What is R.F. Heat Sealing?
R.F.(Radio Frequency) Heat Sealing/Welding
a.k.a. Dielectric Sealing, Electronic Sealing/Welding, High Frequency Heat Sealing/Welding
R.F. heat sealing is accomplished by sending a high frequency (heating) current through two or more layers of thermoplastic material placed between two sealing electrodes or dies. One die is shaped in the image of the required seal. The other die may have the same shape or may be a flat plate. The dies are usually mounted on a pneumatic or hydraulic press to provide pressure for fusing the materials. The high frequency energy produces localized heating by exciting the molecules of the materials to 27.12 MHz, causing them to melt, thus allowing their molecules to intermingle, where upon the pressure exerted on the material brings about a thorough fusion. The current is then shut off, the material is allowed to solidify during a brief cooling period and the materials become joined together at the point of the seal. The resulting seal can be stronger than the original workpiece materials.
The Quality of a seal is determined by three factors:
1. Sealing Current (R.F. Power)
2. Sealing Time
To some extent these three factors are independent of one another: for example, more current or more pressure does not necessarily reduce the sealing time. The type and thickness of the material and the total area of the seal determine these factors.
Pre Seal time and a heated platen can also change these factors:
Material Sealability Chart
Sealing Area Chart
Glossary of Terms