Q: Why does the needle cause drag on the zipper during sewing?
Needle drag comes from the wrong needle for the material, a dull point, or heat build-up on coated tape. Check the needle before adjusting the machine, because a machine setting changed to compensate for a worn needle will cause a new fault elsewhere.
- Note the needle size and point type fitted, and whether the drag started after a needle change.
- Check the needle for a blunt or hooked point under a loupe.
- Sew a scrap with a new needle of the same size and compare drag.
- Check for adhesive or coating build-up on the needle and the tape.
- Confirm the needle is correct for the tape and film, because a sharp point on coated fabric can grab.
Drag that disappears with a fresh needle is a needle issue, and a needle change every few hours of production is a practical control. Drag that continues with a new needle points to feed or pressure settings rather than the needle. Record the change interval, since it is the simplest way to keep the fault from returning.