Time study procedure - overview

1. Time study procedure - overview • Perform methods analysis. • Identify elements. • Observe one or more operators to find observed time. • Give a rating to adjust observed time and find normal time. • Add allowances to normal time to find standard time. • Procedures attempt to reduce inaccuracies of going from the sample to the population and from the present world to the future world.

2. Step 1: Methods analysis • Purposes: • Establish a safe, productive job. • Leave a permanent record of method for future use. • Most of effort should be in job design and productivity rather than time standards. • Once the best method is established, break the job into elements. • Use the following forms as needed …

3. Forms • Flow chart • product / people flow • motion patterns • Process chart • Right and left hand chart • Multi-activity chart • Operator / Machine chart

4. In-class exercise • Time to fill peg board – old method • Follow the method given in the handout • Determine the time to completely fill one board • Repeat 5 times and calculate the average … • Redesign workspace and work method … (5 minutes)

5. Step 2: Break the job into elements • Why … • Makes it possible to reuse the data. • Permits different ratings for different elements. • Permits consistency checks. • Improves methods descriptions. • Makes incomplete data useful.

6. Step 2: Break the job into elements • How … • Identify complete actions, e.g. • Get a part • Assemble two pieces together • Define action endpoints (EP) or terminal points (TP) • Easily recognizable • Logical in context • Example: Get part A, TP is part A at center Assemble two parts, TP is release of assembly in bin • Endpoint of one action is beginning of the next • Always keep manual and machine time separate

7. Operator selection • Treat the operator with dignity and respect. • Try to make the sample representative of the population. • Select experienced rather than inexperienced workers. • Select average or typical workers. • Vary the times and days of studies.

8. Timing techniques • Stopwatch • Use snapback mode. • Use electronic watches. • Avoid using continuous mode. • Videotape • Provides a permanent record of the method. • Analysis can be done by person other than camera operator. • Elements can be performance rated.

9. Snapback recording

10. Statistical approach – pg. 492 • Number of observations depends on: • Accuracy desired • Confidence desired • Data variability • Example: A time study is being planned. A preliminary sample of 20 times is shown to have a mean of 16 seconds and a standard deviation of 0.4 seconds. If a relative accuracy of 10% and a 95% (round to 2) confidence interval are desired, how many observations are required?

11. Statistical approach – example (cont.) • Standard deviation method: • Alternatively, use range method (see box 25.1)

12. Importance-of-decision approach • Number of observations depends on: • Importance of accuracy of the time standard • Cycle time • Activity/year • Cost of an inaccurate standard • See table 25.2, pg. 493

13. Irregular and foreign observations • Irregular elements: operator activity that the observer did not anticipate • include like other elements • determine how often per unit produced • example: clear hopper, change blade, etc. • Foreign elements: operator activity that is outside normal work

14. Delays • Avoidable delays will not be included in standard. • Drinking coffee • Chatting with coworker • Unavoidable delays will be included in standard. • Talking to supervisor about work • Waiting for supplies • Breaking a tool

15. Recording technique for unusual events • Missed readings • ‘M’ in time slot • Omitted elements • ‘-’ in time slot • Elements out of order • see columns 6-8, next page • Unexpected elements • code events (A, B, C, etc.) • explain code elsewhere in short (1-3 word) note

16. Sample time study form (fig. 25.2, pg. 495)

17. Rating • Ensures that the standard is based on the method, not the operator. • To improve rating accuracy, study an average operator. • Studying average operators also improves worker acceptance of the standard.

18. Normal pace • Normal pace must be defined prior to observation. • Define motivated productivity level (MPL) first. • Acceptable productivity level is within expectancy of MPL. • MPL is the work pace of a motivated, skilled, physically fit worker.

19. Motivated productivity level

20. Rating techniques - problems • Micromotions change their proportions of the total task as the pace changes. • Low-skill micromotions change less than the overall task. • High-skill micromotions change more than the overall task. • Levels of methods detail Level 1: Management-controlled Level 2: Management attempts to control Level 3: Operator-controlled

21. Rating techniques: solutions • Pace rating: Observer estimates the pace. • Objective rating: • Observer rates the speed. • Observer estimates task difficulty. • Observer multiplies speed factor by difficulty factor to get pace. • Improve accuracy • number of observations • skilled operator • observer skilled at job • Train raters

22. Setting allowances • Personal and fatigue allowances are set from tables. • Delay allowances are set from delays actually occurring on the job. • Delays during a time study may provide estimate for the delays to allow for the standard.