Manufacturing - thermoplastics

Question 1

Injection molding - usage and qualities

Answer 1

• Cost efficient
• Very fast process
• Most common technique for plastic manufacturing
• Typical products: smaller parts
• Cyclic process = goes on 24/7

Question 2

Injection molding - process

Answer 2

• Plastic pellets get melted by a rotating screw
• Melted plastic pushed into mold

Question 3

Injection molding - types

Answer 3

• 2-component: uses two different plastics which are pushed into same mold
  1. First plastic gets injection molded and stiffens
  2. The mold rotates 180 degrees
  3. Sedcond plastic get injected, surrounding the first one
• Sandwich: molds together recycled (bad) and better materials
• Gas: gas is injected before plastic solidifies = hallow products
• Water: same as gas but uses water instead

Question 4

Extrusion - usage and types

Answer 4

• Profile extrusion: Make plastic profiles
  Plastic profile = plastic with continuous shape made out of different plastic materials, ex. tubes
• Can be used to make films/sheats as well

Question 5

Profile Extrusion - process

Answer 5

1. Dry products get fed into an extruder
2. Rotating screws melt and push plastic forward
3. Pumped into a callibrator to get right dimensions
4. Cools down and get meassured
5. Cutting to finish product

Question 6

Blow molding - usage and types

Answer 6

• To make hallow products - mostly bottles like PET
• Extrusion blow molding: cheap but products can’t keep CO2
• Injection blow molding: expensive but can keep CO2 (good for fizzy drinks)
• Film blowing: fast and mostly uses PE, ex. plastic bags

Question 7

Blow molding - process

Answer 7

• Extrusion: extruder die with parison (tube of plastic) - into mold - mold closes - air blows into tube = hallow product
• Injection: pre-form by injection molding - heated - into mold - air blows in - hallow product
• Film: plastic pellets - extruder melts it - blow ring - thin sheets - rollers - film roll created

Question 8

Thermoforming - usage and qualities

Answer 8

• Slower than injection molding
• Used for sockets to prosthetics
• Female mold - inward “hole” mold
• Male mold - outward “hill” mold

Question 9

Thermoforming - process

Answer 9

Plastic sheat -> heat -> gets flexible

• -> Draping over mold if male mold
• -> Plug pushing sheat into mold if female mold

Question 10

Other manufacturing methods

Answer 10

• Calendering
• Rotational molding
• Machining
• Additive manufacturing = layer by layer (3d-printing) ex. FDM, SLA, SLS