TI 2111 Work System Design and Ergonomics 4. Time Study The major objective of this chapter is to...

TI 2111 Work System Design and Ergonomics

4. Time Study

The major objective of this chapter is to learn how to calculate a time standard based on stopwatch time study procedures.


Time Study A process for measuring the required time for

performing a given task, by a given method, by a trained worker, working in a normal pace.

Why needed? For methods improvement

For determining time standards


Needs for Time Standard

Developing schedules Determining wage payment plans Estimating production costs Providing a base for estimating productivity

goals Appraising employee performance Evaluating alternative process, equipment


Methods for Creating Time Standards Direct time study

Cyclic work Non cyclic work

Work sampling Synthetic data

Predetermined times


Direct Time Study - Tools


Direct Time Study

Methods improvement Selection of the examined workers Explanation (union, managers, workers) Collecting and recording information Task division into elements


Methodology

Who to choose? Select an Average Worker (What is average?) Experienced operator Normal pace

Consistency (well defined, understood by all) No undue strain for entire day (speed/effort) Pace that should be performed, not average of current rate

Rating accuracy Worker acceptance

Can you suggest a better method?


Preparation for Timing

Identify the TASK/ CYCLE to be studied before time study Analyze the Complete Task

Method Layout of workplace Equipment used Environmental conditions Machine speeds and feeds Inspection equipment

Communications with foreman, workers Documents for process, task instructions Establish relationship

Elemental analysis Break task into elements


Fundamental definitions

What is an ELEMENT? Element is a component of job or task that

are logical divisions with easily identifiable starting and end points, and are repeated on a regular basis

What is a CYCLE? Cycle is the completion of the activities

(elements) required to perform the job under study.


Element Analysis

Every element must have an easily identifiable starting and ending point (breakpoints)

No discontinuities between elements Elements times: 0.04min (short), 0.25min

(reasonable) Relative frequency must be included


Timing Methods

Continuous Advantage: Clock never stops, no time omitted Disadvantage: observer does not know at the job

how individual elements vary Snapback

Advantage: Observer can note individual variability within an element and eliminate substraction

Disadvantages: difficult to coordinate eye, watch and task! Especially when operations are short


Determining Number of CyclesTime measurement

Measuring time of each element

The number of observation of each element depends on the significance level and required level of accuracy

Primary time study(normally 5 to 10

observation)

Examination of therequired number of

observations (N)

Continue study up to Nobservations

Re-checking the requirednumber of observations (n)

N>=n

End the time study

N=n

No

Yes


Recommended number of cycles/observations


Maytag Company Approach


Rules for Performing Time Study Don’t comment to the worker during the task Stand (don’t sit) beside the worker Write every event (even though it may seems not

important) Have a good position to observe Stop the study if the worker seems to be under

pressure and it affects his/her work


Time Study On Cyclic Work

Rating evaluation may be written once in a couple of cycles

Elements times: 0.04min (short), 0.25min (reasonable)

Denoting non-cyclic elements The breakpoint between elements should be

clear (touch, push, etc.).


Types of Elements

Manual/machine (determines the task duration)

Cyclic/non cyclic Fixed time/ variable time (i.e. loading time as

a function of weight) Avoidable/unavoidable unproductive

elements (sometimes hard to identify)


Time Study on Non Cyclic Work Use continuous timing Divide the task into relatively large elements Write the evaluated performance rate at the

end of each element Multiply the observed time with the rate and

summarize the data


RATING FACTORS


Do we expect the average worker to work in normal rating ?


Rating Evaluation Methods

Subjective judgment Practice by watching movies For a study with long elements, rate each

separately Methods:

Speed rating Westinghouse


Performance Rating Table (Westinghouse)


Criteria for Successful Speed Rating Evaluation

Experience in the class of work performed Selection of an operator who gives

performances between 85 and 115 Use of the average value of three or more

independent studies


Elements of Allowances

Normal Time

Extra Allowances

Unavoidable Delays

Special AllowancesConstant Allowances

Basic Fatigue

Personal Need

Variable Fatigue

Avoidable Delays

Standard Time

Total Allowances Allowances + =


Standard Data Systems

Elemental times, based on previous time studies, which have been proven to be accurate and reliable.

Tabulated element standards that allow the measurement of a specific job without the use of timing devices.


Construction Cost Estimating

Given we have the plans for a new building, how much labor is needed and what will it be

used for?


Punch Press Standard Data(40” strip)

Given we have a new part to run through the punch press,

what will be the standard time for the part?


Advantages Over Direct Time Study More consistent standards results Duplicate time studies on similar operations

are eliminated Standards are established more rapidly Less experienced analysts can calculate

standards (use the formula not develop it) Accurate labor costs and production times

can be estimated before production begins


To Illustrate the development of standard data…

Model

Element119 130 220 310 311 322 329

10 0.24 0.22 0.23 0.23 0.24 0.22 0.23

20 0.38 0.35 0.35 0.37 0.36 0.36 0.37

30 12.06 10.44 8.71 6.58 10.83 6.34 7.25

40 3.66 4.81 0.00 2.79 5.84 4.55 4.10

50 0.00 1.63 1.91 1.69 1.80 1.45 0.00

60 0.12 0.12 0.13 0.11 0.14 0.14 0.13


Possible Drivers

Model NT 3/4/5 D1 D2

119 15.72 18.00 27.25

130 16.88 23.50 33.50

220 10.62 2.50 1.50

310 11.06 3.00 7.25

311 18.47 25.00 44.00

322 12.34 12.00 18.25

329 11.35 3.00 8.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.00 10.00 20.00 30.00 40.00 50.00

Dimensions (D1 and D2 - inches)

Tim

e 30

/40/

50 (

Hrs

/100

0)

D1

D2


Correlation

2

222

2

121

2121

XXnXXn

XXXXnr


Is there a relationship between D1 and the combined time for elements 30, 40, and 50?n X1 X2 X1^2 X2^2 X1*X2

1 15.72 18.00 247.1184 324.00 282.96

2 16.88 23.50 284.9344 552.25 396.68

3 10.62 2.50 112.7844 6.25 26.55

4 11.06 3.00 122.3236 9.00 33.18

5 18.47 25.00 341.1409 625.00 461.75

6 12.34 12.00 152.2756 144.00 148.08

7 11.35 3.00 128.8225 9.00 34.05

Sums 96.44 87.00 1389.3998 1669.50 1383.25

r = 0.977


Linear Regression

Y = b0 + b1XY

X

221

22

2

0

XXn

YXXYnb

XXn

XYXYXb


Standard Times for Machining Operations How long will it take

to drill a 1-inch hole through two inches of malleable cast iron?

TI 2111 Work System Design and Ergonomics 4. Time Study The major objective of this chapter is to...

Documents

Transcript of TI 2111 Work System Design and Ergonomics 4. Time Study The major objective of this chapter is to...