Flatness terms: waviness, crossbow, wedge, crown and camber
Flatness issues affect cut-to-length, slitting and stamping. Waviness and crossbow are flatness; wedge and crown describe cross-section thickness. Specify and inspect them separately.
Flatness (shape) is a frequent acceptance dispute for stainless strip. Clear up the terminology:
1) Waviness: waves along the length — edge wave, center buckle, quarter wave; measured as steepness (mm/m or I-units).
2) Crossbow / lengthwise bow: overall curvature across or along the strip, like a bow.
3) Edge wave: caused by uneven elongation at the edges; very visible after slitting or cut-to-length.
4) Wedge: one edge thicker than the other across the width.
5) Crown: thicker in the middle than at the edges — a hot- and cold-rolling control parameter.
6) Camber: the strip centreline deviates from a straight line.
Acceptance advice:
• Agree flatness limits (waviness/crossbow) in the standard or contract (e.g. ≤10 mm/m or I-units).
• For cross-section, agree measurement positions and permitted wedge/crown values.
• For cut-to-length, slitting or stamping, specify tighter flatness because downstream operations amplify defects.
• Measure with feeler gauges, a surface plate or a shape meter, and keep records.
Flatness is linked to rolling, levelling, cooling and coiling tension — inspect incoming flatness together with process parameters.
