Plastic Mold Steels
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 gases trapped by the flow of molten
resin in a cavity pocket. Using Porcerax II venting steel, gases are permitted
to evacuate through the steel to the outside atmosphere, thus eliminating the
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, gases 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
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
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
Eliminates Short Shots
Short shot is another condition caused by too low of an injection pressure, or
trapped gases, 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 gases, both causes of
short shots are eliminated.
Enhances Part Appearance
Webbed, ribbed, and other difficult to fill thin-walled designs are greatly
cosmetically defined using Porcerax II in the mold. Molding these high-detailed,
thin-walled, and aesthetic parts is easily accomplished with the reduced back
pressure and added venting of Porcerax II.
Automotive Speaker Grill
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.
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 venting steel in the cavity with an air blow setup
accomplishes the same result. This helps break the vacuum seal and aids the
ejector pins in doing their job.
It is imperative that anyone coming into contact with Porcerax II during the
mold building or molding operations understand the characteristics and
sensitivity of this material. Any questions should be directed to International
Mold Steel at 859.342.6000.
All technical and engineering data and suggested procedures, specifications and
applications contained in this publication are for general information only.
Sintokogio, Ltd., International Mold Steel and/or their distributors disclaim
any and all express or implied warranties of merchantability, suitability for
any particular purpose or use, or freedom from infringement of any patent,
trademark or copyright. Porcerax II® is a registered trademark of International
Mold Steel, Inc. and Sintokogio, Ltd..