Ultrasonic Technology in Nonwoven and Textile Industry

Flexible technology for a flexible market:

Today’s textile and nonwoven market is so complex that fields of application, production techniques and technologies for further processing as well as the variety of new products are difficult to grasp, even for specialists.The variety of new composite materials of fleece, paper, films and fabric as well as the numerous possibilities in terms of combinations have one requirement in common: a safe and reliable process.

Ultrasonics is also the method of choice for these materials, for example for parting fabrics so that there is no thickening of the material along the cut edges.

No consumables such as glue, staples or sewing thread are needed. The fabric remains intact, because no external thermal energy is directed into the fleece. Position, shape and displacement of the welding points can even support the desired properties of the composite.

Textiles is thus a field where ultrasonic technology can prove its uniqueness.

The Functioning Principle of Ultrasonic Welding:

Low frequency mains voltage is transformed into high frequency electrical energy. A converter connected in line converts these electrical oscillations into mechanical vibrations. This is done using a piezoelectric transducer having an efficiency above 95 %.

The mechanical vibrations are transferred to a transformer element coupied to the converter, the so-called booster. This booster optimises the amplitude for the horn.

The horn is individually manufactured for each application and transfers the ultrasonic energy to the material to be processed. To build up a mechanical clamping force, a so-called anvil is required enabling the energy to effect melting on account of physical processes (internal and external absorption).

The Optimum Process for any Application:

Cycle-controlled process:

The actuator applies a defined pressure onto the anvil and hence onto the part to be welded between the two components. Usually, the ultrasonic irnpulse applied  simultaneously is time-controlled. Using the weld depth or the amount of energy applied as criteria for deactivation is also possible.

Main fields of application for cyclecontrolled welding:

• Overlapping welding of belts and tapes
• Linear welding of fabric and nonwoven
• Welding textile materials with thermoplastic contents
• Joining the end of a material strip to the start of a roll to prevent costintensive drawing in of material into the production equipment.

Seal and cut edges can also be manufactured to excellent quality. This only requires a special design of horn and anvil which is important for the following particular applications:

• Cut belt strips to length and/or punching
• Parting of edge binding for blankets
• Manufacturing buttonholes and eyes applying a certain structure to the rim in order to leave the impression of a sewn edge
• Parting colour ribbons in bureau machine industry

Continuous Process:

Two or more overlapping material strips are fed between horn and anvil which, if required, is rotating. Again, different systern combinations are possible:

Fixed Horn/Rotating Anvil:

This is the most commonly applied combination. Material strips (e. 9. fleece for use in agriculture) are joined at very high speeds using special profile wheels. Using profile wheels, sandwich structures can be generated. Combinations of different materials such as paper, films and textiles are particularly interesting applications. This combination can also be used for cutting processes. This usually involves cutting without sealing or with only slight edge sealling. The extension of the service life as well as the reduction of the cutting force and hence an increased cutting speed are strong arguments for the application of ultrasonic technology. Non-thermoplastic materials can also be cut. In this case ultrasonic energy supports breaking of the materials. Maximum precision is of course a prerequisite in such applications.

Rotating Horn/Rotating Anvil:

In this combination horn and anvil serve both to weld and to transport the welded product. In most cases both horn and anvil are driven synchronously. As in this system only a limited amplitude can be generated. This method is usually used for thin materials having a low mass per unit area.

Fixed HornlFixed Anvil:

This combination is usually used for cutting/ parting applications with simultancous sealing. However, it can also be used for continuous welding of paper, films, or textiles.