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Roll Forming End Flare and Flying Cutoff: What to Specify Before Blaming the Shear

ENGINEERING BRIEF

Core Technical Takeaways & Executive Summary

  • Measure flare on both the lead and trail ends, on the same coil, with the same cutoff recipe.
  • Flying cutoff, stop-cut and saw-cut leave different end conditions — do not mix their samples.
  • Residual stress from the flower pattern can open the section after the strip is freed by the cut.
  • Blade clearance, die match and exit support belong in the written trial plan.

Separate the cut from the forming

End flare is the local opening, lip kick or web kick at the cut face. It can come from residual stress in the formed section, from how the cutoff supports the profile, or from blade wear and mismatch. Treating every flare as a shear problem leads to unnecessary die recuts. Related residual-stress behaviour is covered in the high-yield springback guide.

Name the cutoff system on the sample

Do not mix evidence:

  • Flying cutoff — the die travels with the strip; speed match, clamp and in-die support all matter.
  • Stop-to-cut — the line pauses; end condition depends on clamp and blade, not tracking error.
  • Saw or cold saw — heat and tooth condition dominate; flare mechanics differ from a shear.

Label each sample with cutoff type, line speed setting and coil ticket. Workshop footage of cutoff discharge is on the workshop video page; it is a process illustration, not an acceptance record.

What to measure

Agree measurement points before the trial: opening at a stated distance from the cut, lip angle, and whether the lead end and trail end are both in scope. A photograph without a scale is not a measurement. If only one end is out, the cause is less likely to be the entire flower pattern.

Support, clearance and exit handling

Ask, in writing, whether the quoted cutoff includes in-die support matched to the section, how blade clearance is set for the thickness range, and how the piece is supported on exit. Unsupported discharge can add a kick that looks like flare. Guardrail, racking and purlin sections often need different support geometry — compare the highway guardrail line and the purlin line rather than copying one die to the other.

Trial plan, not a promised die

A useful request is: profile revision, thickness range in millimetres, cutoff type, sample length and the acceptance opening. Send it through the enquiry form. This page does not rate a shear, promise a flare-free end or include a particular die feature in every offer.

ENGINEERING FAQ & TROUBLESHOOTING

Frequently Asked Questions

Can flying cutoff completely eliminate end flare?

Complete elimination cannot be promised for every profile and material. Define an acceptable opening at a stated distance from the cut face and verify it on samples from the intended coil and cutoff system.

Why is flare worse on high-strength coil than on mild commercial steel?

Higher yield relative to stiffness stores more elastic recovery. When the cutoff frees the section, that recovery can show as opening or lip kick. Confirm with the intended grade rather than a universal multiplier. See the high-yield springback note.

Is a dimple die or mandrel always required in the flying shear?

Not always. Support at the cut depends on section geometry, thickness and the quoted cutoff type. Ask whether the offer includes in-die support, exit tables or only a straight blade, and write that into the trial plan.

Should I judge flare on a short offcut?

Short offcuts can look worse because there is little body length to restrain the end. Agree a sample length that matches how the part is used or nested, then measure both ends.

HEBEI TOOLING ENGINEERING GROUP

About Taibang Tooling & Engineering Review

Cangzhou Taibang Machinery Equipment Co., Ltd. discusses roll forming equipment requirements with customers. Confirm the forming review method, electrical requirements, acceptance trial and commissioning scope in the project offer.

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