Roll Bending

Roll bending (section rolling) forms tube, pipe, or profiles into large-radius curves using three rollers, best for gentle arcs and repeatable radii.

Overview

Roll bending (section rolling) forms tube, pipe, and structural profiles by passing them through three (or more) rollers that progressively induce curvature. It excels at long, smooth arcs, large diameters, and repeatable radii without dedicated hard tooling for each bend.

Choose roll bending for rings, hoops, curved rails, and architectural/structural members where the radius is relatively large and gradual. It handles long lengths efficiently and can run as one-off prototypes through moderate production with quick radius changes.

Tradeoffs: it’s not ideal for tight CLR bends, short straight legs near the ends (end distortion/“flats” are common), or strict angular location of a single bend. Cross-section distortion (ovalization) and surface marking can occur, especially on thin-wall tube, small diameters, or soft materials; expect some trial-and-adjust to hit final radius and springback.

Common Materials

  • Aluminum 6061
  • Steel A36
  • Stainless Steel 304
  • Stainless Steel 316
  • Steel DOM tubing
  • Copper C110

Tolerances

±0.030" on radius/contour (typical), ±0.060" achievable on long sweeps depending on size and springback

Applications

  • Handrail and guardrail sweeps
  • Rolled rings and hoops for tanks and vessels
  • Curved architectural mullions and frames
  • Trailer and chassis curved members
  • Canopy and awning frames
  • Spiral stair stringers and curved supports

When to Choose Roll Bending

Roll bending fits parts defined by a constant or smoothly varying large radius over long lengths, especially when you need arcs, rings, or gentle sweeps. It’s a strong choice for prototypes through production where quick setup and repeatable radii matter more than tight bend radii or precise bend location. It works best when the design can tolerate some end flats and minor cross-section distortion.

vs Mandrel Bending

Choose roll bending when you need large-radius sweeps, rings, or long curved members where a mandrel setup would be unnecessary cost and complexity. Roll bending also makes it easier to tune radius across long lengths, while accepting more ovalization risk than mandrel bending on thin-wall tube.

vs Rotary Draw Bending

Choose roll bending for gentle, continuous arcs and large diameters rather than a discrete, tightly located bend. Rotary draw bending is better when you need a tight CLR, defined tangent lengths, and high positional accuracy; roll bending favors long curves and fast radius changes.

vs Compression Bending

Choose roll bending when you need controlled, repeatable large radii on heavier wall tube/pipe or structural sections with less risk of wrinkling. Compression bending is typically for simpler, larger-radius bends with lower tooling cost, but it’s less consistent for long sweeps and tends to distort thin-wall sections more.

vs CNC Tube Bending

Choose roll bending when the part is primarily a sweep/ring and does not require multiple programmed bend angles, rotations, and straight lengths between bends. CNC benders excel at complex 3D routed tubes; roll bending is more efficient for constant-radius arcs and profiles.

vs Stretch Forming

Choose roll bending when the section can be formed by progressive rolling without needing full-length tension to control springback and minimize wrinkling. Stretch forming can deliver very smooth, accurate large-radius contours on certain profiles, while roll bending is generally more flexible and faster to set for varied radii.

Design Considerations

  • Specify centerline radius (CLR), arc length, and allowable radius tolerance; avoid defining the curve only by chord/angle if you can.
  • Allow for end flats and grip marks by adding extra straight stock on each end for trimming after rolling.
  • Call out allowable ovality/flatness change (or minimum acceptable ID/OD) for thin-wall tube where fit-up matters.
  • Provide section orientation and any twist requirements; rolled profiles can rotate during forming without clear datum guidance.
  • Avoid very tight radii relative to section size; state minimum CLR or allow the shop to propose a feasible radius.
  • If surface finish matters, specify cosmetic side and masking/roller marking limits to guide tooling and handling.