November 3, 2026 · admin
When ultrasonic welds are weak or inconsistent, the cause is usually one of a few things: the settings, the joint, the material, the tooling or the machine. This guide helps you work through them in a sensible order.
Common Causes and What to Check
| Cause | What you may see | What to check |
|---|---|---|
| Too little energy or time | Weld separates easily, incomplete fusion | Increase weld time or amplitude within limits; check pressure |
| Too much energy | Flash, burn marks, part damage | Reduce amplitude, time or pressure |
| Poor joint design | Inconsistent welds even with good settings | Review energy director or shear joint design |
| Material mismatch | No bond between two plastics | Check material compatibility. See suitable materials |
| Fillers, additives, release agents | Weak or variable welds on a new batch | Check the resin grade and any mould release or contamination |
| Horn or fixture problems | Marking, uneven welds, misalignment | Inspect horn wear and fixture support. See horn repair |
| Loose or worn stack | Low output, overheating, alarms | Check stack tightness. See converter failure causes |
A Simple Troubleshooting Order
- Confirm the parts are the correct material and clean.
- Check the fixture holds the part firmly and supports the joint.
- Check the horn for wear or cracks and the stack for tightness.
- Adjust one setting at a time and record the result.
For more, read our defects and solutions guide and troubleshooting guide. If the problem continues, contact JSB Ultrasonic.
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