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CLOSE THIS BOOKMachining of Material/Metal - Course: Manual working of metal. Methodical course-guide for instructors (Institut fr Berufliche Entwicklung, 62 p.)
3. Accomplishment of the training
VIEW THE DOCUMENT3.1. General recommendations for the procedure of the course
VIEW THE DOCUMENT3.2. Introductory instruction
VIEW THE DOCUMENT3.3. Exercises with accompanying instructions
VIEW THE DOCUMENT3.4. Final instruction

Machining of Material/Metal - Course: Manual working of metal. Methodical course-guide for instructors (Institut fr Berufliche Entwicklung, 62 p.)

3. Accomplishment of the training

3.1. General recommendations for the procedure of the course

The training course proceeds in the succession of the individual training units. The training units “Setting up and operation” should always be started with, since they will impart the basic knowledge required for the other training units. The training should then proceed with the training units according to the serial number of the training units. The knowledge and skills in the relevant working technique should be taught by an alternation of instructions and exercises. The instructions shall teach the knowledge required for accomplishing the working technique. In the exercises to follow the trainees shall put into practice the theoretical knowledge acquired. Practising of the work routines should take most of the time available for training and go on until a specified level of perfection has been reached. The practical exercises are to be considered the heart of the training. At the end of the exercises each trainee should be informed of the level of skills developed. Therefore, the following procedure of teaching a working technique is recommended to the instructor:

- introductory instruction,
- exercises with accompanying instructions,
- final instruction.

3.2. Introductory instruction

This lesson shall teach the theoretical knowledge required for the relevant working technique. It is to be given by the instructor at the beginning of each training unit. After that instruction the trainees should be able to carry out the exercises properly and with as good results as possible.

Related to the individual training units, the whole group of trainees is to be informed of

- the purpose and meaning of the relevant working technique,

- the construction, maintenance, types of machines, cutting tools, clamping tools, measuring and testing tools,

- the technological flow of work on the respective machine in the relevant working technique.

The instruction should also include labour safety instructions. This is absolutely necessary before each exercise is started in order to avoid accidents. The labour safety instructions should be as vivid as possible explaining accidents and incidents that actually happened in the factory. The trainees should be informed of general rules of labour safety and be referred to further specific hints to be given during the practical work. The trainees must be convinced that accidents cannot be avoided unless the labour safety instructions are strictly followed. A control book is to be prepared to give proof of labour safety instructions given outlining in brief the hints and explanations given to the trainees. Each trainee has to sign in the control book the labour safety instructions for ready reference in the event of any neglect.

General rules of labour safety:

- Wear close-fitting clothes! Loose clothes may be caught and pulled about by rotating machine parts.

- Never work at machines without protective headgear!

- Protect your feet by solid footwear!

- Never remove any protective devices from the machine!

- Do not reach into rotating machine parts! Switch off the machine first!

- Use tools in proper condition only!

- Clamp workpieces and tools safely and firmly!

- Use safety goggles (particularly with short-chip material) to avoid injuries of the eyes!

- Do not remove metal chips by hand! Use a chip hook, chip brush or hand broom!

- Keep naked hands off workpieces with burrs! Use protective gloves or a piece of cloth!

- Cover with sand and remove any oil slicks resulting from oiling of the machine!

- Never do any measuring or testing unless the machine is at rest!

- Do not set the speed or operate any switches unless the machine is at rest!

- Do not open any gear or motor covers until after switching off the main switch!

The introductory instruction may have the form of a lecture or dialogue or combination of these two forms.

The lecture by the instructor shall introduce the trainees into the new working technique and inform them of the aim of the instruction. Moreover, this is a way of teaching unknown knowledge, such as of the construction and operation of the relevant machine, of the construction and type of working tools to be used.

For more vividness of the lecture it is necessary to show and explain, e.g. to demonstrate, all working tools to the trainees. The construction and operation of the machine should be demonstrated in the workshop directly on the respective machine, the engine lathe, for example. The following steps are recommended for the demonstration of a working process:

- Demonstration at normal pace of work.

The instructor mentions the individual steps of work. The trainees get an idea of the entire process.

- Demonstration at decelerated pace

The process is disassembled into single components with the emphasis being on explanations.

- Repetition of difficult steps.

- Demonstration of the entire process at normal pace of work.

- One or two trainees repeat the demonstration of the working process.

- Evaluation of the demonstration.

It is important that all trainees can match the demonstration.

The lecture by trainees should be used as a means of recapitulating and consolidating knowledge already taught. For this purpose the trainees should be requested to deliver a continuous lecture, e.g. about the construction of vertical and horizontal milling machines.

The teaching dialogue shall serve to jointly elaborate (instructor with trainees) new knowledge, e.g. of technological processes. The dialogue is based on existing knowledge which is to be applied to new situations. For example, the dialogue may be preceded by reading some sections in the “Trainees' Handbook of Lessons”.

The elaboration of new knowledge in the dialogue can be considerably supported by the use of various visual aids, such as original cutting, clamping, measuring and testing tools, of the illustrations in the “Trainees' Handbook of Lessons”, of transparencies and models. The dialogue may also be used as a means of recapitulating known knowledge. All trainees can be involved in the recapitulation by the form of questions and answers of the dialogue. So the instructor can easily judge the level of knowledge of the trainees. The questions contained in the “Trainees' Handbook of Lessons” should be included in the teaching dialogue. Immediately upon elaboration of one or more key points, the trainees may requested to answer orally or in writing. In this way, the instructor can find out whether or not the trainees have understood everything. On the other hand, the questions in the individual sections of the “Trainees' Handbook of Lessons” are a means of control if the trainees had been requested to elaborate some technical key points on their own.

3.3. Exercises with accompanying instructions

Immediately before any exercises the trainees should be given specific hints for the workpiece to be practised.

According to the individual instruction examples, the trainees should be provided with information

- on the aim of the exercise,
- on the raw material of the workpiece,
- on the cutting, clamping, measuring and testing tools and accessories immediately required,
- on the steps of work (difficult steps should be demonstrated again),
- on certain dimensions and critical points of the workpiece,
- on criteria for judging the performance at the workpiece and on intermediate controls,
- on the time of the exercise to be kept.

A finished workpiece should be shown to the trainees to make clear the aim and key points of the exercise. It is useful when the instructor has previously made the workpiece himself so as to know the problems connected with its manufacture.

So he can clearly state the performance rating criteria and point out critical points of the workpiece. During such instructions each trainee should have the sequences of operations and the working drawings of the “Instruction Examples for Practical Vocational Training”. The trainees may then add necessary hints under headline “Comments” of the “Instruction Examples...”.

The aim of the exercises is to learn and to develop the skills of important operations in machining of metal workpieces up to an intended level of perfection. Therefore, the exercises must be repeated several times and be carried out purposefully. If the instructor is of the opinion that the first example of any training unit would make too high demands on the trainees' skills, preparatory exercises must be planned in terms of time and availability of material. Such preparatory exercises could comprise:

- Practising of the manipulation for setting up and operating the machines without workpieces.
- Practising of the possibilities of clamping of any blanks desired.

It is also possible to start immediately with the exercises based on the “Instruction Examples for Practical Vocational Training”. If the “Instruction Examples for Practical Vocational Training” offered are not used for the exercises, it is also possible to select other workpieces. In this case, attention should be paid to the fact that the workpieces selected lend themselves to practising of all working techniques already discussed. Before the trainees start practising, the instructor should make sure that the labour safety instructions and the instructions on how to behave in the workshop have been given. If not, they should be given now. For the exercises on lathes, the existing engine lathes should be assigned to the trainees according to their body height. The height of the machine can be compensated by footboards (gratings).

Upon assignment of the working places to the trainees including checking for completeness and serviceability of all cutting, measuring, testing tools and accessories, the trainees should receive their material. Each trainee should produce his workpiece himself, from cutting the blank until completion of the part. This is the only way of fair rating of the trainee's performance. The performance rating criteria are to be made known to the trainees before they start with the exercises. Each trainee should start practising based on the sequences of operations and working drawings.

All trainees should carry out the exercises on the same workpiece in the same sequence!

In this way the instructor keeps control of things. In the event of any difficulties the instructor must find out whether they face individual trainees only or the whole group. Individual trainees may be guided individually. If the whole group is facing the difficulties, the exercises should be interrupted for additional hints to be given to all trainees. The instructor should always walk from one trainee to another one to get exactly informed of the state of machining. He should praise good results and criticize bad results.

The instructor must always keep control of things.
The trainees must not practise unsupervisedly.

If the instructor finds out that the working techniques are carried out wrongly, he must make corrections immediately.

Since the trainees are working with machines, special attention is required. The trainees must not operate the machines unless they have first been instructed in the operation or the controls and in the hazards of injuries. One trainee only should work at the machine at a time.

In the event of waiting times because of occupied machines it is useful to keep the trainees busy with intermediate jobs, such as

- sharpening of worn-out cutting tools,
- repair of damaged working tools,
- refilling of coolant and lubricant.

With increasing level of intricacy of the exercises intermediate controls are recommended. This is an opportunity for the instructor to rate the performance already prior to the completion of the exercise. Workpieces of bad workmanship can be eliminated already in this stage if reworking is required or a good final result cannot be expected any more. This is all the more important if single parts are to be matched and one part cannot be made fit because of pour quality of machining.

It is a waste of time if trainees continue machining of parts which are of no use.

In this case it is more useful if the trainee stops the exercise and starts again with new raw material.

Intermediate controls, which are announced to the trainees in advance, stimulate the trainees and make them feel confident to go on with the exercises.

The instructor should note down the results and observations of the intermediate controls to take them into account for the final control.

Upon completion of each exercise the workpiece must be rated.

It is important that the rating is based on the rating criteria stated before the beginning of the exercise.

In preparation of the control and evaluation of the results the instructor must ensure that

- each trainee is informed of the rating criteria,
- a sheet of paper is prepared to fill in the results of rating.

Experience showed that the trainees are stimulated by seeing and comparing their performances on a rating sheet visible for anybody.

This rating sheet may have the form of a clearly arranged table:

Table 1: Example of a rating chart

Training unit 1

1st instruction example

2nd instruction example

3rd instruction example

Rating criteria

accuracy to size

surface finish

time of exercise

accuracy to size

surface finish

time of exercise

accuracy to size

surface finish

time of exercise

1st name

2nd name

3rd name

The rating sheet should be open to inspection by all trainees. During the controls, whether intermediate or final, the trainees should have the opportunity of self-assessment of their performance. In this way, the trainees learn to exercise self-control. Observations and results of the intermediate controls noted down during the exercises are to be taken into account for the rating. Irrespective of the form of rating (mark, point or percentage system), general rules of rating the quality of the workpieces and the way of working are to be observed. The following rules of rating are recommended:

Very good performance

The workpiece is faultless. All specified sizes have been complied with. The workpiece surfaces are clean. Full use of the workpiece is ensured. The workpiece has been produced within reasonable time and with no additional help by the instructor. The trainee has a good command of the working techniques and properly uses the tools and accessories.

Good performance

The workpiece shows minor faults in terms of compliance with specified sizes and cleanness of the workpiece surfaces. The use of the workpiece is ensured. No reworking is required. The trainee basically works on his own. With certain reservations the trainee has a good command of the working techniques.

Fairly good performance

The workpiece shows several faults which can be removed by reworking, such as deviations from specified sizes, unclean surfaces. The use of the workpiece is ensured.

The trainee works with little help. He has no good command of the working techniques.

Satisfactory performance

The workpiece shows major faults in terms of accuracy to size and quality. It can just be used. Reworking is necessary.

The trainee needs the help of the instructor because he has a poor command of the working technique and doss not always find faults himself.

Unsatisfactory performance

Specified sizes have not been complied with. The workpiece is of no use. The trainee is not able to work on his own. He has no command of the working techniques.

3.4. Final instruction

At the end of each exercise and immediately on completion of each training unit the results must be evaluated. Such evaluation should have the form of discussions with the whole group of trainees to find out:

To which degree did each trainee achieve the aims envisaged? It is recommended to guide the trainees, based on the rating criteria made known before the exercise, to assess their results themselves. The instructor should

- complete the trainees' assessment,
- rate the results,
- generalize the experience gathered by the trainees,
- point out typical faults made by the trainees in their work and the causes,
- show to the trainees ways of removing and avoiding faults in preparation of the next exercise.

The results of the evaluation should be recorded in a table (see table 1). At the end of a training unit it is useful to have a prepared test. In this may the instructor will get a comprehensive survey of the trainees' knowledge actually acquired and of their practical experience. The complex of questions and answers of each training unit (see section 4) facilitates the preparation and evaluation of such tests.