Filter Pleating

Automotive filters have pleated paper which is the filter medium. The paper needs to be heatset after pleating process so that it retains its shape and does not open up. The paper immediately after pleating is passed through a chamber consisiting of ceramic infrared heaters. These ceramic IR heaters provide quick and uniform heat. As a result, the paper then stays in its pleated form only. 
The pleated paper then needs to be attached to the top and bottom cap. In case of metal caps, it is attached with the help of an adhesive only. 
Now a lot of filters have these top and bottom caps of Nylon. It becomes very difficult for the paper to adhere to nylon in case there are no grooves on the nylon cap. So, the end caps are passed in a chamber where short wave IR lamps are installed. These IR lamps quickly soften the caps. Immediately on softening, the caps are pressed by a punch and grooves to accomodate pleated paper are formed on it. Now, when the paper is attached to the nylon caps, it fits into the grooves and there are no chances of any leakages.