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Automatic C/Z Interchangeable Purlin Roll Forming Machine
Table of Contents
- 1. Definition
- 2. What this is not
- 3. How it is formed
- 4. Published numbers on this mill
- 5. Buyer FAQ
1. Definition
An automatic C/Z interchangeable purlin machine is a cold roll forming line that produces C purlins and Z purlins on the same machine, one section at a time. Purlins are the cold-formed members that span between the frames of a steel building and carry the roof and wall sheeting. On this build the line covers a web of 80-300 mm, a flange of 40-80 mm and a lip of 10-25 mm, from strip of 1.5-3.0 mm.
The interchange is done from the control panel. The operator selects C or the required size, and changeover servos move the stands and the forming station to that recipe: a size change takes 1-3 minutes and turning the section from C to Z takes 5-10 minutes, with the line stopped. The two sections are never formed at the same time: a C batch and a Z batch are separated by a changeover. No roll set is dismantled, which is what separates an interchangeable machine from a machine that is simply re-tooled.
The host carries 18-20 driven stands on a Ø85-Ø95 mm 40Cr shaft, driven through a distribution gearbox or a heavy-duty chain, and works at 8-25 m/min. Holes are punched on the flat strip ahead of the forming stands by three hydraulic punch dies, and the cut is made by a universal hydraulic shear that follows the section setting.
2. What this is not
| Not this machine | Why |
|---|---|
| Not a dedicated C purlin machine. | A fixed C line is a different host and its own quotation. On an interchangeable machine C is one of two recipes. |
| Not a dedicated Z purlin machine. | A fixed Z line has its own lap geometry and its own flip-cut arrangement; it is not this machine with the recipe changed to Z. |
| Not a C/U/Z three-section machine. | A three-section host is a different build. This machine covers C and Z. |
| Not a stud and track machine for drywall or light-gauge framing. | Drywall stud and track run far thinner strip with a completely different punch pattern and a different product family - do not compare the two on thickness alone. |
| Not sigma, hat or omega forming. | Those sections use their own flower patterns, not C/Z lips. |
| Not an I purlin machine. | Most inquiries for "I purlin" resolve to a hot-rolled beam rather than a cold-formed section. |
| Not a roofing sheet line, a keel line, or a guardrail line, | even where the strip thickness looks similar. |
3. How it is formed
The strip coil is loaded on a 5 t hydraulic cantilever decoiler, where pinch feed and hydraulic expansion hold the coil and pay the strip out under control. It then passes a 7-roller centring leveller that removes coil set and cross-bow and brings the strip onto the machine centre line, so the web forms straight along the length. Holes are punched while the strip is still flat, which keeps the hole pattern on a flat datum instead of letting it drift with the formed section.
The strip then runs through 18-20 driven stands. Each stand adds one part of the bend, so the section builds up gradually and the coating survives the forming pass. When the size or the section changes, the servos reposition the stands and the forming station to the new recipe. Finally a following hydraulic shear cuts the purlin to length and the pieces discharge onto two 6 m support tables for bundling. The first piece of each batch is checked against the signed section drawing. Note that the line makes one section at a time: a C run and a Z run are separate batches, with a changeover in between and no simultaneous output.
- • Decoiling
- • Levelling and centring
- • Punching on flat strip
- • Forming the C or Z section
- • Changeover, when the size or the section changes
- • Universal hydraulic shear
- • Outfeed and first-off check
4. Published numbers on this mill
The figures below are the ones on file for this build. They are not averaged across other purlin configurations, and they are not taken from the C-only machine or from a different delivered configuration. Where a value depends on the customer's section, it is left to the signed drawing instead of being published as a universal figure.
| Item | This build |
|---|---|
| Sections | C purlin and Z purlin, interchangeable - one section at a time, changeover between them |
| Web height range | 80-300 mm |
| Flange width range | 40-80 mm |
| Lip range | 10-25 mm |
| Thickness | 1.5-3.0 mm (2.0-2.5 mm typical) |
| Material | Hot-rolled, cold-rolled or galvanized strip (Q235 / Q355 / G550) |
| Forming stands | 18-20 |
| Shaft | Ø85-Ø95 mm, 40Cr quenched and tempered |
| Drive | Distribution gearbox, or 1.5 in / 2.0 in heavy-duty chain |
| Speed | 8-25 m/min; about 10-18 m/min with punching in line |
| Changeover | Size 1-3 min; C to Z 5-10 min; one section at a time, and the line is stopped during a changeover |
| Punching | 3 hydraulic punch dies, on flat strip before forming |
| Cut | Universal hydraulic shear, no blade change between sizes |
| Power | Main motor 18.5-22 kW; hydraulic station 7.5-11 kW; changeover servos 3 x 0.75 kW |
| Decoiler | 5 t hydraulic cantilever |
| Leveller | 7-roller centring |
| Outfeed | Two 6 m support tables |
| Acceptance | Section squareness 90°±1°; straightness ≤1.5 mm/m; hole pitch ±0.5 mm; hole centring ±0.5 mm |
Exact web, flange and lip, the hole pattern, the lap detail and the cut lengths are frozen on the signed customer drawing before the rolls are manufactured. Section capacity design and project certification are settled by the project's own specification and testing rather than published here.
5. Buyer FAQ
Why would one machine make both C and Z instead of buying two?
Because a plant that sells both sections would otherwise carry two hosts, two sets of tooling and two changeover procedures. An interchangeable line covers both from one control panel - one section at a time, in separate C and Z runs - at the cost of a changeover each time the section changes, and that changeover time comes out of production.
What actually differs between a C and a Z purlin?
A C section has one flange each side of the web, both facing the same way. A Z section has the two flanges pointing in opposite directions, which is what lets Z purlins lap over one another end to end along a roof.
How long does the changeover really take?
A size change is 1-3 minutes from the touch screen. Switching the section from C to Z takes 5-10 minutes, with the line stopped. Neither involves dismantling a roll set.
Are the holes punched before or after forming?
Before. Three hydraulic punch dies work on the flat strip ahead of the forming stands, so the hole pattern keeps a flat datum and does not drift with the formed section.
Is 42 kW the power of this machine?
No. The main motor on this build is 18.5-22 kW. A 42 kW servo figure belongs to a different delivered configuration, and the C-only machine carries about 15 kW. Power figures should only be compared within a single quotation.
Can it run drywall stud and track as well?
No. Drywall stud and track are a different product family - far thinner strip and a different punch pattern. They are made on a different line.
How thick a strip can it run?
1.5-3.0 mm, with 2.0-2.5 mm the common working band. Confirm the grade on the inquiry.
What does the buyer have to send with the inquiry?
Whether C, Z or both; the section or drawing (web, flange, lip); thickness and grade; the hole map; the lengths sold; coil data; working voltage; and the destination port.
