Bar or Thermal Sealing

Bar sealing or thermal sealing (reprinted with permission from [6]) 

The edges of the heat-seal bars are often rounded so that they do not puncture the packaging material. Often the contact surface of one of the bars contains a resilient material to aid in achieving uniform pressure in the seal area. Bar sealing is the most commonly used method of heat-sealing packaging materials, and Is often used in form-fill-seal operations. 

A variation on bar sealing uses only one heated bar, with the other bar not heated, resulting in heat conduction occurring only in one direction. Another variation uses heated rollers instead of bars, with the materials sealed as they pass between the rollers. In this type of system, preheating, slow travel through the rollers, or both, are generally required due to the very short contact time between the rollers. A third variation uses shaped upper bars for sealing lids on cups and trays. 

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