1. Plastic Process
AS Graphics

2. Injection Moulding

3. Injection Moulding Description
A highly automated production process for producing large quantities of identical items
For producing 3D shapes (can be complex)

4. Injection Moulding Materials HIPS (High Impact Polystyrene) ABS HDPE
LDPE

5. Injection Moulding Keywords Hydraulic system Mould Heater Hopper
Ejector pins

6. Injection Moulding Stages
Plastic powder or granules are fed from a hopper into a hollow steel barrel which usually contains a rotating screw.
The barrel is surrounded by heaters which melt the plastic material as it is carried along the barrel by the screw towards the mould.
The screw is forced back as the melted plastic collects at the end of the barrel.
Once a sufficient charge of melted plastic has accumulated a hydraulic ram forces the screw forward injecting the thermoplastic through a sprue (small channel) into the mould cavity.
Pressure is kept on the mould until the plastic has cooled sufficiently for the mould to be opened and the component ejected (ejector pins can be used)

7. Injection Moulding Advantages Complex 3D shapes
Excellent surface finish
Variety of materials
Quick
Good for batch and mass production
Disadvantages
No inverse angles
Expensive set up

8. Extrusion

9. Extrusion Description
A continuous process used to produce both solid and hollow products that have a constant cross-section.

10. Extrusion
Materials
PVC
PET

11. Extrusion
Keywords
Die
Coil
Heater
Hopper
Tubes

12. Extrusion
Stages
Thermoplastic granules are fed from a hopper by a rotating screw through a heated cylinder.
The tapered shape of the screw compacts the plastic as it becomes plasticised. The softened material is allowed to flow out through a die in a continuous stream.
The die which is fitted to the end of the extruder barrel determines the cross-section of the extrusion.
As the extrusion leaves the die it is cooled by passing through a cooling trough containing cold water.

13. Extrusion Advantages The length of the part is potentially infinite
Quick
Good for batch and mass production
Disadvantages
Parts must be the same all the way along

14. Vacuum Forming

15. Vacuum Forming Description
Vacuum forming is usually, though not always, restricted to forming plastic parts that are rather shallow in depth.

16. Vacuum Forming Materials HIPS Acrylic PET PVC Polypropelene
It is relatively cheap, comes in a wide range of colours and is easy to form. Typical thicknesses of sheet material used range from less than 1mm up to 6mm.
Acrylic
PET
PVC
Polypropelene

17. Vacuum Forming Keywords Platen Heater Bow Air Vacuum Draft angle
Vent holes
Rounded corners
Mould (MDF / stainless steel / aluminium)

18. Vacuum Forming Stages A mould is attached to a platen (bed).
The platen and mould are then lowered and rigid thermoplastic sheet material is clamped onto an air tight gasket and heated from above.
Once the thermoplastic sheet is softened enough (i.e. reaches a plastic state) then air is blown in to raise the sheet in a slight bubble before the platen is raised bringing the mould into contact with the plastic.
Any trapped air remaining between the platen and the heated plastic sheet is then evacuated by a vacuum pump.
Once the plastic sheet has cooled down to below it's freeze (solid) point the air flow is reversed to lift the forming off the mould. If this is not done quickly the forming tends to grip onto the mould and attempts to prise them apart often result in damage to the forming.
Trim and finish the edges.

19. Vacuum Forming Advantages
Can be inexpensive to set up (mould can be MDF)
Good for batch production (stainless steel / aluminium mould)
Disadvantages
Limited to hollow objects
Thin sheets only

20. Blow Moulding

21. Blow Moulding Description
an automated process that is used extensively to make bottles and other lightweight, hollow parts from thermoplastic materials.

22. Blow Moulding Materials High density polyethylene (HDPE)
low density polyethylene (LDPE)
Polypropelene

23. Blow Moulding
Keywords
Parison
Extruded down
Flash
Cold mould
Air

24. Blow Moulding
Stages
The cycle starts with the mould open. A hollow length of plastic, called a parison, is extruded down between the two halves of the mould.
The mould closes and compressed air is blown into the inside of the parison which inflates it, pushing the soft plastic hard against the cold surfaces of the mould. The plastic is cooled by the mould, causing it to harden quickly.
The mould is then opened (below), the moulding ejected and the waste (called flash) is trimmed off with a knife.

25. Blow Moulding Advantages Quick Good for batch and mass production
Complex bottle shapes can be produced
Disadvantages
Bottles only
Expensive setup cost
No inverse angles

26. Rotational Moulding

27. Rotational Moulding Description
Rotational moulding is a process used mainly to manufacture hollow shaped products such as footballs, road cones and storage tanks

28. Rotational Moulding Materials
90% of rotational mouldings are made from polyethylene

29. Rotational Moulding
Keywords
Mould
Rotated
Plastic powder
Coating

30. Rotational Moulding Stages
Moulds are attached to the end of each arm and are rotated continuously.
Open mould is filled with plastic powder
Mould is closed and begins to rotate
Mould is heated and the plastic melts, coating the inside (As the mould rotates its inner surface passes continually through the mass of powder at the bottom of the mould. The powder in contact with the hot metal fuses and sticks to the mould surface. As the mould rotates more plastic melts and sticks to the inner surface finally producing an even layer up to 10mm thick).
Mould is cooled to set the plastic (Still rotating, the mould moves into a cooling area or chamber where it is cooled by air or water jets).
Mould is opened and the product removed
Mould materials:
aluminium
Mild steel
copper (producing very detailed surface finishes)

31. Rotational Moulding Advantages
Great flexibility in terms of the shape and size of product that can be produced. Both symmetrical and asymmetrical designs can be formed as well as complex,
both tough rigid shapes and for flexible mouldings with deep undercuts such as inflatable rescue craft and toys.
best suited to making medium to large mouldings.
Rotational moulding does not involve high pressures and so moulds can be lighter and costs are lower.
It is one of the few processes in which undercuts in the mould are allowable.
Disadvantages
Hollow shapes only
Not as fast as other processes

32. Safety Features of all these processes
Full guards (1) protecting cutting blades / moving parts (1)
Light beam (1) which stops operation if the beam is broken (1)
Emergency stop button (1) to isolate power/stop machine quickly (1)