Roll Forming
Also: cold roll forming, roll formed profiles, rollforming, contour roll forming, roll formed shapes, roll formed channels, roll forming line
Roll forming bends coil through a line of roller stands, a few degrees per stand, into a constant cross-section: long uniform profiles, cheap per foot.
66 shops tagged Roll forming among 504 metal forming companies in the Noramark directory
A roll forming line uncoils strip and passes it through a series of driven roller pairs, typically 8-30 stands, each bending the profile a few degrees further than the last until the section is complete. Because the bend forms gradually, the strip is not stretched or scarred the way a press brake would leave it, the line runs at 10-60 m/min (30-200 ft/min), and the profile is the same on the first foot and the ten-thousandth. Pre-punching, notching, embossing and a flying cutoff run in line, so parts come off the line finished to length.
Tooling is a set of rolls per profile, $15,000-150,000 depending on the section, and setup takes hours, so roll forming is a volume process: thousands of meters a year of one section. Per foot, it is the cheapest way to make a steel or aluminum profile, cheaper than extrusion in steel and cheaper than a press brake past a few hundred pieces. Pre-painted, galvanized and stainless coil survive the rolls with the right materials and care.
The limits are the constant section and the tolerances. Sweep, bow, twist and flare at the cut ends are inherent and are held by the roll design and straightening stands, but ±0.5 mm (±0.020") on a section dimension is good work. A profile that must change along its length, or that needs ±0.1 mm (±0.004"), belongs on a brake, an extrusion press or a machine.
At a glance
| Typical tolerances | Cross-section dimensions ±0.5-0.8 mm (±0.020-1/32") standard, ±0.25 mm (±0.010") with care; angles ±1°, ±0.5° with care. Cut length ±1.5 mm (±1/16") with a flying cutoff, ±0.8 mm (±1/32") with a stop-and-cut. Straightness (bow and camber) about 1.5 mm per m (1/16" per 3 ft); twist about 1° per m. Pre-punched hole positions ±0.4 mm (±0.015") along the length. |
|---|---|
| Size limits | Strip widths 25-1,500 mm (1-60"); thickness 0.3-6 mm (0.012-0.25") on most lines, to 12 mm (0.5") on heavy structural lines. Profiles up to about 500 mm (20") across. Lengths from 150 mm (6") to 12 m (40 ft) and beyond, limited by handling and freight. Inside radii of 1t are normal, 2t for HSLA and 6061-T6. |
| Surface finish | As-coil: galvanized, pre-painted, 2B stainless and mill-finish aluminum keep their surface with polyurethane rolls and protective film. Tight radii show light roll marks; sharp corners cannot be formed, only coined. Post-finishing is powder coat, galvanizing of the formed part, or anodize for aluminum. |
| Lead time | Roll tooling 6-12 weeks; production runs in days once tooled, scheduled against a minimum run length. Standard profiles (studs, tracks, angles, hat channels) are stocked. |
Typical of U.S. job shops; confirm with the shop for your part.
Materials
Galvanized and galvalume steel, cold-rolled and hot-rolled pickled steel, HSLA (A572 Grade 50, A1011 Grade 50) and pre-painted steel are the bulk of the work; stainless 304, 316 and 430 for architectural and food-service profiles; aluminum 3003, 5052 and 6061 (6061-T6 with radii of 2t or more); copper and brass for trim and busbar. High-strength steel above about 700 MPa (100 ksi) yield and thick plate need heavy lines and large radii. Titanium and nickel alloys are rarely roll formed.
What drives the cost
- Roll tooling: the number of stands and the complexity of the section
- Setup per run, which sets a minimum run length of hundreds to thousands of meters
- Material: coil price, thickness and coating
- In-line features: pre-punching, notching, embossing and their die changes
- Tolerances on straightness, twist and section that need extra straightening stands
- Length, packaging and freight
- Annual volume in linear meters
When to use it
- Constant cross-sections in thousands of meters a year: channels, angles, hat sections, tracks, rails, panels
- Thin gauges and long lengths that a press brake cannot handle
- Pre-painted, galvanized or stainless coil that must keep its surface
- Steel profiles where extrusion is not an option
When not to
- Short runs or a few hundred pieces: press-brake forming
- Sections that change along the length
- Tolerances tighter than ±0.25 mm (±0.010") on the section, or ±0.5 mm on length
- Thick-walled aluminum profiles with fine detail: extrusion
- Parts still in design; roll tooling is not easily modified
Design tips
- Keep the section constant, symmetrical where possible, and the inside radii at 1t or larger (2t for HSLA and 6061-T6).
- Avoid blind corners and return flanges that the rolls cannot reach; ask the roll former what the line can close.
- Keep wide flat areas short or add a stiffening rib; long flats oil-can and show sweep.
- Put pre-punched holes and notches in flat areas away from the bends, and tolerance their position along the length loosely.
- State the straightness, twist and length tolerances you need; every tighter number adds straightening stands.
- Specify the coil: grade, thickness, coating and which face is exposed.
- Compare against extrusion for aluminum and against stock profiles before paying for rolls.
Frequently asked questions
- Roll forming vs press brake bending?
- A press brake bends one part at a time with general tooling and is right for short runs and any length under the bed; roll forming needs a set of rolls but forms continuous lengths at high speed with a better finish on pre-coated stock. The crossover is usually a few hundred pieces or a few thousand meters a year of one profile.
- Roll forming vs extrusion?
- Extrusion makes solid and hollow aluminum profiles with varying wall thickness from a cheap die; roll forming makes constant-thickness profiles in steel, stainless, aluminum and coated coil. Roll forming wins in steel, in thin gauges and for pre-painted stock; extrusion wins for aluminum with thick walls, hollows or detail.
- What is the minimum quantity for roll forming?
- Most lines want at least a few thousand meters (about 10,000 ft) per run to cover setup, and annual volumes of tens of thousands of meters to justify the rolls. Standard stocked profiles have no minimum; custom profiles below a thousand meters a year are usually press-brake formed.
- What tolerances can roll forming hold?
- About ±0.5-0.8 mm (±0.020-1/32") on section dimensions and ±1° on angles as standard, ±0.25 mm (±0.010") and ±0.5° with care; length ±1.5 mm (±1/16") on a flying cutoff; bow and camber about 1.5 mm per m. Twist and end flare are controlled with straightening stands, at a cost.
