Time Study Procedure - Overview

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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. ISE Ch. 28

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 … ISE Ch. 28

Forms Flow chart Process chart Right and left hand chart
product / people flow motion patterns Process chart Right and left hand chart Multi-activity chart Operator / Machine chart ISE Ch. 28

In-class exercise Time to fill peg board – old method
Redesign workspace and work method … (5 minutes) ISE Ch. 28

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. ISE Ch. 28

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 ISE Ch. 28

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. ISE Ch. 28

Timing Techniques Stopwatch Videotape 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. ISE Ch. 28

Snapback Recording ISE Ch. 28

Statistical Approach – pg. 552
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 97% (2) confidence interval are desired, how many observations are required? ISE Ch. 28

Statistical approach – example (cont.)
Standard deviation method: Alternatively, use range method (see box 28.1) Z = 2 A =.1*16 = 1.6 ’x = 4 N’ = ((2/1.6)*4)2 = 25 Note: for relative accuracy of 5%, N’ = 1600! ISE Ch. 28

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 28.2, pg. 553 ISE Ch. 28

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 ISE Ch. 28

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 ISE Ch. 28

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 ISE Ch. 28

Sample time study form (fig. 28.2, pg. 555)
ISE Ch. 28

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. ISE Ch. 28

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. ISE Ch. 28

Motivated Productivity Level
ISE Ch. 28

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 Micromotions – move, reach, grasp, etc. low-skill micromotion: e.g., move, reach high-skill: e.g., position, grasp ISE Ch. 28

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 ISE Ch. 28

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. ISE Ch. 28