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Chapter 24: Determining Time/Job

Uses for time/unit information Cost allocation Production and inventory control Evaluation of alternatives Determining acceptable day’s

work Determining incentive pay

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Establishing time standards

Choice of time measurement technique depends on: Cost of obtaining the information Benefits of using the information Inaccurate information leads to wrong decisions. If the standard is set 5% too low, there is a 5% loss

in productivity.

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Nonengineered (type 2) estimates

“Did take” or “Should take” Used as a temporary measure, based on

Historical records Expert opinion Time logs Occurrence sampling

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Engineered (type 1) estimates

Provide accurate estimates Must be preceded by a methods and quality

analysis Have few subjective and many objective

characteristics May be found through stopwatch time study or

standard data

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Time study: 3 levels Observed time: “raw” data Normal time = Observed time × Rating

Rating:

Standard time = Normal time + Allowances Standard time is normal time plus allowances.

Shift allowances are a percentage of shift time. Work allowances are a percentage of work time.

Personal Allowances

Fatigue Allowances

Delay Allowances

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Standard data

Are expressed in normal time

Are set by analyst visualizing the work method

Have three advantages: Cost of determining the standard is low. Consistency is high. Standards can be calculated ahead of production.

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Learning

Amount of time to perform a task depends on how much practice the person has.

Learning occurs in both the individual and the organization.

The primary cause for incorrect standard times is failure to adjust for learning.

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Individual learning

Improvement in time/unit even though the product, tools, and equipment don’t change.

Individual improvements come from: Better eye–hand coordination Fewer mistakes Reduced decision time

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Organizational learning

Improvement in time/unit due to changing product design, changing tools and equipment, or changing work methods.

Organizational learning includes individual learning.

Organization improvements come from: Operator learning New technology Substitution of capital for labor

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Quantifying improvement Manufacturing progress curves are placed on a

log–log scale. On a log scale the physical distance between doubled

quantities is a constant. The progress curve becomes straight.

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Example learning curve

Assembling a part

This is an ____________ learning curve.

Mathematically, ______________

# CyclesLog # Cycles

Cycle Time, min.

Log Cycle Time

% Decrease

1 0 12.00 1.08 20

2 0.301 9.60 .982 20

4 0.602 7.68 .885 20

8 0.903 6.14 .788 20

16 1.204 4.92 .692 20

32 1.505 3.93 .594 20

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Working with the curve

Determining the learning factor, b, for the 80% curvelog10 y = log10a + b*log10x

or, rearranging and solving for b:

Solve for a using the cycle time for 1 cycle

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Using the learning curve

1. MTM-2 analysis shows a standard time of 2 min. How many cycles does it take to reach it?

2. How long will this take (in minutes)?

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Your turn …

You have conducted a time study for an operation. At the 50th cycle the cycle time is 20 minutes and at 100th cycle the cycle time is 15 min. (i.e.,

(x1,y1) = (50,20) and (x2,y2) = (100,15))

1. What is the learning curve? What are a and b?

2. How many cycles would be required to meet a standard time of 10 minutes?

3. How long will this take? What is the average cycle time?

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Organization progress

Rate of improvement depends on amount that can be learned.

Amount that can be learned depends on: Amount of previous experience with the product Extent of mechanization

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Individual learning Has two components:

Cognitive learning Motor learning

Motor learning is slower. Cognitive learning has greater improvement.

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Applications of learning

Cost allocation

Scheduling

Evaluation of alternatives

Acceptable day’s work

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Documenting, using, and maintaining standards Quantification of output Audits Feeding information back to workers