PVD - Coatings in Injection Molding Machines for Processing Optical Polymers

Transparent parts with faults down to a tenth of a micrometer lead to reject parts. For processing transparent polymers, injection molding machines (IMMs) are most commonly used. To reduce these faults, plasma vapor deposition (PVD) coatings for injection tools are used in this paper to reduce adhesion, wear, and corrosion. All the investigations were carried out on the two steel types ASTM A422 and plasma-nitrided ASTM A355. The coatings of TiN, (Ti0.4Al0.6)N, (Ti0.4Al0.6)ON, CrN, (Cr0.6Al0.4)N, and (Cr0.6Al0.4)ON were developed with good adhesion to the substrate. With the PVD coatings of (Ti0.4Al0.6)ON and (Cr0.6Al0.4)ON the lowest adhesion of the polymers to the surface could be realized. These two coatings were applied on screw tips and used. After all the tests were performed, the coated parts could be cleaned much easily from the polymers.