Department of Industrial Engieering. Chapter 28: Stopwatch Time Study

Transcription

1 Department of Industrial Engieering Chapter 28: Stopwatch Time Study Assistant Prof. Abed Schokry Overview Select time study method. 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. 1

2 What is Work Measurement? Determining the amount of worker time required to generate one unit of output Provides labor standards Target amount of time required to perform a job under normal working conditions 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. Break the job into elements. 2

3 Reasons for Breaking a Job into Elements Makes it possible to reuse the data. Permits different ratings for different elements. Permits consistency checks. Improves methods descriptions. Makes incomplete data useful. 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. 3

4 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. 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. 4

5 Snapback Recording Statistical Approach Number of observations depends on: Accuracy desired Confidence desired Data variability 5

6 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 Irregular and Foreign Observations Irregular elements: Operator activity that the observer did not anticipate Foreign elements: Operator activity that is outside normal work 6

7 Delays Avoidable delays will not be included in standard. Taking a coffee break Unavoidable delays will be included in standard. Talking to supervisor about work Breaking a tool Recording Technique for Unusual Events Missed readings Lost elements Elements out of order Unexpected elements 7

8 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. Motivated Productivity Level 8

9 Rating Techniques Problem: Micro-motions change their proportions of the total task as the pace changes. Low-skill micro-motions change less than the overall task. High-skill micro-motions change more than the overall task. Levels of Methods Detail Level 1: Level 2: Level 3: Management-controlled Management attempts to control Operator-controlled 9

10 Rating Techniques: Solutions Pace rating: Observer estimates the pace. Objective rating: 1. Observer rates the speed. 2. Observer estimates task difficulty. 3. Observer multiplies speed factor by difficulty factor to get pace. Improving Rating Accuracy Ideally, rate each element. Rate each element twice. Do not use ratings under or over threshold amounts. Rate an experienced operator. Observe sufficient cycles. Use observers who have done the job themselves. 10

11 Rating Training Show the rater a videotape of a reference operation. Show a number of paces for each operation. Give the rater the true pace immediately after putting down the estimate. If the estimate is in error, show the operation again. 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. 11

12 Motion Study Motion study Systematic study of the human motions used to perform an operation In developing work methods that are motion efficient, the analyst attempts to Eliminate unnecessary motions Combine activities Reduce fatigue Improve the arrangement of the workplace Improve the design of tools and equipment End of Chapter 12