Ultrasonic 

Metal-Weld Tips

The weld tip is part of the horn. The purpose of the tip is to grip the top weldment component and transfer ultrasonic energy from the horn to the weldment. The tip can be an integral part of a solid horn, or a removable component.

When designing an ultrasonic weld tip it is important to recognize that the tip is part of the horn to which the principles of Conservation of Energy apply. To satisfy these principles, the forces in both quadrants of the horn must be in a state of equilibrium. Do not alter an ultrasonic weld tip from its original design without first consulting a qualified design engineer. Modifications to the tip can offset the equilibrium and alter the performance of the horn. 

Operation: During a weld cycle the tip moves in unison with the horn. In doing so, Newton’s First Law of physics applies- “A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force”. Once in motion the tip is acted upon by the horn to which it is securely attached. Problems can occur when the tip design contains an excessive “moment”, or is too long. As the tip’s length increases, the weld efficiency starts to diminish due to the energy consumed in overcoming the inertia of the tip. This adds stress, causing the ultrasonic system to overload or possibly break the tip. The exception is when a weld tip is designed as a resonant component with a tuned length. Extended lobe tips designed as components of a full acoustic wave have been used successfully for years.  

Design Considerations: For the tip to transfer energy into the weldment, it must physically contact and mechanically engage the top component of the weldment. The most common method involves designing a pattern into the tip surface that allows it to grip the top weldment component.

The pattern design incorporates high ridges and low valleys. These can have sharp points (teeth) or radiused edges (waves) and can also be machined as straight or angled serrations to produce individual peaks (knurls). Efficiency of the energy transfer depends upon how well the tip can grip the weldment.

If the weld pattern is excessively aggressive, or the tip does not have sufficient transition, it may cause physical damage to the top weldment component. If the weld pattern is not aggressive enough for the particular application, the pattern may not seat properly in the weldment and excessive frictional heat will be generated. Usually, the height of the weld pattern does not exceed 50% the thickness of the top weldment component. 

Tip pattern design issues also include the hardness, thickness and size of the material being welded. Tool wear on the pattern face is inevitable, and eventually the tool will need to be resurfaced or replaced. Removable tips are seldom refurbished. 

To ensure maximum tool life, ultrasonic metal weld tips are fabricated from very hard, durable steel alloys. The specific metal used for a tip is determined by the application. Tips are heat treated to maximizes durability. Once heat-treated, tips undergo specialized surface treatments that aid in maximizing tool life.