1. Design and Manufacture National 4/5 Commercial Manufacturing Processes

2. Injection Moulding Video Injection moulding
Injection Moulding is a process which allows large quantities of plastic components to be made quickly. Thermoplastic granules are heated until they soften. Then the material is forced under pressure into a mould. When cooled, the mould is opened and a component, which is the exact shape of the cavity is taken out. Injection Moulding is one of the most important industrial processes in the mass production of plastic goods. The cost of producing the moulds can be very high, therefore it is necessary to manufacture and sell large quantities of the product being manufactured to recover costs.
The Process
A feed hopper if filled with thermoplastic granules.
A rotational screw mechanism passes the granules through a heater.
The heater causes the granules to plasticise.
The soft plastic is injected into the mould where it is cooled.
The mould is opened automatically.
The finished component is ejected.
No further finishing is required. The quality of the product is identical to the surface of the mould.
Uses
Components produced by injection moulding vary from golf tees, spoons, wash basins, buckets, airfix models to product casings.

3. Identifying Features
Ejection pin marks on the inside of the product
Mould split Lines
Injection mark (sprue pin)
Advantages
Large quantities of identical plastic components can be made quickly
High quality surface finish
Complex accurate shapes can be produced
Strengthening ribs and webs can be included
Disadvantages
High tooling cost
Expensive set up costs/costs of machinery

4. Rotational Moulding Video Rotational Moulding
Rotational moulding is a method of creating medium to large sized hollow components from plastics. It involves melting plastic inside a closed mould which is rotated so the plastic coats the inside of mould. The plastic is then cooled and solidifies in the shape of the mould.
Stage 1 At this stage the liquid plastic is poured into the mould. The mould is then sealed and the process of rotating it begins.
Stage 2 This stage shows the plastic being heated as it is rotated around the mould. The heated plastic coats the inside wall of the mould.
liquid plastic
mould
Stage 3 The completed plastic mould is now cooled before ejection from the mould.
Stage 4 The moulded shape is ejected from the mould. The picture here shows a hollow sphere.

5. Identifying Features
Mould split Lines
Uniform wall thickness
No joining processes evident
Advantages
Large, identical plastic components can be made quickly
Good quality surface finish
Strengthening ribs and webs can be included
Disadvantages
High tooling cost
Expensive set up costs/costs of machinery

6. Vacuum Forming Video Vacuum Forming
In Vacuum Forming, a sheet of thermoplastic is held in a clamp and is heated until it is soft and flexible. Air is sucked out from underneath the sheet so that air pressure pulls the sheet down onto a specially made mould. This process enables thermoplastics to be formed into complicated shapes such as packaging, masks, storage trays and seed trays.
Stage 1 The first stage of vacuum forming is to clamp the sheet across the top of the machine and heat it until the plastic is soft and flexible. This can be judged by watching the material, which will start to sag under its own weight when soft. If touched with a stick it will feel soft and rubbery.
platform raised
Stage 2 The pattern is then raised up to meet the hot soft plastic.
air sucked out
Stage 3 At this stage the air has been sucked out from beneath the plastic pulling it onto the pattern.
formed plastic
Stage 4 The final stage is to remove the pattern from the plastic leaving the finished article.

7. Air holes- for removing air from around the mould
Identifying Features
Rounded Corners – The pattern should have rounded corners and not sharp edges so that the plastic does not rip or tear as it forms round the pattern.
Tapered Edges - The pattern should have tapered edges or sloping sides so that the pattern can be easily removed from the plastic after forming.
Internal curves – The pattern should not have internal curves as these cause folds in the plastic to occur during the forming process.
Air holes- for removing air from around the mould
Advantages
Repeatable
Low cost
Disadvantages
Limited Strength
Stretching and tearing can occur in plastic
Pattern with rounded corners and sloping/tapered sides.

8. Extrusion Video
This process can be compared to squeezing toothpaste from a tube. It is a continuous process used to produce both solid and hollow products that have a constant cross-section.
Extrusion can be used to produce products such as gutters, window frames and electrical trunking.

9. Identifying Features
Uniform profile along it’s length
Available in long lengths
Advantages
Continuous Process
High production volumes
Low cost per meter
Many types of raw materials are suitable
Disadvantages
Limited complexity of parts
Uniform cross-sectional shape only

10. Die Casting
Video
This process is the equivalent of the plastic process of ‘injection moulding’, where molten material is forced into a mould (die) to cool and set. The dies used are made of special alloy steel and are very expensive to produce, being made in sections for easy removal of the components. The high operating costs make this process viable for high-volume production or ‘mass production’ where accuracy of shape, size and surface finish is essential.
Process
A measure of molten metal is poured into the charge chamber.
An injection piston then forces the metal into a water-cooled die through a system of sprues and runners.
The metal solidifies rapidly and the casting is removed, complete with its sprues and runners.
Video 2

11. Uses Engine casings, toy cars, pencil sharpeners etc.
This pencil sharpener has been ‘die cast’. It has ejector pin marks on each corner.

12. Identifying Features
Mould split Lines
Injection mark (sprue pin)
Ejector pin marks
Advantages
Repeatability
High quality surface finish
Complex accurate shapes can be produced
Strengthening ribs and webs can be included
Disadvantages
High tooling cost
Expensive set up costs/costs of machinery

13. Sand Casting Video Uses
This is the most frequently used metal casting process. ‘Green’ foundry sand is a blend of silica grains, clay and water. Oil-bound sand gives good results but is difficult to reconstitute (re-use). The quality of the casting depends on the quality of the pattern, which is normally made of wood. The pattern requires radiused corners, drafted sides and a good surface finish. The sand mould is produced around the pattern, which is removed to leave a cavity. Molten metal is poured into the mould and solidifies. When cold, the mould is broken up to retrieve the casting.
Uses
Engine parts, machine tables, tools and tool handles, stoves, taps, propellers

14. Identifying Features
Simple components which can be solid or hollow
Rough texture
May show signs of shrinkage
Can be used with a wide variety of metals
Advantages
Low cost
Repeatable
Relatively easy to carry out
Disadvantages
Low quality surface finish
Parts may require secondary processing

15. Press Forming Video 2 Video Uses Pans Kettles Kitchen sinks Car bodies
Press forming involves squeezing sheet metal between two matched metal moulds (dies). This gives a very strong shell-like structure. One die is the mirror image of the other, apart from an allowance for the thickness of the material being formed. The machining of these dies is a specialised skill as they are complicated and therefore time-consuming and expensive to produce.
Uses
Pans
Kettles
Kitchen sinks
Car bodies
Aircraft panels
Process
A blank is cut out to the required size.
The blank is placed in a press.
The product is formed using immense force. (1 thousand tonnes are required to manipulate 3.5mm thick steel plate.)
Video 2

16. Identifying Features
Uniform thickness sheet material
Bending and forming to increase strength
Advantages
Repeatable
Relatively easy to carry out
Can produce a wide range of strong products
Disadvantages
Set up costs of machines is high
Limited material thickness

17. Centre Lathe Turning Video
Centre lathes are used to make cylindrical components from metals and plastic materials. The process is called turning – never use the term lathing. The principle of turning is straightforward. Work is held firmly and is rotated whilst a single-point cutting tool, located in the tool post, cuts the work using the familiar wedge-cutting action. The shape of the work produced depends upon the path taken by the tool, the two principle shapes being cylindrical and flat, produced by parallel turning and facing.
Centre lathes, like the one shown have four main
elements:
lathe bed – very rigid and usually made from cast iron. The bed keeps the other parts in alignment.
headstock – containing the gearbox, controls and the means of holding the work, most commonly a 3-jaw or 4-jaw chuck.
tail stock – for location of drills and drill chucks and for supporting long work.
saddle – travels along the bed and carries a cross slide upon which is mounted the tool post.
Centre lathe

18. Uses
Bike hubs, engine parts, door handles, bolts, screws
Identifying Features
Can be manual or computer controlled
Cylindrical components
Advantages
Highly accurate
High quality surface finish
Relatively easy to carry out
Disadvantages
Skilled process
Parts may require secondary processing

19. Traditional Woodworking Joints Video
Found in traditional carpentry and joinery, using hand tool and basic machinery.
Advantages
Used for high quality products
Aesthetically pleasing
Can be strong and durable, so products will have a long lifespan
Disadvantages
Time consuming
Easy to make errors

20. Knock-down fittings/CNC
Video
Knock down fittings are commonly used in flat pack furniture, in particular by brands such as Ikea.
Advantages
Low cost
Quick to assemble
Repeatable
No skill required to build products
Allows products to be dismantled
CNC machining reduces human error and is highly accurate
Disadvantages
Perceived as being low quality
High set-up costs of machines

21. Laminating Industrial Laminating for Buildings- video 1
Laminating Furniture- video 2
This method of shaping wood involves building up a curved form with layers (‘lamina’). The layers may be thin veneers, thicker constructional veneers or saw-cut strips. They are assembled so that the grain of each layer is running in the same direction, following the curve (unlike plywood which has interlocking grain).
The layers are glued together with a strong adhesive and are sandwiched between the waxed faces of a former or a jig using cramp pressure. The layers bend to the shape of the jig and ‘set’ together.
Advantages
Low cost
Can be used to create complex curves
Strong
Repeatable
Disadvantages
Time consuming
Relatively difficult to carry out