Since melamine impregnated papers were too brittle for rewinding they always have been sheeted in earlier days. Modern resin technology now allows rewinding even for light overlay papers. Sheeting is associated with inefficiencies in transport, storage, collating, and idle capital.
From the very beginning the laminating industry has cut impregnated papers into sheets. This was based on the necessity to supply the raw material to presses. And since traditional presses have a platen size that defines the size of sheets that can be processed between them it is only logical that the impregnated papers were cut to that size.
On the other hand the melamine impregnated papers for the top layers of the laminate were so brittle that they could not be rewound in earlier days.
That has changed with the introduction of short cycle papers that were much more flexible. And it changed even more drastically later when continuous double belt presses were introduced. Double belt presses need reeled papers for their continuous process.
This and other influences created the necessity to make melamine resins more flexible. And the chemical industry responded by designing the appropriate resin.
So today it is not a problem anymore to even rewind lightweight overlay papers that have the typical high
resin content.
Traditional presses, of course, still need paper sheets that have been collated in the proper sequence. These sheets are cut to size at the end of a treater, stacked, transported, and stored. Storing binds a lot of capital, of course. There are many more disadvantages associated with sheeting like the enormous amount of space the sheets need for being stored properly.
Handling and transporting them is also difficult due to their size and weight and there is always the danger that they could become dirty or marred in any one of those steps.
The sheets are later pulled out of their storage racks when they are needed and brought to the collating area where they are manually collated and assembled to the appropriate sets.
Collating so far has generally been a work performed by humans. The humans have to separate the different sheets from their stack and combine them with sheets from other stacks in the proper sequence. It is a tiresome and time consuming work process but still needs a lot of constant attention. It again requires a lot of space, and the area itself has to be dust free and air-conditioned, which is another big cost factor. All these disadvantages have initiated an impulse in the industry to develop an automatic collating system for the sets that will be inserted between two press plates.
Automatic Collating of Impregnated Papers in Laminates and Prepregs; Coordination of Embossed Press