1. ENM 301 Work Study ‐ Time Study ‐ ENM 301
END 202 – Work analysis and design
Time Study

2. Time study
Time study is a technique for recording times and rates of working for specific job elements to establish standards
Why do we measure time?
The most meaningful and useful measure of work is the amount of time it takes to accomplish it
Time is objective
Time is quantifiable
People understand time
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Time Study

3. Standard time
Standard Time is the time that a person suited to the job and fully trained in the specified method will need to perform the job if he/she works at a normal or standard tempo
Includes some additional time called allowances to provide for the worker’s personal needs, fatigue, and unavoidable delays
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Time Study

4. Time study Methods to determine time standards: Estimation
Historical records
Time study techniques:
– Direct time study (with chronometer)
Engineered standards
Standard data and formulas
Predetermined time systems
Work sampling
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5. Direct time study
Involves direct observation of a task using a stopwatch or other chronometric device to record time
The task is divided into work elements and each work element is timed separately
Performance rating: The worker’s performance (pace) is evaluated
Normal time is calculated considering the performance rating
Allowance is added to the normal time to determine the standard time
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6. Standard data and formulas
Finding normal time values for work elements used in tasks using previously determined standard data or formulas
Steps:
Identify the work elements that make up the task together with the values of variables
Access the database to find the normal time for each element or use analytical formulas
Sum to determine the normal time for the task
Add allowances to determine standard time
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Time Study

7. Predetermined time systems
Relies on a database of basic motion elements (therbligs) such as reach, grasp, move
Associated with each motion element is a set of normal times depending on distance, weight, etc.
List of all the basic motion elements, find the normal time for each element from the data base, sum the normal times and add allowances
Advantages
Performance rating is not required
Can be applied to determine time standard for a task before production
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8. Work sampling
Purpose is to determine proportions of time spent in different activities using randomized observations
Examples: to determine machine idle times, to determine operator utilization
When used to establish time standards statistical errors cause the standard times to be less accurate than obtained by other techniques
To be studied later…
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9. Prerequisites Prerequisites for valid time standards
The task is performed by an average worker
The worker s pace represents standard performance
The worker uses the standard method
The work is performed on a standard work unit ’
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10. Direct time study (with chronometer)
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11. Analyst’s responsibility
The analyst should be trained on this job
The correct people should be warned (supervisor, worker, etc.)
Be sure that you have all the equipments with you
Be respectful with the worker, avoid to make unnecessary comments
Be honest with the performance of the worker
Accurately record and note the times taken (time study results can influence the firm policy)
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Time Study

12. Operator’s responsibility
Worker should
cooperate in helping to work
assist the time study analyst in breaking the job down into elements
work at a steady, normal pace
use the exact method prescribed
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Time Study

13. Time study equipment Stop watch Videotape camcorders Time study board
Analog – outdated
Electronic
Split = continuous
Lap = snapback
Videotape camcorders
Time study board
Holds time study form and stop watch
Left and right handed
Time study software
Available for PC, for palms
Time study form
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Time Study

14. Time study form
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15. Time study form – zoomed
Performance rating (100% is the standard performance of a qualified operator)
For continuous timing
OT NT W R
Cycle (Rating) (Watch
(Observed
(Normal
Time) 1 85 5
4.25 2
100 12 7
7.0 3
110 23 11
12.1 4 90 32 9
8.1
Normal time (NT): OT x R/100
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Time Study

16. Time study procedures Select the job Select the operator
To implement wage incentives
To control costs
To compare methods/jobs
Select the operator
Qualified (intelligence, education, training, fit)
Average
Slow worker: loose standard times (not good for the firm)
Fast worker: tight standard times
(not good for the workers)
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Time Study

17. Time study procedures Record all details about the job
Machines, hand tools, fixtures, working conditions, department, a sketch of layout, …
Examine the job and break it down into elements
Use sight and sound for breakpoints
Relatively fine but not less than 0.04 min (3 sec)
Keep manual and machine elements separate
Separate constant elements from variable elements
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Time Study

18. Time study procedures Examine the job and break it down into elements
Types of elements
repetitive: occurs each cycle
occasional: not every cycle
foreign: not necessarily part of the job
machine: the time is fixed (no rating)
manual: depends on worker (rating)
constant
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Time Study

19. Time study procedures Determine the number of cycles to be timed
Statistical estimations
n =
t: t‐distribution value
s: standard deviation
k: an acceptable fraction for error
: sample mean value
x =individual values of observed times collected during the study
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20. Example
A time study analyst has collected 10 readings on a particular work element of interest and would like to consider how many more cycles to time. Based on the sample, the mean time for the elements is 0.40 min and the sample standard deviation is 0.07 min. At a 95% confidence level, how many cycles should be timed to ensure the actual element time is within ± 10% of the mean?
Example 3
Time Study

21. Example Example: solution
We have 10-1=9 degrees of freedom in the t distribution, ta/2 at the 95% confidence level (a/2=0.025) is
Since 10 cycles have already been timed, the analyst needs data from 6 more cycles.
Now we are 95% confident that the true value of Te is within ( (0.04), (0.04))
That is, P(0.036 ≤ Te ≤ 0.044) ≥ 0.95
or P(0.036 ≤ Te ≤ 0.044) = 0.95
Time Study

22. Time study procedures 5. Determine the number of cycles to be timed
b) Approximate guide (from General Electric Company)
Cycle time (min)
Recommended number of cycles
0.10
200 (20 min)
0.25
100 (25 min)
0.50
60 (30 min)
0.75
40 (30 min)
1.00
30 (30 min)
2.00
20 (40 min) 15 10 8 5
>40.00 3
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23. Time study procedures Measurement Continuous timing Snapback timing
Stopwatch is never reset
You record the cumulative times
At the end you need to subtract times
Snapback timing
Stopwatch is reset each time (each elemental work)
Read direct times from zero
No decimal point R W OT NT 5 12 7 23 11 32 9 R W OT NT 5 7 11 9
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24. Comparison btw continuous and snapback timing
Continuous timing
Better adapted to measure and record very short elements (3 successive elements of <0.04 min followed by 0.15 min)
A complete record of the entire observation period
All delays and foreign elements are recorded
More clerical work is involved
Snapback timing
More suitable for long elements
No need to make successive subtractions
Delays are not recorded
Some individual elements are removed or are studied independently of preceding and succeeding elements
Overall time is obtained by summing: prone to error
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25. Performance rating Different options for rating the operator
one rating to entire study (for short cycle)
an average rating for each element
evaluate the performance of each element as it occurs (for long and diversified movements)
Normal time (NT): OT x R/100
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26. Finding standard time Adding allowances
Different interruptions can take place. We must provide extra time to take them into account.
Personal interruptions (trips to the restroom, drinking fountain)
Fatigue
Unavoidable delays (tool breakage, supervisor interruptions, material variations, etc.)
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27. Finding standard time ST = NT x (1 + allowance)
Adding allowances to obtain the standard time
ST = NT x (1 + allowance)
15% is the average allowance used for manual elements
10% is the average allowance used for machine elements
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28. Time study steps
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29. Performance rating and allowances
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30. Performance rating Rating of 100%
Standard (normal) performance = 100% = rate of output achieved by a qualified worker, without exertion, using correct method.
Some examples
Distributing 52 cards in 0,5 min
Walking with 5.4 km/h Rating can change due to
Environmental conditions, fatigue, quality of raw material, changes in method, …
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31. How to rate the performance?
Rating methods:
Speed rating
Westinghouse system
Synthetic rating
Objective rating
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Time Study

32. 1. Speed rating
Speed rate considers only the rate of work per unit time
Measurement of the effectiveness of the operator by the ratio of the observed performance to standard performance
Can be used for elemental, cycle, or overall rating
Works needing great precision (aircraft engine parts fabrication) can appear slower than a simple work
Record the rating in the R column before reading the stopwatch time! Do not rate by the watch!
Begin by rating only by 10s (80,90,110) then move onto 5s (85,95,105)
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33. 1. Speed rating – example Rating Verbal anchor points Walking
Cards dealt
speed (mph)
in 0.5 min
No activity 67
Very slow, clumsy 2 35
100
Steady, deliberate 3 52
133
Brisk, businesslike 4 69
167
Very fast, high dexterity 5 87
200
Upper limit for short period 6
104
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Time Study

34. 2. Westinghouse system
Westinghouse Electric Corporation (Lowry et al ) developed a system of 4 factors in evaluating the performance of the operator:
Skill: The proficiency at following a given method
Effort: Demonstration of the will to work effectively
Conditions: Include temperature, ventilation, light, noise
Consistency: Evaluated as the study is worked up
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35. 2. Westinghouse system
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36. 2. Westinghouse system – example
Once each four factor are rated sum the four values and add 1 to give the performance rating factor
The Westinghouse System is appropriate for either cycle rating or overall study rating but not for elemental rating
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37. 3. Synthetic rating R  F OT
Determines a performance factor based on fundamental predetermined motion times (F)
R  F OT
R: Performance or rating factor F: Fundamental motion time OT: Observed mean time
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38. 3. Synthetic rating – example
Element no.
Observed time (OT)
Fundamental motion time (F)
Rating factor (R) 1
0.08
0.096
123% 2
0.15 – 3
0.05 4
0.22
0.278
R1 = F1/OT1 = 0.096/0.08 = 120 %
R4 = F4/OT4 = 0.278/0.22 = 126 %
Average rating factor is 123%
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39. 4. Objective rating R  P  D
Eliminates the difficulty of establishing a standard pace for every type of work
R  P  D
R: Performance or rating factor P: Pace rating factor
D: Job difficulty adjustment factor (amount of body used, foot pedals, bimanualness, eye‐hand coordination, handling or sensory requirements, weight handledor resistance encountered)
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40. Rating application and analysis
0.16
0.20
> 100
= 100
< 100
0.25
Normal time (NT): OT x R/100
NT = 0.2 x 100/100 = 0.2
NT = 0.16 x 125/100 = 0.2
NT = 0.25 x 80/100 = 0.2
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41. Rating application and analysis
Potential mistakes
Subjective rating
Capacity of working memory
Cultural norms (UK, 100% = 4 mph)
Training is crucial:
Tight rater = rates below actual, unfair
Loose rater = rates above actual, easy
Conservative = rates close to mean
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42. Allowances Normal time does not include unavoidable delays
Need to make adjustments to compensate for such losses
Allowances can be applied to 3 parts of the study
The total cycle time
Machine time only Manual effort only
2 methods for developing allowances:
Direct observation
Work sampling
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43. Noting allowances
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44. Types of allowances
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45. Types of allowances Constant allowances Variable fatigue
Personal needs (≈ 5%): restroom, smoking, drinking, lunch
Basic fatigue (≈ 4%)
Variable fatigue
Special allowances
Unavoidable delays: interruptions from supervisor, material irregularities, machine interference
Avoidable delays: socializing, idleness other than rest
Extra allowances: attention time, cleaning, tool maintenance
Policy allowances: new employees, differently ables, workers on light duty
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46. Variable fatigue allowances – 1
Source: International Labour Office (ILO)
Time Study
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47. Variable fatigue allowances – 2
Source: International Labour Office (ILO)
Time Study
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48. Revised table of allowances – 1
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49. Revised table of allowances – 2
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50. Applying allowances ST = NT x (1 + allowance) Example:
ST: standard time NT: normal time
Example:
Personal needs
5.0 %
Basic fatigue
4.0 %
Unavoidable delay
1.0 %
TOTAL
10.0 %
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51. How to use allowances? Generally we use it to take a rest
30 min lunch time is included
2 times 10 min of rest are included
For a 8 h of work, 50 min of rest ≈ 10%
Frequent short breaks are preferred over infrequent, long breaks
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52. Standard data and formulas
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53. Standard data and formulas
Use standard data, tabular or graphical collections of normal times, for common work elements
Use formulas to provide quick and consistent normal times for variable elements
When properly applied, standard data permit the rapid establishment of accurate time standards before the job is performed
A time study formula can establish standards in a fraction of the time required for direct time study
Advantage of formulas over standard data is that a less skilled person can plug data into formulas more quickly than adding standard data elements
END 202 – Work analysis and design
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54. Standard data and formulas
Steps:
Identify the work elements that make up the task together with the values of variables
Access the database to find the normal time for each element or use analytical formulas
Sum to determine the normal time for the task
Add allowances to determine standard time
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Time Study

55. Predetermined time systems
END 202 – Work analysis and design
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56. Predetermined time systems
Relies on standard times assigned to the basic elements of work:
basic motion times: further refinement is both difficult and impractical
synthetic times: often the result of logical combinations of therbligs
predetermined times: used to predict standard times for new work
These fundamental motions are difficult to evaluate with stopwatch time study
Associated with each motion element is a set of normal times depending on distance, weight, etc.
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57. Predetermined time systems
Advantages
They are realized on several workers under controlled conditions
The analyst doesn’t need to determine the performance rating which can be subjective
The operation is not interrupted
The level of complexities for each elemental work can also be computed
There are more than 50 systems, such as: Work‐ Factor, MTM, MOST, etc.
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58. Methods‐time measurement (MTM‐1)
Maynard et al., 1948
Results of frame‐by‐frame analyses of motion picture films
Time values for the fundamental motions are given Ex: reach, move, turn, grasp
Assigns to each motion a pre‐determined time standard which is determined by the nature of the motion and the conditions under which it is made
Westinghouse technique of rating is used
Ex. Reaching depends on distance and type of reach. Reach is divided into five distinct cases and Move into 3 cases
TMU: Time Measurement Unit = 0,00001 hour
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59. Methods‐time measurement (MTM‐1)
Steps of MTM‐1
Determine all left‐hand and right‐hand motions required to perform the job properly
Determine the rated times from the methods‐time data tables in TMU for each motion
Tables I‐X: reach, move, turn and apply pressure, grasp, position, release, disengage, eye travel time and eye focus, body, leg and foot motions, simultaneous motions
Sum the TMU values (consider only limiting values)
Add allowances
The tabulated values do not carry any allowances
Some analysts state that no fatigue allowance is needed
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60. Methods‐time measurement (MTM‐2)
The data are adapted to the operator and are independent of the workplace or equipment
Used in work assignments where
The effort portion of the work cycle is more than 1 min
The cycle is not highly repetitive
Does not involve a large number of either complex or simultaneous hand motions
In addition to basic MTM motions, there are combinations of them
GET: reach + grasp + release
PUT: move + position + release
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61. Methods‐time measurement (MTM‐2)
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62. Methods‐time measurement (MTM‐2)
11 classes of actions (categories)
Get (reach‐grasp‐release)
Put (move‐position)
Get Weight
Put Weight
Regrasp •
Apply Pressure Eye Action Foot Action Step
Bend and Arise
Crank
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63. Methods‐time measurement (MTM‐2)
Cases for GET(G) Cases for PUT(P)
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64. Methods‐time measurement (MTM‐2)
Principle of Simultaneous Motion: If two hands make the same task simultaneously, more time can be assigned depending on the difficulty
Principle of Limiting Motion: If two hands make different tasks at the same time, we consider the slowest one
Principle of Combined Motion: If one hand makes two distinct movements, we take the slowest time
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65. Methods‐time measurement (MTM‐?)
MTM‐3: helpful for works where there is an interest in saving time at the expense of some accuracy
MTM‐V: for use in metal cutting operations, to establish setup times for all typical machine tools
MTM‐C: widely used in banking and insurance industries, for work tasks such as filing, data entry, and keyboarding
MTM‐M: for operator working on a microscope, microminiature manufacturing
MTM‐TE: for electronic tests
MTM‐MEK: one‐of‐a‐kind and small‐lot production
MTM‐UAS: for a process description, batch production
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66. Maynard Operations Sequence Technique (MOST)
Developed by Zandin in 1967, applied in Sweden
Simpler than MTM, but faster than MTM‐1 and MTM‐2 (at least 5 times faster than MTM‐1)
There are three levels:
MaxiMOST: analyzes long, infrequent operations (range from 2 min to several hours and occur less than 150 times per week)
MiniMOST: very short and very frequent (less than
1.6 min in length, more than 1500 times a week)
– BasicMOST: 0.5 min to 3 min of length
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67. Predetermined time systems
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