Let's talk about 3D substrates such as containers and complex geometric shapes. For these substrates the flame geometry produced from a three slot burner will provide better coverage of the surface. For flat surfaces, the single slot burner provides the best flame geometry for uniform flame treatment.
Let's now consider flat substrates such as paperboard, polymer films and PE and other coated substrates.
For all of these substrates except paperboard prior to extrusion coating or lamination, the single slot burner is the best choice because the flame geometry produced will provide uniform flame treatment in the cross machine direction. In flame treating paperboard , the process burns off fibers as well as transferring heat into the board to promote adhesion. A three slot burner has the ability to provide 50% more energy than a single slot burner.
Recent developments had shown that for hard to treat flat substrates, a wide single slot burner will provide the best results as it combines the best features of both burners.
The photo shows a wide single slot burner