polymer forming processes

Uses of Vacuum forming

Lightweight trays, box inserts, liners, coffee cup, yogurt pots

Stock material used in vacuum forming

Sheet of thermoplastic polymer < 6mm thick

What do you need to make sure you add to your mould so it comes out easily? (vacuum forming)

draft angle and air holes

Most common scale of production for vacuum forming

small batch production

What happens if vacuum forming happens at a larger scale

moulds are made from aluminium to provide a consistent high quality surface finish

What is the process of vacuum forming? (1/6)

Mould is placed on the bed and is lowered to the bottom of the machine.

What is the process of vacuum forming? (2/6)

Polymer sheet is clamped over the mould

What is the process of vacuum forming? (3/6)

Heater is pulled over sheet

What is the process of vacuum forming? (4/6)

When the polymer has softened, the heater is removed and the mould is raised.

What is the process of vacuum forming? (5/6)

Vacuum pump is turn on, sucking polymer onto mould

What is the process of vacuum forming? (6/6)

Once polymer has cooled, it is removed and mould is removed

What is the process of vacuum forming?

Excess polymer is trimmed off.

Uses for thermoforming

additional detail into the surface or for thicker polymer sheets

Scale of production for thermoforming

industrial production

Process for thermoforming

Similar process to vacuum forming but a positive mould is pressed onto the surface at the same time the vacuum is on into the negative mould.

Uses of calendering

making thin polymer sheet and film

Scale of production for calendering.

industrial production: continuous

Process for calendering (1/4)

Heat pellets of thermoplastic until dough like consistency

Process for calendering (2/4)

Then it is shaped between multiple heated rollers so it gets squashed and becomes thinner

Process for calendering (3/4)

Finished on cooling rollers

Process for calendering (4/4)

Either chopped up into standard stock sheet sizes or rolled up

Use of line bending

to produce bends in thermoplastic sheet

Examples of line bending

acrylic boxes, shelves, menu holder

scale of production for line bending and why?

one off or batch as it's slow and labour intensive.

process of line bending

Uses electrically heated element that provides heat along a line

Uses of lamination (lay-up)

3D products from fibre based composites

Examples of products that were made using lamination

Boats, props for theatre

Process for lamination (1/6)

Mould is made and covered with a release agent or parcel tape

Process for lamination (2/6)

Top layer of gel coat is applied (polyester resin mixed with pigment or additives)

Process for lamination (3/6)

Fibreglass sheets are cut to size and laid over mould

Process for lamination (4/6)

Polyester resin is brushed on and a small roller is used to smooth the matting

Process for lamination (5/6)

Process 3-4 is repeated until desired thickness

Process for lamination (6/6)

GRP is left out to set while CFRP is put into an autoclave.

What is injection moulding used for?

To make complex items from thermoplastics

What scale of production is injection moulding?

mass production or continuous production

Process of injection moulding (1/6)

Thermoplastic granules poured into a hopper

Process of injection moulding (2/6)

An Archimedean screw thread is rotated pulling the granules through a chamber past electric heaters

Process of injection moulding (3/6)

Heaters melt the polymer

Process of injection moulding (4/6)

When melted polymer is at the end of the screw, a hydraulic ram forces the screw forward, injecting polymer into mould

Process of injection moulding (5/6)

Mould is cooled quickly using water

Process of injection moulding (6/6)

Mould opens and ejector pins push the mould out and excess material is trimmed

Uses of blow moulding

to produce hollow thin-walled products like bottles

Most common polymers used in blow moulding

PET, LPDE, HDPE, PP

What scale of production is blow moulding and why?

continuous production due to high setup cost

Process of blow moulding (1/6)

Polymer fed into hopper

Process of blow moulding (2/6)

Archimedean screw pulls polymer through heated section, melting polymer

Process of blow moulding (3/6)

Extruded as a tube called parison

Process of blow moulding (4/6)

Mould sides close around parison

Process of blow moulding (5/6)

Air is injected into the mould, forcing the polymer to the sides

Process of blow moulding (6/6)

polymer is cooled, mould opens and product is ejected

Uses of rotational moulding

Produces heavy duty seamless hollow objects that need a thick wall (e.g. traffic cones)

Most common polymers used for rotational moulding.

HDPE, PP

What is the scale of production for rotational moulding and why?

High setup cost so only used for large scale batch production or mass production

What can you do with the moulds in rotational moulding?

Moulds can be changed relatively quickly so different products can be made on the same machine

Process for rotational moulding (1/5)

Polymer powder are loaded into a mould, which is clamped and sealed

Process for rotational moulding (2/5)

Mould is put into a oven at 260-370℃

Process for rotational moulding (3/5)

Then is is rotated slowly around 2 axes, making the polymer coat the inside

Process for rotational moulding (4/5)

When polymer reached right thickness, mould is cooled

Process for rotational moulding (5/5)

When polymer solidifies, it shrinks slightly, allowing it to be removed.

Uses for Extrusion

Used to produce solid rod, hollow tube, angle/I/T sections or channels and coat electrical wire for insulation.

What scale of production is extrusion?

continuous production of stock material

process of extrusion (1/4)

Polymer granules are loaded into hopper

process of extrusion (2/4)

Archimedean screw moves granules past heaters, which soften the polymer

process of extrusion (3/4)

The hydraulic ram pushes the screw forcing the polymer through a steel die

process of extrusion (4/4)

Extrusion is cooled and cut to desired length.

Uses of compression moulding

to mould thermoset polymers

Process of compression moulding (1/4)

A slug of polymer is inserted into pre-heated mould

Process of compression moulding (2/4)

Moulds are closed and hydraulic pressure is applied, making the polymer take the shape of the mould

Process of compression moulding (3/4)

Mould is kept closed while curing takes place

Process of compression moulding (4/4)

When the product has finished curing, the mould is open and excess polymer (flash) is removed