Production Flashcards
One off production:
Advantages: made to personal specifications, skilled craftsman ensures high quality product
Disadvantages: expensive in comparison to large scale products, labour intensive and time consuming
Applications: bespoke furniture
Batch:
Advantages: flexibility in adapting production to another product, fast response to market trends, lower unit costs than one off products
Disadvantages: poor production planning results in large numbers of products needing storage meaning storage costs, changes in production cause costly re-tooling
Applications: seasonal garden furniture
Mass:
Advantages: automated and efficient, quality control ensures identical goods, large production means set up costs are recovered quickly, low unit and labour costs.
Disadvantages: high set up costs, inflexible; can’t respond to market trends
Applications: electronic products, phones & games consoles
Continuous:
Advantages: mass production, low unit costs, runs continuously 24/7
Disadvantages: no flexibility as running 24/7
Applications: cans and bottles for drinks.
Sand casting:
1) drag is placed upside down and half of the pattern is placed in the centre and sprinkled with parting powder.
2) Facing sand should cover the pattern. Sand should be rammed down to compact it and then levelled off.
3) drag turned over and cope placed on top. 2nd half of the pattern is placed on the first half.
4) Parting powder is sprinkled over the pattern and spruce pins are placed into the sand.
5) Cope is then filled with facing sand. Hollows are placed around the tops of the pins.
6) Remove the pins and separate cope and drag.
7) metal is placed into a crucible in a furnace to make it metal.
8) The metal is then poured slowly and evenly into the holes. The metal is poured into the runner and the air is released from the riser.
9) The metal should be cooled and allowed to solidify before being removed and fettled.
Advantages: inexpensive, produces complex and large components
Disadvantages: only used once, finish not always good, labour intensive, slow production rate.
Applications: engine blocks, garden furniture, caterpillar tracks
Die casting
Producing non ferrous products by - high pressure casting - gravity die casting
Does are reusable moulds made of steel.
1) mould is sprayed with lubricant
2) molten metal is shot under high pressure into die
3) the pressure is maintained until the metal has solidified
4) casting is removed by ejector pins and is fettled
Advantages: high production rate, good surface finish, good control over mould temperature, economical for large production
Disadvantages: high set up costs, long lead time, limited sizes, not all alloys suitable for the process, large volume process needed for economical production.
Applications: Taps, model cars
Glass Reinforced Plastics
1) a high quality mound is made
2) release agent is sprayed onto the mound
3) Gel coat is applied to the mould. This will form the outer skin of the product. Pigments added create colour.
4) layers of resin and a catalyst and glass matting are added to the mould.
5) once completed the work is left overnight to cure. Then it is eased out of the mould
Composite material made from thermosetting plastic reinforced with fine glass.
Resin is compressively strong but not tensile strong. Adding them together improves strength.
GRP can be as strong as steel but unsatisfactory in the place steel in cars.
Good strength to weight ratio, resistant to corrosion
Resin on its own is brittle and can shatter, prone to osmosis leading to delamination of hull.
Milling- process of cutting away metal
Routing- similar process but associated with wood.
Both cut slots in material. There are two types milling machine, vertical and horizontal.
Fences help guide routers to make sure that they are in the correct position/parallel to the edge of the work. It is important to make sure that the edges are square.
Drilling
Twisted drills- high speed steel can be used to produce holes in most materials.
Parallel shank drills - held in place in drilling machine by a chuck.
Taper shank drills - placed into machine and held by friction
Flutes enable swarfs to be carried away from the drilled material. Lubricants should be used to keep the drill cold and the drilling efficient.
Drilling pieces
Flat bits- drilling deep holes in wood
Forstner bits - to drill flat bottomed holes in wood
Auger Bits- to drill deep holes in carpenter’s brace
Counter sink bits - countersunk head screw to be inserted so that the head of the screw is flush with the surface of the material
Hole saws - saws are circular shaped cutting rings that range in diameter
Tank cutters - circular cutters that change diameter for cutting holes in sheet material
Metal turning lathe- Chuck Tool post Saddle Tailstock
Wood turning lathe- Swivel arm Headstock Outside spindle Inside spindle Tool rest Dead centre Tailstock
Turning
Two main uses of a lathe is to face off (smoothing down the end of a material) and turning down (reducing the diameter of some materials)
Safety of a lathe = work securely fastened, aligned correctly with cutting tool at centre height. Timber is free from knots.
Centre drilling- drilling a hole in the end of a rod or bar.
Boring tool is used to create a larger hole within a metal bar.
To stop the drill from becoming blunt and inefficient, a coolant is pumped into the work to keep it cool. Removing the drill from the hole cools down the drill and removes swarf.
Injection moulding
Thermosetting plastics are made using resin and a catalyst. These are most used in injection moulding.
1) moisten plastic injected under high pressure into a mould
2) granules are placed into a hopper and forced into a heat chamber
3) plastic is injected into a two part mould.
4) the component is rapidly cooled with water and ejected from the mould
The moulds are usually made from steel and are high quality. Injection moulding is most commonly used in products such as Bottle tops and garden furniture
Advantages: ideal for mass production, low unit costs, precision moulding: high quality textures and finishes can be added to the mould.
Disadvantages: high initial set up costs
Vacuum forming:
1) high quality former the exact shape of the item needs to he produced. There should be a number of small holes to allow air to escape
2) former is placed into machine with thermoplastic being clamped over it. The plastic is made soft and pliable
3) once the plastic is soft the former is raised into the former and the air is sucked out forcing the plastic around the former
4) the plastic cools and is removed from the machine
Vacuum Forming
Advantages: ideal for batch production and inexpensive, easy the make moulds that can be changed
Disadvantages: mould needs to be accurate to stop webbing, large amounts of waste
Used in yogurt pots, blister packs and the inside of fridges
Extrusion
Used to create long products that have a particular cross section. Long components parts using UPVC such as rainwater gutters.
Instead of being forced through a mould it is forced through a die. Hollow sections can be made by applying pins inside the die.
Can be continuous making long components or semi continuous producing short series components.
This is very similar system to injection moulding
Blow moulding
Produce hollow products from thermoplastics.
1) plastic granules is fed into a hopper and the Archimedean feeds them through a heated chamber.
2) the plastic becomes soft and is extruded into a hollow tube. This is called a parson.
3) parson is clamped into a metal mould and air is pumped into it.
4) parison inflates the shape of the mould
5) once cooled the bottles is ejected
Advantages: creates intricate shapes, produces hollow shapes using minimal material reducing weight and cost, ideal for mass production
Disadvantages: high initial set up costs
Uses: plastic bottles, containers of all shapes,
Drinks bottles and shampoo bottles
Rotational moulding
Creates hollow one piece components.
1) measured amount of powdered polymer is loaded into a mould
2) heat is applied to the mould and at the same time is rotated in a tumbling action until the plastic has melted and stuck to the wall.
3) the mould is then cooled using water and ejected
Advantages: easy to produce large products, product has no seams, uniform thickness, corners are stress free,
Disadvantages: lower volume production, materials are limited, labour intensive, long cycle times limit economic batch sizes.
Applications: buckets, dustbins, oil drums, traffic cones, storage tanks
Cam and Followers.
Three types of movement:
Uniform Velocity, simple harmonic motion,
Uniform acceleration
Flat - lots of friction, cannot follow hollow contours
Knife- most accurate conversion of movement, can follow hollow contours
Roller- least frictions, cannot follow hollow contours, most expensive
Pear shaped cam-
Used to control inlet/outlet valves, symmetrically shaped so rise and fall times are identical
Circular cams-
Simplest cam, smooth rise and fall, constant acceleration, used in fuel pumps
Heart shaped cams-
Symmetrical and so generate continuous motion, used in seeing machines and motor windings
Snail cams-
Output with uniform acceleration and retardation
