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Benefits
The benefits molders derive from using Porcerax
II are primarily, but not limited to, the elimination of trapped gas problems
that occur in inadequately vented areas within the mold. Frequently, it is
difficult, if not impossible, to provide adequate venting in these hard to mold
areas. Traditional methods of venting, such as parting line vents, vent plugs,
and pins often do not provide sufficient surface area to accommodate the large
volumes of gases that can be generated. Porcerax II provides a location-specific
method of venting gas in a targeted area. Since it is 25% air by volume,
one-fourth of the surface area becomes a vent. The larger the surface area of
the piece installed, the greater the venting capacity.
Prevention of Burning
Burning is a condition caused by
compressed gasses trapped by the flow of molten resin in a cavity pocket. Using
Porcerax II venting steel, gasses are permitted to evacuate through the steel to
the outside atmosphere, thus eliminating the burning condition. The enhanced
venting capabilities of Porcerax II are illustrated below. The illustration is
taken from a current production application:

In a typical automotive console application,
gasses have a tendency to settle in areas such as the cup holder recess area or
the CD/cassette storage compartment. This causes short shots and/or material
burning. The illustration above shows Porcerax II inserted in the problem area
and properly vented to the atmosphere. The scrap rate on this part prior to
installation of the Porcerax II insert was over 45%. Upon completion of the
installation, the documented scrap rate dropped to 9% and was unrelated to the
previous burning problem.
Prevention of Knit Lines
Minimizing or eliminating flow and knit
lines is an additional benefit for using Porcerax II. Knit lines occur at points
where resin flows converge after molding around an obstruction, or protrusion
within the mold, usually away from the gate area. There are two primary reasons
for this occurrence:
- The failure of resin to sufficiently fuse due
to the drop in temperature after flowing over long distances.
- The presence of residual air at the resin flow
convergence point at the cavity obstruction, prohibiting the proper fusion
of the flows.
The permeability of Porcerax II prevents defects
arising from residual gases normally trapped inside the mold cavity. Also, using
Porcerax II reduces back pressure and improves the flow rate, allowing the resin
flows to merge while still hot.
Reduction in Cycle Time
Because of the reduction in backpressure
within the mold, the plastic fills the cavity faster, thus allowing for
reductions in temperatures which shortens cooling and cycle times.
Eliminates Shrink
Trapped air bubbles between the resin and
mold steel surface can cause shrinkage or sink that shows as a ripple in the
otherwise straight plastic surface. Using Porcerax II on the trapped air side of
the cavity will eliminate shrink in most cases.

Eliminates Short Shots
Short shot is another condition caused by
too low of an injection pressure, or trapped gasses, in pocket areas of the
cavity. This results in the part not being completely filled out. Porcerax II
reduces back pressure, therefore, less injection pressure is needed, and because
it vents trapped gasses, both causes of short shots are eliminated.
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| Before Porcerax
II |
After Porcerax II |
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Enhances Part Appearance
Webbed, ribbed, and other difficult to fill thin-walled designs are greatly
enhanced and cosmetically defined using Porcerax II in the mold. Molding these
high-detailed, thin-walled, and aesthetic parts, like this automotive speaker
grill, is easily accomplished with the reduced back pressure and added venting
of Porcerax II.

Gloss Reduction
When using Porcerax II as a cavity in an injection mold, the air typically
trapped between the cavity and the resin (causing a gloss to show on the part)
is allowed to escape through the pores, thus leaving a dull matte finish. This
often eliminates the need for costly secondary spray painting operations.
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| Conventional Molding |
Porcerax II |
Tool Simplification and Cost Reduction
When back pressures, injection pressures and cycle times are lowered, fewer
drops are needed to assure proper filling of the cavity. Lowering the number of
drops needed to fill a cavity simplifies design while saving tool costs. In some
cases the entire hot runner manifold is eliminated.
Aiding in Part Ejection
In many situations, an air poppet is needed to help eject the molded
part from the cavity. Inserting Porcerax II in the cavity with an air blow setup
helps break the vacuum seal and aids the ejector pins in doing their job.
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