Purlin Roll Forming Machine
One index for the whole purlin family — C and Z, Sigma and Omega, and long-span truss purlins — with the section ranges and the selection logic behind each.
A purlin is the secondary steel member that spans between the roof frames and carries the roofing sheet. On an industrial building the purlin set is usually the largest single quantity of cold-formed steel on the project, which is why a purlin line is the highest-volume roll forming machine in most factories.
Four section families cover almost all of it, and they are not interchangeable — each solves a different problem, and the machine that makes one does not necessarily make another. If you are choosing between them, read the selection guide below first; if you already know the section, go straight to the variant pages.
The three purlin machines in the range
CZ Purlin Roll Forming Machine
C and Z interchangeable, 60 – 350 mm web, servo C→Z change under 10 minutes
View specs & pricing →Sigma Purlin Roll Forming Machine
Sigma (Σ) and Omega (Ω) sections — higher capacity than a C purlin of the same depth
View specs & pricing →Truss & Roof Purlin Machine
Triangulated truss purlin sections for long-span roofs, 100 – 400 mm depth
View specs & pricing →C, Z, Sigma and truss compared
| Family | Where it is used | Web / depth | Thickness |
|---|---|---|---|
| C purlin | General roof and wall support — simple spans and short continuous runs | 60 – 350 mm | 1.5 – 3.0 mm |
| Z purlin | Long roof runs, where the lap between adjacent purlins carries the moment — the usual choice on wide industrial roofs | 60 – 300 mm | 1.5 – 3.0 mm |
| Sigma (Σ) purlin | Higher load for the same depth than a C section — used where depth is limited | 100 – 250 mm | 1.5 – 3.0 mm |
| Truss purlin | Spans beyond what a single cold-formed section reaches, without a disproportionate weight increase | 100 – 400 mm | 1.5 – 3.5 mm |
How to choose a purlin machine
- C or Z — which one does my roof need?
- A C purlin is symmetric, so it behaves the same either way up and is simple to specify. A Z purlin is point-symmetric, which lets two adjacent purlins overlap at the frame and act as a continuous beam whose lap carries the moment. On long roof runs the Z lap normally beats a deeper C on steel weight — which is why wide industrial roofs are mostly Z.
- When is a Sigma purlin worth the extra cost?
- When depth is the constraint. A Sigma section has a folded web and carries more load than a C of the same depth, which is what you need on refurbishment, low-pitch roofs and service zones where a deeper purlin simply will not fit. Sigma and Omega sections run a 100 – 250 mm web through 18 – 22 stations.
- Do I need a truss purlin machine?
- Only when the span is beyond what a single section can reach economically. A truss purlin gets its depth from geometry — two chords joined by a zig-zag web — so it spans further without the weight penalty of a very deep single section. It costs more per metre because of the assembly step, but can be cheaper per unit of span.
- What steel thickness and grade do purlins run in?
- C, Z and Sigma purlins run 1.5 – 3.0 mm; truss purlin lines go to 3.5 mm because the two chords take the bending. Standard rolls cover up to about 550 MPa yield, with hardened rolls above that. Material is normally galvanised or pre-painted — purlins sit inside the envelope but still see condensation, so the coating is doing real work.
- How are the web holes produced?
- Inline on the forming line. Purlin web holes are what the roof and wall fixings pass through, so they run the length of every member — the standard punch produces 11, 13 or 14 mm holes at an automatically indexed pitch. Punching inline keeps the holes registered to the section and removes a drilling operation from the erection site.
- What actually limits the output of a purlin line?
- Cutting, not forming. Purlin lines form at 8 – 25 m/min, but a roof contains hundreds of different member lengths, so the line spends its time changing cut length rather than forming. A programmed length list with a batch counter is what keeps it productive — a fast former feeding a slow cut still produces at the speed of the cut.
What to fix before you order a purlin line
Settle C-only or C↔Z interchangeable before you order
A C-only machine and a C and Z interchangeable machine are different purchases. If there is any chance of Z work, specify interchangeability at order stage: servo changeover is under 10 minutes, the manual arrangement takes 30 – 45 minutes, and the alternative later is a second machine.
Pay for servo changeover only if your orders mix sections
If orders run as single-section campaigns, a manual C→Z change of 30 – 45 minutes is irrelevant. If a typical order mixes C and Z for the same building, the change happens several times a shift and the servo version pays back quickly. Decide from your order book, not from the brochure.
Match the web range to the spans you are actually asked to quote
A 350 mm machine costs more than a 250 mm one and is wasted if your market builds at 200 mm. Buy for the section table you quote from. Also check the adjustment ranges — flange 45 – 90 mm and lip 10 – 25 mm are what a standard C and Z line gives you to cover that table.
Inline punching is a productivity feature, not an accessory
Web holes at automatic pitch remove a drilling operation from the erection site, which is where labour is most expensive. A purlin line without inline punching produces members that somebody has to drill or punch afterwards, and that cost lands on every project.
Specify cut to a length list, not to a single length
One roof has many member lengths. The control needs to run from a programmed list with batch counting; the mechanical choice — hydraulic flying saw or post-cut — is settled at order stage and is not a setting you can change later.
Bring the engineer's section to the order stage
Purlin sections are specified from a span table written around local design codes. A machine ordered against a nominal C200 may need different flange and lip geometry for the section the code actually requires, so send us the section you are quoting rather than the name of it.