Vacuum bag forming and pressure bag forming

All credit goes to the creators, my colleagues.

1. Vacuum bag forming
and pressure bag
forming

2. What is Vacuum-Bag Forming ?
•also known as vacuum bagging and vacuum bag molding.
•It’s an open mouldingtechinque.
•It’s a clamping method which is used to hold adhesive and
resin coated components of a lamination.
•(When discussing composites, “resin” generally refers to the
resin system—mixed or cured resin.)
•simplified version of thermoforming

3. What are applications
•can be used in place of complex fabricated sheet
metal, fiberglass, or plastic injection molding.
•In automated teller machines
•for medical imaging and diagnostic equipment such as
magnetic resonance imaging (MRI) machines
•engine covers in a truck cab
•often used by hobbyists, for applications such as RC
cars and masks.

4. Apparatus
•Vacuum pump
•Two way shut-off valve
•Vacuum tubing
•Vacuum gauge
•Vacuum connector
•Vacuum bagging film
•Breather and bleeder
•Release peel ply
•Release film (optional)
•Sealant Tape
•Mold.
•Part / laminate

6. Process of vacuum forming•First, a mouldis made. This is made in the shape to which the plastic will
form around.
•the mouldshould have angled edges, in order to allow the tooling to
pop out of the plastic when made.
•The mouldis then placed into the vacuum former oven. A plastic sheet is
then clamped above, but not on the mould.
•In the oven, the heater is positioned above the plastic. This will heat up,
warming the plastic & allowing it to become flexible & mouldable.
•. After a few minutes, the plastic should be at a temperature to allow
moulding.
•The shelf on which the mouldis sat on, is moved upwards & into the
flexible plastic using a handle.
•The vacuum is then switched on, removing all air from the oven. This
allows the plastic to form to the shape of the mould.
•Once cooled, the sheet is then removed from the oven, the mouldis
removed & any excess trimmed.

8. Materials Options
•Resins: Primarily epoxy and phenolic. Polyesters and
vinylestersmay have problems due to excessive
extraction of styrene from the resin by the vacuum
pump.
•Fibres: The consolidation pressures mean that a
variety of heavy fabrics can be wet-out.

9. Advantages of vacuum bag
forming
•Higher fibrecontent laminates can usually be achieved than
with standard wet lay-up techniques.
•Lower void contents are achieved than with wet lay-up.
•Better fibrewet-out due to pressure and resin flow
throughout structural fibres, with excess into bagging
materials.
•Health and safety: The vacuum bag reduces the amount of
volatiles emitted during cure.

10. Disadvantages of vacuum bag
forming
•The extra process adds cost both in labourand in
disposable bagging materials
•A higher level of skill is required by the operators
•Mixing and control of resin content still largely
determined by operator skill

11. What is Pressure-Bag Forming ?
•Almost the same process
as vacuum bag molding
except a bag is inflated
forcing the composite
into the mold.

12. Difference between vacuum and
pressure bag forming
•In pressure forming process,Positive
pressure is used in addition to the vacuum
to push the sheet in to the shape
•More complex shapes can be made than
vacuum bagging.
•Surface finishing is good in pressure bag
forming.

14. Applications of pressure bag
forming
•Outdoor plastic housings
•Medical enclosures
•Point of Purchase displays & retail items
•Recreational equipment
•Bezels
•Bases

15. Advantages of Pressure-bag
forming.
•Lower cost tooling than injection molding (less
than 1/3 injection molding cost)
•More cost effective for moderate quantities
(300 –5,000)
•Able to form very large parts
•Able to form parts with fine cosmetic or
functional details, such as vents or louvers
•Able to confirm to stringent tolerances
•Rapid prototyping and quick time to market

16. Disadvantages of Pressure-
bag forming.
•The extra process adds cost both in labor
and in disposable bagging materials.
•A higher level of skill is required by the
operators.
•Mixing and control of resin content still
largely determined by operator skill.

17. Materials used for this process
•ABS –impact resistant, available in a variety of colors,
textures, flame retardant grades
•PC –impact & high temperature resistant
•HDPE –inexpensive; impact, chemical and cold
temperature resistant
•TPO –good durability, impact resistant
•HIPS –cost effective, available in a variety of colors
•PVC –impact resistant, available in a variety of colors,
textures, flame retardant grades

18. Thank You
!