The ultrasonic welding horn, also called a sonotrode, delivers vibration to the plastic part and shapes how the weld forms. A worn, cracked or mistuned horn is one of the most common causes of weld quality problems. JSB Ultrasonic supports customers across India with horn inspection, repair guidance and replacement horn advice.
Signs a Welding Horn Needs Attention
- Weak, uneven or inconsistent welds on parts that previously welded well.
- Visible marking, wear or pitting on the working face.
- Cracks, especially near slots, the mounting stud or sharp internal corners.
- Generator alarms or difficulty holding resonance after a horn change.
- Horn running hot or producing unusual noise.
Why Horns Wear or Fail
Horns are under continuous cyclic stress, so material, design and tuning all matter. Typical causes of failure include fatigue cracking, repeated contact wear on the working face, loosened mounting that damages the contact surfaces, and fillers or abrasive materials in the plastic being welded. Our ultrasonic horn design guide explains how horn shape and material affect performance.
Horn Inspection
A horn should be inspected visually for cracks and wear, checked for flatness and condition at the mounting faces, and checked for correct resonant frequency for the stack. A horn that has been re-machined or repaired must be re-tuned before use, because any change in dimensions shifts its resonant frequency.
Horn Repair and Re-machining
Minor wear on the working face can sometimes be corrected by re-machining and re-tuning, depending on the horn material and design. Cracked horns should not be used. Replacement is the safe option when a crack is found.
Custom and Replacement Horns
A new horn is designed around your component: its shape, material, weld area and required amplitude. To quote or design a custom horn, share:
- A sample or drawing of the component to be welded.
- The plastic material and any fillers.
- Machine frequency (for example 15kHz or 20kHz) and booster in use.
- The existing horn, if you have one, with its dimensions.
See our ultrasonic welding horns and customized welding solutions, or contact JSB Ultrasonic to discuss your application.
Frequently Asked Questions
Can a cracked ultrasonic horn be repaired?
A cracked horn should not be kept in use. Replacement is the safe option, because a crack can grow quickly under vibration.
Does a re-machined horn need re-tuning?
Yes. Changing a horn’s dimensions changes its resonant frequency, so it must be re-tuned to match the stack.
What information is needed for a custom horn?
The component sample or drawing, plastic material, machine frequency, booster details and, if available, the existing horn.
