Roll Backs/Sicaring/Skinning – Reducing the risks

What are they?

 

Roll backs (or roll ups) are surface delaminated areas on the top or, more commonly, the bottom of a sheet of paper (usually a board weight) which rolls back on itself to form a hard tight bundle. The roll back usually starts from the edge of the sheet and works its way towards the middle.

What is the problem?
When a roll back goes through the press, the vastly increased thickness of the board at the roll up can indent (smash) the rubber litho printing blanket to a point where it cannot recover. The single sheet will smash every blanket it goes through - an 8 unit press will have 8 blankets smashed. A severe roll back can also indent the metal jackets covering the cylinders.

Where do they come from?
This is very difficult to pin point but there are a number of “higher risk” operations which need to be examined in an effort to minimise the potential for roll backs.

These areas are:
Guillotine Operations - the bottom sheet of a stack may catch an edge when it is being moved - always remove the bottom sheet from a guillotined stack.

Press Loading - care should be taken to lower the reams on top of each other rather than slide one ream over the edge of another. As one ream slides over another, the risk is that an edge catches and rolls up and as the
ream slides over. This could be the topside of the ream underneath or the underside of the ream on top.

Wedging Stacks - to try to keep stacks (before and after printing) flat, printers often use wedges. If a wedge is driven into the side of a stack, this may induce the roll back. Poor quality (ragged) wedges obviously run a greater risk. Care should be taken when using wedges

General
It is unfortunate that roll backs are very hard to spot as they are very few in numbers but can be expensive if they go through the press. Printers can help avoid roll backs by correct handling of unprinted and printed materials.

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