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Time: 20 hours
Level: Introductory
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 Introduction Resource- How are designs turned into products? What resources, materials and methods used and what set of activities that goes under the heading of ‘manufacturing’ ? This unit will introduce manufacturing as a...
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- 1.1 Making a product Resource
- In this unit you are going to study how designs are turned into products: the resources, materials and methods used; and specifically the set of activities that goes under the heading of ‘manufacturing’....
- 1.2 The manufacturing process Resource
- Let’s first consider what is meant by the term ‘manufacturing’. You probably have a general feeling for it already. The word ‘manufacture’ derives from two Latin words: manu (meaning ‘by hand’) and factum...
- 1.3 Component parts Resource
- One thing you will have noticed from Exercise 1 is that several items, such as the personal computer, are assemblies of components made from quite different materials. Others are single objects which need...
- 1.4 What is manufacturing? Resource
- Manufacturing is a very broad activity, encompassing many functions – everything from purchasing to quality control! Later, we will concentrate on some of the manufacturing processes used to convert materials...
- 1.5 Product design specification (PDS) Resource
- We can model the production of the PDS for a given product using a process flow diagram. One example of such a diagram is given in Figure 3.
- 1.6 A PDS checklist Resource
- The product design specification, or PDS, should contain all the facts relating to the product. It should not lead the design by presupposing the outcome, but it must contain the realistic constraints...
- 1.7 Product form and function Resource
- Another important aspect that affects the balance of the PDS is the relative importance of a product’s form compared with its function. These attributes of a product are often ascribed to two subdivisions...
- 1.8 Product design Resource
- Clearly, an important part of the design activity is designing a product that will sell, and several of the items in the PDS checklist concern how the product would be perceived by the potential buyer....
- 1.9 Engineering or industrial design? Resource
- Design is commonly split into two distinct but connected disciplines, engineering design and industrial design. Engineering design concentrates on the factors in the PDS which concern the function of a...
- 1.10 Marketing Resource
- The Institute of Marketing defines marketing as:
- 1.11 Product value Resource
- What a marketing perspective provides is information to help the manufacturer to sell products in the market at an identifiable target price. The price might just cover the manufacturing cost of the article,...
- 1.12 Manufacturing processes: making things Resource
- We can’t hope to cover all the manufacturing processes that exist, so instead, you’ll meet a selection of some of the more important ones. This should allow you to appreciate the main principles involved...
- 1.13 Gears and gearing Resource
- Gears and gearing (Figure 7) are a feature of practically all machinery and are by no means confined to food mixers. The function of gearing is to transmit rotary motion and power from one place (for example,...
- 1.14 Getting into shape: some basics Resource
- If you think about it, the number of different things you can do to a raw material to get it into a desired shape is pretty limited.
- 1.15 Scales of material structure Resource
- Exactly what influences the properties of a component can depend on many things: We’ve already mentioned the importance of materials properties and the component geometry, for example.
- 1.16 Classifying shapes Resource
- If the profile of an artefact does not change along its length – like a pipe, electrical cable or aluminium cooking foil – then it can be classified as having a simple (continuous) 2D (shorthand for two...
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- 2.1 Introduction Resource
- Casting is one of the easiest classes of process to understand. Casting is simply a process where a mould is filled with a fluid, which then solidifies in the shape of the mould cavity. Provided the liquid...
- 2.2 Properties for processing – casting Resource
- The casting (or pouring) group of processes is one of the most convenient for making three-dimensional shapes, especially if repeated copies are required. However, you do have to be able to get your material...
- 2.3 Types of casting Resource
- This type of casting uses a model, or pattern, of the final product to make an impression which forms the mould cavity. Each mould is destroyed after use but the same pattern is used over and over again....
- 2.4 Casting processes Resource
- Casting is used to produce ingots which are then used as the raw materials for forming processes such as rolling or extrusion. As an intermediate processing step, casting needs to be less carefully regulated...
- 2.5 Casting metals Resource
- Sand casting is illustrated in Figure 20. A solid replica of the required object is made: the ‘pattern’. Sand is then rammed around the pattern in a ‘moulding box’. When the pattern is removed it...
- 2.6 Casting plastics Resource
- Injection moulding is used mainly for thermoplastic polymer materials. When heated, thermoplastics do not become as fluid as metals so they cannot be shaped by gravity-fed casting methods. The injection...
- 2.7 Casting microstructure and defects Resource
- Metal castings have very specific microstructures. When a liquid metal cools and begins to solidify in a mould, grains (crystals) of the metal start to form, both on the mould walls and in the bulk of...
- 2.8 Casting our gearwheel Resource
- Let’s now consider the problem of how best to make the food mixer gearwheel we discussed in Section 1. Could it be made by any of these casting processes? Since it is a simple solid object the answer must...
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- 3.1 Introduction Resource
- Forming processes involve shaping materials which are solid. As mentioned before, a simple example is moulding with Plasticene. However, metals can be moulded using forming processes as well, as long as...
- 3.2 Properties for processing – forming Resource
- Forming processes involve applying forces to the material being shaped. A good way of telling how a given material responds to applied force is to look at diagrams representing its stress-strain behaviour....
- 3.3 Forming v casting Resource
- As the stresses needed to make solids flow are considerably higher than those required for liquids, forming processes normally require a lot of energy and strong, resilient tooling. This means high expenditure...
- 3.4 Forming processes Resource
- Forming processes are used to convert cast ingots into basic product forms such as sheets, rods and plates, as was noted in the previous section. However, here we will concentrate on forming processes...
- 3.5 Extrusion Resource
- The principle of this process is very similar to squeezing toothpaste from a tube. Material is forced through a shaped hollow die in such a way that it is plastically deformed and takes up the shape of...
- 3.6 Rolling Resource
- In rolling (Figure 32), material is passed through the gap between two rotating rollers that squeeze the material as it passes between them. The rolled material emerges with a thickness roughly equal to...
- 3.7 Metal forging Resource
- Forging is typified by countless generations of blacksmiths with their hammers and anvils. Besides still being used for special ‘hand-made’ items, this type of forging is similar to that used, on a somewhat...
- 3.8 Forming our gearwheel Resource
- We have just seen that simple 2D ‘linear’ objects can be produced by rolling, drawing or extrusion. So could our gearwheel be made using these techniques?
- 3.9 Failure of replacement gears Resource
- A heavy commercial vehicle company announced that it would no longer supply spare parts for one of its vehicles. This was a problem for customers, as the two largest gears in the gearbox tended to wear...
- 3.10 Powder processing techniques Resource
- Before we leave forming we should consider powder processing techniques, (Figure 40), which have elements of both casting and forming. Essentially all powder processing routes involve filling a mould with...
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- 4.1 Introduction Resource
- Cutting is perhaps the most familiar type of manufacturing process. Whilst few of us have cast polymers or formed metal, shaping material by cutting is part of everyday experience. I am sure you have used...
- 4.2 Cutting processes Resource
- The most common cutting operations are carried out on electrically-driven machine tools; hand tools, which include electric drills, orbital sanders and the like, are also used extensively, but because...
- 4.3 The mechanics of machining Resource
- During any machining operation, the cutting tool comes in contact with the material to be cut, called the workpiece. The cutting machine has to hold both the tool and workpiece, and to move one relative...
- 4.4 Hardness Resource
- Hardness is related to the strength of a material and is a measure of a material’s resistance to plastic deformation by scratching or indentation. Scratching the point of a pin across a material can be...
- 4.5 Types of tool material Resource
- There are basically three types of tool material:
- 4.6 Machining our gearwheel Resource
- Having described some machining processes, let’s now consider whether they can be applied to the problem of making gearwheels for a food mixer. These wheels are quite complicated shapes. Could our gearwheel...
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- 5.1 Introduction Resource
- In addition to manufacturing an individual component using a single casting, forming or cutting process, we could assemble it from a number of simpler shapes joined together. There are other reasons for...
- 5.2 Mechanical joining Resource
- In mechanical joints, various methods are used which clamp or fasten the parts of the assembly together (e.g. nails, screws, bolts, rivets and circlips). Mechanical joints find innumerable applications...
- 5.3 Adhesive joints Resource
- The essential feature of adhesive joining is that two parts are joined by placing a liquid between them, which then solidifies. The strength of the joint depends both on the strength of bond between the...
- 5.4 Brazing and soldering Resource
- Brazing is defined as the joining of metals using a filler rod which melts at temperatures above 450°C but below the melting temperature of the metals being joined. Typical features of the brazing process...
- 5.5 Glues Resource
- The word ‘adhesive’ is usually taken to mean a type of glue. Adhesives now come in a vast array of different types; some stick in seconds (cyanoacrylate – Superglue), some take a day or so to cure (thermosetting...
- 5.6 Welding Resource
- An ideal welded joint between two pieces of metal or plastic could be made by softening the materials sufficiently so that the surfaces fuse together. Bonding forces hold the atoms, ions or molecules together...
- 5.7 Solid-state welding Resource
- In highly deformable materials, such as metals and thermoplastics, the above aims can be achieved by solid-state welding, that is, forcing the two surfaces together so that plastic deformation makes their...
- 5.8 Fusion welding Resource
- In fusion welding, the parts to be joined are brought together, melted and fused to each other. In some processes the interface is filled with a molten substance, supplied by a filler rod that is similar...
- 5.9 Joining (assembling) our gearwheel Resource
- Whilst we cannot make our food mixer gearwheel just using joining processes, we could assemble it out of several pieces which must be joined together. In practice, any of the joining processes (soldering,...
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- 6.1 Introduction Resource
- Our short review of manufacturing processes is now complete. There are many processes which have been omitted, but in the main they are variations on or adaptations to the major processes that have been...
- 6.2 Production costs Resource
- By comparing the unit costs of making 105 gears of this type by all the feasible processes considered earlier, it should be possible to identify why this particular process was adopted.
- 6.3 Looking ahead Resource
- All these choices represent a best attempt to provide adequate performance by the gears at minimum cost. ‘Adequate’ means providing trouble-free service for a given design life. Notice that when the material...
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- 7.1 Introduction Resource
- So far we have considered how we might manufacture an artefact from a single material, or at most by joining together two components made from different materials. Quite often, however, the key properties...
- 7.2 Case study 1: The kitchen knife Resource
- A kitchen knife is an everyday item that can be treated by surface engineering to greatly improve its performance. Great demands are made on kitchen knives: they are expected to retain their sharpness...
- 7.3 Stainless steel Resource
- Steel is an alloy of iron and carbon. But it can also have other elements added to it to enhance its properties. Stainless steel has a minimum of 12 per cent chromium added to improve its corrosion resistance....
- 7.4 Wear Resource
- Wear can be defined as the unintentional, progressive loss of material from a surface. All surfaces are rough at the microscopic scale. Figure 55 shows the trace taken of a surface using a stylus profilometer...
- 7.5 Physical vapour deposition Resource
- Physical vapour deposition (PVD) processes involve depositing a source material (which can either be from a solid, liquid or gas) onto the surface of the component. There may be a chemical reaction between...
- 7.6 Plasma spraying Resource
- A number of processes have been developed where particles of coating material are heated to a molten state and projected at a substrate which is relatively cold (
- 7.7 Case Study 2: Optical coatings Resource
- Should you need spectacles, you will doubtless be aware that opticians can now offer a bewildering choice of different materials and an array of surface treatments to enhance the spectacle lenses, from...
- 7.8 Optical terms Resource
- Refractive index (given the symbol n) is an important optical property, as it is a measure of how much a particular material can change the direction of a ray of light (i.e. refract it) as it passes through...
- 7.9 Materials selection Resource
- What properties does a spectacle wearer require from the lenses in the spectacles? Well, first and foremost, the lens must transmit light and not distort the image. Secondly, as spectacles need to be worn...
- 7.10 Scratch-resistant coatings Resource
- All polymer lenses ideally require coating to provide at least a similar scratch resistance to glass. The thickness of a typical scratch-resistant coating is about 2 μm. PMMA lenses are generally coated...
- 7.11 Anti-reflective coatings Resource
- In a normal lens, about 4 per cent of the light is reflected as it passes through each side of the lens. This means that approximately only 92 per cent of the light reaches the eye. Some of the reflected...
- 7.12 Concluding remarks Resource
- A bewildering number of surface engineering techniques is available to the modern engineer. How do you decide on the correct process for your particular application? Essentially, an iterative process is...
| | | | | References and Acknowledgements | | |
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