USE OF COGNITIVE PSYCHOLOGY AND MUSCLE MOVEMENT MECHANICS IN WELDER’S TRAINING

By Instytut Laczenia Metali (Institute Joint of Metals) 31-837 Krakow ul.Fatimska 41a, Poland  www.ilm.pl

engineers:         Ryszard Jastrzebski, Marian Godniak and dr Andrzej Trojnacki

psychologists:   Tomasz Skakuj, Anna Stencel

Translated from Polish Katarzyna Ojrzyńska

Introduction

Strong competition among welders’ training courses organized in Kraków, Poland, in the 1990s forced the authors of this text to improve the quality of the courses they offer. The market, dominated by private enterprises, demanded from the newly trained welders all the necessary skills enabling them to do the jobs commissioned by western-European companies. The demands of the German market specifically boosted the search for new solutions in such fields as have never before been dealt with in connection with welding.

Program of research

At the moment, no welding technology in use enables an industrial welding robot with optical sensors to produce a pipe joint on the basis of image analysis, if the joint is set inaccurately and a weld groove is not precisely prepared (shifted edge, changing sill size and crevice).  This has to be done by a well-trained welder.  In order to intensify the welders’ training and render it more efficient we tried to isolate the factors responsible for the quality of welding.  The following factors have been chosen: physical training, visual control and the co-ordination of movement and observation.

Physical training

One could easily assume that the relationship between a welding training’s participant and the welding supervisor was similar to that between an athlete and a coach. In such a case, it would suffice to teach a physically fit person how to weld, and let him supervise the welding process. The research done in co-operation with the movement mechanics’ specialists aimed at identifying the influence of muscle development on welding efficiency. The aim was to develop alternative training methods for the muscles vital in the welding process.

As a result, the following tasks have been assigned for the welders’ physical training: 

·         Development and training of muscles, including wrist muscles, teaching the technique of the right grip and grip movements,

·         Reflex consolidation for greater stability of welding and proper welding bead formation.

Cognitive processes

Physical training variables alone are not sufficient for correct prediction of changes in the welding quality which occur during regular training.  A joint effort of engineers and psychologists, which resulted in the above division of the factors determining welding quality, proved the usefulness of cognitive psychology, as if predestined for this task. Visual control and co-ordination of movements and observation are both problems, the solutions to which are to be found within the field of this most modern branch of psychology. Cognitive psychology interprets knowledge about the human psyche in terms of data processing mechanisms.

Use of those three models of cognitive psychology : multistage analysis of characteristics, analysis by means of synthesis of experiences and comparison with the pattern during theoretical training gives an egual chance to those who, among 10% of  people predisposed to welding, are less skilled. The engineers used the multistage analysis of the image characteristics to create an overcoloured model of the weld pool environment which was then very useful  during the training.

Knowledge of these mechanisms at the training level could optimize the teaching process and improve the skills of a chief welder, enabling him to correct the welders’ movements.

Welding process engineer’s expectations

The following tasks for a psychologist were formulated with the new possibilities in mind:

¨       to collect the available information concerning the means of perception and filtration of an image by the perceptive apparatus, especially in a case when a vital part of an image finds itself not in the figure (the bright elements of an image), as usual, but in the background (the obscure, barely visible elements). (“Figure” and “(back)ground” are technical, perceptive terms drawn from the Gestalt psychology),

¨       to consider the possibility of gaining the information about a welding process phenomena on the unconscious level of data processing,

¨       to collect information concerning the studies on learning the skills (praxis) based on the feedback between eyesight and muscles movements,

¨       to prepare methods of theoretical training.

Cognitivistic methods of image identification[1]

Cognitivistic theories of image identification may add vital information to the characteristics of cognitive processes actively participating in the welding operation. The rapidly developing cognitive psychology enables us to grasp these characteristics, and may therefore be employed in welding. Three models of image identification systems have been analyzed:

¨       a system of comparison with the original pattern (the simplest model – the key term is “original pattern”: the representation which is being identified. The identification is based on matching the outside signal with the inner original pattern. To find a pattern which matches the signal better than the others means to identify the signal),

¨       the so called Pandemonium (this system consists of succeeding demons working on an received image, each of them performing a separate task. The first demon team – image demons, has the simplest task: they record the original image of an outside signal. Then the image is analyzed by characteristics demons, each of which looks for a certain characteristics in the image: a specific line or angle, a unique curve or outline. Cognitive demons observe the characteristics demons’ reactions. Each cognitive demon is responsible for identification of a certain pattern of characteristics. The last stage consists of decisive demons which judge the intensity of the reactions of individual cognitive demons. The Pandemonium System describes the stages in image characteristics analysis.)

¨       a model of analysis by means of synthesis (the sensory data interpretation is based on the knowledge of what the signal should be. This knowledge is provided by a context of a sensory incident, which is described as a huge load of information stored and usually automatically used for explaining the incidents. This context-based information evokes expectations which focus our attention on certain stimuli and are responsible for their selective reception. This model has an ability of self-teaching).

The three models differ in the way they deal with difficulties created by the problem tasks concerning sensory data processing, at the end of which process the image is identified. This theory employed in context of processing the information gathered during an intentional act of welding, the contents and form of which has been registered, is presented below on the bases of experiences acquired during the welding training.

Cognitive process and learning the welding technique

The process of welding learning usually begins when a trainee accidentally produces a correct weld and registers in the subconscious the image of the welding pool. After many trials he learns how to stabilize the process and achieve the recorded image of the pool. That is why, when GMA welding, after the welding material is heated and the weld seam widens, the welder shortens the welding arc, regulating the welding machine voltage instead of the current in a wire feeder.

In order to teach a trainee how to make a smooth face, it is better to make him “lead an edge of a weld pool along an upper surface of a former bead,” than to “move each new bead half the width of a former one,” since division of the distance into two equal parts is imprecise.  A similar technique is used when teaching forming or filling beads without sticking or undercuts.  Further training consolidates the newly created connections in the brain.

The decisive factors in fast and efficient learning of welding are: eyesight, sense of hearing, knowledge and the way of perception, physical fitness, intensity of training and its duration, experience and training in welding. 

The traditional welding training – model of analysis by means of synthesis of experiences

Traditionally, the training consists of welding tasks that gradually become more and more difficult. Since the processes in a welding pool and algorithms of welder’s movements automatics are still insufficiently researched, an instructor will try to show the process in practice rather than explain it (in many cases he may not realize why he actually did something in that particular way).

Many experienced welders cannot explain why the welds they make are correct while those of other welders are faulty. That is why even the certified or experienced welders would rather entrust their sons to instructors at a welding center than personally teach them.

Influence of perception mechanisms on welding quality – psychological system of comparison with the pattern

Each candidate for a welder has his eyesight examined.  Certain welding difficulties were noticed with those who had problems distinguishing the shades of red corresponding with the color of liquid slag and metal.

Some of them could learn welding in easily accessible places after a long training, but could not cope with welding in more difficult circumstances. Amongst the most experienced welders there were some who would use their sense of hearing rather then eyesight. This would come out when working in a hardly accessible and dark place, where such an expert would produce a weld next to a weld groove.

As a rule, during construction work in difficult conditions, when the well-practiced motions are distorted, it is eyesight that decides about the quality of a joint and movements are corrected.  The ability to observe is necessary for the learning process.  The intensity of an electric arc during welding makes a trainee at first overlook the vital elements in welding: the previous bead, liquid metal pool and liquid slag pool. Only after a long period of training a trainee stops paying attention to the arc, and concentrates on the more important elements.

According to research conducted by Institute for Joining of Metals in the welders’ training center of Technolkonstrzebski Company, a thorough analysis of pictures showing the welding place shortens the time required by the welder to learn to observe the weld pool.  The same mechanism lets us identify the familiar faces in the crowd rather than those we barely know.

Frequently, after a long practice a trainee would not follow given instructions. But when an instructor pointed at a liquid metal pool and liquid slag, the learning process would become very fast. This shows that a trainee has initial problems identifying the less visible liquid metal pool, a former bead and a welding groove against a bright welding arc.

The participants of “ Engineering Supervision and Inspection of Welding Course” were repeatedly and over a long period of time shown the mechanisms of weld forming, elaborated by Institute for Joining of Metals, as well as the way of directing the heat source and the technique of feeding the weld metal. The relationship between process dynamics and an observed image was also revised. As a result trainees who had never before held a welding gun were able at the first attempt to make a correct weld penetration and weld face using MIG and TIG methods.

Thus we can conclude that eyesight and the ability to distinguish between liquid slag and liquid metal against a very bright electric arc and a dark image of the previous bead and welding groove is important in the welding process control. It should be emphasized, however, that even more important are the style and technique of observation and perception of the welding process.

The importance of the sense of hearing in welders’ training

A skillful welder will be able to control the glowing of a welding arc and the creation of a proper bead basing on the sense of hearing. It lessens the eyestrain and decreases the welders’ fatigue. A characteristic sound in the pipe means the granite layer (called penetration) has been made correctly. With the use of the sense of hearing one can also control the proper glowing of a welding arc. One can then concentrate on watching the weld pool.

An experiment was held, during which some trainees could only rely on their sense of hearing (no observation allowed) while they listened to the noises accompanying welding of course samples. These trainees achieved better course results as compared with the other trainees.

Physical development

A long training experience showed that tall, well-built and athletic people had more difficulties learning the practical skills of welding than those slender and unfit. They usually had problems with firm and precise gun-leading.  At first it looked as though there was no correlation.  Painstaking research showed, however, that the muscles responsible for a firm grip are wrist muscles, not biceps.

What is particulary important, is the proportion between the muscles of wrist and of biceps. The mechanics who work very hard have to stress on practising more the muscles of wrist so that  the biceps doesn’t limit the precision of mouvements of the welding touch.

What also proved important are habits and learned patterns of behavior. Those welders who used to work with covered electrode and switched to MIG welding with granite layer still try, out of a habit, to weld with weaving with a gap of 1.5 mm and they have problems with weld penetration. TIG welders who used to do gas welding before are less efficient and produce low quality granite layers. Gas welding habits also hinder the production of the first layer with no undercuts.

People motioning the whole arm had problems with welding. The welders who only moved their wrists and fingers performed much better. Many instructors insist that the training should finish only when a trainee stops thinking about welding and leads the gun automatically, without any conscious control. The conscious control slows down the whole computer program.  People with dysequilibrium are unable to learn welding.

Intensity and duration of a course

Too many course hours a day are tiresome for trainees and make them persist in bad habits.  Also, breaks during a training period that are too long negatively influence the efficiency of training.

An experiment was conducted: a more advanced trainee trained 12 hours a day and a beginner trainee trained 4 hours a day.  The trainee who trained less, but systematically, learned welding faster and better.  The course time is the time for developing muscles.  Experience shows that training cannot less than 20 working days and longer breaks negatively affect the training.

Achieving welding proficiency

Welding training

Once the technique is acquired, it is the training that decides about welder’s reliability. Pressure vessel welders coming back after a longer leave produce a few incorrect joints at first. The same results may be caused by too much intensive work or training.

Stamina is also very important in long-term welding. Those welders with the proper leading and gripping technique do not get tired easily. Intensive welding requires a 2-3 days’ rest. A longer break might negatively influence the quality of welding. On the first day after a longer break one should not work on important welded joints.

Experience

Quite frequently it happens that older welders who wear glasses and whose hands shake make important joints better than their younger and fitter colleagues with only a few years of experience.  The decisive factors are:

·         Knowledge of the experienced welders

·         Thorough understanding of the subject

·         Care in preparing and putting together the edges of a groove

·         Maintaining a welding machine in working order

·         Mental strength.

It is often said that a young welder finishing a course is like an inexperienced athlete, who, unlike the elder    ones, cannot mentally endure the tension during an important sports event.  An experienced welder works not only subconsciously, but also consciously – mental processing means a better gun leading and weld metal feeding in non-standard conditions.

The role of course training in acquiring welding mastery

At times the so called “self-taught welders” enroll for a course. They have many years’ experience, and are regarded specialists by their managers.  They are expected to pass a qualification test without any additional training. It is only when they are shown the requirements and skills possessed by other, trained, specialists that they become less ambitious and decide to prolong the training period before the exam. During the course it turns out that the time is further prolonged, and as a result a self-taught welder needs 50% more time than a complete novice.

It is partly due to the instructors’ reluctance to train the  “specialists” and also due to the fact that the latter do not immediately notice the necessity of getting rid of bad habits, which itself is far from easy. In welding it is clear that mastery requires knowledge and experience of a few generations, without which an amateur is rather helpless. The level of proficiency attained by a welder depends on proficiency of his instructor and his colleagues, who share their experience with him, on how responsible the tasks are and on the skills of the chief welder, who supervises the work.

Conclusions

Following conclusions have been drawn:

·         Course training teaches the skills based on experience of many generations and is therefore indispensable in gaining high professional skills.

·         Practical training, performing demanding tasks under supervision of a welding engineer, is vital.

·         Use of the cognitive psychology based methods facilitating the welders’ training, such as repetitive display of over-exaggerated weld-pool pictures, can reduce the training to 4 hours a day, but the total number of training days must remain at least 20 for TIG and MIG welding.

·          

·         Knowledge of cognitive psychology and mechanisms of visual data processing helps the chief welder to achieve better welding movements’ correction.

·         European norms that set the total number of training hours, and not days and welds, are inaccurate.

·         Teaching gas welding before TIG training, and covered electrode welding before MIG training may facilitate the first stage, but may prove harmful for the final results of the training.

·         Better results are achieved when teaching the TIG method before gas welding, and the MIG method before the covered electrode welding.

·         An experienced welder has a greater mental strength as compared with a beginner, and thus he is more reliable when making demanding welds.