal Time + Allowances

  22. Work Sampling Advantages: compared with Direct time Study • No continuous observation • Normally less cost • Study crew operation by one analyst • Study long cycle time operation • Easy to observe • Don’t need specialist • Operator would not feel under too much attention

  23. Work Sampling Disadvantages • No details about operation • Not suitable for short cycle task • ??

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