1.4 Polymer processes Flashcards
What are the 11 polymer forming processes
Vacuum forming, thermoforming, calendaring, line bending, extrusion, injection moulding, extrusion blow, injection blow, rotational, layup, compression
What are the 5 steps to vacuum forming
1.The mould and sheet is placed and clamped in then
a heater is pulled over and turned on softening the plastic
2.The mould is then pushed up into the plastic sheet
and the heater is removed and turned off
3.Then the plastic sets over the mould with a strong
vacuum below the mould
4.The mould is then lowered after the polymer has cooled
5.Any excess polymer can then be trimmed off
What are the steps for thermoforming
1.The plastic sheet is placed in the machine
2.The plastic sheet is heated
3.The plug pushes the sheet into the -ve mould
4.The sheet is removed after it has set and excess is trimmed
What are the 2 adv of thermoforming over vacuum forming
achieves more detail and is more suitable for mass production
What volume of production is calendering
Calendering is a process for continuous production and a purely industrial method
What are the steps for calendering
- Small pellets of thermoplastics are heated and melted to a dough like consistency and fed into a feedstock
- The plastic is then extruded through a series of heated rollers to stretch and squash the material to the correct size
- The material is then feed through cooling rollers then chopped up in standard sizes and or rolled up for distribution
What volume of production is line bending
One of prototype or limited batch production
What is the process and -ve of line bending
Very slow and labour intensive -Heating and cooling for a new form
What type of polymer process can wires and tubes be extruded with
extrusion
What volume of production is extrusion
Continuous production
What are the steps for extrusion
- Polymer granules are loaded into a hopper
- The granules are pushed along via an Archimedes screw and heated
- The liquid is then compressed into the desired form and cooled
- The extrusion is then cut to the desired length
What volume of production is injection moulding
Mass to continuous production
What are the steps for injection moulding
- Thermoplastic granules are poured into the hopper
- A screw thread pulls the granules through a heater system that melt the polymer
- After melting the polymer is forced into a mould via a hydraulic ram
- The mould is water cooled which allows rapid hardening
- Ejection pins push the moulding out and is trimmed for excess
What volume of production is blow moulding
mass
What are the steps for extrusion blow moulding
- The heated granules are fed into a tube and cut between the 2 mould pieces to force the plastic into the mould
- The mould is then blown into which makes the plastic take the shape of the mould
- The formed plastic is then left to harden
- The moulds are separated and the formed plastic can be removed
What is the volume of production for rotational moulding
Large scale batch or mass production
What are the steps for injection blow moulding
- The preform is inserted between the mould halves
- The mould closes around the preform and air will be injected into the mould making the polymer take the shape of the mould
What is the adv and disadv of rotational moulding
Slow but even wall thickness
What are the steps for layup
- +ve or -ve moulds made from timber, manufactured boards or high density foam is coated in a release agent such as wax or PVA
- The gel coat is then applied made from a composition of polyester resin and a pigment used to give colour to the moulding or contain additives to prevent degradation
- Woven matting / Chopstrands is then cut to size and laid over the former for strength or reinforcement
- Then a thermoset resin (Polyester resin/epoxy resin) is brushed onto the matting and any air bubbles removed with a roller used for bonding the fibres together
- Roller / Vacuum bag used to remove air pockets and enhance detail for the mould
- The GRP/CRFP is then left to set overnight then released and trimmed into shape
What are the steps for rotational moulding
- Thermoplastic powder or granules are loaded into the mould
- The mould is clamped and sealed
- The mould is transferred to a oven and heated then the mould is slowly rotated and the heated polymer coats the mould sides
- Then the mould is cooled with water
- When the polymer has solidified the part will shrink and can be removed
What is the volume of production for compression moulding
Batch to mass production
What are the steps for compression moulding
- Pre heated thermoset dough is inserted into the die
- The mould is closed and the hydraulic pressure is applied making the polymer take the shape of the mould
- Then the product is removed from the mould when it has cured and any excess(Flash) is cut off and removed
What is the polymer process for making a water bottle
blow moulding
What is the polymer process for making a plug casing
compression moulding
What is the polymer process for making a guttering
extrusion
What is the polymer process for making a games console
injection moulding
What is the polymer process for making a carrier bag
calendering
What is the polymer process for making a speed boat
lay up
What is the polymer process for making a storage barrel
rotational moulding
What polymer is used in a water bottle
HDPE
What polymer is used in a plug casing
ABS
What polymer is used in a carrier bag
LDPE
What polymer is used in a guttering
uPVC/PVC
What polymer is used in a games console
ABS
What polymer is used in a storage barrel
HDPE
What polymer is used in a speed boat
HDPE
