The study of times and movements is a tool for measuring work that has been used successfully since the end of the 19th century, when it was developed by Taylor. Over the years, these studies have helped solve many production problems and reduce costs.
Definitions
- Time study: activity that involves the technique of establishing a standard of permissible time to perform a given task, based on the measurement of the content of the work of the prescribed method, with due consideration of fatigue and personal delays and inevitable delays. Movement study: careful analysis of the various movements that the body makes when executing a job.
Background
It was in France in the 18th century, with the studies carried out by Perronet about the manufacture of pins, when the study of times in the company began, but it was not until the end of the 19th century, with Taylor's proposals that it spread and he knew this technique, the father of the scientific administration began to study the times in the early 1880's, there he developed the concept of the "task", in which he proposed that the administration should be in charge of planning the work of each of its employees and that each job had to have a time standard based on the work of a highly qualified operator.
After a time, it was husbands Frank and Lilian Gilbreth who, based on Taylor's studies, expanded this work and developed the study of movements, dividing the work into 17 fundamental movements called Therbligs (their last name upside down).
The study of times
Requirements
Before undertaking the study, the following should basically be considered:
- To obtain a standard, it is necessary for the operator to master the technique of the work to be studied perfectly.The method to study must have been standardizedThe employee must know that he is being evaluated, as well as his supervisor and union representativesThe analyst must be trained and must have all the necessary tools to carry out the evaluation The analyst's equipment must include at least a stopwatch, a preprinted worksheet or format and a calculator. Complementary elements that allow a better analysis are the camcorder, the recorder and, if possible, an electronic stopwatch and a personal computer. The attitude of the worker and the analyst should be calm and the second should not exert pressure on the first.
There are two basic methods of conducting time study, continuous and zero return.
- In the continuous method, the stopwatch is allowed to run for the duration of the study. In this technique, the stopwatch is read at the end point of each item, while the hands are in motion. If you have an electronic stopwatch, you can provide a stationary numerical value. In the zero return method, the stopwatch is read at the completion of each item, and then immediately returns to zero. When the next item starts, the stopwatch starts from zero. The elapsed time is read directly from the stopwatch at the end of this item and is reset to zero again, and so on throughout the study.
Time study objectives
- Minimize the time required for the execution of works. Conserve resources and minimize costs. Perform production without losing sight of the availability of energy or energy. Provide a product that is increasingly reliable and of high quality.
The study of movements
The study of movements can be applied in two ways, the visual study of movements and the study of micro-movements. The first is applied more frequently due to its greater simplicity and lower cost, the second is only feasible when highly active tasks whose duration and repetition are high are analyzed.
Movement study objectives
- Eliminate or reduce inefficient movements.Accelerate or optimize efficient movements.
THERBLIGs
Within the study of movements we must highlight the fundamental movements, these movements were defined by the Gilbreth spouses and are called THERBLIGs, they are 17 and each is identified with a graphic symbol, a color and a letter or acronym:
| THERBLIG | LETTER OR ACRONYM | SYMBOL | COLOR |
|---|---|---|---|
| Search for | B |
|
Black |
| To select | I KNOW |
|
Light grey |
| Take or grab | T |
|
Red |
| Reach | TO THE |
|
Olive green |
| Move | M |
|
Green |
| To hold | SW |
|
Golden |
| Release | SL |
|
Carmine |
| Place in position | P |
|
blue |
| Pre-position | PP |
|
Sky Blue |
| To inspect | I |
|
Burnt Ocher |
| Join | AND |
|
Dark violet |
| Disassemble | OF |
|
Light violet |
| Use | OR |
|
Purple |
| Inevitable delay | GAVE |
|
Ocher yellow |
| Avoidable delay | DEV |
|
Lemon yellow |
| To plan | PL |
|
Chestnut or Coffee |
| Rest | DES |
|
Orange |
These movements are divided into efficient or effective and inefficient ineffective as follows:
Efficient or effective movements
- Physical or muscular in nature: reach, move, release and pre-position in position. Objective or concrete in nature: use, assemble and disassemble.
Inefficient or ineffective movements
- Mental or Semi-mental: search, select, position, inspect and plan Delays or delays: avoidable delay, inevitable delay, rest and hold.
The following is an original video, from the Gilbreth era, in which you can see how they carried out some of their experiments on the study of work:
The principles of the economy of movements
There are three basic principles, those relating to the use of the human body, those relating to disposition and conditions in the workplace and those relating to the design of equipment and tools.
Those related to the use of the human body
- Both hands must simultaneously begin and end the basic elements or divisions of work and must not be inactive at the same time, except during rest periods. Hand movements must be symmetrical and performed simultaneously when moving away from and approaching the body. Whenever possible, physical momentum or momentum should be harnessed to assist the worker and minimized when counteracted by muscular effort. Continuous straight-line movements are preferred over rectilinear movements involving sudden changes in direction and Abrupt.The smallest number of elements or therbligs should be used and these should be limited in the lowest possible order or classification. These classifications,Listed in ascending order of the time and effort required to carry them out, they are:
-
- Finger movements. Finger and wrist movements. Finger, wrist and forearm movements. Finger, wrist, forearm and arm movements. Finger, wrist, forearm, arm and whole body movements.
- Care must be taken that all work that can be done with the feet is carried out at the same time as that carried out with the hands. It must be recognized that simultaneous movements of the feet and hands are difficult to perform. The cordial and thumb fingers are the strongest for work. The index finger, the ring finger and the little finger cannot support or handle considerable loads for a long time. The feet cannot efficiently operate pedals when the operator is standing. Torque movements must be performed with the elbows flexed. phalanges or finger segments, closest to the palm of the hand
Those related to the provision and conditions in the workplace
- Fixed sites should be allocated for the entire tool and all the material, to allow the best sequence of operations and to eliminate or reduce the therblings to search and select. reach and move; It is also advisable to have ejectors, whenever possible, to automatically remove the finished parts. All materials and tools should be located within the normal working perimeter, both horizontally and vertically. It is advisable to provide a comfortable seat to the operator, where it is possible to have the appropriate height so that work can be carried out efficiently, alternating sitting and standing positions. Adequate lighting, ventilation and temperature must be provided.Visual or visibility requirements at the workstation should be taken into account to minimize eye fixation.A good pace is essential to smoothly and automatically carry out an operation, and work should be organized in a manner that enables an easy and natural rhythm whenever possible.
Those related to the design of the equipment and tools
- Wherever possible, multiple operations should be carried out with the tools by combining two or more of them in one, or by arranging multiple operations in the feeding devices, if applicable (for example, in cross-carriage and hex turret lathes All levers, handles, steering wheels and other control elements should be easily accessible to the operator and should be designed in such a way as to provide the maximum possible mechanical advantage and the strongest muscle assembly could be used. The workpieces should be held in position by means of clamping devices. Whenever there is a possibility of using mechanized (electric or other) or semi-automatic tools such as motorized screwdrivers and screwdrivers and speed wrenches, this should be done.
Here are four video lessons to complement this important topic of operations management:
- In the first, Professor Víctor Yepes, from the Polytechnic University of Valencia, explains how the study of work can improve productivity, explains the concepts of a skilled worker and work rhythm, and teaches how to calculate the type time of an activity. Second, it is Professor Cristóbal Miralles, also from the Polytechnic University of Valencia, who presents the methodology for carrying out a study of times with acyclic elements of work, but first he reviews the general procedure for the study of times. third, professor Silvia Flores, from SENATI of Peru, explains how to measure work using the stopwatch technique. The fourth is a very didactic video, from the National University of San Agustin of Peru, about the study of movements,specifically the principles of economy of movement in jobs.
Surely they will be useful to deepen the subject of the study of times and movements.
Bibliography
- Chiavenato, Idalberto, Introduction to the general theory of administration, McGraw-Hill, 1995. ME Mundel, Study of Times and Movements, Continental, 1984. Niebel, Benjamin, Industrial Engineering. Time and movements study. Alfa Omega, 1996.Sáinz Yunes, Luis Rafael. Design of the work, ITESM, 2001.
