Ultrasonic bonding assembles two or more layers of materials by passing them between a vibrating horn and a rotary drum (often referred to as ananvil). The rotary drum is usually made from hardened steel and has a pattern of raised areas machined into it. The high frequency mechanical motion of the vibrating horn and the compressive force between the horn and the rotary drum create frictional heat at the point where the horn contacts the material(s). The frictional heat bonds the material together only at the horn/material contact points. This gives the bonded material a high degree of softness, breathability and absorption. These are the exact same properties which are critical for hospital gowns, sterile garments, diapers and other applications used in the medical industry and clean room environments.
Ultrasonic bonding requires far less energy than thermal bonding which uses heated rotary drums to bond materials together. As a result, ultrasonic bonding is economical and requires no consumables, adhesives or mechanical fasteners.
When a thermoplastic material is slit ultrasonically, its edges are also sealed. Sealing the edges of a woven fabric is beneficial because the yarns are prevented from unraveling and the smooth, beveled edges prevent buildup of the roll material. When two or more layers are ultrasonically slit together, the layers will become joined. The strength of the bond is determined by the material and anvil geometry.
Many factors influence the speed at which fabric can be ultrasonically slit. Some of the parameters are the geometry of the cutting wheel (anvil), the material composition, material weight and thickness.
In the plunge method, the material remains in a fixed location and is periodically contacted by the horn. The horn operates perpendicular to the material that is on the anvil. The horn can also be used to cut and seal. Typical plunge applications include but are not limited to: Filters | Strapping | Vertical Blinds | Bra Straps | Belt Loops | Buckles | Embossing | Hook and Loop.
Dukane's Rotary 30kHz Ultrasonic Sonotrode (Horn) is ideal for sealing thin films and non woven materials. The unit can be easily integrated into automation. The Rotary horn design eliminates drag issues associated with conventional static ultrasonic sonotrodes. Ultrasonic bonding is a greener solution than conventional heat sealing as power consumption is greatly reduced, requires no adhesives and produces no smoke or fumes. Applications for the rotary horn include film sealing for packaging machines, bonding of nonwoven materials and many others.
Film & Fabric bonding, slitting and sealing
You may not realize it, but ultrasonic film applications are all around you everyday.