What are all the moulding processes for thermoplastics?
- injection moulding
- blow moulding
- rotational moulding
- extrusion
- calendaring
What are all the moulding processes for Thermosetting plastics?
-Compression moulding
What is Injection moulding (thermoplastics)?
This is the process used to produce complex 3D shapes.
- plastic granules in the hopper
- screw rotated towards heaters
- ram forces heated polymer into mould
- cools
What are some advantages and disadvantages of injection moulding?
Advantages: -complex 3D shapes -high volume can be produced consistently -Metals inserts can be included Disadvantages: -set up cost is high -expensive moulds
What is blow moulding (thermoplastic)?
Process in manufacture of hollow products i.e.bottles.
- a heated tube is extruded vertically
- mould closed
- hot air is then blow into mould shape
- cools
What are some advantages and disadvantages of blow moulding?
Advantages:
-rapid method of producing hollow products
- non-circular shapes can be produced
Disadvantages:
- expensive moulds
- triangular shape bottles are difficult to produce.
What is rotational moulding (thermoplastic)?
Used in manufacture of 3D hollow products.
- a number of mechanical arms rotate about a fixed central point. The moulds ,filled with thermoplastic powder, attached to the end of each arm are rotated continuously to form a hollow 3D thermoplastic.
What are the advantages and disadvantages of rotational moulding?
Advantages: -ideal for both rigid, tough and flexible shapes - big sizing range -surface textures can be applied in mould -cheaper moulds -low production runs Disadvantages: - only hollow shapes
What is extrusion (thermoplastic)?
- The process used where products with a continuous cross-section are required.
- The process forces molten plastic through a die that has the reared cross-sectional shape.
What are the advantages and disadvantages of extrusion?
Advantage:
-low cost process for simple dies
Disadvantage:
-can only produce continuos cross-sectional shapes
What is calendaring (thermoplastic)?
- Used for manufacturing thermoplastic, generally PVC is used.
- involves rolling out a mass of pre-mixed plastic material between large rollers to form a continuous, accurate film/sheet.
What are some advantages and disadvantages of calendaring?
Advantages: -control over thickness - increases the strength of material -any pattern or texture can be applied Disadvantages: -high operating cost -low tolerance
What is compression moulding (thermosetting)?
Compression moulding is a combination of heat, pressure and time is needed to ensure all of the material’s form and structure changes.
- compressed powder is placed between two halves of a mould
- the mould is heated to a temperature that will allow cross-links to form within a material
- moulds are held closed together
- ejected while it is still hot
What are the advantages and disadvantages of compression moulding?
Advantages: -moderately complex parts can be produced over production runs -start up costs are relatively low -moulds are cheaper -little waste material Disadvantages: -necessary to manufacture preform -less complex shapes
