Time study procedure - overview

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# Time study procedure - overview - PowerPoint PPT Presentation

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.

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Presentation Transcript
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.
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 …
Forms
• Flow chart
• product / people flow
• motion patterns
• Process chart
• Right and left hand chart
• Multi-activity chart
• Operator / Machine chart
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)
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.
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
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.
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.
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?
Statistical approach – example (cont.)
• Standard deviation method:
• Alternatively, use range method (see box 25.1)
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
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
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
Recording technique for unusual events
• ‘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
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.
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.
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

Rating techniques: solutions
• Pace rating: Observer estimates the pace.
• Objective rating:
• Observer rates the speed.