Calendering: Plastic Sheets & Paper Roll Manufacturing Explained

Has anyone wondered how plastic sheets or paper rolls are manufactured? Well, the
process is called ‘Calendering’, heard of it? Yes, it is the manufacturing process by
which plastic or paper sheets are formed. Using this process basically any thickness of sheet can be formed. This process incorporates the use of heavy cylinders and a simple transmission mechanism. In other words the cylinders themselves guide and transfer sheets forward.

The process goes like this. The raw material to be used, present in the form of dough is made to pass through two heavy cylinders, which apply pressure on it and convert it in the form of a sheet.


Usually there are many rollers as you can see in the diagram. The more number of
cylinders the better but the thing to be taken in mind is that the process should be
economical. You should not use these cylinders unnecessarily in your enthusiasm
which can make the set-up complicated and costly.

The processed sheet is then wound on a cylinder and thus the bundle is formed.
Calendering generally takes place hot, because hot plastics often are soft and easy
to shape. As a thumb rule always remember that heated things are easy to work with.
They are easily forged. Even if less pressure is applied you will get superior quality
of sheets. The pressure which is generally applied is about 890N/Cm2.But it actually
depends as to how thin sheet you want. There is also an arrangement some times to
make the cylinders hot so that the plastic does not cool in the process.

You must have seen big rollers guiding the newspapers whenever there is a scene of
paper industry in a movie well, actually you are seeing the calendaring machine.

Still not got? Well, try visiting your local bakery next time.

There is also a type of calendaring called belt calendering applying a pressure of about 1/10 that in hot calendaring.

Some companies provide a thickness of 0.17mm to 1.27mm.The process then is to
smooth, polish and glaze to get the required surface quality.
The products are many and this is the major and possibly single process to make the sheets.

The construction is rugged and the thickness obtained varies from 0.5mm but different
manufacturers claim different ranges. The advantages include no wastage of material.
The process can be stopped at the precise moment you want. So what more do we
want?