Q: Why does the slider pull off the zipper under load?
Pull-off is the slider leaving the chain when the garment is pulled hard, often on a bag or a close-fitting jacket. It is a strength question, so it needs a measured test and a clear picture of how the item is used.
- Identify the load direction: a sideways pull at the slider, or a pull along the tape.
- Check whether a stop is present at the loaded end and whether it suits the tape.
- Inspect the slider for deformation or a widened channel after the failure.
- Measure the force at which a spare assembly releases, using a simple spring gauge, and compare it with the maker's range.
- Confirm the slider size matches the chain and that the garment does not load the slider sideways in use.
A slider that releases well below the maker's range is a zipper defect. A garment that pulls sideways on the slider is a design issue, and fitting a stronger slider will only postpone the failure. Record the use case, because it changes the specification that will solve the problem.