When designing for Porcerax II venting steel, the following guidelines
should be considered:
Depending on the emissions or gas residue given off during the molding
process, the molder will have to evaluate whether to use a 7 or 20-micron pore
size. Resins such as ABS, polypropylene, soft type PVC, polyethylene, acrylic,
polyurethane, and styrene work very well with a 7-micron pore size. For low
viscosity or talc-filled resins, it may be
necessary to have an automated system reverse the airflow after each shot to
impurities from the pores. Rigid PVC resins will work, but only until the
close the pores. This can still be a feasible method if disposable inserts are
used. Where extreme venting is needed, a 20-micron pore size is recommended.
The 20-micron grade was developed to be used with a milled finish. When milled
properly this process with the 20-micron material leaves a pore that is
partially open (about 40-50 %). However, using the 20-micron pore size
material and maintaining the 20-micron pore size, by EDM or polishing after
milling, will vent better than 7-micron, but it will also clog faster.
Size of Area to be Vented
The producing mill recommends that at least 10% of the core and cavity area be
Porcerax II to insure proper venting. While this is not always possible, it is
to remember that the more square inches used in the core and cavity area, the
the back pressure will be in the cavity. Due to the larger surface area, the
not require cleaning as often as a smaller piece. If Porcerax II is used as a
cavity half, instead of as an insert, there may not be a need for parting line
Note:The thinner the Porcerax or the shorter the distance air has to
travel to the exhaust
line the better the venting will be. Keep in mind the physical properties of
Note:Porcerax is typically inserted on the core side of the mold in
the problem area in
order to hide insert lines.
Surface Finish Requirements
Since most applications can be addressed using inserted pieces on the core
EDM finish is acceptable and will vent better than any other surface finish.
Should EDM be impractical, a stoned or polished surface will provide the next
best venting surface. It is important to remember that if the venting steel is
used on the cavity side of a mold, the gloss level will be severely reduced
(#9 to a #2-3 with PP), so matching should be considered.
If a low gloss level on a textured part is desired, it can be accomplished
with the 7-micron Porcerax II. Certain procedures must be followed to prevent
the possible, irreversible damage to the internal pore structure of the
material. The texturing house selected for this procedure must be advised that
they will be texturing porous, venting steel. The pores must be thoroughly
cleaned and sealed prior to texturing. This insures the acid used to etch the
surface does not run through the material corroding the interior
structure. Performed properly, texturing Porcerax II will give the molder an
unmatched finish in terms of definition.
Porcerax II can be used in slide or lifter applications. However, it is
important to consider lubrication requirements on such a design. Lubricants
will, in all likelihood, reduce or eliminate permeability in areas that come
into contact with Porcerax II.
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 1.800.625.6653.