15 - Polymer processes Flashcards

1
Q

Vaccum forming process (6)

A
  • Mould is placed on the bed of the platen which is then lowered to the bottom
  • Polymer sheet is clamped over the mould and a heater is pulled over the polymer sheet
  • When the polymer sheet has softened the platen is raised over the sheet
  • Vacuum pump is switched on which sucks the polymer onto the mould
  • Once polymer has cooled and returned to a solidified state, the platen is lowered and vacuum is switched off
  • Mould is removed from the moulding and excess polymer is trimmed off
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Vacuum forming:

  • Polymer stock form
  • Products
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Key features of vacuum forming (3)

A
  • Moulds are relatively easy to make but need a draft angle, air holes and rounded corners
  • Not cost effective for one-off manufacture
  • Small-scale batch and mass production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Thermoforming process (2)

A
  • Similar to vacuum forming but there is an additional mould that is pressed onto the surface of the polymer sheet at the same time the vacuum is applied
  • The two moulds trap the softened polymer in between them giving extra detail to the moulding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Thermoforming:

  • polymer stock form
  • products
A
  • Thermoplastic sheet approx 6mm
  • Bath, food packaging (fruit punnets, cake boxes, sandwich boxes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Key features of thermoforming

A
  • Good for fine detail such as moulding in logos
  • Slow process used in industrial production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Calendering process (4)

A
  • Pellets of thermoplastic is heated so that it melts into a dough-like consistency
  • It is then extruded between a series of heated rollers to make it thinner
  • Its then finished on cooling rollers
  • It is then chopped into standard stock sheet sizes, or in the case of polymer film it is rolled up for storage and distribution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Calendering:

  • Polymer stock form
  • products
A
  • Thermoplastic pellets
  • Thin polymer sheet and film
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Key features of calendering

A
  • Is an industrial production method, carried out by specialist manufacturers
  • Used for continuous production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Line bending process

A

Uses an electrically heated element that provides heat along a line to bend sheet of termoplasric shuck as acrylic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Line bending:

  • Polymer stock form
  • Products
A
  • Thermoplastic sheet
  • Acrylic boxes, sheet or point-of-sale displays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Key features of line bending (2)

A
  • Quite slow and labour intensive - commonly used in school or college workshops
  • Suitable for one-off or limited batch production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lamination (lay-up) process (6)

A
  • a mould or former in the shape of the product or component is prepared - made from timber, manufactured boards or high density foam
  • Mould or former coated in related agent e.g wax or PVA or parcel tape
  • A top layer of gel (gel is polyester resin mixed with a pigment) is applied to give colour and addititives such as prevent UV degradation and hydrolysis
  • Fibreglass matting is cut to size and laid over the former then begins the stippling process the matting is available in a range of stock forms including chopped strand, woven and ‘tissue’ which is a fine grade matting for covering the surface
  • Step 3 is repeated until the desired thickness is achieved and fine tissue matting is used on the top layers - a vacuum bag may be used to compress the layers of GRP before it sets
  • GRP is allowed to set
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the stippling process that takes place during lamination?

A

polyester resin in brushed onto matting and a small roller is used to push out any air bubbles that may form and to smooth out the matting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Lamination:

  • polymer stock form
  • products
A
  • Fibre-based composite sheets (GRP, CFRP)
  • Boats hulls, kayaks, train carriages, theatre and film props, theme park rides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Key features of lamination (lay-up) (4)

A
  • Requires a former to mould around
  • Polymer resin used as the polymer
  • A top gelcoat is applied which may contain pigment
  • CFRP requires an autoclave for the product to ‘cure’
17
Q
A
18
Q

Injection moulding process (5)

A
  • Thermoplastic granules are poured into the hopper
  • A screw thread is rotated by a motor thus pulling the granules through the chamber and past electric heaters
  • The heaters melt the polymer
  • When a sufficient charge of polymer has been melted and formed at the end of the screw, a hydraulic ram forces the screw thread forward injecting the polymer into the mould
  • The mould is water cooled to allow it to harden quicker
  • Any excess polymer is trimmed of the moulding - formers or jigs May be used the dimensional accuracy of the moulding while it cools and gardens completely
19
Q

Injection moulding:

  • polymer stock form
  • products
A
  • Thermoplastic granules
  • Electrical product casings (computers, TVs, vacuum cleaners, calculators
20
Q

Key features of injection moulding (4)

A
  • Complex 3D shapes can be easily made
  • Fast industrial production method
  • Used for large-scale mass or production
  • High initial tooling cost
21
Q

Blow moulding process (5)

A
  • The polymer is fed into the hopper
  • An Archimedean screw pulls the polymer through a heated section melting the polymer
  • The melted polymer is extruded as a tube called a parison
  • The mould slides close around the parison and air is injected into the mould, forcing the polymer to the sides
  • The polymer is allowed to cool for a few seconds the mould opens and the finished bottled is ejected
22
Q

Blow moulding:

  • polymer stock for
  • products
A
  • Thermoplastic tube ‘parison’
  • Drink bottles, shampoo bottles, detergent bottles etc
23
Q

Key features of blow moulding (3)

A
  • Produces hollow thin-walled components
  • High initial tooling cost
  • Used for continuous production
24
Q

Rotational moulding process (4)

A
  • Polymer powder or granules are loaded into a mould, which is clamped and sealed
  • Mould is transferred to an oven where it is heated to 260-370°c, depending upon the polymer used then the mould is slowly rotated around two axes and as it’s heated it costs the inside of the mould
  • Once the polymer has achieved the correct thickness the mould is cooled - usually a fan and/or water is used to cool the polymer
  • When polymer has solidified, the part will shrink slightly, allowing it to be removed
25
Q

Rotational moulding:

  • polymer stock form
  • products
A
  • Thermoplastic powder or granules
  • Traffic cones, kayaks, water tanks, kerosene tanks, children’s play equipment
26
Q

Key features of rotational moulding (3)

A
  • Seamless hollow components with a large wall thickness
  • Mould continuously rotated through heating and cooling
  • Large-scale batch of mass production
27
Q

Extrusion process (6)

A
  • Polymer granules are loaded into the hopper
  • The Archimedean screw moves the polymer granules past heaters
  • The heaters soften the polymer
  • When sufficient polymer has melted, the hydraulic ram pushes the Archimedean screw, forcing the polymer through a steel die the shape of the die determines the shape of the extrusion
  • The extrusion may be supported by rollers as it leaves the die and is cooled by water or air
  • The extrusion is then cut to the desired length
28
Q

Extrusion:

  • Polymer stock form
  • Products
A
  • Thermoplastic granules
  • Solid rods, tubing, angle sections, curtain track
29
Q

Key features of extrusion

A
  • Industrial production method
  • Continuous production
30
Q

Compression moulding process (5)

A
  • A ‘slug’ of ore-weighed thermoset polymer is inserted into pre-heated moulds
  • The moulds are closed and hydraulic pressure is applied this pressure ensures that the polymer takes the shape of the mould
  • The moulds remain closed while cross-linking takes place and the thermoset ‘cures’
  • When the moulding has cured, the machine opens and the product is removed
  • Excess polymer known as ‘flash’ is removed
31
Q

Compression moulding:

  • polymer stock form
  • Products
A
  • Thermoset polymer charge ‘slug’
  • Electrical light fittings, switches, plugs, picnic plates and cups
32
Q

Key features of compression moulding (3)

A
  • Uses a pre-weighed ‘slug’ of polymer
  • Polymer removed from moulds
  • Large-cale batch production