Vacuum system design

            I recently had an e-mail discussion with Dr William (Bill) Llewellyn VP of AWA BV regarding system design which might give everyone something to think about.  

 

            It is interesting to note that in many essentials the basic aluminium metallizing systems are largely unchanged from those around decades ago.  Yes there have been improvements but it is interesting that a number of changes that could have made life easier for operators and reduced downtime have not been adopted. 

 

            For example here is the comment from Bill regarding the use of rotating source turrets.

‘On rotating sources, I was part of the team that initiated the concept with Galileo back in the late 1980s/early 1990s. The concept was to improve cycle efficiency by reducing the amount of time lost to source maintenance........and as a more cost effective alternative to air to air machines. The idea was to have one source in use within the machine, and a second source mounted on the same turntable that was being maintained outside the chamber.......boats and wire changed, wire feeds cleaned and checked, aluminium residues cleaned from source walls, etc, etc. When the source in use neared the end of its useful life, it was "unplugged" from the chamber, the turntable rotated through 180 degrees and the fresh source introduced with minimum time loss to production.

            The concept works well and was later copied by GVE for machines in the US. It does add cost, but there are gains in lower downtime for source maintenance, cleaning, etc. It also has the advantage that if a source is damaged, for example in a web break or shield leak, you have an effective "spare" to continue operations.’

 

 

            Another area that was developed and dropped was that of roll changing. As you will already know the polymer film makers regularly use flying splice technology. They can cut and remove completed rolls and re-attach the web to new cores without slowing down the film production.  In metallizing rolls have got larger and heavier and this makes them harder to handle and so automated handling has attractions.

 

Here is another comment from Bill.

‘However, web maintenance is just a part of the downtime, and the greater problem was changing the large reels that were in use for paper and OPP metallizing, especially changing reels often weighing greater than 3 or 4 tons some 3 to 4 meters in the air. This required cranes or specially designed handling equipment and added both to the complexity of there equipment in use, and the time taken.

            Aerre addressed this issue with their innovative design. All reels were handled at floor level reducing the need for highly specialised equipment, reducing operator fatigue, improving safety and reducing time.’

 

            I contrast this to the solution to this problem from GVE who went a different direction and produced a fully automated reel changing system that could remove the metallized roll and add a new uncoated roll.  This was used on the heaviest of paper metallizing systems with rolls of 4 tonnes or so.  

 

 

            The argument against these developments has always been cost and complexity. The trouble is that unless more systems with these features are built and the designs refined then it is very hard to reduce the complexity and cost.  A classic chicken and egg situation; where if the cost is not less then none will be bought but unless some are bought the costs cannot be reduced.   The cost benefits are much harder to assess as these are often very specific to the way customers operate their systems and will be affected by local costs.  Also over the years the frequency of web breaks looks to have reduced. I do not know if this is due to improvements in web quality or improved winding control or both.  Whatever the reason, the reduced frequency means that the benefits of having a reduced downtime after these events becomes of less importance.  Similarly with boat lifetimes being extended the number of boat exchanges per year is reduced and so the benefit of the faster source exchange is reduced. With these benefit reductions the cost justification becomes harder to achieve unless the system cost is similarly reduced.  

            Those who lose out are the operators. Their work remains the same rather than becoming easier.  Replenishing wire feeds, boats and cleaning feed tubes, etc, will remain a high pressure operation as it is all compressed into the time between deposition cycles. Operators working under pressure are prone to mistakes. Taking time to properly seat boats, clean and check wire feeds are fully and easily working can have production advantages. 

            As it is the margins on metallized products often means that the systems bought are chosen on minimum cost alone.  This again compounds the problem of making design advances as the only developments of interest appear to be those that reduce costs.  

 

 

Finally a comment from Bill that suitably summarises current systems design.

‘There has been no shortage of innovation in chamber design over the years, but it is still a surprise to me that in many instances, the designs of today do not ease the operator workloads, and areas such as reel changing, source maintenance, and chamber access is still as problematical as they were many years ago.’