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At Molder’s World Inc. we take pride in being the leading experts in Porcerax II® mold steel. We have developed industry standard guidelines and have compiled best tips and practices for the best results!

Porcerax II® Design Guidelines

When designing for Porcerax II® venting steel, the following guidelines should be considered.

Due to limited physical toughness, Porcerax II® inserts are usually produced more than 1″ thick, so relief for proper venting can be npt holes machined then burned on the backside instead of mere EDM flat spots on the bottom.

Resins Used
Depending on the emissions or gas residue given off during the molding process, the molder will have to evaluate whether to use 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 (.ooo3″) 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 purge the impurities from the pores. Rigid PVC resins will work, but only until the corrosive gasses close the pore. This can still be a feasible method if disposable inserts are used. The 20-micron pore size (.0008″) will vent about 25% more gas than the 7 micron pore size.

Size of Area to be Vented
The product mill recommends that at least 10% of the cavity area br Porcerax II® to ensure proper venting. While this is not always possible, it is important to remember that the more square inches used in the cavity area, the lower the back pressure will be in the cavity. Due to the larger surface area, the insert will not require cleaning quite as often as a smaller piece. If Porcerax II® is used as a core or cavity half, instead of as an insert, there may not be a need for parting line vents.

Note: The thinner the Porcerax II® 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 Porcerax II®.

Surface Finish Requirements
Since most applications can be addressed using inserted pieces on the core side, an EDM finish is accepted and will vent better than any other surface finish. Should an EDM finish be impractical the surface may be stoned or polished for a better finish after the EDM process. The 7 micron pore size provides the best polished finish. 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 (from #9 to #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®.

Slide/Lifter Applications
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 coming into contact with Porcerax II®.

Porcerax II® Insert Installation

Porcerax Installation Molder's World

Various designs for the bottom of a Porcerax insert pocket

Grooved Channels Molder's World

Porcerax II® Pin Installation

Best results can be achieved by drilling a vent hole into the bottom of the pin (See Below). This procedure considerably shortens the “escape route” for gas.

Venting Hole Pin Molder's World

Since highest permeability can be achieved with an EDM finish, it is desirable to EDM the bottom and sides of the drilling hole for better efficiency. Be sure all EDM fluids are cleaned out before installing the pin into the tool.

Porcerax II® Insert Installation

Porcerax II® Insert with improper venting

Porcerax II® Insert with improper venting

Porcerax II® Success Tips

Proper Cleaning and certain designs work better than others.

For a quote on designing, building or cleaning Porcerax II® inserts please contact:
Molder’s World, Inc,
Phone: 513-469-6653 or Fax: 513-469-7212

Porcerax II® can be machined, but it should be machined wet to prevent work hardening. Because Porcerax II® is porous and will corrode, an oil-based coolant should be used if possible.

Finish machining should be done at a slower feed rate than other mold steels due to its tendency to chip or splinter as the tool exits the work piece “Picture framing” or machining the parameter of the insert first will also help in this matter.

Traditional welding of Porcerax II® is not recommend by the manufacturer of Porcerax II® due to its tendency to crack. It is best to re-machine the Porcerax II® insert and the weld or shim in the core pocket. Silver soldering or brazing is acceptable, however it is important to realize that where the material is soldered it will lose permeability. Laser welding is also acceptable due to its low heat properties.

The machining process will smear the pores closed on the surface of Porcerax II®. After machining the pores must be reopened by EDM.

Be aware of your resins flash points. Seven (7) micron Porcerax II® has pores that average .0003″ in diameter, twenty (20) micron has pores that average .0008″ in diameter. Nylon 6 for instance will flow into the pores that are .0008″ but polypropylene and ABS will not.

Texturing the 7 micron Porcerax II® is possible, however your texture house must be aware that they are working with Porcerax II® and if not familiar with the material they should contact Molder’s World Inc. immediately.

Mold releases such as silicon mold release will clog the surface pores of Porcerax II® if sprayed onto the material. Therefore positive air pressure should be blown back through the exhaust line while the tool is being sprayed. Inserts protected with mold saver must be cleaned before use unless BioCorr® is used.

Strategically placed high-pressure clean out or back flush/exhaust holes drilled & EDM machined into the Porcerax II® insert help to vent as well as assure proper cleaning.

The more square inches of Porcerax II® used in the cavity area the better the venting will be. The thinner the Porcerax II® or the shorter the distance the distance air has to travel to the exhaust line the better the venting will be. Keep in mind the physical limitations of Porcerax II®.

The more square inches of Porcerax II® used in the cavity area the better the venting will be. The thinner the Porcerax II® or the shorter the distance the distance air has to travel to the exhaust line the better the venting will be. Keep in mind the physical limitations of Porcerax II®.

An exhaust line through the core block must be adjacent to an EDM machined area on the side or back of the Porcerax II® insert. The cavity side of the Porcerax II® must also be EDM machined.

Porcerax II® must be cleaned both before it goes into production for the fist time to remove EDM cutting fluids and periodically (after 20,000-30,000 shots) during production to remove resin gas buildup.

Because of heath safety and fire risks it is recommended that Porcerax II® be professionally cleaned by Molder’s world, Inc. This is the only way to ensure renewed life for your Porcerax II® inserts.

Avoid running water lines through Porcerax II®, since they are difficult to seal and Porcerax II® will rust.

All technical and engineering data and suggested procedures, specifications and applications contained in this publication are for general information only. Sinto Steel, Molder’s World, Inc. International Mold Steel and/or their distribution disclaim any and all express or implied warranties of merchantability, suitability for any particular or use, or freedom from infringement of any patent, trademark or copyright. Porcerax II® is a registered trademark of International Mold Steel, Inc. and SintoSteel. 

Speaker Grill Best Practices

Grade Selection:

7 Micron should always be used for Core Speaker grill inserts due to rib sidewall release properties and toughness issues with 20 micron.

Where to buy:

Porcerax II® should be purchased from a licensed Porcerax II® distributor for traceability and warranty concerns.
All Porcerax being machined and or molded in North America should be purchased by licensed North American Distributor for warranty and counterfeit steel concerns. Molder’s World, Inc. is the authorized exclusive Porcerax II® distributor for the Midwest United States and Ontario.

Porcerax II® Speaker Grill Best Practices:

Minimum surface area
Molder’s World, Inc. recommends that the entire area where the hole pin shut offs make audio holes in the grill to be Porcerax II®. The outer round or oval sound rib is the best place to split the parting line between the Porcerax II® core insert and the P20 core.

Minimum Thickness
Molder’s World, Inc. recommends that for speaker grill inserts
6” OD and under to be a minimum 1-5/8” thick at the thinnest cross section. Inserts over 6” OD should be at least 2-1/8” thick at the thinnest cross section.

Shut off hole pin height
If the design calls for a split pin configuration, then the height of the Porcerax II® pin should not be more than 40% of the depth of the hole. 30% is better. The Porcerax II® pins should also be larger in diameter to assure alignment with no flash. Any pin that is lees than 80% of a full diameter should be eliminated or made into a “dummy pin” with no shut off pressure from the cavity side, due to toughness.

Porcerax II® part surface machining
Porcerax II® machines like a 40 HRc 400 series stainless steel. It should be machined with coolant to prevent work hardening. This water soluble coolant does need to be cleaned after the insert is complete. (See cleaning)
The insert should be CNC machined on the part molding surface with enough stock (.010 – .015”) to then be EDM burned to open the pores that will be closed by the machining process. The lower the amperage used the better the finish will be. Do not blast the surface with any media to attempt a better finish. This includes AQR or talc media. EDM low amperage finish will be better and will not close the pores.
Inserts with standing shut off pins that mold the holes in the grill should be burned with at least 2 electrodes. One for roughing & one for finish orbiting work. This will provide better part release. For inserts that have a web thickness less than .7mm between the pins, three electrodes may be needed. Two for roughing the pins and one for finish orbit.

Cooling Porcerax II® inserts
Molder’s World, Inc. does not recommend running water through the Porcerax II® insert due to the nature of the material being porous & the difficulty in sealing the water line pores. A cooling plate bolted to the bottom of the Porcerax II® insert works well.

Draft angles
Draft angles for the shut off pins and the rib area should be as generous as possible due to the nature of an EDM burned sintered metal like Porcerax II® and its rougher than P20 surface.
Rib sidewall areas may need to be stoned to remove EDM slag. Rib areas may also be milled if filling of the ribs is not an issue. Pins should always be EDM burned however. If the ribs are milled and filling the rib area becomes an issue, an electrode should then be made to burn the bottoms of the rib areas.

Grill mesh thickness
In general, the smaller the web or mesh thickness, the higher the melt temperature needs to be to push the plastic between the shut off pins to fill the grill, creating an exaggerated shrink situation that grips the shut off pins, hindering release. This, along with the tendency to over pack the part in order to fill it, creates poor release.
Molder’s World, Inc. recommends at least .7mm thick mesh to avoid the above problems.

Outside taper on the inserts
The outside of the Porcerax II® insert should not be tapered. It is acceptable to relieve the OD below the parting line, but if the OD is tapered, then repairing a damaged insert by lowering the surface by 1/8” to 1⁄4” is not possible. Lowering the surface is sometimes the best way to repair the molding surface when damaged. (See repairs)

Rib Design

Because of plastic shrinkage, it is best to put .015” to .020” rads on the 6 vertical corners of the hexagon bosses that mold the rib pattern. This will aid in release.

Rib Design Molder's World

Part Ejection
It is not necessary to have ejector pins through the Porcerax II® insert for part release, but it is possible to do that without damaging the Porcerax II® insert. Lifters that slide up the outside diameter of the insert and lift on the outer ring of the speaker grill work well.

Venting Design

Venting the Core Block
It is necessary to have a drilled exhaust line through the core block pocket to atmosphere. This drilled hole should line up with the drilled and EDM burned center vent hole on the backside of the Porcerax II® insert.

Molder's World

Venting the backside of the Porcerax II® core insert
In order to get optimum venting through the Porcerax II® insert,a series of drilled & EDM burned flat, 3/8” NPT blind holes need to be machined on the backside of the insert. By using NPT holes the insert can be pressurized & back flushed during cleaning. Molder’s World, Inc. recommends a minimum of 6 holes in a bolt hole pattern with an extra 7th hole in the center of the insert. (See Right) These holes should be within 5/8” to 3⁄4” of the molding surface and connected to the center hole by mill grooving the bottom of the insert or grooving the bottom of the pocket in a wagon wheel pattern.

Typical Porcerax Insert With Vent Hole Pattern Molder's World

Cleaning Porcerax II® inserts:

Heating Porcerax II® to a temperature over 500°F will only cook the contaminants inside making it harder to clean and will make the surface of the material brittle.

A professional that has Porcerax II® cleaning experience as well as explosion proof ultrasonic cleaning equipment should ALWAYS clean Porcerax II® inserts. Molder’s World, Inc. provides that service.