Production Planning & Manufacturing Processes PDF

Production Planning & Manufacturing processes  PRODUCTION PLANNING Manufacturing in vast quantities poses problems for companies due to the range and volume of different materials, parts and ‘off the shelf’ components which need to be bought, stored and used on a consta...

Production Planning & Manufacturing processes  PRODUCTION PLANNING Manufacturing in vast quantities poses problems for companies due to the range and volume of different materials, parts and ‘off the shelf’ components which need to be bought, stored and used on a constant basis. The quality of the component parts and overall product also has to be checked so that it works properly and is up to the standard of quality that is required or expected by the consumer.  The production of complex ‘one off’ products like ships, buildings and bridges has to be planned carefully so that stages in the manufacture occur in the correct order and expensive materials and specialised labour are on site when they are needed. To assist them in the manufacture of products companies use production planning systems that will help to plan the order of processes and build in quality control in advance. Production planning is also use to keep track of the volume of materials and components that they have at any one time which eradicates costly mistakes. Flow charts Flow charts are used to plan a production system in advance. The stages of production and quality control checks are planned in order. The consequences of decisions taken regarding quality control are also planned and shown on the chart. Depending on the decision taken by the quality checker a part may be sent back to an earlier stage for further work, recycled or binned. By having multiple quality control stages throughout the manufacturing process waste is kept to a minimum (saving money) and problems in particular manufacturing stages can be identified and corrected. These are used regularly on large ‘one off’ projects, like buildings, which Gantt Charts have a lot of separate stages and require a lot of different equipment and specialist tradesmen at different stages of manufacture. Some stages can only be started after others have been completed. Some stages can start at the same time or part of the way through an earlier stage. This has the effect of reducing the overall time spent to complete the project (lead time) and will save the company money. Materials can be ordered to arrive when they are needed for particular stages in the manufacture which saves the amount of space that is needed to store them.  Just in Time (JIT) Just in Time production is a system which was pioneered by the Toyota motor company in order to maximise profits and reduce the capital investment that would have to be laid out. Just in Time is an ‘orders led’ business model where the customer making an order will prompt the factory to start production to meet that order. One of the aims of Just in Time is to have ‘zero inventory.’ This means that a company will aim to have as little material as possible in storage and as few sub assembled parts as possible in the factory. This relies on very good working relationships with suppliers so that they can reliably supply the quantity of materials needed to fulfil an order quickly and as often as is needed. This will minimise the capital investment of the company on materials and will save money on wastage. It will also mean that little expensive warehousing space is needed for storage. The system relies heavily on ‘Kanban’ usually a visual sign that work should stop on one part of the manufacture and move on to another. For example if a worker notices that stocks of a particular part or sub assembly are quite high or low work will move to another stage of the manufacturing process as necessary. This relies heavily on skilled and independent workers on the factory floor who can perform a variety of stages in the overall process. The equipment and machinery used is carefully organised so that any changes to moulds and dies can be made as quickly as possible. This eliminates ‘down time’ through changeovers.  Advantages Disadvantages 1. Little capital outlay for stock and 1. Relies heavily on relationships with materials in rolling inventory. More suppliers and their ability to meet cash is available. variations in demand. 2. Little or no warehouse or storage 2. There is not spare unfinished stock costs. to meet sudden rises in demand. 3. Fast turnaround on profit because the 3. Traffic jams can affect deliveries process is so efficient. and the factories ability to function 4. Multi skilled employees improve effectively. efficiency of the process and can 4. Constant flow of deliveries adds to adapt to meet demand. transportation costs and 5. Stock will not perish, become obsolete environmental impact. or be vulnerable to a drop in demand 5. There is less room for mistakes are for the product. there is little extra material 6. Less time is spent reworking parts and available to rework faulty parts. on quality control as the emphasis is on ‘getting it tight first time.’  Plastics Processes Plastics manufacturing processes are mostly mass production processes with high volumes of output. The high cost of machinery and tooling is offset by the speed and volume of production. Processes Advantages Disadvantages Identifying Products features + highly accurate - high set up Injection Mobile phone casings are + very cheap per part costs (sprue) marks, produced by injection Injection Moulding + very fast - have to hide ejector pin moulding. This is because the + excellent surface visible identifying marks, split accuracy of individual parts texture features lines, can be assured so that they + complex shapes - flashing has to shrinkage can be assembled and the + webs can be added be removed marks, high cost of the parts will be low. for strength quality surface The phone casings can also + metal components can finish, be produced quickly in large be placed inside the complex form volumes. mould prior to forming of parts, draft angle, flash. + highly accurate - high set up Ejector pin Electrical plugs are produced + very cheap per part costs marks, split by compression moulding. This (Thermosetting + fast - have to hide lines, is because the accuracy of Compression + excellent surface visible identifying shrinkage individual parts can be Moulding plastics) texture features marks, high assured so that they can be + complex shapes - flashing has to quality surface assembled and the cost of the + webs can be added be removed finish, parts will be low. The plugs for strength complex form also have to be made from a + metal components can of parts, draft thermosetting plastic. be placed inside the angle, flash. mould prior to forming  + fast production - high set up Long parts with Drain pipes and guttering (9-60 meters per costs same cross section are made by extrusion. Extrusion second) - extrusions throughout, The process allows them + accurate will have to be lines/scratches to have the same cross + cheap process cut and along length, section down the entire + same cross assembled to shrinkage marks, length and to be section throughout make products good surface produced cheaply. They + complex cross (extra finish. have to be cut to the sections are processes) correct size. possible + produces - high set up Small hollow Bottles are produced hollow parts costs parts, plastic will cheaply and quickly by Moulding + accurate - only small be thinner at blow moulding extruded + cheap products can corners, split tubes. Screw threads on Blow + fast be produced lines. the tops of the bottles + screw threads due to draw can be applied during can be added to (stretching) on the process and they bottles the plastic will fit well with the lids - split lines are to form a watertight seal visible because the process is accurate.  + produces large - slow cooling Large hollow Large plastic oil hollow parts time limits objects, drums are produced Rotational + uniform wall speed of uniform wall by rotational thickness makes production thickness, split moulding. They are Moulding products strong + accurate - high set up costs lines, draft angle. strong due to the uniform wall + sides can be - split lines thickness of the designed with ribs are visible whole product – to make them - may require unlike blow moulding stronger/more further work which is weaker at rigid to make holes the corners. etc. + low cost of - draw on Plastic sandwich machinery makes plastic makes cartons are produced it suitable for it weaker at quickly and cheaply by Forming small scale the corners vacuum forming and Vacuum production the lips fit well + accurate because the process is + cheap accurate. The bottom + fast corners of the sandwich cartons will be thinner and weaker due to the plastic having been stretched.  Metals Processes Metals processes can be described as thermal or mechanical. Different processes are suitable for different forms of material (e.g. sheet materials) and they all have a variety of advantages and disadvantages. Proces Advantages Disadvantages Identifying Products ses features + fast production (15- - high set up costs Long parts with Copper water pipes are made by 40 meters per - extrusions will same cross extrusion. The process allows Extrusion second) have to be cut and section them to have the same cross + accurate assembled to throughout, section down the entire length + cheap process make products lines/scratches and to be produced cheaply. + same cross section (extra processes) along length, They have to be cut to the throughout good surface correct size and bent to shape as + complex cross finish. required. sections are possible + highly accurate - high set up costs Injection Wine bottle ‘corkscrew’ openers Die Casting + very cheap per part - have to hide (sprue) marks, are produced by die casting. All + very fast visible identifying ejector pin of the parts will fit together + excellent surface features marks, split because they are accurately texture - flashing has to be lines, high made and there will be a high + complex shapes removed quality surface quality surface finish to help + webs can be added - parts are quite finish, complex them look good and stay for strength weak form of parts, hygienic. draft angle, flash. Piercing and Sand Casting + cheap small scale - poor surface Rough surface Anvils and vices are production texture texture, draft produced by sand + cheap set up costs - time consuming angle, complex casting. They are + very complex parts - needs skilled shapes. irregular shapes of can be produced labour varying thickness and + parts with varying - needs machined will require additional thicknesses can be to clean up work to have holes produced surfaces, drill holes drilled and screw +no wastage of and remove threads applied. materials additional metal - creates brittle outer shell + accurate - high set up costs Thin sheet Car body panels are cut + fast - sheet material only material, shear quickly and accurately Blanking + cheap marks. from rolls of sheet metal in automated factories. The sheet with holes in it is called a piercing. The left over metal parts are called blacks. Excess material is recycled.  + highly accurate - high set up costs Circular/cylindric Cam shafts and circular + CNC produces - skilled labour al parts, highly engine parts which need to Turning identical parts (non CNC) accurate parts, be highly accurate are + CNC can be - large volume of high quality produced by turning with programmed to waste material surface finish, metalwork lathes. produce different - not as strong as machining marks. parts drop forging + CNC will be fast (cutting through grains) + highly accurate - high set up costs Complex shapes, Engine blocks which have + CNC produces - skilled labour highly accurate already been cast will have identical parts (non CNC) parts, high quality faces milled so that they + CNC can be - large volume of surface finish, perfectly flat and holes will Milling programmed to waste material machining marks. be drilled accurately in the produce different correct position so that all parts the intricate parts will fit + CNC will be fast together and be able to move properly. Moulds and dies for injection moulding and die casting are also made by this highly accurate process.  + accurate - high set up Thin sheet Car body panels are shaped + fast costs material, bends, accurately by press forming Forming + cheap - sheet material folds, ridges. so that all of the individual Press + bends, folds only panels will fit together. The and ridges will bends, folds and ridges in the make the metal sheets make it stronger product and protect passengers from stronger and impacts. more rigid + fast - not very Strong parts, Tools like spanners and Drop Forging + very strong accurate complex shapes, hammers are produced by drop parts produced - flashing has to cold to touch, forging which makes them very (not cutting grain) be removed draft angle, flash. strong so that they do not bend + varying or deform when being used. thicknesses can be achieved + patterns can be added + complex shapes can be produced  Woods Processes Processes for manufacturing in wood usually require a high degree of human input from skilled craftsmen. Please also refer to the sections on assembly and finishes in wood. Processes Advantages Disadvantages Identifying features Products + cheap process - expensive Circular/cylindrical Banister posts are + CNC produces skilled labour parts, good quality produced by turning Turning accurate and (non CNC) surface finish, on a lathe. The identical parts - large volume of possible machining material has to be + CNC can be waste material marks. prepared prior to programmed to - material has to turning so that it is produce different be cut to correct the correct size and parts size and shape in shape. Can be + CNC will be fast advance automated with CNC. + cheap process - expensive Wooden boards with Decorative edges and + CNC produces skilled labour accurately placed slots in traditionally Routing accurate and (non CNC) holes, decorative crafted furniture will identical parts - large volume of edges and holes with be applied by a router + CNC can be waste material uniform section. which can be programmed to - material has to automated to repeat produce different be cut to correct the same process parts size and shape in accurately and + CNC will be fast advance cheaply (flat pack furniture).  +cheap - requires skilled Long parts, Skirting boards and Spindle Moulding + accurate labour uniform cross wooden mouldings are strips of wood which - material has to be section, high have been passed cut to correct size quality through a spindle and shape in surface finish. moulder to produce a advance uniform, decorative edge along their length. + large, wide - expensive manual Wide boards of Dining table tops boards produced labour natural timber, (Beams) (Boards) (Sheets) which will not bow - time and labour alternating end intensive grain on ends of + thin, strong strips. Skateboard tops sheets of wood - expensive manual Laminating which can be bent labour Thin and strong to shape during - time and labour boards, layering forming for extra intensive visible at the structural strength edges. Roof beams in large - expensive manual halls + large, possibly labour Long beams curved beams made - time and labour made of smaller from small pieces intensive individual pieces of timer of timber. + strong as grain runs throughout