What is Porcerax II
General Properties
Benefits  
Machining Capabilities
Post-Machining Treatments
Design Guidelines
Cleaning, Maintainance and Resin Removal
Venting Pins &
Venting Ejector Pins
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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:

  1. The failure of resin to sufficiently fuse due to the drop in temperature after flowing over long distances. 
  2. 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. 

Before Porcerax II After Porcerax II

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.

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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