Novel ‘Stack Die’ Debuts at NPE2018

Germany’s Kuhne Anlagenbau GmbH will be showing at NPE2018 the Mo-Con, a new type of modular, expandable blown-film die.

So-called stackable “pancake” dies have become common since Brampton Engineering introduced the Streamlined Coextrusion Die in the early 1990s. Numerous other die makers soon followed suit with variations of that design. Kuhne says the Mo-Con die is similar to other types of stack dies because its modular design allows processors to add layers as the need arises. In the case of Mo-Con, the die can be designed from five layers on up. The highest number of layer produced so far is 13 layers for a Kuhne’s Triple Bubble line, says Adolfo Edgar, the company’s v.p. blown film sales, U.S. and Canada. An undisclosed U.S. processor recently installed a nine-layer Cool Bubble water-quenched line with the plan of expanding it to 11 layers in the future, Edgar adds.

But what’s different about the Mo-Con die is that while the binary splitting and distribution is flat, the spirals towards the center of the modules are on a cone. This makes the die body more compact and directs the melt flow in a shallower angle to merge with the other layers. The binary distribution is done on the flat portion of the modules as with the pancake dies. Both sides of the modules are machined for this purpose. Also, whereas in pancake dies the melt is fed between the modules or plates, with the Mo-Con it is fed into the center of each module.

As a result, the assembly of the melt adaptor to the die is straightforward and achieves a leakproof metal-to-metal seal, says Edgar. “There is less risk of having a leak at the interface where the melt adaptor meets the module since only two surfaces contact each other instead of three,” he adds.