Tempo - Rating
WFC Times blauw0202

 

Tempo rating or Performance rating

Why?
Suppose an assembly is executed manually and the quantities are large enough for more people continuously executing this activity. During direct observation at the work stations with a stopwatch, differences in time will be seen for each assembly and also for each person. Dependent on the experience and the effort that is made the times will fluctuate. However, in order to make a validation of performance possible or a daily planning, balancing of work, a capacity planning, a calculation of the cost price or a good arrangement of work, there is a need of a normal performance or normal tempo. This is an average time that can be used as a standard: that is to say, a time which, under normal circumstances, an experienced worker making a good working effort will need to do the job, the basic time.

Concepts
By basic time (BT) or task time (TT) is understood the time in seconds (or centi-minutes) that is needed for the execution of the prescribed task, when the necessary actions are executed at the "basic tempo" or “task tempo” or "normal tempo", leaving out any considerations about any allowances.

The necesssary and required actions or motions for the execution of a task are the actions or motions actual executed minus the superfluous and redundant actions or motions.

Tempo, the degree of performance (or merit rating), is the resultant of the speed of the motions and the useful effect with which the motions are executed, expressed in a number which is inversely proportional to the real processing or assembling time:
Tempo = speed x useful effect.

The “speed” or velocity of a motion has to do with knowledge: knowing where and how, and has to do with knowing a lot about the product and its parts and how to assemble the parts and knowing the quality facts and requirements. All these aspects are part of the knowledge of the worker and therefore have  to do with the efficiency.

The “useful effect” or effectiveness has to do with expertise, virtuosity, proficiency, skillfulness and smartness. It is therefore dependent on the exerted input (work of the operator) and the delivered output (quality).

All these variables must be rated and evaluated during the measuring of the time with a stopwatch or other means of time recording. It will be clear that it is very hard to do this reliable and acurately.

Each organization or factory has to settle, à priori, for the standard tempo or rate that will be its standard performance for working. This will be indicated f.i. with the number 80 on the Bedaux scale or with 100 on the BSI scale or 133 on the ASME scale or with 133%. The normal tempo or task tempo will now (mostly) be set equal to the standard tempo, being the tempo that corresponds with the working skill of the average, seasoned worker, who is able and motivated, while working with good effort under normal (good) circumstances, to execute the task according to the prescribed method and qualty requirements.

Below in one table can be found 3 general internationally recognized rating scales, a German well known scale and scale well known in The Netherlands , onwhich the standard tempo and the estimated working tempo can be indicated. Also a brief characteristic description of the tempo is given. In the column on the right an indication of tempo (mainly speed) can be found for the long distance (> tens of meters) and for the very short distance (< some steps or meters).
 

 

Bedaux
scale


(Bdx)

British
Standard
Institute
scale
(BSI)

American Society for Mechanical Engineers
(%) scale

REichsaus-
schuss Für
Arbeitszeit-
ermittlung
(REFA)

Raadgevend
Bureau
Berenschot
scale
(RBB)

Description of tempo or rate

Corresponding walking speed in km or (miles)
per hour

60 - 80

75 - 100

100 - 133

85 - 115

83 - 110

 

long distance short

40



60




80




100




120




_______
70
73

50



75




100




125




150




________
88
91

67



100




133




167




200




_________
117
121

57



85




114




142




170




_________
100

55



83




110




138




165




_________

100

Very slow; clumsy and hesitating motions; the worker appears to be asleep and is not interested in his work.

Measured, without hurry, works without interest, with proper supervision; appears rather slow, but no conscious waste of time during the observation.

Fast and precise motions of average worker after training; with interest; the requested standards for quality and accuracy are met without hesitation.

Very fast motions; worker works with certainty, the coherence between his motions is much better than with a trained mediocre worker.

Exceptionally fast motions, this tempo demands a very intense endeavour and concentration and cannot be maintained for a long time; “acrobatic” performance which can only be achieved by a few exceptional workers.

3,2                  2.9
(2.0)                (1.8)


4,8                  4,4
(3.0)                (2.7)



6,4                  5,8
(4.0)                (3.6)



8,0                  7,3
(5.0)                (4.6)



9,6                  8.7
(6.0)                (5.5)
 

Bdx

BSI

ASME-%

REFA

RBB

 

 

 

Two other more or less known tempo scales for time study in the Netherlands in those days, were the scale of Raadgevend Efficiency Bureau Bosboom en Hegener NV, REB, and the scale of Adviesbureau voor Bedrijfsorganisatie Dr.Ir. M.G. Ydo, YDO. These two tempo scales are comparable with the scale of RBB. As with RBB, the task times were set at the level of 100% performance, identical with T72 Bdx. At RBB the tireless performance of 100% was also known as P10.

In general, we do not know the normal tempo at which a certain job is executed. As a reference for the normal tempo we only know some examples:
- dealing 52 playing cards blindly in 23.4 seconds, (deck in LH and moving with LH, top card moved with thumb and finger, RH grasps card
  and throws it on staple, in about 3/4 foot square, 4 distinguished staples on the corners)
- assembling 30 pins (bevelled on 1 side) lying at random, with two hands in 30 holes, 5 rows of 6 holes; bin with pins above plate with holes
  in 18,5 seconds
- walking freely on a hard smooth road at a speed of 6.4 km per hour (4 mile per hour) for an experienced walker over a long distance; ~ 5,8
  km per hour over a very short distance.
  This is true for people of the US or from Europe. So, on an average
  US/EU women: 1 step = 2.2 feet = 67 cm; in general it is taken: steplength = height of woman x 0.413,
  US/EU men    : 1 step = 2.5 feet = 76 cm; in general it is taken: steplength = height of men x 0.415.

Rating tempo
On basis of tempo rating films the analists-to-be are taught the sense of tempo and the elements to be noticed. Learning how to rate the tempo will have to take place in practice with many examples. The rating of tempo of a working process requires a lot of exercising and experiencing to be able to do this with a reasonable reliability and accuracy.
In a Work-Factor environment students are trained to compare with a normal tempo of Bdx 80 (100 BSI or 133 ASME or 133%), while students in a MTM environment are mostly trained to compare with a normal tempo of Bdx 60 (75 BSI  or 100 ASME or 100%).
Tempo rating is forming a subjective opinion about the intensity of work shown. Nevertheless it will always remain "rating" and although with a lot of training and by paying great attention an acceptable degree of reliability can be attained, nothing must be left undone to raise this reliability to and keep it at as high a level as possible.

With the aid of analyses with a system of predetermined (elemental) motion times, PD(E)MTS, like Ready Work-Factor or Very easy Work-Factor, analysts may acquire skills in rating tempo. The “select” time of RWF and VWF times are set to a working tempo of 75 Bdx (94 BSI or 125 ASME or 125%).

Below a table is given in which the “intrinsic tempo or rate“ of various PMTS are reflected with a reference to internationally recognized rating scales. Attention: Work-Factor and MTM are no rating scales.
 

 

           Scale

System

Bedaux
Bdx or
60-80 scale

BSI
or
75-100 scale

ASME
 % scale
100-133

REFA
scale

RBB
scale

Level

Work-Factor

MTM
(Westinghouse
100-120 scale)

         tempo



----------
DWF
RWF
VWF
BWF

MTM-1
TMC II
MTM-2
MTM-3
UAS
MEK
MOST *)
BAT
MODAPTS

100
80
70
60
------------
78
75
75
72

(69)
65
65
63
60
< 60
< 60
Comparable

125
100
87
75
------------
98
94
94
90

(86)
83
81
79
75
< 75
< 75
with MEK ?

167
133
117
100
------------
130
125
125
120

(115)
111
108
105
100
< 100
< 100
 

143
115
100
86
-------------
112
108
108
103
(100)
95
93
91
86
< 86
< 86
 

139
111
97
83
-------------
108
104
104
100
(96)

92
90
88
83
< 83
< 83
 

Maximum
Standard/Opt.

Basic tempo
------------------








 

128
103

77
------------
100
96
96
92
(88)
88
85
84
81
< 77
< 77
 

151
120

90
------------
117
113
113
108
(104)
100
98
95
90
< 90
< 90
 

 

*) MOST  From tests executed in 1986 in England and The Netherlands it was concluded as follows. The intrinsic tempo of MOST was set to 66 Bdx, while that of VWF and RWF is 75 Bdx. Many comparitive analyses of motions (General Move, Controlled Move and Tool Use) were executed and recalculated to Normal Seconds 60 Bdx. It turned out that the normal times of MOST were always higher that those of VWF and RWF. So, the real intrinsic tempo must be less than 66 Bdx (probably even lower tha 60 Bdx).

For the international rating scales (indicated in blue) the optimum tempo (or standard tempo or normal tempo) of the scale is indicated in green, whereas  the historic basic tempo or minimum tempo is indicated in red. For the various PD(E)T systems the internationally set tempo of the system for the given scale is indicated in blue.
N.B. It is essential that it is fully understood what is meant by “normal tempo”.

Education and Training
History untill ~1960-ies: A new worker will be prepared for the work by the department “Education and Training” and educated and trained to do his task up to a level of tempo Bdx 60. This basic or minimum tempo, Bdx 60, was the tempo with which a willing, somewhat trained/instructed worker could earn his basic wage which was based on number of products produced by the worker. From tempo Bdx 60 onwards, it is the responsibility of the factory department (and the worker) to get the worker as fast as possible at the level of the task tempo and at the rate to earn the standard wage at Bdx 80. Performing over tempo Bdx 80 meant an over-salary and a contribution to the “petty cash for illness” of the department. Tempo Bdx 80 indicates the most favourite ratio between effort and the resulting speed ánd provides the optimum effectiveness of the movements/motions complying with the safety and quality standards. The task tempo of a factory or organization is often set equal to the standard tempo.
Nowadays, many factories work with a union contract which forces the company to pay the workers for a performance level of standard tempo, and encourages the worker to achieve as fast as possible a performance level of standard tempo of Bdx 80.

APL
The Bedaux 60B system, the Lowry, Maynard and Stegemerten system (LMS), MTM and many other systems are based on times referred to as “normal”. The times in the Work-Factor system however, are referred to and termed “Work-Factor Times”.
A problem that may arise while using a MTM system or a LMS system, could be that the “select time” of any MTM-system, by definition, is set equal to the normal time (100%) and consequently is set equal to the standard time by the IMD. Sic non!
A description of that normal time or average time was given in November 1943 by Harold B. Maynard in a paper entitled “Average Performance - What is it?” presented at the Time and Motion Study Clinic for the Industrial Management Society in Chicago, which stated:
It was to be the effort given by the Conscientious Dayworker when he was working. It was to be a pace which appears somewhat slow when observed and which could be accelerated without too much difficulty under the encouragement of a wage incentive system”.
“With regard to skill, the operator considered as giving an average performance was to be one qualified for the job who had been at the work long enough to do it without undue hesitation, planning, or errors. He was not expected to be noticeably good at doing the job. At the same time, he was not expected to be noticeably poor.
This is very close to the notion under Time Study of Average Performance/Production Level, APL.


However, internationally it is generally acknowledged that the intrinsic tempo or rate (select time) of MTM-1 on the BSI scale should be positioned between BSI 75 and BSI 83. For convenience sake (and to end the discussions) one has settled for BSI 83 (or 66 Bdx or ASME 110 or 110%).
Following Work-Factor, the other MTM systems have been scaled with respect to MTM-1 (for MEK and MOST it is even more difficult).
With the little information at hand about the systems of BAT and MODAPTS the tempo of these systems is estimated as comparable with that of the MOST system.
With the little information available on and about REFA an attempt was made to define a REFA scale, especially useful for analists in Germany and Austria. See also the page under WFGD.

MPL
The Work-Factor Select Time is defined as that required for the “Average Experienced Operator, working with good skill and good effort(commensurate with physical and mental well-being) under standard working conditions to perform one work cycle, or operation, on one unit or piece, according to prescribed and specified quality. Incentive factors, if used, are determined by area wage condition and policy formes within the organization concerned”.
So, indeed, a motivated worker. This is very close to the notion under Time Study of Maximum Performance/Production Level, MPL.
Further .....

“Work-Factor Select Time is not comparable with times referred to as normal, daywork performance, sixty-minute-hour performance, or other terms used to indicate the work pace expected of the average worker who performs without incentive or at a level of productivity commen-surate with ‘base rate’ output”.

Time study therefore, by using a number of techniques, sets the time in which
- a well seasoned and trained,
- and motivated worker, who is
- fully suitable to do his task,
- and the prescribed task, according
- to prescribed working method,
- and working under good circumstances, with
- good and correct tools, can perform.


This is defined as working at standard tempo Bedaux 80 or 100 BSI or 133 ASME or 133%.

N.B. The reverse is also applicable: if the above mentioned requirements (about training, suitability, method, circumstances, tools, etc.) can not be met, the worker can not perform his work at T 80 Bdx, and his tempo will drop drastically, and productivity will decline very fast.

Below a visual interpretation is presented of the aspect “speed” of the notion tempo..

Tempo plaatje02

Back