When designing cooling channels for a mold, the mold designer is frequently looking at deep-draw sections of a molded part and attempting to get as much heat as possible out of these areas. They tend to be the hottest of the hot-spots in most molds.

The best way to get the heat out of the deep-draw sections of the mold is with baffle blades.
Almost all toolmakers cool molds the same way—with drilled cooling channels. Brass baffle blades tend to be about 0.095” thick, with about 0.020" clearance on each side to allow the blade to be screwed into the threaded tap at the end of the drilled cooling channel. As the clearance is necessary for installation, the gap cannot be eliminated.

  Fluid Flow in a Mold Cooling System
Fluid dynamics assert that fluid will travel the path of least resistance, and that is the case with coolant flowing through a mold cooling system. Coolant will use the gaps between the baffle blades and the coolant channel as the preferred route of travel, rather than flowing all the way to the top and over the baffle blade as the mold designer intended. This is commonly referred to as blow-by.

 When blow-by occurs, the coolant tends to stagnate past the area of the blow-by. At a minimum, the coolant flow on the other side of the blow-by will be greatly reduced. This stifles the thermal transfer capabilities of the mold cooling system—a fundamental drawback of the brass baffle blade.

  Eliminating Blow-By
Significant improvements in heat transfer from these hot-spots (and thus vastly improved overall mold cycle times) can be achieved if blow-by around baffle blades is eliminated.
The new patented plastic baffle offers a tremendous advantage in that, being made of polypthalamide, it can include a patented wiper on each side of the blade.

  The wiper acts as a seal between the cooling channel and the edges of the plastic baffle blade, effectively eliminating the gap between the baffle blade and the coolant channel so that there is no blow-by. Coolant flows throughout all of the cooling channels, including up to and around the tip of each plastic baffle blade. The result is excellent thermal transfer out of the hot-spots, as the mold designers intended.

  Additional Polypthalamide Advantages
Another set of advantages of using polypthalamide for baffle blades is that plastic baffle blades are molded rather than extruded. Thus, it is possible to include design features on the flat surfaces of the baffle blades. Waved ribs are designed onto the flat surfaces to act as chevrons or turbulence enhancers. Turbulent coolant flow transfers significantly more heat than laminar flow.

 Finally, inch increments are also included on the flat surfaces of the plastic baffle blades, allowing mold builders to conveniently measure and snap the plastic baffle blades to the correct length during installation. This allows for much quicker installation than brass baffle blades, which must be measured, cut, ground and then installed.   

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