- - General.
This Organization technique is used to calculate the time it takes for a qualified operator to perform a certain task following a pre-established method. Knowledge of the time it takes to perform a job is as necessary in the industry as it is for man in his social life. In the same way, the company, to be productive, needs to know the times that allow solving problems related to manufacturing processes.
- To control the operation of the machines, departments; to know the% of shutdowns and their causes, to program the loading of the machines, select new machinery, study the distribution in the plant, select the means of transporting materials, study and design the work equipment, determine the machining costs, etc.
- To determine the number of necessary operators, establish work plans, determine and control labor costs, as a basis for direct incentives, as a basis for indirect incentives, etc.
- To compare designs, to establish budgets, to program production processes, to compare work methods, to avoid stops due to lack of material, etc.
- To simplify management problems, providing interesting data that allows solving some of your problems, to improve relations with customers when delivery deadlines are met, to determine the date of: acquisition of materials, to eliminate downtime, etc.
The good operation of the companies will depend on many occasions on the fact that the various activities listed are correctly solved and this will depend on the goodness of the calculated working times.
Furthermore, the calculated times must be fair because:
- Its duration depends on what the operator is going to charge, and what the company has to pay. Poorly calculated working times are the ideal breeding ground for the birth of most labor problems.
2.- Basic concepts
The technical procedure used to calculate working times consists of determining the so-called standard time or standard time, understanding as such, that which is required by a qualified worker to execute the task to be measured, according to a defined method. This type time, (Tp), includes not only the time necessary to execute the task at a normal pace, but also the work interruptions that the operator needs to recover from the fatigue caused by his performance and for his personal needs.
- The time of clock (TR)
It is the time that the operator is working in the execution of the entrusted task and that is measured with the clock. (The stoppages made by the producer are not counted, both to attend to his personal needs and to rest from the fatigue produced by the work itself).
- The factor of rhythm (FR).
This new concept serves to correct the differences produced when measuring the TR, motivated by the existence of fast, normal and slow operators, in the execution of the same task.
The correction coefficient, FR, is calculated by comparing the rate of work carried out by the producer performing the task, with that which would be carried out by a normal trained operator, who is familiar with the task.
- The time average (TX).
It is the TR that a trained operator, familiar with the work and developing it at a "normal" rate, would use in executing the task under study.
Its value is determined by multiplying TR by FR:
TN = TR x FR = Cte
and it must be constant, as it is independent of the rhythm of work that has been used in its execution.
- The supplements of work (K).
As the operator cannot be working all the time of presence in the workshop, due to being human, it is necessary to take some breaks to allow him to recover from the fatigue caused by the job itself and to attend to his personal needs. These periods of inactivity, calculated according to a K% of the TN, are valued according to the characteristics of the worker and the difficulties that the task presents.
In reality, these periods of inactivity occur when the operator wishes.
Supplements = TN x K = TR x FR x K
- The time rate (Tp)
The 18 micromovements called therblig have been replaced in this system by the following eight basic elements:
- Reach. Move. Turn. Apply pressure. Take. Position. Release. Disassemble, whose amount, measured in LMT, and collected in tables, varies depending on the distance traveled, weight of the object, eye focus, etc.
It is by far the most widely used preset timing system in the industry.
The basic micro-movements of the MTM-2 are basic concepts classified and defined by categories. The tables of the predetermined times, valued in IJTM, indicate the symbol, the distances traveled, the complexity of the concept, the weight of the object and the values of each micromovement given in UMT.
Although the calculation of the times using the predetermined time systems gives results of great precision, their application can only be carried out by those operators who, being good professionals, are also timekeepers and have been trained theoretically and practically in these predetermined time systems.
The application of Improvement of Working Methods, together with the objective nature of the determination of standard times by the predetermined time system, are the fundamental reasons that would justify its importance.
8.- Timing.
The calculation of working times by means of the stopwatch is the most widely used systems in the industries.
The following actors need to be calculated:
TR = Time measured with the watch, which in this case will be the stopwatch
FR = Rhythm Factor, defined above
TN = Normal Time, and
K Supplements, 9.- Type Data.
In a similar way to that explained in the predetermined times, they are also measured in the industry and standard times are calculated with the help of tables, prepared in-house, whose values have been determined by making measurements with a stopwatch. The standard time of a task is also the sum of the standard times of each of the elements that make it up.
This measurement system is widely used in companies that work on demand, since its application allows predetermining the execution times of the various tasks. The timekeepers must be very good.
10.- Work learning.
The operator to be measured must be: a trained worker, must know the task well, must follow the pre-established method. In order for these conditions to be met, the calculated standard times are valid.
The learning period is usually very short for those simple operations, extending its duration, with the need to apply knowledge and manual skills. These periods are calculated in the industry on an experimental basis. The reasons given justify the fact that work times should not be established until the learning period has elapsed. If it were done before, the operator would lack the necessary skill while at the same time gradually improving the working method.
The type times (Tp), must always be calculated once the learning period has elapsed, since it is then, when the times necessary to do a given task remain stable and the knowledgeable operators dominate the execution of the task and can follow the preset method.
Chapter 8
THE Timing.
8.1. Introduction.
Timing is the most widely used procedure by industries to calculate the standard times of the various tasks. Its determination is made according to the well-known expression:
Tp = TR x FR x (1 + K)
being the meaning of the various factors explained above, that is: Tp = type time
TR = clock time FR = rhythm factor
K = work supplement.
Later we will use the factor
TN = Normal Time whose value is:
TN = TR x FR
as already defined in the previous chapter.
2.- Timing process
The technique used to calculate the standard time of a given task is to break it down into the various parts that make it up, called elements, and calculate each of them. The sum of the elementary type times determine the value of the task time.
Timing process
1.- IN THE WORKPLACE
- Analysis of the Observation and annotation of the information. - Identification of the job Choice of the operator to measure Analysis of the conditions of the job Environmental Machines Tools Tools characteristics of the machinery Characteristics of the job Description of the method and its decomposition into element Taking of Assessment of rhythms.Annotation of clock times.Calculation of the number of observations.
2.- IN THE OFFICE
- Data count. Supplements and grants. Type time calculation.
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1.- The one carried out in the workplace when analyzing the task to be timed. 2.- The one carried out in the office or dispatch, in which the timekeepers must carry out the studies and calculations necessary to determine the value of the standard time.
3.- Observation and annotation of the information.
Before starting to measure the elements, the work to be timed must be well defined so that the calculated type times are true. It is necessary to analyze the work in as much detail as possible and clearly define the following data:
- The operation to be measured, the operator who performs the work, the name of the timekeeper, the part to be machined, the material to be worked, the tool used, the work process used, the existing environmental conditions, the elements of transport used, the sketch of the workplace, the elements that make up the task to be timed, etc.
The description of the method used (if possible already improved) is essential, since the calculated standard time is for the indicated process and not for another, which can be improved later. That is, if for any circumstance the working method is modified (due to changing the process, the machinery, the tools, the sketch of the station, the environmental conditions, etc.). The value of the type time would also vary because the elements that constitute the task being measured are different.
If we define each part by element, in which we divide the work to be measured and by work cycle the ordered set of elements whose integration forms the specified work unit, we can find the following classes of elements:
CLASSIFICATION OF THE ELEMENTS
1.- CYCLE
- Regular or repetitive. Irregular or frequency. Casual to strangers.
2.- EXECUTOR. - Manuals.
- Mechanics
3.- DURATION.
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TN = --------- n
- Triangle - hyperbola.
This procedure is based on knowing that, the geometric place of the product of two variable factors, when it remains constant, is a hyperbola.
As in theory, and for each of the measurements made of a given element, the product.
TR x FR = TN = Cte.
if we operate with the clock times and the peresentative rhythm factors, the product obtained by multiplying both, will determine the representative normal time of the studied element.
- Computer
It is easy to understand that if you have a computer or a programmable calculator, the calculations outlined above are greatly simplified.
These programs can be obtained on magnetic cards for calculators or on cassettes for minicomputers, giving us with great precision and speed: The errors made, the frequency histograms and the normal times of each element
9.- Supplements and Grants.
- a) Supplements
Until now we have considered that the operator is always working and it has only been detected that he is stopped when the activity has appeared in the DATA SHEET SHEET, 0. These stops recorded in the timing are totally necessary at work because the worker As a human being, you need to recover from the fatigue caused by work; needs to meet personal needs; etc, and sometimes, perform a series of complementary tasks such as: filling out worksheets, consulting plans, preparing tools, etc. All these activities. called complementary. although necessary. they are totally unrelated to the execution of the task itself.
Therefore, the time necessary to do a job is made up of two addends:
-The time spent executing the work, corrected in its performance factor, and called Normal Time »(TN).
-The additional time necessary for breaks and complementary tasks, which are valued as a percentage (K) of normal time (TN · K)
The sum of these two times forms the so-called Type Time (Tp), whose value is:
Tp = TN + TN · K = TN (1 + K)
The standard time, according to the previous expression, is not a timed time It is the time spent by a worker in carrying out a certain task carrying out a normal activity, plus the time spent recovering from fatigue caused by one's own work and by complementary activities, that is forced to carry out.
The various supplements to consider when timing are usually divided into:
- Fatigue supplements, supplements for personal needs, supplements for accessory occupations
"Ancillary occupations" are real jobs that the operator does, but because they are not part of the timed job, they are valued as if they were real supplements
Among the main supplements for accessory occupations, we can highlight the following:
- Prepare tools, tidy up and clean the workplace, examine plans, fill out worksheets.
The most used way in Spain to determine the value of supplements is the one that calculates the one that corresponds to each of the elements that make up the task to be timed.
- b) Awarded
When an operator is working on a machine whose process is automated, and even if there are automatic work items on the job, the operator cannot perform any activities. Production is determined by the automatic process and cannot be increased, however great the worker's interest in reducing the cycle time.
In these cases, the Company grants supplements to the operator, so that the premium that he will receive for the performance calculated in his "Worksheet" is similar to that of the other operators, whose work is not automated.
Two procedures are used in determining those awarded:
- When the automatic elements are of long duration and the operator can do other tasks during the execution of the machine element. When the duration of the machine element is relatively short and the operator cannot carry out other tasks during its execution.
10.- Frequencies.
This concept indicates the times that an element intervenes in the work cycle, which is necessary data if a working time is to be well determined.
The total time of a work cycle is given by the sum of the partial times of each of the elements, each multiplied by a factor that takes into account its repetition or frequency within that cycle.
Undoubtedly it can happen that an irregular or frequency element only appears after a certain number of work cycles. In these cases it is necessary to assess its weight or frequency, to include it within each cycle, and not overlook those irregular elements that would deform the concept of the productions that must be demanded of the operators.
11.- Calculation of the standard time.
Obtained the normal times of each of the elements in which the work has been divided, calculated the work supplements (K) and determined the frequency of each element (F), with respect to the unit that we want to measure, the elementary type time comes given by:
TP pi = TN i · (1 + K i) · F i
The type time of the cycle of the unit considered is the sum of the elementary type times, duly weighted, of each of the n elements into which it has been decomposed.
As it is usual to point out "required productions" and "optimal" in the timing, we will indicate that:
Required production or number of pieces that an operator must do at least in one hour, is calculated by dividing the number of units that the hour has, by the cycle duration (measured in those same units).
Optimal production is the maximum that an operator can perform, if he follows the method indicated in the timing.
In the case of being free all the work elements that make up the cycle, it can be worth 1.4 times the required amount; but if there are machine elements, their value is variable, since it depends on those granted to those elements and whose duration depends on the machining process.
Chapter 9
Type data and Sampling.
1.- Introduction to the Type Data.
The companies that work under order, characterized by manufacturing few equal products, cannot calculate their required productions by the timing procedure explained in the previous chapter, because they do not have the number of measurements necessary to guarantee the accuracy of the standard times. In these cases, companies, using graphs or tables prepared for themselves, can calculate their elementary type times, and from their sum, predetermine that of the task to be measured.
The Type Data is established by the company through the values obtained in the timing made in its own workshops.
It is worth emphasizing the idea of good timekeepers (professionals in the trade to be timed), because they must previously establish the working method to be followed in the process to be measured, and this must be the best possible, so that its execution is the shortest possible.
It should also be noted that if the graphs, formulas or tables established in the company for the calculation of the elementary standard times have been prepared by operators of the company itself, it is necessary to recommend that high-level technicians be held responsible for them, because its use can cause serious problems.
- - Graphics, formulas and standard tables.
If a workshop breaks down the various tasks that can be carried out in it, according to homogeneous elements, and has several timings that indicate the values of the standard times that correspond to each magnitude of the element considered, a careful and orderly study of these two variables (values of the type times and magnitudes of the element), will allow us to establish the law that determines the type times based on the various values that the considered element may present.
3.- Standard elements.
The standard elements that constitute the task to be measured with their sum, can be classified into:
- Constant elements. They are those whose values vary slightly from what has been established as representative. They are calculated according to the arithmetic mean of the values obtained when timing various tasks in which the considered element appears. Variable elements. They are calculated through graphs or formulas.
4.- Calculation of standard times.
The calculation of the standard time of a task is based on the principle that it can be decomposed into its constituent elements, specific to each workshop. and determine the total time of its execution, by the sum of the standard times of the various elements that comprise it.
The timekeeper, once the work process to be followed has been established, defines the elements that comprise it and determines the frequency with which each of them intervenes. Subsequently, making use of the graphs, tables and formulas corresponding to the elements that intervene in the process, it determines the elemental type values, and writing them down in the corresponding place. The sum of all elementary type times determines the type time to do this task.
9.5. Data Sampling.
The calculation of standard times, applying the sampling techniques, consists of evaluating the factor p, of the expression:
Tp = TE · p · FR · (1 + K }
n
since the remaining factors are measurable. Its meaning is as follows:
TE = Measured time, which indicates the time it actually took to make the n pieces. p = mean, deduced by sampling, of the time that the operator is working.
FR = Rhythm Factor. K = Supplements for breaks.
n = Number of pieces that the operator has made in the TE.
The technique of determining standard times by sampling, has its practical application when it is necessary to determine the productions required in various workplaces and can only be applied in the measurement of times, the calculation in each position of the value of p% that the operator uses. find working
Another of the great applications of sampling in the industry is to determine the value of numerous activities, both workshops and offices, of great interest to managers and whose knowledge by other procedures would be prohibitive.
9.6.- Samples.
The sampling technique is based on descriptive statistics that allow us to know what happens in a population or universe, just by studying a certain number of random instantaneous observations, culled from the population or universe itself. In other words: By analyzing a sufficient number of measurements, made through instantaneous and random observations, what happens in the population or universe to be measured is predicted, with an error and a certain level of confidence.
It is said that a random sample has been taken when the method followed in the choice of the elements that compose it, ensures that all those who are part of the universe to be measured have had the same probability of belonging to the sample. Two systems are usually used to obtain random samples:
- The lottery. Random numbers
The lottery procedure requires the possibility of placing a drum on all the elements or their representation, which is to be controlled. When the possibility does not exist, the technique of enumerating the elements and choosing those whose coincide with those of some tables of random numbers and that have been chosen according to a certain law is usually used
7.- Statistical control by attributes.
The sampling applied in the industry focuses on saying the activities that you want to measure and analyzing in each one of them, whether or not you work at the times when the observation is made.
When you want to calculate the standard time of the tasks that are being carried out in various workstations, the only activity that is measured is to record whether the observed operator works or not. As sampling is by attributes, the main fundamental concepts are recalled below:
- Frequency distribution and Gauss curve, confidence levels, number of necessary observations, control diagrams
8.- Sampling example.
Any sampling exercise, which must be carried out in a workshop, must clearly define the following stages
- Set the sampling objective. Prepare the necessary forms. Determine the number of daily observations. Calculate the timing of the measurements. Make the instantaneous and random measurements. Calculate the number of necessary observations and establish the control limits. Interpret the results.
