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.
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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 …
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3. 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
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4. In-class exercise Time to fill peg board – old method
Redesign workspace and work method … (5 minutes)
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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.
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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
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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.
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8. 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.
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9. Snapback Recording
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10. 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?
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11. 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!
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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 28.2, pg. 553
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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
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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
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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
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16. Sample time study form (fig. 28.2, pg. 555)
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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.
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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.
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19. Motivated Productivity Level
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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
Micromotions – move, reach, grasp, etc.
low-skill micromotion: e.g., move, reach
high-skill: e.g., position, grasp
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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
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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.
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