WWORKORK MMEASUREMENTEASUREMENT

PPURPOSEURPOSE OFOFWWORK MEASUREMENTORK MEASUREMENT

Cost allocation

Scheduling production and staff

Make/evaluate decisions

Acceptable day’s work

Work Measurement

Direct – Stopwatch– Sampling

Indirect– Standard Data– Predetermined time system

STOPWATCHSTOPWATCH TIME STUDYTIME STUDY

Stopwatch Time study should be preceded by a methods analysis so the resulting standard is a“should take” time not a “did take” time.

Stopwatch time study is one of the two methods to establish a type I time standard.

STOPWATCH TIME STUDYSTOPWATCH TIME STUDY (Cont)(Cont) Non-engineered Estimates (Type II)

– “Quick and dirty”, or historical data. Not usually preceded by methods analysis, should be upgraded to Type I.

Engineered Estimates (Type I)– Objective estimates after methods analysis– Need good documentation for employee and management

buy-in.

OVERVIEWOVERVIEWThe analyst observes one or more operators continuously and records the time taken to accomplish a task. This is called Observed Time

Observed Time x Rating = Normal Time

OVERVIEWOVERVIEWStandard time = (Normal time) (1+Allowances)

Example:

Observed time = .01 hr./unit

Rating = 120 %

Normal time = .012 hr./unit

Allowances = 10%

Standard time = .0133hr./unit

PREPARATIONPREPARATION

There are basically two steps involved in Preparation

1. Methods Analysis2. Operator Selection

METHODS ANALYSISMETHODS ANALYSIS

•The primary reason for doing a methods analysis before doing a time study is to establish a safe, productive job.

•The secondary reason is to leave a permanent record of the methods for future audits and improvements.

The typical items that are recorded are :

Date of observation(Improvement curve)Person observed (Skilled…..)Person observing (Viewpoint)Machine used (Improvement curve)Tools used (Improvement curve) Part no. processed etc..

METHODS ANALYSISMETHODS ANALYSIS

METHODS ANALYSISMETHODS ANALYSISAfter a good method has been established (using checklists), the job should be broken into Elements

METHODS ANALYSISMETHODS ANALYSIS Four Reasons to divide the tasks into

elements:– Elements make it possible to reuse the data– Elements permit different ratings for

different elements(Machine time and manual time)

– Elements permit consistency checks, within the study and between studies

– Elements improve methods descriptions

HHOWOW TOTO B BREAKREAK E ELEMENTSLEMENTS Develop good method / break job into elements Ensure all elements necessary Select elements that can be timed accurately Break down as small as possible, but do not sacrifice

accuracy Elements may include several movements End of one element is exact beginning of next

TTYPEYPE OFOF E ELEMENTSLEMENTS Regular elements Irregular elements

– Unanticipated, but related to job – (must be included)

Foreign elements– Interruptions in work cycle– Avoidable (not included in standard)

• social conversations• coffee• personal and fatigue allowances

– Unavoidable (included in standard)• lack of materials• machine down

OPERATOR SELECTIONOPERATOR SELECTION Select experienced “normal” or above

average operator Avoid inexperienced or extreme

operators Careful selection improves acceptance

by others Generally, people work at standard, not

more unless there are incentives

NUMBER OF OBSERVATIONSNUMBER OF OBSERVATIONS

There are two approaches to determine the number of observations

•Statistical

•Importance of Decision

DDECISIONECISION I IMPORTANCEMPORTANCE

The number of sample size depends on three factors Accuracy Desired Confidence Desired Data Variability Increase sample size when

– cycle time short– activity per year large– costs of inaccurate standards high

RRATINGSATINGS

Normalize the readings to the “average operator”

Can be for the entire element or individual cycles

NT=OT x R/100

AALLOWANCESLLOWANCES Typically about 15% Personal interruptions Fatigue Unavoidable delay Standard Time (ST) = NT (1 + allowance)

Percent Efficiency

E = 100 x He/Hc = 100 x Oc/Oe

Where: He: standard hours earned Hc: clock hours on job Oc: current output Oe: expected output

Example The standard time for operation is 11.46 minutes per

piece. In an 8 hours shift, the operator would be expected to produce:

(8 hr x 60 min/hr)/(11.46 min/piece) = 41.88 pieces

However, if operator produces 53 pieces in a given working day, the standard hours would be:

He = (53 pieces x 11.46 min/piece)/(60 min/hr) = 10.123 hours

The operator’s efficiency would be:E = 100 x 10.123/8 = 126.5% or

E = 100 x 53/41.88 = 126.5%

ALLOWANCESALLOWANCES

AllowancesAllowances

Normal Time + Allowances = Standard Time

• Allowances are the interruptions that occur during the typical working day– personal - for personal needs– fatigue - for rest– delay - reasons beyond his/her control

• Should be applied separately from the rating

Allowances by FunctionAllowances by Function

Personal AllowancePersonal Allowance

• Include going to restroom, blowing your nose, making personal phone calls, etc.

• Can be determined by making all-day time studies or work sampling

• For low-task work, usually 2 to 5 % per day is used

• For high-task work, more than 5% is used, esp. in unfavorable (hot, humid) settings

Basic Fatigue

Accounts for the energy expenditure to perform the given work

Typically 4% under Normal Conditions

Variable FatigueVariable Fatigue

• Lessening of the will to work• Can be mental or physical, or a combined

effect• Factors include: Noise, heat, humidity,

posture, muscular exertion, tediousness, general health of the worker, Abnormal posture, Atmospheric conditions, Noise level, Illumination levels, Monotony

• Can be directly measured by declining output production over the course of the day

Delay AllowanceDelay Allowance

• Can be avoidable or unavoidable• Does assume that machinery is kept

in repair• Due to tool breakage, interruptions

by supervisors, minor adjustments, etc.

• Non-cyclic elements that occur as part of the job are not to be treated as delays

• Can be determined by TS or work sampling

Unavoidable DelaysUnavoidable Delays

Interruptions from: supervisor, dispatcher, time study technician, material faults, interference from servicing multiple machines

Avoidable Delays Social visits Day-dreaming Idleness Unnecessary work interruptions

Policy AllowancesPolicy Allowances

Different performance under exceptional circumstances

new-employees, light duty, elderly, etc.

Rating Methods

Westinghouse System Synthetic Rating Speed Rating Objective Rating

The Westinghouse System

Evaluates performance with respects to 4 Factors - Skill: expertise, coordination at method Effort: will to work, motivation Conditions: temperature, lighting,

noise, etc. Consistency: done after study Skill,

effort, conditions, and consistency

Skill

“Proficiency at following a given method.”

Proper coordination of mind and hands

Six skill degrees/classes: Poor, fair, average, good, excellent, and super

+ 15 to – 22 range

Effort

“Demonstration of the will to work effectively.” Stopwatch

Six effort classes: Poor, fair, average, good, excellent, and excessive

+ 13 to – 17 range

Conditions

Present conditions with respect to normal conditions

Temperature, ventilation, light, noise, etc…

Six condition classes: Poor, fair, average, good, excellent, and ideal

+ 06 to – 07 range

Consistency

Elemental times that continually repeat would be consistent

Six consistency classes: Poor, fair, average, good, excellent, and perfect

+ 04 to – 04 range

Synthetic Rating

Determines a performance factor for elements of the cycle by comparing actual elemental observed times to those developed by analyzing fundamental motion data, such as MTM or MOSTP = Ft/OWhere:Ft: Fundamental Motion timeO: observed mean elemental time

Speed Rating Only considers the rate of

accomplishment of the work per unit time First determine if the performance is

above or below normal Quantify the difference between the

actual output and that expected by a “NORMAL OPERATOR”

Can be tied to benchmarks such as walking, dealing cards, VO2

Objective Rating

The observer rates the speed Observer estimates the task

difficulty Task difficulty factor is multiplied

with speed to get actual pace

Rating Example• Observed time = 2.3 min• Ratings - • Skill: C1 (Good) +0.06• Effort: C2 (Good) +0.02• Conditions D (Ave) 0• Consistency C (Good) +0.01• Total = + 0.09 • Rating = 1.09• NT = (2.3)(1.09) = 2.51

• Observed time = 2.8 min

• Ratings - • Skill: E1 (Fair) -0.05• Effort: E1 (Fair) -0.04• Conditions D (Ave) 0• Consistency D (Fair) -0.02• Total = - 0.11 • Rating = 0.89• NT = (2.8)(0.89) = 2.49

So, good operator faster than ‘normal’ and bad operatorworse than ‘normal’

STANDARD DATA

What is Standard Data?

• Tabulated element standards, plots, formulas, etc.

• Elemental times from time studies that are stored for later use.

• Can be broken down into: motion, element, and task.

Advantages

• Quicker than trying to perform redundant time studies.

• Can be performed off-line. In words when there is little else to do.

• If you develop modifiable models (equations / formulas from the data), slight changes to the process are easily made, resulting in updated standards.

Example

• Go back to the OPC on page 33. We were manufacturing small wooden stands. Suppose for an instance that management wanted to change the size of the stands (alternate markets) and asked you how these changes would impact the standard. How would you approach this?

Some Considerations

• What sizes of materials are within the realm of possibility?

• What about materials of different types?

• Is there any impact on saw sharpening, replacement, or other machine related maintenance?

Some Data

• Let’s look at operation (O-3): Joint Two Edges 0.30 Minutes for 2.5”x2.5”x16” maple.

• Some of the things they are interested in knowing is softwood vs hardwood, lengths, widths.

Maple 8”

.15

12”

.225

16”

.30

20”

.375

White Oak

8”

.20

12”

.275

16”

.35

20”

.425

Pine 8”

.10

12”

.15

16”

.20

20”

.25

Some Sample Data

Formula Development

• Take enough measurements (times) that you comfortable with the numbers

• Plot the data in a spreadsheet and run some analysis on it to determine a function.

• Test the function to see if another curve fits the data more correctly.

• Extrapolate the data you need for the standard.

WWORK SAMPLINGORK SAMPLING

Work SamplingWork Sampling

• A technique that discovers the proportions of total time that various activities contribute to the job by taking a relatively large # of observations at random intervals.

• Used to determine: production standards, machine and personnel utilization, and job allowances. Typically faster and cheaper than other techniques.

AdvantagesAdvantages• Well suited for high cycle time and low

repetition rate jobs.• Does not require the analyst to continually

observe the job.• Reduced clerical time.• A smaller # of hours are required to collect the

data.• Operator not subjected to long

periods of observations.

Advantages (con’t)Advantages (con’t)

• Single analyst can study a small crew (or # of subjects)

• Cost of the study may be cheaper (up to a certain # of samples)

• Conducted over a long period of time (more of a normal performance)

• Study can be postponed if something more urgent arises (no change in study criteria)

DisadvantagesDisadvantages

• Will not produce as good a standard as direct time study

• Cost maybe higher than suspected if sampling rates are frequent

• Operators need to be located close together to eliminate travel

• Doesn’t provide the detailed data (C/I ideas) that direct study does

• Statistics of why it works is confusing for most personnel

TheoryTheory

• Probability based on the binomial distribution (p + q)n = 1

• Mean = np, Variance = npq• As n becomes large, the binomial distribution

approaches the normal distribution• This proportion has distribution of

Mean = p, Variance = pq/n

Standard time

ST = (T/P)*(ni/n)

• T = total time• P = total production• ni = number of occurrence

• n = number of observation

Number of observation

Example

Study Plans (Protocol)Study Plans (Protocol)

• Start with preliminary estimate of the variable. This can be historical data, conducting pilot study, or an educated guess (least desirable)

• Determine the desired accuracy of the results (confidence interval)

• Estimate the # of observations• Develop a sampling schedule• Design the data collection form, and

control charts if applicable