09 Higher Revision Notes (Recovered)

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  • 1. Revision notes Higher and Intermediate 2 Product design Safety and the environment You will be asked to consider safety aspects in the following contexts: Safety and the consumer Safety and the manufacturer Safety and the environment In answer to any question always refer to the product in the question and give clear examples. Safety and the consumer U Answers should include: the weight of the product, warning labels, advice on carrying and storing. Moving parts, which may trap or injure the user, abrasive surfaces and good surface finishes. Choice of materials, which will not poison or contaminate. Good electrical insulation, which meets current European safety standards. Quality control during and after production. Safety and the manufacturer U Answer should include: Staff training, use of appropriate machinery, safety inspections by government agencies. Responsibility for the safe storage and disposal of materials, consideration to be given to air, water and soil pollution. Consideration given to the energy used in the manufacture of products. Safety and the environment (social responsibility) U Responsibility for the safe storage and disposal of materials, consideration to be given to air, water and soil pollution. Consideration given to the energy used in the manufacture of products. FB/MGS/09
  • 2. Manufacturing systems (methods of manufacture) Manufacturing systems refers mainly to the volume of products manufactured. The choice of manufacturing systems are as follows: Mass production Batch production One offs JIT (Just in time) Ghent chart Mass production U Many thousands of copies of a product are made. Mass production suggests that there is a large, probably international market, for this product. It might be the case that the product is sold at low cost, Biro pens for example. Tooling and machine setting might be initially very expensive, but costs are recuperated by wide distribution and mass marketing. Mass production systems are usually automated and use the minimum of labour. Automated systems are more reliable and cost effective than using manual labour. Mass production systems will probably use CAD / CAM systems. Batch production U Lesser quantities of a product are made, usually in hundreds. For example garden furniture. The availability and distribution of products might be limited to particular stores and seasons. The method of manufacture might be semi automated, using Jigs and fixtures to assist the craftsman manufacture the product. It is likely that the products will be hand finished. This attention to detail will be reflected in the cost to the consumer. FB/MGS/09
  • 3. Manufacturing systems (methods of manufacture) One offs U A limited number of high quality products are made to order. The product might be unique, for example a reception desk in the new Scottish parliament. The demand for high quality will be expensive to the customer. The product will undoubtedly be made by a skilled craftsperson using the minimum of automation. It might be very difficult to replace or maintain such a unique product. JIT U To reduce the cost of storage the Japanese have a developed a system which delivers materials, Just in time (JIT). If materials are delivered to the factory just in time for manufacture then taken away at the point of production, then labour and storage costs can be reduced. This economic efficiency can be passed onto the customer, in low cost products. FB/MGS/09
  • 4. Ghent chart 0BU Planning for success is essential for any manufacturer. How the product will be made is worked out in advance of beginning production. Often this is done on a Ghent chart. A Ghent chart plans out what must be done against the time taken to do it. Look at this example: Process Job Time A Varnish the box 1 hour B Sand the box 2 hours C Make the box 3 hours D Get supply of timber 4 hours E Make lid 2 hours F Varnish lid 1 hour Below shows how all of these stages can be illustrated and put into a logical order. Ghent Chart A B C D E F 1 2 3 4 5 6 7 8 9 10 11 12 Number of working hours Information found from the chart: 1. Total time taken = 12 hours. 2. Time saved if lid started when box was varnished = 1 hour. FB/MGS/09
  • 5. Production methods Production methods, directly refers to the machining and manual production of products. Depending on which Manufacturing system (method of manufacture) is required will determine the choice of Production methods. Extrusion Injection moulding Compression moulding Vacuum forming Blow moulding Metal Casting Piercing and Blanking Press forming metal Welding Steam bending wood CAD / CAM Extrusion: Plastic U For making continuous lengths, for example curtain rails. Materials: thermoplastics, polypropene (pp). Suitable for mass production of products. 1. Plastic granules are fed into the machine through a hopper. 2. The plastic is heated and forced through a die. 3. A long continuous length is produced and is trimmed to size. FB/MGS/09
  • 6. Extrusion: Metal U For making continuous lengths, for example domestic water or gas pipes. Ideally suited to mass production. Materials: Copper, Aluminium alloys. Remarks: Uniform thickness, uniform section, light weight, easily bent. 1. A billet (A block of metal) is put into a ramming machine. The heated billet of either copper or aluminium is forced under pressure and heat, through a die to form the continuous length. 2. Reverse ramming will produce a hollow extrusion. Hollow tube Billet Ram FB/MGS/09
  • 7. Injection moulding: Thermoplastics U Ideally suited to the mass production of plastic buckets, bins and storage boxes. Thermoplastic granules are fed into a hopper and are forced under pressure and heat, into a mould. The plastic is injected into the mould and the product is quickly made. The mould is opened, the product removed and the process starts again. Materials: Polypropene (pp), Polythene (HDPE) Remarks: Injection marks, push pin marks, Ribs. Compression moulding U A similar process to injection moulding, though this time a slug (block) of a thermosetting plastic is used. This process is used to make light switch covers and similar products that need thermosetting plastics. Materials: Urea formaldehyde. Remarks: Smooth high quality surfaces, intricate detailing, flash edges. FB/MGS/09
  • 8. Vacuum forming: Thermoplastics U A thin layer of a thermoplastic is heated, becomes flexible (plastic) and is drawn down into a pattern (mould) under vacuum pressure. This is a very quick, economical and reliable process. Used to form food packaging, inserts for drawers and vehicle parts. Ideally suited to mass production. Material: Styrene, acrylic sheet. Remarks: Rounded corners, tapered edges, smooth surfaces, good surface detail. Blow moulding: Thermoplastics U As the title suggests air is blown into a hollow tube of plastic. The plastic tube is nipped closed at one end and as the air pressure is increased the hot plastic tube known as the Parison, then forms to the shape of the mould. This is a very quick, economical and reliable process, typically used to form plastic bottles. Materials: Polypropene (pp), styrene. Remarks: Uniform thickness, Mould separation lines, flash lines and clamping point. FB/MGS/07
  • 9. Metal casting Sand casting: One offs or batch production U Where complex heavy shapes in metal have to be formed and it is not practical to cut out the form from a solid, then casting is used. A source metal, Aluminium alloy for example is heated and melted into liquid form. The hot metal is poured into a sand filled flask. The sand contains the impression of the project to be made and it is this impression that is filled with the hot metal. When cooled the shape is broken out of the sand and finished by hand. Sand casting is not suitable for mass production. Materials: Aluminium alloy, Brass, Lead. Remark: Fillets, ribs, Flash, Runner riser (sprue pins), flask, Due to poor surface finish needs machine finishing. Die casting: Mass production U Where many copies need to be produced a die or solid moulding box is used to form the casting. In this case the molten metal is pushed into the mould with a plunger. When cooled the dies are opened and the casting remove