Engineering functions

You need to be able to identify the various functions within an engineering company. These include both commercial and engineering aspects of the company's operation. The commercial functions include sales, marketing, distribution, commissioning, finance and purchasing. The engineering functions can include R&D, design, manufacturing, product development, quality and planning. Product support is another, extremely important, area of engineering. You should also be aware that non-engineering companies often require input from engineering services, such as maintenance of services and equipment. In addition to understanding the functions performed within an engineering company you must also be able to recognize the main responsibilities attached to key job roles within both the commercial and engineering functions.

The most important function within an engineering company (or any company for that matter) is overall management and control so this is where we will begin our investigation of how engineering companies operate.

Management

The production workflow and some of the functions in an engineering firm are shown in Figure 1.1. This production workflow starts with suppliers that provide an input to the various engineering processes. The output of the engineering processes is delivered to the customers. You may find this easier to recall by remembering the acronym SIPOC.

The three functions that we have included in the diagram (there are many more in a real engineering firm) operate as follows:

Planning           The planning function ensures that the correct engineering processes are in place and also that the workflow is logical and timely.

Control              The control function ensures the quality of the output and the cost-effectiveness of the processes.

Purchasing      The purchasing function ensures that supplies are available as and when required by the engineering processes.

Planning

The essential business activities performed in an engineering company can be grouped together under the general headings of planning, controlling and organizing (see Figure 1.2). The first of these activities, planning, is absolutely fundamental to the correct functioning of an engineering company. If no planning is done then activities are almost certainly going to be very ineffective. What is planning? It is the sum of the following activities:

• setting the goals for an engineering company
• forecasting the environment in which the engineering company will operate

Business Systems for Technicians

Business Systems for Technicians

This unit is designed to provide you with an introduction to the business and commercial aspects of engineering. It aims to broaden and deepen your understanding of business, industry and the effects of engineering on the environment. It also aims to provide you with a firm foundation for employment in the engineering industry together with an understanding of the financial, legal, social and environmental constraints within which an engineering company operates.

When you have completed this unit you will understand how an engineering company is organized and you will be aware of the external factors and the economic environment in which it operates. You will also have an understanding of the impact of relevant legislation and the effect of environmental and social constraints on its operation.

To help you understand more about the financial aspects of running an engineering business, you will be introduced to the techniques used in the costing of an engineering operation including those that will tell you whether a business is operating at a profit or a loss.

This unit is assessed through a series of assignments and case studies, and it has strong links with the core units Communications for Technicians (Unit 2) and Engineering Project (Unit 3). Wherever possible, you should apply the techniques that you have developed in the communications unit to work that you undertake in this unit. There are also links to several of the optional units including Quality Assurance and Control and Production Planning and Scheduling.

Case studies (based on real or invented engineering companies) are an important part of this unit. When you carry out a case study you will be presented with sample data to analyse. You might find it useful to relate your experience of employment or work experience periods in industry to the case study as well as to work covered elsewhere in the unit.

Engineering Companies

All engineering companies must operate as commercial enterprises in order to survive. In this section you will look at how an engineering company operates. You will learn about the various sectors in which engineering companies operate and the functions that are performed within a typical engineering company, such as research and development (R&D), design and manufacture. You will also learn about the various types of organization and how they differ. You will also gain an insight into how information flows within an engineering company. This section is important not only because it sets the scene for the sections that follow but also because it will help you to understand your eventual role within an engineering company. We start by looking at the areas within which engineering companies operate: we call these `engineering sectors'.

Engineering sectors

Some of the engineering sectors, engineered products and engineering companies with which you are probably familiar include:

Chemical engineering            Fertilizers, pharmaceuticals, plastics, petrol, etc. Companies in this field include Fisons, Glaxo, ICI and British Petroleum.

Mechanical engineering        Bearings, agricultural machinery, gas turbines, machine tools and the like from companies such as RHP, GKN and Rolls-Royce.

Electrical and electronic         Electric generators and motors, consumer       electronic engineering                                                    equipment (radio, TV, audio and video), power cables,         computers, etc. produced by companies such as GEC,   BICC and ICL.

Civil engineering                     Concrete bridges and flyovers, docks, factories, power stations, dams, etc. from companies like Bovis, Wimpey and Balfour-Beatty.

Aerospace engineering          Passenger and military aircraft, satellites, space vehicles, missiles, etc. from companies such as British Aerospace, Westland and Rolls-Royce.

Telecommunications              Telephone and radio communication, data communications equipment, etc. from companies such as Nokia, GEC, Plessey and British Telecom.

Motor vehicle engineering     Cars, commercial vehicles (lorries and vans), motorcycles, tractors and specialized vehicles from companies such as Rover, Vauxhall UK and McLaren.

As you work through this unit, it will help you to put things into context by relating the topics to those engineering companies with which you are familiar. This will give you an appreciation of the factors that affect their operation as well as the constraints under which they operate.

Some companies operate within more than one sector. For example, a company may produce products and provide services in both the electronic engineering and telecommunications sectors. Other companies may be active in one sector only and their products and services may only relate to that sector.

Test your knowledge 1.1

An engineering company specializes in the design and manufacture of wind generators. In which two sectors of engineering does this company operate?

Activity 1.1

Identify the sector(s) in which each of the following engineering companies operate:

1. Perkins (http://www.perkins.com)

2. Thales Group (http: //www. thalesgroup. com)

3. Dean and Dyball (http://www.deandyball.co.uk)

4. RPS Group (http://www.rpsgroup.com)

5. Bayer-Wood Technologies (http://www.bayer-wood.co.uk)

6. Smiths Group (http://www.smiths -group. com)

Activity 1.2

Identify three engineering companies in your area that are active in three different engineering sectors. For each company, identify the range of products or services that it supplies and the nature of its business (e.g., manufacturing, maintenance, design, etc.). Present your work in the form of a data sheet for each company and include full company name, address and website.

Written communication

Written communication

This is a more reliable method of communication since it usually provides a permanent written record of the key information. The same information is available for all those who require it.

Anyone who has ever marked an English comprehension test will know that the same written passage can mean very different things to different people. Therefore, care must be taken in preparing written information. To avoid confusion, the normal conventions of grammar and punctuation must be used. Words must be correctly spelt. Use a dictionary if you are uncertain. If you are using a word-processing package use the spell checker. However, take care, many software packages originate in the USA and the spell checker may reflect this.

Never use jargon terms and acronyms unless you are sure that those reading the message are as equally familiar with them as is the writer.

An engineer often has to write notes, memoranda and reports. He/she often has to maintain logbooks and complete service sheets. An engineer may also have to communicate with other engineers, suppliers and customers by letter. Being able to express yourself clearly and concisely is of great importance.

Activity 2.41

Prepare a brief article for the local press (using not more than 1000 words) on any one of the following topics:

• A sporting event that you took part in.
• A recent school or college activity.
• A newly available product or technology.

Include contact or other details for further information. Present your work in word-processed form and include relevant photographs, diagrams or sketches.

Activity 2.42

Prepare:

(a) a word-processed letter

(b) an e-mail message

to an engineering supplier requesting details of a product or service. This may simply take the form of a request for a short-form catalogue or for the supply of a data sheet or application note. Present your work in the form of printed copies of correspondence and e-mail messages.

Verbal and written communication

Verbal and written communication

Verbal communication (i.e. speaking and listening) is widely used in everyday situations, including:

• Informal discussions either on the telephone or face to face.

• Formal presentations to groups of persons who all require the same information.

Where a group of persons all require the same information, a formal presentation must be used. On no account should information be `passed down the line' from person to person because errors are bound to creep in. There is a story that during World War I the message `send reinforcements, we are going to advance' arrived at headquarters, by word of mouth, as ^`send three and four pence (old money), we are going to a dance'. We will let you decide on the truth behind this story, but we feel it makes the point.

In any event, it is important to remember that the spoken word is easily forgotten and oral communication should be reinforced by:

• Notes taken at the time.
• Tape recording the conversation.
• A written summary. For example, the published `proceedings' of formal lectures and presentations. Another example is a `press release' that is provided to journalists and reporters in order to ensure: the factual accuracy of information intended for the public.

Oral communication must be presented in a manner appropriate to the audience. It must be brief and to the point. The key facts must be emphasized so that they can be easily remembered. The presentation must be interesting so that the attention of the audience does not wander.

When communicating by the spoken word, it is as equally important to be a good listener as it is to be a good speaker. This applies to conversations between two or three people as well as to formal presentations.

Activity 2.39

Use presentation software to prepare a 5-minute presentation to the rest of the class (using appropriate visual aids) on any one of the following topics:

• How to choose a digital camera.
• How to connect to the Internet.
• What to look for when purchasing a second-hand car.

You should prepare a set of brief printed notes summarizing the key points for your audience. Also include printed copies of any screens or overhead projector transparencies that you use. At the end of your talk you should invite questions from your audience and provide appropriate answers.

Activity 2.40

Conduct a brief interview (lasting no longer than 15 minutes) with another student and take notes to summarize the outcome. Do not forget to allow time for questions at the end of the interview. Your interview should be based around the following questions:

• Why did you decide to take a course in Engineering?
• Why did you choose the BTEC National Diploma course?
• What made you choose this school/college?
• What subjects/topics have you enjoyed the most?
• What subjects/topics have you enjoyed the least?
• What plans have you got for the future?
• Where would you hope to be and what would you hope to be doing in 10 years' time?

You should add further questions to clarify the above. Do not forget to thank your interviewee! Present your findings in the form of hand-written interview notes.

Non-return valves and shuttle valves

Non-return valves and shuttle valves

The non-return valve (NRV), or check valve as it is sometimes known, is a special type of directional control valve. It allows the fluid to flow in one direction only and it blocks the flow in the reverse direction. These valves may be operated directly or by a pilot circuit. Some examples are shown in Figure 2.88.

• Figure 2.88a shows a valve that opens (is free) when the inlet pressure is higher than the outlet pressure (back pressure).
• Figure 2.88b shows a spring-loaded valve that only opens when the inlet pressure can overcome the combined effects of the outlet pressure and the force exerted by the spring.
• Figure 2.88c shows a pilot controlled NRV. It opens only if the inlet pressure is greater than the outlet pressure. However, these pressures can be augmented by the pilot circuit pressure.

(i)      The pilot pressure is applied to the inlet side of the NRV. We now have the    combined pressures of the main (primary) circuit and the pilot circuit acting against the outlet pressure. This enables the valve to open at a lower main            circuit pressure than would normally be possible.

(ii)     The pilot pressure is applied to the outlet side of the NRV This assists the      outlet or back pressure in holding the valve closed. Therefore, it requires a             greater main circuit pressure to open the valve. By adjusting the pilot pressure in these two examples we can control the circumstances under   which the NRV opens.

• Figure 2.88d shows a valve that allows normal full flow in the forward direction, but restricted flow in the reverse direction. The valves previously discussed did not allow any flow in the reverse direction.

• Figure 2.88e shows a simple shuttle valve. As its name implies, the valve is able to shuttle backwards and forwards. There are two inlet ports and one outlet port. Imagine that inlet port A has the higher pressure. This pressure overcomes the inlet pressure at B and moves the shuttle valve to the right. The valve closes inlet port B and connects inlet port A to the outlet port. If the pressure at inlet port B rises, or that at A falls, the shuttle will move back to the left. This will close inlet port A and connect inlet port B to the outlet. Thus, the inlet port with the higher pressure is automatically connected to the outlet port.

Conditioning equipment

The working fluid, be it oil or air, has to operate in a variety of environments and it can become overheated and/or contaminated. As its name implies, conditioning equipment is used to maintain the fluid in its most efficient operating condition. A selection of conditioning equipment symbols is shown in Figure 2.89. Note that all conditioning device symbols are diamond shaped.

Filters and strainers have the same symbol. They are normally identified within the system by their position. The filter element (dashed line) is always positioned at 90° to the fluid path.

Water traps are easily distinguished from filters since they have a drain connection and an indication of trapped water. Water traps are

particularly important in pneumatic systems because of the humidity of the air being compressed.

Lubricators are particularly important in pneumatic systems. Hydraulic systems using oil are self-lubricating. Pneumatic systems use air, which has no lubricating properties so oil, in the form of a mist, has to be added to the compressed air line.

Heat exchangers can be either heaters or coolers. If the hydraulic oil becomes too cool it becomes thicker (more viscous) and the system becomes sluggish. If the oil becomes too hot it will become too thin (less viscous) and not function properly. The direction of the arrows in the symbol indicates whether heat energy is taken from the fluid (cooler)

Pressure relief and sequence valves

Pressure relief and sequence valves

 an example of a pressure relief (safety) valve. In Figure 2.84a the valve is being used in a hydraulic circuit. Pressure is controlled, by opening the exhaust port to the reservoir tank against an opposing force such as a spring. In Figure 2.84b, the valve is being used in a pneumatic circuit so it exhausts to the atmosphere.

Figure 2.84c and d shows the same valves except that this time the relief pressure is variable, as indicated by the arrow drawn across the spring. If the relief valve setting is used to control the normal system pressure as well as acting as an emergency safety valve, the adjustment mechanism for the valve must be designed so that the maximum safe working pressure for the circuit cannot be exceeded.

Figure 2.84e,f shows the same valves with the addition of pilot control. This time the pressure at the inlet port is not only limited by the spring but also by the pressure of the pilot circuit superimposed on the spring. The spring offers a minimum pressure setting and this can be increased by increasing the pilot circuit pressure up to some predetermined safe maximum. Sometimes the spring is omitted and only pilot pressure is used to control the valve.

Sequence valves are closely related to relief valves in both design and function, and are represented by very similar symbols. They permit the hydraulic fluid to flow into a subcircuit, instead of back to the reservoir, when the main circuit pressure reaches the setting of the sequence valve. You can see that Figure 2.85 is very similar to a pressure relief valve (PRV) except that, when it opens, the fluid is directed to the next circuit in the sequence instead of being exhausted to the reservoir tank or allowed to escape to the atmosphere.

Flow control valves

Flow control valves, as their name implies, are used in systems to control the rate of flow of fluid from one part of the system to another. The simplest valve is merely a fixed restrictor. For operational reasons this type of flow control valve is inefficient, so the restriction is made variable as shown in Figure 2.86a. This is a throttling valve. The full symbol is shown in Figure 2.86b. In this example the valve setting is being adjusted mechanically. The valve rod ends in a roller follower in contact with a cam plate.

inlet pressure to the valve does not affect the flow rate from the valve. Under these circumstances we use a pressure compensated flow control valve (PCFCV). The symbol for this type of valve is shown in Figure 2.87. This symbol suggests that the valve is a combination of a variable restrictor and a pilot operated relief valve. The enclosing box is drawn using a long-chain line. This signifies that the components making up the valve are assembled as a single unit.

Fluid power schematic diagrams

These diagrams cover both pneumatic and hydraulic circuits. The symbols that we shall use do not illustrate the physical make-up, construction or shape of the components. Neither are the symbols to scale or orientated in any particular position. They are only intended to show the `function' of the component they portray, the connections and the fluid flow path.

Complete symbols are made up from one or more basic symbols and from one or more functional symbols. Examples of some basic symbols and some functional symbol.

Energy converters

Let us now see how we can combine some of these basic and functional symbols to produce a complete symbol representing a component. For example, let us start with a motor. The complete symbol.

The large circle indicates that we have an energy conversion unit such as a motor or pump. Notice that the fluid flow is into the device and that it  

is pneumatic. The direction of the arrowhead indicates the direction of flow. The fact that the arrowhead is clear (open) indicates that the fluid is air. Therefore, the device must be a motor. If it were a pump the fluid flow would be out of the circle. The single line at the bottom of the circle is the outlet (exhaust) from the motor and the double line is the mechanical output from the motor.

Now let us analyse the symbol 

• The circle tells us that it is an energy conversion unit.
• The arrowheads show that the flow is from the unit so it must be a pump.
•  The arrowheads are solid so it must be a hydraulic pump.
• . The arrowheads point in opposite directions so the pump can deliver the hydraulic fluid in either direction depending upon its direction of rotation.

• The arrow slanting across the pump is the variability symbol, so the pump has variable displacement.
• The double lines indicate the mechanical input to the pump from some engine or motor.

Summing up, we have a variable displacement, hydraulic pump that is bi-directional.

Orthographic drawing

Orthographic drawing

GA and detail drawings are produced by the use of a drawing technique called orthographic projection. This is used to represent 3-D solids on the 2-D surface of a sheet of drawing paper so that all the dimensions are true length and all the surfaces are true shape. To achieve this when surfaces are inclined to the vertical or the horizontal we have to use auxiliary views, but more about these later. Let us keep things simple for the moment.

First angle projection

Figure 2.42a shows a simple component drawn in isometric projection. Figure 2.42b shows the same component as an orthographic drawing. This time we make no attempt to represent the component pictorially. Each view of each face is drawn separately either full size or to the same scale. What is important is how we position the various views as this determines how we `read' the drawing.

Engineering drawing techniques

Engineering drawing techniques

Engineering drawings can be produced using a variety of different techniques. The choice of technique is dependent upon a number drawing of factors such as:

Speed                          How much time can be allowed for producing the drawing. How soon the drawing can be commenced.

Media                          The choice will depend upon the equipment available (e.g. CAD or conventional drawing board and instruments) and the skill of the person producing the drawing.

Complexity                  The amount of detail required and the anticipated amount and frequency of development modifications.

Cost                            Engineering drawings are not works of art and have no intrinsic value. They are only a means to an end and should be produced as cheaply as possible. Both initial and ongoing costs must be considered.

Presentation                This will depend upon who will see/use the drawings. Non-technical people can visualize pictorial representations better than orthographic drawings.

Nowadays technical drawings are increasingly produced using computer aided drawing (CAD) techniques. Developments in software and personal computers have reduced the cost of CAD and made it more powerful. At the same time, it has become more `user friendly'. Computer aided drawing does not require the high physical skill required for manual drawing, which takes years of practise to achieve. It also has a number of other advantages over manual drawing. Let us consider some of these advantages:

Accuracy                    Dimensional control does not depend upon the draftsperson's eyesight.

Radii                            Radii can be made to blend with straight lines automatically.

Repetitive features      For example, holes round a pitch circle do not have to be individually drawn, but can be easily produced automatically by `mirror imaging'. Again, some repeated, complex features need only be drawn once and saved as a matrix. They can then be called up from the computer memory at each point in the drawing where they appear at the touch of a key.

Editing                         Every time you erase and alter a manually produced drawing on tracing paper or plastic film the surface of the drawing is increasingly damaged. On a computer you can delete and redraw as often as you like with no ill effects.

Storage                       No matter how large and complex the drawing, it can be stored digitally on floppy disk. Copies can be taken and transmitted between factories without errors or deterioration.

Prints                           Hard copy can be produced accurately and easily on laser printers, flat bed or drum plotters and to any scale. Colour prints can also be made.

Pictorial techniques

Engineering drawings such as general arrangement drawings and detail drawings are produced by a technique called orthographic drawing using the conventions set out in BS 308. Since we will be asking you to make orthographic drawings from more easily recognized pictorial drawings, we will start by introducing you to the two pictorial techniques widely used by draftspersons (Figures 2.38 and 2.39).

Oblique drawing

Figure 2.38 shows a simple oblique drawing. The front view (elevation) is drawn true shape and size. Therefore, this view should be chosen so as to include any circles or arcs so that these can be drawn with compasses. The lines forming the side views appear to travel away from you, so these are called `receders'. They are drawn at 45° to the horizontal using a 45° set-square. They may be drawn full length as in cavalier oblique drawing or they may be drawn half-length as in cabinet oblique drawing. This latter method gives a more realistic representation, and is the one we will be using.

Activity 2.24

(a)     Obtain a sheet of quadrille ruled paper (maths paper with 5 mm squares) and draw the box shown in Figure 2.38 full size. Use cabinet oblique projection.

(b)     Now use your compasses to draw a 50 mm diameter hole in the centre of the front (elevation) of the box.

(c)     Can you think of a way to draw the same circle on the side (receding) face of the box? It will not be a true circle so you cannot use your compasses.

Present your results in the form of a hand-constructed drawing with hand­written notes.

Isometric drawing

Figure 2.39a shows an isometric drawing of our previous box. To be strictly accurate, the vertical lines should be drawn true length and the

receders should be drawn to a special isometric scale. However, this sort of accuracy is rarely required and, for all practical purposes, we draw all the lines full size. As you can see, the receders are drawn at 30^° to the horizontal for both the elevation and the end view.

Although an isometric drawing is more pleasing to the eye, it has the disadvantage that all circles and arcs have to be constructed. They cannot be drawn with compasses.           Figure 2.39b-d shows you how to construct an isometric curve. You could have used this technique in Activity 2.24 to draw the circle on the side of the box drawn in oblique projection.

First, we draw the required circle. Then we draw a grid over it as shown in Figure 2.39b. Next number or letter the points where the circle cuts the grid as shown. Now, draw the grid on the side elevation of the box and step off the points where the circle cuts the grid with your compasses as shown in Figure 2.39c. All that remains is to join up the dots and you have an isometric circle as shown in Figure 2.39d.

Activity 2.25

(a)  Draw, full size, an isometric view of the box shown in Figure 2.39. Isometric ruled paper will be of great assistance if you can obtain some.

(b)  Draw a 50 mm diameter isometric circle on the TOP face of the box (remember that Figure 2.39 shows it on the side of the box).

Present your results in the form of a hand-constructed drawing with hand­written notes.

Another way of drawing isometric circles and curves is the 'four-arcs' method. This does not produce true curves but they are near enough for all practical purposes and quicker and easier than the previous method for constructing true curves. The steps are shown in   Figure 2.40.

1.   Join points B and E as shown in Figure 2.40b. The line BE cuts the line GC at the point J. The point J is the centre of the first arc. With radius BJ set your compass to strike the first arc as shown.

2.   Join points A and F as shown in Figure 2.40c. The line AF cuts the line GC at the point K. The point K is the centre of the second arc. With radius KF set your compasses to strike the second arc as shown. If your drawing is accurate both arcs should have the same radius.

3.   With Centre A and radius AF or AD strike the third arc as shown in Figure 2.40d.

4.   With Centre E and radius EH or EB strike the fourth and final arc as shown in       Figure 2.40e.

5.   If your drawing is accurate, arcs 3 and 4 should have the same radius.

Activity 2.26

Use the technique just described to draw a 40 mm diameter circle on the side face of our box. Start off by drawing a 40 mm isometric square in the middle of the side face. Present your results in the form of a hand-constructed drawing with hand-written notes.

Activity 2.27

(a)  Figure 2.41a shows some further examples of isometric drawings. Redraw them as cabinet oblique drawings.

(b)  Figure 2.41b shows some further examples of cabinet oblique drawings. Redraw them as isometric drawings. Any circles and arcs on the vertical surfaces should be drawn using the grid construction method. Any arcs and circles on the horizontal (plan) surfaces should be drawn using the 'four-arcs' method.

Present your results in the form of a hand-constructed drawing with hand­written notes.

Circuit and related diagrams

Circuit and related diagrams

Circuit diagrams are used to show the functional relationships between the components in an electric or electronic circuit. The components are represented by symbols and the electrical connections between the components drawn using straight lines. It is important to note that the position of a component in a circuit diagram does not represent its actual physical position in the final assembly. Circuit diagrams are sometimes also referred to as schematic diagrams or schematic circuits.

Figure 2.28a shows the circuit for an electronic filter unit using standard component symbols. Figure 2.28b shows the corresponding physical layout diagram with the components positioned on the upper (component side) of a PCB. Finally, Figure 2.28c shows the copper track layout for the PCB. This layout is developed photographically as an etch-resistant pattern on the copper surface of a copper-clad board.

The term `wiring diagram' is usually taken to refer to a diagram that shows the physical interconnections between electrical and electronic components. Typical applications for wiring diagrams include the wiring layout of control desks, control cubicles and power supplies. Wiring diagrams are directly related to circuit schematics (circuit diagrams). As an example, architects use circuit schematics to show the electrical wiring and components inside a building or plant. They will also provide installation drawings to show where the components are to be sited.

In addition, they may also provide a wiring diagram to show how the wires and cables are to be routed to and between the components. The symbols used in architectural installation drawings and wiring diagrams are not the same as those used in circuit diagrams.

Schematic circuit diagrams are also used to represent pneumatic (compressed air) circuits and hydraulic circuits. Pneumatic circuits and hydraulic circuits share the same symbols. You can tell which circuit is which because pneumatic circuits should have open arrow heads, while hydraulic circuits should have solid arrowheads. Also, pneumatic circuits exhaust to the atmosphere, while hydraulic circuits have to have a return path to the oil reservoir. Figure 2.29 shows a typical hydraulic circuit.

Just as electrical circuit diagrams may have corresponding installation and wiring diagrams, so do hydraulic, pneumatic and plumbing circuits. Only this time the wiring diagram becomes a pipework diagram.