A roll forming machine is an industrial machine used to bend metal strips into different structural shapes. The roll forming process uses a series of consecutive pairs of rollers to gradually shape the material into the desired cross-section profile. Roll forming is an efficient and cost-effective way to produce consistent, high-quality metal parts with custom profiles at a high production rate.
How does a roll forming machine work?
A standard roll forming machine consists of a unwinder, a straightener, a series of rolling stations, and a cutoff station. The basic operating principle is quite simple:
- Sheet metal coils are loaded onto an unwinder which feeds the material into the roll forming machine.
- The strip passes through a straightening mechanism to remove coil curvature and align the strip.
- The straightened strip moves through consecutive sets of contoured rolls that gradually shape the material by bending it incrementally as it passes through each rolling station.
- Finishing operations like punching, cutting or hole placing can be added between stations.
- The fully formed profile is cut to length at the cutoff station.
The rolling stations apply pressure on the strip to incrementally form the material to the desired profile shape. The rolls operate at the same speed to grip and gradually bend the metal strip as it passes through. By controlling the roll contour design, material thickness, feed rate, and spacing between stations, roll formers can produce parts with precise dimensional accuracy and structural integrity.
What are the benefits of roll forming?
Here are some of the main advantages of the roll forming process:
- High production rates – Roll forming is a continuous production process that can operate at speeds over 100 feet per minute.
- Consistency – Roll formed parts have a high degree of dimensional accuracy and repeatability along the length of each profile.
- Material savings – No material is wasted in the roll forming process. Unformed material can easily be recoiled and reused if needed.
- Flexibility – Roll form designs can be easily adapted to produce different custom profiles by changing the roll tooling.
- Strength – The incremental bending action work hardens the metal, resulting in high strength parts.
- Cost-effectiveness – Roll forming requires lower equipment investment than other metal forming processes like stamping or extrusion.
- Simple operation – Roll forming systems are easy to set-up, operate, and maintain with proper training.
What materials can be roll formed?
Roll forming is primarily used to form various types of steel into structural profiles, but other ductile metals can also be roll formed including:
- Aluminum
- Copper
- Brass
- Stainless steel
- Nickel alloys
- Titanium
The primary requirements are that the material is malleable enough for cold working and can withstand the bending stresses without cracking. The maximum material thickness that can be roll formed depends on the material strength, typically ranging from 16 gauge (.060″) for softer metals up to about 3/8″ thickness for steel and stainless steel.
What products can be made by roll forming?
Roll forming is used to mass produce metal parts and profiles for a wide range of industries. Here are some of the most common roll formed products:
- Roofing and siding – Metal panels, standing seam roofs, roof drainage components
- Framing and trusses – Studs, joists, metal framing components
- Automotive – Body panels, bumpers, wheel rims
- Appliances – Washing machine tubs, refrigerator liners
- Shelving – Supermarket gondolas, storage racks, metal shelving
- Furniture – Metal desks, filing cabinets, tables
- Transportation – Train cars, truck trailer panels
- Construction – Metal studs, roofing, drainage, siding
- Infrastructure – Guardrails, lighting poles, traffic sign posts
- HVAC – Air conditioning ducts, tubing
Essentially any long metal parts with constant cross sections can be economically mass produced by roll forming.
What are the different types of roll forming machines?
There are two main categories of roll forming machine designs:
In-line roll formers
- Sheet coils are fed in one end, formed parts come out the other end
- Production rates from 10 to over 500 feet per minute
- Fixed forming stations for continuous production
- Require roll tooling specific to each profile
- Offer the highest throughput for long production runs
Roll forming mills
- Forming elements are contained in a mill housing
- Strip is fed in increments through the mill
- More flexible for short runs and custom profiles
- Slower production rates than in-line machines
- Easier to changeover between different configurations
In addition, there are some other variations of roll forming equipment:
- Portable roll formers – Compact mills used for on-site forming of siding, panels, roofing
- Wheel machines – Rotary style roll formers for HIGH volume roofing and siding applications
- Extruder/roll formers – Combines profile extrusion and roll forming in one machine
- Press roll formers – Use mating male/female dies instead of rolls to form parts
What are the steps in the roll forming process?
A complete production roll forming process generally involves the following steps:
- Design – The desired profile shape and dimensions are modeled using CAD software. The number of rolling stations required is calculated.
- Roll tooling – Rolls are CNC machined in progressive sets to incrementally form the profile. Backup rolls support the forming rolls.
- Setup – Roll tooling is installed on the rolling stations. Forming stations are aligned, leveled and spaced properly.
- Trial runs – Initial trial runs help calibrate the process for the optimal feed rate and roll adjustment settings.
- Production – Coiled sheet is processed through the roll former at speeds typically between 50-200 feet/minute. Real-time adjustments are made as necessary.
- Secondary operations – Additional operations like cut off, hole punching or notching can be added between or after forming stations.
- Inspection – Dimensional checks and quality control procedures ensure the roll formed parts meet specifications.
- Material handling – Formed sections are typically stacked for shipping to customers or transferred to additional fabrication or assembly processes.
What are some examples of roll formed profiles?
Here are some common structural shapes and profiles that are frequently manufactured using roll forming techniques:
| Profile Name | Cross Section Shape | Typical Uses |
|---|---|---|
| Cee channel | C-shaped | Framing, studs, furring |
| Zed section | Z-shaped | Purlins, girts, fascia |
| Sigma section | Σ-shaped | Roofing, cladding, siding |
| Hat channel | Squared U-shaped | Framing, floor joists, roof trusses |
| Angle | L-shaped | Shelving, bracing, supports |
| Tube/pipe | Circular or rectangular | Fencing, handrails, tent poles |
These profiles provide strength and rigidity from their particular shapes. Changing dimensions like wall thickness, flange widths, and section depth allows the profiles to be adapted for specific loading requirements.
What types of rolls are used?
The main roll types used in roll forming machines include:
- Forming rolls – Shaped rolls that bend the material to the contour of the profile
- Sizing rolls – Refine the shape and control tolerance
- Finishing rolls – Apply final shape correction and surface finish
- Backup rolls – Support the thin strip opposite the forming rolls
- Idler rolls – Guide and support the strip between forming stands
- Feed rolls – Pull the material through the roll former
The rolls are typically machined from hardened steel to withstand the rolling forces without deformation. Back-up rolls may also use various polymers or elastomers to provide better support on thin strips. Roll selection and design is critical to producing quality roll formed parts efficiently.
How are rolls designed for a profile?
An iterative process is generally followed when designing the roll set for a new profile:
- The final profile shape is modeled in 3D CAD and analyzed using FEA.
- An initial roll set is designed based on past experience and estimation.
- Prototyping and trial runs help determine the minimum number of stands needed.
- The roll contours are refined and modified based on measured part geometry until the profile dimensions are achieved.
- More rolls may be added to prevent defects like buckling, cracking or springback.
- The process settings like feed rate and roll adjustment are optimized for the best throughput and yield.
Powerful roll design software programs are available which automate much of the FEA and roll contouring using the input profile shape. However, experienced engineering judgement is still required to account for the complex deformation mechanics in roll forming.
What defects can occur in roll formed parts?
Some potential defects that can arise in roll formed parts include:
- Flaring – Edges spread outward due to excessive deformation.
- Twisting – Non-uniform deformation causes distortion.
- Cracking – Localized strain from bending causes cracks.
- Folding – Strip bends excessively between rolls.
- Springback – Elastic recovery causes shape changes after forming.
- Surface damage – Rolls can scratch or mark the strip surface.
- Thickness variations – Inconsistent roll gaps cause thickness changes.
Defects are minimized through proper roll design, precision machining, ongoing monitoring, and corrective actions during the production run. The roll forming process can be fine-tuned to eliminate defects and consistently produce high quality profiles.
What machinery is used in a roll forming line?
A complete roll forming production line includes equipment for:
- Handling – Coil cars, uncoilers, decoilers, stackers
- Feeding – Feed tables, roll feeds, servo drives
- Straightening – Levelers, roller straighteners
- Forming – Roll forming mill or stands
- Finishing – Cutoffs, punching, notching, tapping
- Automation – PLC controls, sensors, software
The strip accumulates velocity through the process so all the components must be properly aligned and controlled. The latest roll forming lines are highly automated for precision control and monitoring.
How much does a roll forming machine cost?
The cost of a roll forming machine varies considerably depending on the size, production rate, and level of automation. Here are some rough cost estimates:
- Small portable roll former – $50,000 to $150,000
- Standard 10-50 station in-line roll former – $150,000 to $500,000
- High production over 50 stations – $500,000 to $2,000,000+
- Additional finishing equipment – $50,000 to $500,000
Total installed cost including building, foundations, and site preparation can range from under $200,000 for simple machines up to $5 million or more for very large high volume lines.
Who are the top roll forming machine manufacturers?
Some of the leading global suppliers of roll forming equipment include:
- Samco Machinery (USA)
- Bradbury Group (UK)
- Formtek (USA)
- Metform (USA)
- Dimeco (USA)
- Joubert (South Africa)
- Gasparini (Italy)
- Botou Xianfa (China)
- Howick Ltd. (UK)
- Shreejee (India)
Many manufactures offer standard roll former models as well as highly customized machines designed for specific applications. It’s recommended to evaluate multiple suppliers to find the right balance of cost, production rate, and capabilities.
Conclusion
Roll forming provides a continuous, efficient method for producing lengths of custom metal profiles. The incremental bending action of contoured rollers can form a wide variety of structural shapes with good accuracy and repeatability. Roll formed components are used in many industries to reduce material and manufacturing costs while maintaining high strength and reliable performance. With proper machine selection and setup, roll forming is an economical way for manufacturers to convert flat strip steel into finished parts with custom cross-section geometries.