What is cold bending?
Bending is a mechanical process used to deform a tube or bar to a defined radius and angle. Performed cold at Lyon Cintrage Seignobos, it is carried out using rotary draw bending machines. This process applies to all types of parts, whether round tube, square tube, rectangular tube, or solid round bar. Multiple bends can be made on the same tube, including complex shapes with several different radii.
This mastery of bending gives us expertise in manufacturing spiral heat exchangers (sometimes called “coils”), made up of a sequence of bends forming spirals, or even multi-spirals when they are nested.
Lyon Cintrage Seignobos specialises in tight radii: we master bends where the ratio between bending radius and tube diameter (R/D) ranges from 1 to 10, with most jobs between 1 and 3. This expertise enables us to produce technical parts in square-tube bending or rectangular-tube bending, even with demanding geometries.
Our workshop is equipped with around ten CNC bending machines, with a wide variety of tooling. This enables us to meet forming requests for tubes from 4 mm to 170 mm in diameter, whether it is bending round tube, bending square tube, or special shapes such as serpentine bending or spiral bending.
We bend all types of materials:
Tooling is essential in our business. A tight-radius bend requires tooling specific to the diameter and radius. Lyon Cintrage Seignobos has more than 700 tooling combinations, expanded every year for several decades.
Precision operations.
Our skilled technicians work on tube ends, prepare specific sub-assemblies, and create complex openings that cannot be produced before tube bending.
This hands-on technical know-how is part of our expertise in prototyping and small batches.
Thanks to this range of operations, we are able to produce any type of part: from the simplest elements to highly complex assemblies, always with the same commitment to precision.
The workshop carries out a wide range of operations tailored to the needs of each project:
• Trimming: straight, bevel or fishmouth cuts
• Bulging: deformation to locally increase the section
• Expanding: increasing the diameter at the end
• Coning: expanding with a conical shape
• Necking: reducing the diameter at the end
• Slits: 3 or 4 cuts to weaken the end for clamping with a collar
• Flaring: opening the end for assembly with a collar
• Crimping: maintaining mechanical strength
• Drilling and punching
• Gauging: re-forming a section near the bend to restore a circular geometry
Expertise dedicated to bent parts.
We produce tubular welded assemblies that incorporate at least one bent part—the core business of Lyon Cintrage Seignobos. This mastery covers both round-tube bending and square- or rectangular-tube bending, enabling the manufacture of technical, robust, and durable assemblies.
Each first production part is inspected using a 3D scanner, ensuring traceability and process conformity from the outset. This rigour applies to all our work: from the simplest tube bending to the most complex serpentine or spiral bending.
A response to every requirement, whether simple welds (e.g., mounting tabs) or complex sub-assemblies with tight tolerances combining machined parts, sheet metal work, and bent tubes… We support demanding projects, including parts fully rebuilt by welding when bending becomes economically unviable.
A strategic, versatile department
Welding is the department with the largest headcount. We work with all types of metals using TIG, MIG and MAG processes.
Since 2023, we have also been equipped with an aluminium welding robot, strengthening our automation capacity and consistent quality.
A team of experienced fitter-welders. Our technicians are all qualified fitter-welders, trained to meet the highest quality standards.
Custom tools to ensure compliance. We design and manufacture an in-house set of assembly and inspection jigs, updated every year to keep pace with the evolution of industrialised parts.