Cold-formed open sections (C, U, Z, sigma, omega and bespoke profiles) are made in one of two ways: progressively, on a continuous roll forming line, or bend by bend on a press brake. In both cases flat steel is turned into a section by plastic deformation at room temperature. Beyond that the two processes have little in common. Tooling, economic batch size, dimensional behaviour and achievable geometry all differ.
The choice is often made on unit price alone. A sound decision weighs total length over the product's life, the number of bends in the section, profile length, the role of the hole pattern in assembly, the coating and how settled the design is. This article compares the two processes on the parameters a production engineer actually looks at, and closes with a checklist you can use on your own part.
Roll forming: continuous, progressive forming
On a roll forming line, coil is paid off a decoiler, levelled where necessary and fed through a series of roll stations. Each station bends the strip a little further than the one before, so the section reaches its final shape gradually. How the bending is distributed across the stations is defined in the flower pattern. Its purpose is to keep longitudinal strain at the strip edges and bend zones under control, which in turn prevents edge wave, twist and bow.
Holes, slots and notches are applied on the line, either before forming (pre-punching) or after it (post-punching), and the profile is cut to length at the exit. The line becomes a continuous cell that turns coil into assembly-ready profiles. Because the rolls define the section, every section needs its own roll set. Once that tooling exists, labour and machine time per metre fall to a very low level.
In Europe, dimensional and shape tolerances for roll-formed sections are referenced to EN 10162 (cold rolled steel sections; technical delivery conditions, dimensional and cross-sectional tolerances). Our lines run 1–6 mm material on rolls designed and machined in-house; see roll forming for the technical detail.
Press braking: one stroke, standard tooling
On a press brake a pre-cut blank is placed over a bottom die (the V opening) and the top punch drives it into the die to form a single bend line. The most common technique is air bending: the sheet never touches the bottom of the die, and the bend angle is set by how far the punch penetrates. One set of tools therefore covers a range of angles. Bottoming and coining need considerably more force in return for tighter angle consistency.
Required tonnage depends on bend length, thickness, tensile strength and die opening. It rises steeply with thickness, and high-strength steels need wider V openings and larger inside radii. For long parts, the length of the bed and ram is the limiting factor. With 1,000 tonnes of force and an 8-metre bed we bend plate up to 25 mm and parts up to 8 m long in one piece; see sheet cutting and bending.
The strength of the press brake is flexibility. No section-specific tooling is needed, and a drawing change means a new CNC program and perhaps a different die. The limitation is that every bend is a separate operation and the part has to be repositioned for each stroke.
Dimensional and shape behaviour
Both processes have to deal with springback: when the load is removed, the material opens up by the elastic part of the deformation. Springback grows with yield strength and with the ratio of inside radius to thickness. In high-strength structural galvanized grades such as S350GD–S450GD it is markedly larger than in forming grades such as DX51D, and it must be compensated in the roll design and in the press-brake program alike.
In roll forming, springback is compensated once, in the tooling. From then on every metre passes through the same stations, so the section is highly repeatable along the length and from batch to batch. Typical roll forming defects show up along the length rather than in the section itself: bow, camber, twist and end flare. A well-developed flower pattern and properly set straightening stands keep them under control.
On a press brake the angle responds directly to batch-to-batch variation in thickness and strength; in air bending a small difference in thickness produces a measurable change in angle. Servo control and angle measurement reduce this. On long parts, ram and bed deflection are compensated by crowning, yet holding angle and straightness over the full length remains harder. In multi-bend sections each bend inherits the error of the one before, so tolerances stack up.
Geometric limits
Roll forming comes into its own on sections with many bends. An extra bend usually means one or two more stations and has little effect on line speed. Interlocking edges, lipped C and Z sections, web stiffeners in sigma purlins and stepped flanges on omega profiles are routine roll forming geometry. The limits are the requirement for a constant section along the length, deep and narrow forms that need many stations, and the available strip width.
On a press brake geometry is limited by tool access. Short flanges may not sit across the V opening; deep U shapes and near-closed forms collide with the punch or ram; consecutive reverse bends need special punch profiles. On a long part with many closely spaced bends, the blank has to be turned and re-gauged for each stroke, which costs time and tolerance.
Conversely, a press brake makes parts that roll forming cannot: sections that vary along their length, tapered forms, parts with different bend angles in different zones, and heavy plate.
Side-by-side comparison
The table summarises both processes on the parameters that drive the decision. Capacity figures refer to our own equipment; the other rows reflect general production practice.
| Parameter | Roll forming | Press braking |
|---|---|---|
| Section-specific tooling | Required (roll set) | None; standard punches and dies |
| Economic volume | High, repeating lengths | Prototypes, low and medium quantities |
| Part length | Long profiles are routine; handling and shipping set the limit | Limited by bed length (8 m here) |
| Thickness | Thin to medium gauge (1–6 mm on our lines) | Up to heavy plate (25 mm here) |
| Multi-bend sections | Extra stations; limited cost impact | Each bend adds an operation and stacks tolerance |
| Repeatability | Very high; consistent batch to batch | Depends on material, gauging and program |
| Holes and slots | In-line at fixed pitch | Separate operation, usually laser cut before bending |
| Pre-coated material | Well suited; coating preserved on faces | Possible; marking risk on long parts |
| Design changes | Require roll rework | Quick, by reprogramming |
| Typical products | Purlins, solar mounting profiles, racking uprights, facade sections | Brackets, chassis members, covers, heavy plate parts |
Cost: when does the tooling pay back?
The two cost structures are different. In roll forming, total cost is a one-off tooling investment plus a low cost per metre. A press brake needs no tooling investment, but its unit cost is higher because every part carries cutting, handling and bending operations, and it rises with the number of bends.
The break-even length is roughly tooling cost ÷ (cost per metre on the press brake − cost per metre roll formed). If your total length exceeds that figure, roll forming is the cheaper route. Use the total length the section will be ordered over the product's life, not just the first order: repeat orders carry no tooling cost.
Items outside the unit price also count. Fed directly from coil, roll forming produces less scrap than cutting blanks from sheet. Punching and cut-to-length happen on the line, so intermediate stock, internal handling and second operations disappear. Where the rolls are designed and made in-house, tooling cost and set-up time drop well below outsourced tooling, which moves the break-even point to shorter total lengths.
The influence of material and coating
Galvanized (DX51D+Z, S250GD–S450GD) and zinc-aluminium-magnesium coated steels are supplied as coil to EN 10346. Roll forming shapes them pre-coated, so no post-galvanizing is needed and the coating stays uniform over the whole surface. On thin gauges, cut edges and hole walls are protected cathodically by the zinc; Zn-Al-Mg coatings perform better than plain zinc in these areas.
A press brake can bend coated sheet too, but long parts risk marking where they contact the tools, and tight radii can micro-crack the coating. Uncoated and EN 10025 structural steels can be formed either way and then painted or galvanized. Whichever process is chosen, the minimum inside radius increases and springback becomes harder to compensate as strength rises, so this limit belongs in the section design from the start.
A combined route: press brake for prototypes, roll forming for series
In most projects the two processes complement each other. A section that is still evolving can be laser cut and press braked for first samples and field trials, then transferred to roll forming once it is frozen and volumes are clear. This defers the tooling investment until the design risk has gone. A press-braked sample will not have exactly the same inside radii or springback as the roll-formed product, so final dimensional approval should be given on the first roll-formed article.
In series production the two also work side by side: main members are roll formed, while connection plates, brackets, splices and heavier parts are produced by laser cutting and press braking. Making all of them in one plant makes it easier to keep hole positions and dimensions consistent across mating parts. Solar mounting structures are a typical example.
Decision checklist
These questions settle most process decisions:
Total length: what is the expected length for this order and over the section's product life? Design maturity: is the section frozen, or are field trials still running? Geometry: how many bends, and are there lips, stiffeners or interlocks? Length: what is the profile length and its tolerance? Material: thickness, grade and coating (for example S350GD+ZM)? Hole pattern: do the holes mate with other parts in assembly, and are pitch and cumulative tolerance critical? Critical dimensions: which dimensions are functional and which are free?
Send these answers with the section drawing (DXF, DWG or PDF) and our engineers will compare both routes and recommend one. For series profiles see roll forming manufacturer in Türkiye; for low quantities or heavy parts see press-brake bending services. Requests can be sent through the quote form.