FREE ESSAY ON THERMOFORMING

THERMOFORMING

THERMOFORMING
Thermoforming is one of many manufacturing processes that converts plastic resin into
usable everyday products. Thermoforming is greatly relied on in today's society because
of the tremendous need for high volume plastic products. Thermoforming is considered to
be one of the most cost-effective processes in plastics manufacturing. Thermoforming is
considerably economical because of the low molding costs and fast molding cycles. Speed
and cost efficiency are the highlighted qualities that thermoforming offers which lead
the way for the process becoming so important in industry today.
The basic concept of thermoforming is quite simple. A premanufactored thermoplastic sheet
is heated until it becomes soft and pliable. It is then forced against the contours of a
mold until it cools to its original state. Once it has cooled it is removed from the mold
while still obtaining the shape of the mold. Usually the product is then trimmed to
produce the finished product. The operation seems simple and straight foreword but there
are many different applications associated with the process. Thermoforming is a broad
term; there are many different types of thermoforming processes. These processes all have
similar traits but they do differ in certain aspects of the overall process.
Trapped Sheet Forming is a specialized type of thermoforming. In trapped sheet forming a
hot blow plate is used in both the heating and forming process. A plastic sheet is
positioned between the hot blow plate and the female mold cavity. Air forced through the
plate and pressure from the female mold combine to thrust the sheet onto the hot plate.
The sheet is then heated and forced into the female mold by the use of air pressure. One
advantage to trapped sheet forming that is such a simplified process that many products
can be produced from this method. Also the process uses contact heating, which is easily
used and is not subject to temperature fluctuation. The contact heating is a definite
advantage but is also a slight disadvantage. The problem with contact heating is that
heat can only be applied to the underside of the sheet. This slows down the process and
restricts the use of the more durable heavier -gauge sheets. 
Plug-assist forming is one of the most widely used thermoforming processes today. In
plug-assist forming a heated sheet is sealed over a female cavity. Once the plastic is
sufficiently heated the plug-assist, which is shaped like the female cavity but slightly
smaller in size, pushes the plastic sheet and forces it in the cavity. Vacuum force pulls
the sheet onto the mold surface. The main advantage associated with plug-assist forming
is that the walls of the container can be measured precisely with the assist. Wall
thickness is uniformly the same throughout the container. Plug-assist forming works well
with both heavy and light gauge materials and is commonly used to form deep-drawn
containers. 
Pressure bubble plug-assist vacuum forming is similar to plug-assist forming. In this
forming process a portion of the sheet is stretched to guarantee an even thickness of
walls. The heated sheet is positioned over the female cavity. Air is then blown up
through the base plate channel. This air causes the sheet to billow upward. The sheet is
then pushed into the cavity by the plug-assist. Vacuum is then applied to transport the
sheet to the mold. The advantage to this forming technique is that the wall thickness can
be measured with great accuracy. This process, as with plug-assist forming, is used to
create deep-drawn containers.
Pressure bubble snapback forming is similar to bubble plug-assist forming except for one
aspect. The plastic sheet is not formed by the female mold but rather the male mold. The
sheet is snapped back to form against the male mold. This forming process improves
material distribution because of its prestrecthing procedures.
The snapback vacuum forming method is popular because of its simplified process. A sheet
is clamped over a female cavity, air pressure through the base plate then stretches the
plastic. The pressure is then turned off while the vacuum is turned on to pull the
plastic into the mold. This process is widely used to produce auto parts and luggage due
to its ability to create external deep draws. It works well with all medium to heavy
-gauge sheets.
The processes mentioned are just a handful of the many thermoforming processes out in the
industry today. Everyday better more reliable products are being manufactured by
thermoforming methods. Improvements are consistently being applied to the different
processes to ultimately create better products. Thermoformings place in the plastics
industry will continue to remain strong because of the dynamics of its manufacturing
process.