Ultra-Sonic Sealing. This technology uses high-frequency ultrasonic vibrations which generate heat inside the plastic in order to create a sealed joint. The application of ultrasonic technology creates molecular vibrations within the strap as opposed to sealing the strap with heat or friction which are the 2 most common welding methods for plastic strap.
Friction Welding. Friction welding generates heat through mechanical friction. The heat is produced by rotating one component against the other whilst under compression. The strap is sealed (or fused) by using a combination of friction and compressive force. As this sealing method involves the rapid movement of several mechanical components, it requires frequent maintenance and replacement of key components.
Heat Seal Technology. Heat and pressure are applied to the plastic strap in order to create a ‘welded’ joint. Accurate and precise control of the welding blade temperature, blade insertion and strap compression time ensures consistent results. Heat sealing can join two similar or dissimilar plastic materials together (including strap containing a high level of recycled material) without compromising the seal or weld quality. This makes heat seal a popular welding method for both virgin and recycled strapping grades.
An example based on a 16mm wide strap (widely used in the building products industry, for example clay bricks and concrete block paving where void pack security is paramount). Some older Friction Weld strapping heads have a circular seal area. In the example shown below, a typical friction weld area of 12mm diameter would equate to a total welded surface area of 113mm². Heat sealing heads apply heat and pressure across the entire width of the strap to create a seal 25mm in length. This equates to a total welded surface area of 400mm² (a 71% increase in hold down force). Nearly all PET has recycled content in unknown quantities. This can influence the seal quality. By increasing the surface weld area, heat sealing ensures maximum seal efficiency.
Below is a quick overview of Ultrasonic, Friction Weld and Heat Seal welding technologies:
|Ultra Sonic||Friction Weld||Heat Seal|
|More suitable for small sealing area||•||•||•|
|More suitable for large sealing area||•||•|
|Noise level||Quieter <79dB||Louder >79dB||Medium (79dB)|