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Group Participents
 Fahad Rafique
 Muhammad Haseeb
 Topics
 The Thermoforming Process
 Advantages and Disadvantages
 Vacuum Forming
 Advantages and Disadvantages
 Pres...
 Thermoforming is a process in which a thermoplastic sheet is
heated and deformed into the desired shape.
 The process i...
The process involves
 Heating the plastic sheet to a temperature range
where it softens
 Then stretching the softened pl...
Thermoforming:
Advantages:
 Flexible design .
 Rapid prototype development
 High production rate
 Low set up cost
 Le...
Thermoforming Process consists of two main steps:
 Heating
 Forming
 Heating is usually accomplished by radiant electri...
 It is the the earliest method used and also called simply vacuum
forming.It is the proces in which negative pressure is ...
• Vacuum thermoforming: (1) a flat plastic sheet is softened by
heating; (2) the softened sheet is placed over a concave m...
Vaccum forming :
Advantage:
1. Operated comparatively low vaccum pressure.
2. Relatively cheap.
Disadvantage:
1. Uneven wa...
 Pressure forming is an alternative to vacuum forming involves
positive pressure to force the heated plastic into the mol...
 Positive air
pressure
from the
top of the
plastic used
to force the
materials
against the
mold
Advantage:
 High production rate .
 Efficient for large parts.
 Low tooling cost.
Disadvantage:
 Limited shape complex...
 The third method, called mechanical thermoforming, uses matching
positive and negative molds that are brought against th...
 Heating the sheet
 Clamping the
sheet
 Moving the sheet
and mold into
proper
relationship for
forming, a
vacuum or
pre...
Advantages:
 Better dimensional control.
 Opportunity for surface detailing of both sides
of the parts.
Disadvantages:
...
 Female mold- a mold in which the part is pressed into
a cavity
Materials Used:
 ABS (Acrylonitrile butadiene styrene)
 Cellulose acetate
 LDPE (Low density polyethylene)
 HDPE (High...
General properties: more durable, harder, tough, light.
Typical uses: automobile parts, construction materials.
Plastic ty...
Plastic types: Elastomers
General properties: these are thermosets, and have rubber-like properties.
Typical uses: medical...
General properties: low melting point, softer, flexible.
Typical uses: bottles, food wrappers, toys, …
Examples:
Polyethyl...
Thermoforming uses plastic sheet, which is heated, stretched,
cooled and mechanically cut
 The plastic sheet is manipulat...
we can thermoform both amorphous and
crystalline polymers
 Amorphous
 No organization, glass transition
 PS, ABS, PVC, ...
Advantages of thermoforming are
 Low temperature, low pressure required
 Only a single surface mold is required
 Molds ...
Disadvantages of thermoforming
 Plastic material is more expensive because the pellets have
to be made into sheets
 Gene...
It gives us some approximation of the amount of thinning that
will be experienced by the plastic sheet when it is
transfor...
 Is used to estimate the amount of wall thickness
variation that might occur
 High draw ratio result in excessive thinni...
 Mass production thermoforming operations are performed in the
packaging industry
 Thin film packaging items that are ma...
Blister Packs
Skin Packs
Formed blister pack material
Thermoforming
Thermoforming
Thermoforming
Thermoforming
Thermoforming
Thermoforming
Thermoforming
Thermoforming
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Thermoforming

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Thermoforming

  1. 1. Group Participents  Fahad Rafique  Muhammad Haseeb
  2. 2.  Topics  The Thermoforming Process  Advantages and Disadvantages  Vacuum Forming  Advantages and Disadvantages  Pressure Forming  Advantages and Disadvantages  Mechanical Thermoforming  Advantages and Disadvantages
  3. 3.  Thermoforming is a process in which a thermoplastic sheet is heated and deformed into the desired shape.  The process is widely used in packaging of consumer products and to fabricate large items such as bathtubs, contoured skylights, and internal door liners for refrigerators
  4. 4. The process involves  Heating the plastic sheet to a temperature range where it softens  Then stretching the softened plastic against a cold surface mold  When the sheet has cooled, it is removed from the mold and excess plastic is trimmed
  5. 5. 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.
  6. 6. Thermoforming Process consists of two main steps:  Heating  Forming  Heating is usually accomplished by radiant electric heaters, located on one or both sides of the starting plastic sheet at a distance of roughly 125 mm (5in).  The methods by which the forming step is accomplished can be classified into three basic categories: 1. vacuum thermoforming 2. pressure thermoforming, 3. mechanical thermoforming
  7. 7.  It is the the earliest method used and also called simply vacuum forming.It is the proces in which negative pressure is used to draw a preheated sheet into a mold cavity. The process is explained in next slide in its most basic form. The holes for drawing the vacuum in the mold are on the order of 0.8 mm (0.031 in) in diameter, so their effect on the plastic surface is minor.
  8. 8. • Vacuum thermoforming: (1) a flat plastic sheet is softened by heating; (2) the softened sheet is placed over a concave mold cavity; (3) a vacuum draws the sheet into the cavity; and (4) the plastic hardens on contact with the cold mold surface, and the part is removed and subsequently trimmed from the web.
  9. 9. Vaccum forming : Advantage: 1. Operated comparatively low vaccum pressure. 2. Relatively cheap. Disadvantage: 1. Uneven wall thickness at the corner of the product. 2. Bad finishing or non uniform plastic concentration. 3. Therefore the thinnest area occur at the corner, near the clamp Thin corner
  10. 10.  Pressure forming is an alternative to vacuum forming involves positive pressure to force the heated plastic into the mold cavity.  its advantage over vacuum forming is that higher pressures can be developed .. The process sequence is similar to the previous, the difference being that the sheet is pressurized form above into the mold cavity. Vent holes are provided in the mold to exhaust the trapped air.
  11. 11.  Positive air pressure from the top of the plastic used to force the materials against the mold
  12. 12. Advantage:  High production rate .  Efficient for large parts.  Low tooling cost. Disadvantage:  Limited shape complexity.
  13. 13.  The third method, called mechanical thermoforming, uses matching positive and negative molds that are brought against the heated plastic sheet, forcing it to assume their shape. In the pure mechanical forming method, air pressure (positive or negative) is not used at all.  Its advantages are better dimensional control and the opportunity for surface detailing on both sides of the part.  The disadvantage is that two mold halves are required; the molds for the other two methods are therefore less costly.
  14. 14.  Heating the sheet  Clamping the sheet  Moving the sheet and mold into proper relationship for forming, a vacuum or pressure system
  15. 15. Advantages:  Better dimensional control.  Opportunity for surface detailing of both sides of the parts. Disadvantages:  Two mold halves are required  Relatively costly.
  16. 16.  Female mold- a mold in which the part is pressed into a cavity
  17. 17. Materials Used:  ABS (Acrylonitrile butadiene styrene)  Cellulose acetate  LDPE (Low density polyethylene)  HDPE (High density polyethylene)  PVC etc. Applications: Thermoforming has many applications like I. Food packaging II. Automotive parts III. Aircraft windscreens IV. Vehicle doors etc.
  18. 18. General properties: more durable, harder, tough, light. Typical uses: automobile parts, construction materials. Plastic types: Thermosets Examples: Unsaturated Polyesters: varnishes, boat hulls, furniture Epoxies and Resins:… glues, coating of electrical circuits, composites: fiberglass in helicopter blades, boats,
  19. 19. Plastic types: Elastomers General properties: these are thermosets, and have rubber-like properties. Typical uses: medical masks, gloves, rubber-substitutes Examples: Polyurethanes: mattress, cushion, insulation, toys Silicones: surgical gloves, oxygen masks in medical applications joint seals
  20. 20. General properties: low melting point, softer, flexible. Typical uses: bottles, food wrappers, toys, … Examples: Polyethylene: packaging, electrical insulation, milk and water bottles, packaging film Polypropylene: carpet fibers, automotive bumpers, microwave containers, prosthetics Polyvinyl chloride (PVC): electrical cables cover, credit cards, car instrument panels Polystyrene: disposable spoons, forks, Styrofoam™ Acrylics (PMMA: polymethyl methacrylate): paints, fake fur, plexiglass Polyamide (nylon): textiles and fabrics, gears, bushing and washers, bearings PET (polyethylene terephthalate): bottles for acidic foods like juices, food trays PTFE (polytetrafluoroethylene): non-stick coating, Gore-Tex™ (raincoats), dental floss Plastic types: Thermoplastics
  21. 21. Thermoforming uses plastic sheet, which is heated, stretched, cooled and mechanically cut  The plastic sheet is manipulated as a rubbery solid or elastic liquid  The solid or elastic liquid properties are more important than the viscous properties when thermoforming
  22. 22. we can thermoform both amorphous and crystalline polymers  Amorphous  No organization, glass transition  PS, ABS, PVC, PC  Crystalline  Organized region called crystals, glass transition and melting  PE, PP, Nylon, Acetal Important thermal properties  Enthalpy or heat capacity  Thermal conductivity  Temperature dependent density
  23. 23. Advantages of thermoforming are  Low temperature, low pressure required  Only a single surface mold is required  Molds are easy to fabricate and use inexpensive materials  No need for the plastic to flow  Can make very large surface area to thickness ratios
  24. 24. Disadvantages of thermoforming  Plastic material is more expensive because the pellets have to be made into sheets  Generally more waste to reprocess  Can get a great deal of wall thickness variation
  25. 25. It gives us some approximation of the amount of thinning that will be experienced by the plastic sheet when it is transformed  Area ratio = area of the sheet before forming area of the part after forming  If the sheet is 200 cm2, and will be thermoformed into a part that has total area of 400cm2, the area ratio is 1:2  Area ratio x desired thickness of finished part = minimum original thickness (thickness of the blank)  The overall average thickness of the part will therefore be one-half of original thickness  The area ratio is often used to calculate the size of the unformed sheet that must be used to make a particular part
  26. 26.  Is used to estimate the amount of wall thickness variation that might occur  High draw ratio result in excessive thinning and wall nonuniformities  Draw ratio = depth of part / width of part
  27. 27.  Mass production thermoforming operations are performed in the packaging industry  Thin film packaging items that are mass produced by thermoforming include blister packs and skin packs.  Thermoforming applications include large parts that can be produced from thicker sheet stock. Examples include covers for business machines, boat hulls, shower stalls, diffusers for lights, advertising displays and sins, bathtubs, and certain toys.  We had previously mentioned contoured skylights and internal door liners for refrigerators.  These would be made, respectively, out of acrylic (because of its transparency) and ABS (because of its ease in forming and resistance to oil and fats found in refrigerators).
  28. 28. Blister Packs Skin Packs Formed blister pack material

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