Lip Coating Technology

EverSharp™ Lip Coating Technology

The EverSharp system is particularly effective in reducing downtime for BOPET film, glazing-quality sheet, products extruded from highly filled compound, and proximity-coated hot melts and other fluids applied by proximity coating. In BOPET film production, for example, because worn lip edges lead to buildup that causes die lines and other defects, the manufacturer typically takes a die off-line every three months to clean and sharpen the lips, a process that takes at least a day and costs thousands of dollars in lost output. By comparison, the lifetime of a tungsten carbide lip edge is measured in years, during which time a chrome-plated edge will have undergone numerous re-sharpenings.

Praxair estimates that tungsten carbide lasts eight times longer than chrome plating before needing to be reground. The estimate is an extrapolation from the results of standard tests for abrasion resistance, as well as Praxair's experience with tungsten carbide coating on other plastics wear surfaces such as screws, knives, and chill rolls.

Comparative tests by Praxair indicate that tungsten carbide is harder than chrome plating and far more abrasion-resistant, requiring diamond abrasives for finishing rather than the standard media used with chrome plating. Tungsten carbide is also less porous and thus more corrosion-resistant, since there are fewer pathways to the interface where the coating and the substrate are bonded.

Micro-photographs of the edge radii of new die lips show that tungsten carbide-coated lip edges are actually sharper from the very start. Unlike tungsten carbide, chrome plating undergoes micro-fracturing in the very act of being sharpened for the first time. In addition, the normal cleaning required to remove lip buildup will scratch chrome plating, while the higher abrasion-resistance of tungsten carbide prevents scratching.

An agreement with Praxair makes EDI the sole worldwide distributor of the coating technology as applied to flat die lip surfaces, with the exception of Japan, Korea, Southeast Asia, and Taiwan; EDI will serve these nations on a non-exclusive basis. Praxair will coat the lip edges, and EDI will grind them for new or existing dies.