Blow Molding Industry Information
IQS Newsroom Articles on Blow Molding
Blow molded plastic is any hollow plastic product, the most common being bottles, which results from the blow molding process. Plastic blow molding
is arguably the most common plastic molding process due to its high
cost-efficiency, long run capacity and application versatility. Plastic bottles
are the most commonly blow molded product, including blow molded
bottles for a very wide spectrum of applications, such as clear plastic
bottles, plastic water bottles, plastic baby bottles, plastic spray
bottles, peanut butter jars, milk bottles, plastic cosmetic bottles, blow molded cases, garbage cans and many other containers and products. Blow molders
and blow molding companies manufacture toys, CD cases and other
consumer items into almost any hollow, three dimensional shape in any
color and material transparency. Industrial items such as gas tanks,
bulk drums and corrosive liquid containers are blow molded, as are most
household chemical and cleaning containers. Plastic blow molding
presents an excellent, portable containment solution for volatile
substances with maximum cost efficiency.
The blow molding process begins with melting down the plastic and
forming it into a parison, or preform. The parison is a tube-like piece
of plastic with a hole in one end in which compressed air can pass
through. Using a blow pin, air pressure is introduced through the
inside of the parison, forcing it to assume the shape of the mold. The
end product is cooled by conduction or the evaporation of volatile
fluids in the container. The purpose of blow molding services is to
form a uniform finished product that does not need to be joined
together in any way. Blow molding services use three basic methods for
producing blow molded plastic: extrusion, injection and stretch blow
molding.
Extrusion blow molding is the simplest type that allows for a wide
variety of container shapes, sizes and neck openings, along with
handleware of many kinds. Injection blow molding is a hybrid of the
injection molding and blow molding services and is suitable for smaller
containers but not for handleware of any kind. Two types of stretch
blow molding are injection stretch blow molding (ISBM) and reheat and
blow (RHB) molding, both of which are typically used to manufacture
P.E.T bottles for juice, water, etc. In the ISBM process, a preform is
injection molded and then transferred to another station on the
machine, where it is blown. Because ISBM is so costly, it requires long
runs for products such as peanut butter jars, water bottles and liquor
bottles. In RHB, a preform is purchased from a vendor that has already
put it through an injection molding process. It is then reheated in a
relatively simple machine in order to prepare it for blowing. RHB is
advantageous because the purchaser does not have to invest in expensive
injection molding machinery but still has access to a large catalog of
existing preforms.
Distinct advantages exist for choosing the blow molding process over
other plastic manufacturing processes. It is the most well-suited
method for forming hollow plastic parts. It has much lower mold costs
than injection molding. Blow molding has a faster cycle time than that
of rotational molding. In many cases, one blow molded plastic piece can
take the place of many individual parts. However, the scattering of
mold thickness is a potential problem, and quality control is important
to make sure none of the blow molded products have holes, leaks or
unevenly thin walls. Strong, precisely even walls are better created by
rotational molding or plastic extruding, but for the thousands of
applications which require high volume production over precision,
plastic blow molding is an ideal choice.