Polymer processes

Vacuum forming process

How it works:

1. Use a thermoplastic with up to 6mm thickness e.g. HIPS

2. Create a mould for the plastic to wrap around (air gaps, tapers, angles, rounded edges) & is placed on the platen

3. A sheet of plastic is clamped onto the machine

4. A heating element is moved over the sheet & heat until 'bouncy'

5. Raise platen into plastic

6. Vacuum s switched on to draw the plastic around the mould

7. Blow back a little bit of air to help release mould

8. The mould is removed from the plastic and the excess plastic is trimmed to size

Vacuum forming uses, advantages & disadvantages

Used for yogurt pots, blister packaging, inside of fridges & disposable coffee cups

Advantages

• Ideal for small scale & batch production

• Inexpensive

• Easy to make mould/can be modified

• Low temperatures which reduce energy use

• Flexible manufacturing process

Disadvantages

• Moulds need to be accurate to avoid webbing

• Large amounts of waste materials produced - bad for environment

• Can only mould thin products which are weak/prone to cracking

• Can only form open backed shapes

• Cannot mould complex shapes

• Not cost effective for one-off manufacture

Thermoforming process

How it works:

1. Use a thermoplastic that’s approximately 6mm thickness

2. Plastic sheet is heated to a pliable temperature

3. The heated sheet is then formed over a mould (vacuum or pressure applied)

4. Once the sheet has cooled and hardened, it retains the shape of the mould

Thermoforming uses, advantages & disadvantages

Used for packaging, car interiors, plastic trays, baths

Advantages

• Quick process for making large volumes of parts

• Cost-effective for producing thin-walled components

• Suitable for complex shapes and intricate designs e.g. lego

• Minimal waste as sheets can be re-used

Disadvantages

• Limited to thin plastic sheets, making thicker parts harder to form

• Detail may be lost in deeper moulds

• Requires precise temperature control

Calendaring process

How it works:

1. Thermoplastic pellets are fed through a series of rollers (calenders)

2. The rollers squash and squeeze the polymer into thin sheets

3. Temperature and pressure are controlled to ensure the correct thickness and texture

Calendaring uses, advantages & disadvantages

Used for plastic films, synthetic leather, wallpaper, flooring materials

Advantages

• Ideal for producing large quantities of thin, uniform sheets

• Can produce a range of textures and finishes

• Efficient for continuous production

Disadvantages

• Limited to producing flat sheets or films

• Not suitable for 3D moulding or complex shapes

• Requires precise temperature and pressure control

Line bending process

How it works:

1. A heated wire is placed along the line where the bend is to occur

2. The polymer sheet is heated at the wire's contact point, making it pliable

3. Once the material is heated, it is manually bent into shape

Line bending uses, advantages & disadvantages

Used for signage, display stands, product enclosures

Advantages

• Suitable for one off or batch production

• Simple and cost-effective for creating small bends and angles

• Quick process with minimal material waste

• Great for making sharp, consistent bends

Disadvantages

• Limited to simple bends (complex shapes are difficult)

• Not suitable for thicker plastics

• Requires precise temperature control

• Slow process

Laminating (layup) process

How it works:

1. Layers of material, such as fabric or composite sheets (GRP / CFRP), are placed into a mould

2. A resin is applied between the layers to bond them together

3. The top gel coat is applied which may contain pigment

4. The layered material is then cured, often using heat and pressure, to form a solid structure

Laminating (layup) uses, advantages & disadvantages

Used for composite components (e.g., aerospace parts, boat hulls, car panels)

Advantages

• Can create strong, lightweight composite materials

• Allows for complex shapes and large components

• Versatile, as different types of fibres and resins can be used

Disadvantages

• Can be labour-intensive and time-consuming

• Requires a former to mould around

• Requires precise control of temperature and curing time

• Health and safety concerns when handling certain resins

Injection moulding uses, advantages & disadvantages

Used for casings for electric products, containers for storage/packaging

Advantages

• Ideal for mass production

• Low unit cost

• Precise moulding

• High quality finish

Disadvantages

• High initial set up costs

• Moulds are expensice to create

• Can create large mouldings

Injection moulding process

How it works:

1. Thermoplastic granules fed through hopper

2. Heated/melted along the Archimedes screw

3. Plastic injected into the mould

4. Two-part mould "negative" of the product

5. Product rapidly cooled and ejected from mould

Blow moulding uses, advantages & disadvantages

Used for plastic bottles, containers

Advantages

• Intricate shapes can be formed

• Can produce hollow shapes

• Ideal for mass production

Disadvantages

• High initial set up costs

• Moulds are expensive to create

Blow moulding process

How it works:

1. Thermoplastic granules fed through hopper

2. Heated/melted along the Archimedes screw

3. A thermoplastic tube ‘parision’ is formed

4. The mould squeezes either side of the parision, forming the shape

5. Two-part mould "negative" of the product

6. Product rapidly cooled and ejected from mould

Rotational moulding uses, advantages & disadvantages

Used for buckets, traffic cones, dustbins, oil drums

Advantages

• Easy to produce large products

• Uniform thickness, seamless hollow components

• Corners of products are stress free

• Colour is easy to integrate into products

Disadvantages

• Lower volume production (slow process)

• Materials available are limited

• Labour intensive

Rotational moulding process

How it works:

1. Thermoplastic powder / granules loaded into mould

2. Heat is applied to the mould

3. At the same time the mould is rotated on all 3 axis (x, y, z)

4. After some time, the mould is cooled and the component is removed

Extrusion uses, advantages & disadvantages

Used for collapsible tubes, guttering, straws, gear blanks

Advantages

• Low cost relative to other moulding processes

• Uses thermoplastics which can be remoulded

• Waste material can be reused

• Plastic can be manipulated after extrusion before fully cooled (e.g. bends/curves)

• Continuous production

Disadvantages

• Hard to predict die swell (expansion)

• Can only manufacture certain products

Extrusion process

How it works:

1. Thermoplastic granules fed through hopper

2. Heated along the Archimedes screw

3. Plastic forced into the die

4. The plastic is extruded 'pulled' through the die and cooled

5. Rollers pull plastic continuously

6. The extruded product is cut to the desired lengths

Compression moulding uses, advantages & disadvantages

Used for automotive parts, electrical components, appliance housings

Advantages

• Good for producing large and complex shapes

• Produces strong, durable parts

• High efficiency in material use, with minimal waste

• Suitable for thermosetting polymers

Disadvantages

• Requires high pressure, which can be costly

• Can be slower than other methods for high-volume production

• Tooling and moulds can be expensive

Compression moulding

How it works:

1. A pre-measured amount of polymer (often in the form of a resin or compound) is placed into a heated mould cavity

2. The mould is closed, applying both heat and pressure to the polymer

3. The polymer flows and fills the cavity, taking the shape of the mould

4. The mould is then cooled, and the finished product is removed