comment on air-to-air vacuum deposition

From Bill Llewellyn

I read your blog on air to air metallizers and enclosed sources with interest as over the years I have had experience with both types.

 

The air to air machines proved horrifically energy demanding for, as you say, you are continually pumping against a leak. In addition, the seals (then) proved inefficient and the web path required was tortuous to say the least. Additionally the extra costs and investments in such complicated devices could not be justified as there were still breaks in the "continuous" production because of web breaks, the finite lives of evaporation sources, and  the need for cleaning and maintenance of chambers, etc. The frequency of these breaks in otherwise "continuous" production meant that the significant additional investment funding needed for air to air machines and their running cost compared to conventional batch machines could not be justified.

 

The compromise seemed to be the use of machines where the source is maintained at low pressure while reels are changed in atmosphere. In the late 1980s I invested in such a machine - a Galileo 2200 mm machine - that not only included the design feature to maintain sources at low pressure during reel changes, but also included a rotating source device based on a turntable design with a source at either end that included a source in use, with the second source at 180 degrees outside the chamber that would undergo maintenance whilst the first source was in use - the idea was to reduce the time required for source maintenance. The idea of this "source turntable" was later copied by General Vacuum on machines sold in US.

 

There were drawbacks to maintaining a source under vacuum close to operating temperatures. Although it reduced source damage through thermal cycling of the sources there were issues with cooling shields, and once a cycle was broken the benefits were quickly lost.

 

Aerre machines had an interesting layout that was intended to keep unwind and rewind reels at floor level to reduce operator workload, but which also used a series of potential airlocks to introduce the web into a central chamber area that was held under vacuum. This could be modified to air to air use with some design changes to the unwind/rewind chambers. Amsterdam Metallized Products use an Aerre machine that demonstrates the layout, and I have some discs from Aerre that also show the schematic if you have an interest.

 

Dr William Llewellyn
Vice President/Senior Consultant
AWA Alexander Watson Associates BV
Tel: +44 (0) 1443 42 12 57
Fax: +44 (0) 1443 42 12 57
E-Mail wllew@aol.com

Comments

[Grace]

What are the main causes of metal oxidation for metallized films? Kindly also give the specification needed for flexible food packaging. Thanks.