(?) A hard look at. The technology of Gravure doctoring.. ALLISON. Systems Corporation. (PART 9 of 10)

Transcription

1 Copyright 03/01/2009 A hard look at The technology of Gravure doctoring.. (PART 9 of 10) (?) ALLISON Systems Corporation

2 Short history of gravure doctor blade edge profiles: 45 degree hand (?) shaped "chisel point" 15 degree bevel (c Allison) Lamella (c MDC ) 4.5 -degree bevel Superhoned (c Allison ) 2.2 -degree bevel Superhoned Plus (c Allison ) 2003

3 Why go back to the Bevel Superhoned (R) 1. The Superhoned blade tip doesn t get too fat, too fast when the blade wears, and provides 2. More effective tip control in real world doctoring situations, that is, where there is a little too much...

4 FORCE

5 The search for a new doctor blade material with low wear that would also avoid other problems... Plastics,, Stainless alloys, Coatings, Composites, Hi-tech alloys?????? Leads to

6 The science of Tribology ( tribos is a Greek term for rubbing) addresses the often complex interaction of different materials in motion

7 Tribology studies and laboratory results can suggest remarkable Theoretical wear improvements, due to reduced frictional and other But will the resulting doctor blades give the Gravure printer any real advantage in the pressroom with its schedules, quality requirements and, doctoring booby booby traps? traps? wear forces.

8 Booby traps like:. Cylinders with large, non-engraved areas Increasing the surface roughness of the cylinder Rz can sometimes provide enough blade lubrication

9 Booby traps like:. Cylinders with large, non-engraved areas Provided the pattern of scratches Increasing the surface roughness of the cylinder Rz can sometimes provide enough blade lubrication on the cylinder surface doesn t print out!

10 And of metal doctor blades has, since the 50 s, been associated with severe gravure cylinder, (and ceramic anilox roll), damage.

11 (Here s an extreme example that illustrates adhesive wear ). (little or no lubrication here) Metal (soft copper) Burrs! Damage ( grooves) CAUTION: Don't try this without proper precautions!

12 The lack-of of-lubrication issue can now sometimes be dealt with by means of doctor blade coatings that either: Are WEAR RESISTANT and have a lower - Are and have a lower dry friction coefficient than doctor blade steel against the chrome - Provide a LUBRICANT for the blade Or Both!! (that doesn t print out )

13 But.. Fix the blade coatings, may also fill in the engraving unless they re just right!!!!

14 testing has shown that certain specially applied alloy coatings are an effective solution to blade life and lubrication issues Allison Systems CVXX precision coated doctor blade for Gravure

15 But what about Micro-cracks in chrome plating?? * (600+ X magnification) *Crack structure and density can be controlled by the chrome plating process to a limited extent.

16 **********MoS 2 ************* By developing a plastic doctor blade specially filled with molybdenum disulfide, (a material with the remarkable ability to lubricate cylinders by entering the chrome microcracks), we have been able to help a certain customer produce the white letters etc. on a certain common package for over a decade and a half (It would have taken his press about 10 times as long and many more cylinders to do this with fine carbon steel blades )