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1. Thermoforming

2. What isThermoforming ?
•Thermoforming is a manufacturing process where
sheets of thermoplastic or films are heated to a pliable
forming temperature, formed to a specific shape in a
mold and trimmed to create a usable product.
Pliable temperature:-
Sag point (above the glass-transition
temperature (𝑇𝑔), of the polymer)

3. Thermoforming Process :
❑Heating plastic sheet to the temperature where it softens.
❑Stretching the softening polymer against a cold mold
surface.
❑Cooling the finished part and trimming excess plastics.

4. Materials Used:
▪ABS (Acrylonitrile butadiene styrene)
▪Cellulose acetate
▪LDPE (Low density polyethylene)
▪HDPE (High density polyethylene)
▪PVC etc.

5. Steps of thermoforming:•
1. Heating:- Heating is accomplished by radiant electric
heater which is located at a distance of 125mm (5 in.)
either on one or both sides of the sheet.
•
2. Forming:- After heating, the polymer sheet is converted
or
formed into various shapes by either air pressure,
vacuum
pressure or by mechanical pressure.

6. One stage thermoforming machine

7. Types of thermoforming:
• Basically there are three types of thermoforming processes.
❑Vacuum forming
❑Pressure forming
❑Mechanical thermoforming

8. Vacuum forming
❑It is the earliest method of thermoforming.
❑In vacuum forming, vacuum is created below the preheated
plastic sheet to draw sheet into the cold mold cavity.
❑Basic steps of vacuum forming
1. A flat plastic sheet is heated by radiant heater, which is placed on one or both
sides of the plastic.
2.The softened sheet is placed over a concave cavity.
3.Vacuum draws the sheet to the sheet to the cold cavity .
4.The product is cooled and any extra plastic parts are trimmed

9. Vacuum forming

10. Pressure forming❑Alternative to vacuum forming.
❑Here the air pressure is forced to the preheated sheet into a
cold mold. Here the air pressure is much higher than the
vacuum forming.
❑The basic difference from vacuum forming is that the heated
sheet is pressurized from above the mold cavity.
❑Due to high pressure, the heated sheet can be deformed in a
fraction of a second. (High production rate)

11. Pressure forming

12. Mechanical thermoforming❑Here, positive (male) and negative (female) molds are brought
against heated plastic sheet forcing it to the assumed shape.
❑In mechanical forming, air pressure or vacuum pressure are
not used to deform the plastic sheet.
❑Air between the die and sheet is evacuated by using
vacuum pump and the sheet conforms to the mold shape.
❑Formed part is cooled and ejected.

13. Mechanical thermoforming

14. Thermoforming:
•
Advantages:
▪ Flexible design
▪ Rapid prototype development
▪ High production rate
▪ Low set up cost
▪ Less thermal stress
Disadvantage:
▪ Not eligible for thermosets
▪ All parts need to be trimmed
▪ Parts may non uniform thickness

15. Applications:
•
Thermoforming has many applications like;
▪Food packaging
▪Automotive parts
▪Aircraft windscreens
▪Trays for cookies and candy
▪Advertising signs
▪Panels for shower stalls
▪Refrigerator liners etc.

16. ThankYou!