Bobst – Low defect vacuum metallizing with the K4000 Crucible

The new K4000 Crucible metallizing unit is said to give a 90% reduction in the number of pinholes (Source: Bobst)

UK • According to Bobst, the new K4000 Crucible metallizing unit gives a 90% reduction in the number of pinholes and provides a repeatable (when compared to an equivalent boat metallizer), reliable performance using proven manufacturers for all critical equipment.

Low defect metallizing

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The K4000 Crucible is based on the K4000 platform with the advantage of crucible technology which produces low defect metallized films. The machine can metallize a wide variety of materials including Aluminium (Al), Silver (Ag) , Copper (Cu) and  Zinc sulfide (ZnS) for a variety of applications including high barrier food packaging and yarn manufacture. The K4000 Crucible does not compromise on web speed running at a maximum of 840 m/min (2756 fpm)

The source which employs crucible technology provides excellent deposition quality and uniformity. The source is fully water cooled and the design ensures ease of cleaning. The consumable costs involved in running the crucible machine are also lower due to the low cost of the metal ingots in comparison to wire.

The large 600 mm (24“) diameter coating drum allows for increased film wrap which provides better film cooling efficiency. According to Bobst, the drum provides the largest coating window in its class in the industry allowing increased collection efficiency by 16%.

The winding mechanism

The machine incorporates the Bobst winding mechanism from the K5 range of equipment with minimum roller contact and true tension control using load cells for virtually wrinkle-free film. The six drive system consists of six independently driven motors which give 3 independent tension control zones allowing the operator to control accurately the web flatness at critical points in the machine. The positioning of the unwind and rewind rolls allows for easy access and roll loading/un-loading on the same side of the machine.

The machine is designed for handling heat stable (PET) and heat sensitive substrates (CPP) and as such is fitted with a cooling drum and post cooling roller as standard. To increase web cooling, a further gas wedge air injection system is fitted to the machine to improve heat transfer from the web to the cooling drum.

Set up operations

The K4000 Crucible is easier to set up for the operator and consequently easier for less experienced operators to run whilst still giving good results on defects and coating uniformity. The machine can also be fitted with the Bobst Hawkeye optical density monitoring and defect detection system.

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