What causes loose coil unwinding on hydraulic decoiler?

Loose unwinding is a common defect during decoiling,which easily leads to strip deviation,sheet scratch and production interruption on roll forming and stamping lines,mainly caused by hydraulic structure,control parameter,raw coil quality and follow-up matching problems.

First,insufficient hydraulic expansion force of the main spindle is the top reason.If hydraulic pressure of expansion cylinder is too low or sealing rings inside hydraulic cylinder age and leak oil,the four-jaw expanding head cannot clamp coil inner diameter tightly.Under rotating traction,the steel coil gradually loosens from inner core and runs loose during unwinding.

Second,mismatched follow-up speed control.When the infrared/ultrasonic height sensor drifts or installation position tilts,the feedback signal is inaccurate;the decoiler rotating speed fails to synchronize with downstream line speed.Excessively fast spindle rotation pulls the coil apart and generates loose layers.Improper inverter parameter setting also results in unstable rotational speed and loose unwinding.

Third,raw coil inherent defects.Loose winding from steel mill,irregular inner diameter,coil edge collapse or uneven sheet thickness will make layers separate automatically once unwinding starts.In addition,long-time idle storage makes coil inner stress release and turns into loose coil during production.

Fourth,improper operation:operators reduce clamping pressure blindly for convenient coil loading,directly triggering loose unwinding in continuous running.

1.GB/T 7714-2015

[1]Zhou M.Reason Analysis and Elimination of Loose Unwinding Fault for Hydraulic Decoiler[J].Metal Processing Equipment,2025,33(9):41-47.

2.APA 7th

Zhou,M.(2025).Reason analysis and elimination of loose unwinding fault for hydraulic decoiler.Metal Processing Equipment,33(9),41–47.h

3.MLA 9th

Zhou,Ming."Reason Analysis and Elimination of Loose Unwinding Fault for Hydraulic Decoiler."Metal Processing Equipment,vol.33,no.9,2025,pp.41-47,