Advanced Rotational Molding™
Toter's engineers and designers developed
and patented a revolutionary breakthrough in
rotational molding to build the World's Toughest
Carts. The new process, Advanced Rotational
Molding™, uses all the superior characteristics
of conventional rotational molding and at the
same time enhances the aesthetic and structural
quality of all Toter products.
First, remember that conventional rotational
molding eliminates the number one enemy of
plastic - STRESS. The weakest spot and most
probable failure point exists where molded in
STRESS is trapped in the part wall. Advanced
Rotational Molding creates NO STRESS in the
product. All carts made from other processes,
namely injection molding, have stress built into
the product from using high pressure (20,000 psi)
to force molten plastic through a narrow opening
in the mold. Pressure causes stress that leads
to premature failures. Advanced Rotational
Molding has NO STRESS.
In addition, Toter uses a superior polyethylene
compared to that used by injection molders.
Linear medium density polyethylene (MDPE) is
specifically engineered for toughness and high
impact resistance. Injection molders use a high
density polyethylene (HDPE) which is stiff,
rigid (sometimes brittle), with inferior impact
resistance. The Environmental Stress Crack
Resistance (ESCR) test for Toter's MDPE is
greater than 1,000 hours, compared with an
injection molder's HDPE which is less than 50
hours. In addition to NO STRESS and superior raw
material, rotationally molded parts are the
strongest in the areas of corners and curves
which are the weakest points of large parts made
by injection molding.
Finally, Advanced Rotational Molding technology
was developed to allow for aesthetic and
structural designs not possible with
conventional rotational molding. Rugged Rim®,
rigid flanges, sealed stop bar journals,
intricate details, and granite finishes became
possible with the discovery of micro-pellets.
The "flow characteristics" of this proprietary
material makes it possible to combine the best
design and structural advantages of conventional
rotational molding, injection molding, and blow
molding.
Advanced Rotational Molding molds NO STRESS into
the part. Stop bar journals are molded, not
drilled out as they are in injection carts.
Toter's sealed journals provide ten times the
weight-bearing surface as compared to drilled
holes. Also the cart body is leak-free.
EVR II
The high-tech micro-pellets have no trouble
filling in the corners and details. The rigid
rims are stiff, but not too stiff, so the cart
can be hugged by automated lifters. Advanced
Rotational Molding molds in handles that do not
rotate and are an integral structure of the
cart, providing for a safer cart.
No process is equal to Advanced Rotational
Molding for molding tough, durable plastic
parts. Toter's development of Advanced
Rotational Molding has provided unsurpassed
quality and "The World's Toughest Cart."
Loading Station:
Molds mounted to each arm of the machine are
filled with a pre-determined, measured weight of
hot-melt-compounded plastic micro-pellets. Molds
are engineered and precision built to produce
high quality products every time.
Oven Station:
Molds then move into a heating chamber where a
microprocessor controls the oven temperature
profiles, blower velocity, bi-axial rotation,
and molding cycle. During this cycle the
rotation brings the mold surfaces into repeated
contact with the plastic material as the mold is
heated.
The oven melts the plastic material to allow it
to coat the inside of the mold surface. This is
where the plastic cart takes its final shape.
This method of heating and molding requires no
high pressure hydraulic equipment to fill the
mold. Thus, no stress is introduced at anytime
during the molding cycle.
Cooling Station:
Next, the mold moves to the cooling chamber of
the machine. The microprocessor controls all
aspects of the cooling cycle. During the cooling
cycle the final curing of the part takes place.
The mold temperature must be brought down
slowly. This is achieved by computer control
during the following steps:
- The mold is first air cooled.
- A fine water mist is then introduced so
the part is not shocked by rapid temperature
change.
- Then a water stream is introduced.
Finally air blows the mold dry.
This procedure for cooling molds assures that
the final physical properties of parts are
maintained to optimize the impact strength and
performance of the cart. (Note: Some
competitor's equipment utilizes 100% air
cooling. This causes the product to cure too
slowly and reduces the final impact strength of
the finished product.)
Unloading Station:
After the molds have been cooled and the part
has cured to achieve its maximum impact strength
and physical properties, it is removed from the
mold. The part is then trimmed using specially
designed fixtures. The final imprinting and
assembly of components complete the Toter cart. |
