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Discover the Precision and Versatility of Grotnes’ Rotary Roll Forming Technology

Grotnes’ rotary roll forming technology is a cutting-edge cold forming process used to create precise profiles in straight-sided cylinders or rings. This technique involves rolling blanks — made from tubing, pipe or coiled and welded flat banks — between male and female dies mounted on parallel spindles. As the dies rotate, they move together at a controlled rate, gradually shaping the workpiece into the desired profile over several revolutions.

Grotnes offers three types of rotary roll formers: single end, specialty and near net shape. Each type is designed for specific applications and available in various sizes, tonnage capacities to accommodate parts with different diameters, lengths and material thicknesses.

Our roll formers are renowned for their high accuracy, repeatability and versatility, making them ideal for creating complex profiles with excellent surface quality. In this post, we’ll explore the different roll forming technology offered by Grotnes, including its applications, key features and the benefits our machines bring to customers worldwide.

Breaking Down the Roll Former

Grotnes' 10-Ton Roll Former
Grotnes' 10-Ton Roll Former

Grotnes roll formers consist of a welded steel base, front and back columns, a welded steel crown and an articulated spindle assembly. The assembly includes trunnion-type bearing housings, linkages, torque tube, spindle, spindle drive, stationary spindle assembly, adjustable screw jacks and necessary electrical and hydraulic controls.

Key Features

  • Hydrostatic Spindle Drives: Ensure equal torque distribution between upper and lower spindles.

  • Hydraulically Powered Articulated Spindle: Provides maximum machine rigidity and overload protection.

  • Trunnion-Mounted Bearing Housings: Enable optimum loading of spindle bearings and proper tool alignment.

  • Variable Infeed for Forming: Allows for a fast approach rate and slower forming speed, ensuring consistency and control.

Sequence of Operation

  1. Operator places the part on the lower tooling.

  2. Operator clears the safety light curtain.

  3. Operator initiates the cycle.

  4. The lower spindle raises, forming the part against the upper spindle.

  5. Once forming is complete, the lower spindle lowers and stops.

  6. Operator removes the formed part.

  7. The process repeats.

Additional Information

  • Tooling Change and Adjustment: Approximately 30 minutes for upper and lower tooling change and side guide roll adjustment.

  • Cycle Time Factors: Material type, tooling design, amount of forming and part size affect cycle time and require part drawings for estimation.

Roll Formers for Jet Engine Components

Aerospace Ring
Aerospace Ring

Roll forming is often used to create profiles in turbine rings made from materials such as Inconel, titanium and special alloys. Aerospace parts, including cylinders and rings, can be formed from tubing, pipe or coiled and welded blanks, and then placed a Grotnes expander or shrinker for precise diameter and roundness.

Roll Former Benefits

  • High Accuracy and Repeatability: Suitable for long production runs due to their consistent operation.

  • Quick Tool Changes: Ideal for short runs as well, thanks to easily accessible tooling that reduces tool change time.

  • Versatility: The single-end design accommodates a wide range of thicknesses, widths and diameters.

  • Tooling Efficiency: Parts with the same profile and material thickness can be formed in multiple diameters using the same tooling.

Parts with Special Profiles

Grotnes roll formers are used extensively in various industries where precision and high-quality surfaces are essential. When producing parts of different diameters with the same profile, tooling costs and setup times are minimized.

Roll Former Applications

  • Automotive Industry: Used for sizing and forming wheel rims, brake drums and exhaust components. Exhaust components are first profiled on a Grotnes roll former and then calibrated on a Grotnes expander.

  • Seal Rings and Pipe Couplings: Roll forming seal rings for valves, pipe couplings, fittings and spigot joints. Pipe couplings are formed from preformed blanks of mild steel, ensuring a smooth surface finish and precise tolerances.

Specialty Roll Former

Water Heater Combustion Chamber
Water Heater Combustion Chamber

One example of Grotnes’ specialty roll forming technology is the forming of water heater combustion chambers for both the top and bottom skirt. Each tooling set is assembled for specific combustion chamber diameters, with adjustments for material changes or fit requirements made via the expanding cylinder’s stroke. The HMI displays expansion cone settings, allowing operators to make necessary adjustments.

Features & Operation

  • Cycle Time: Approximately 8 seconds (excluding handling)

  • Tooling: Built as a complete set for each diameter, with adjustments possible through the HMI.

  • Electro-Mechanical Cylinder: Used for die expansion, with an AC motor and inverter for die rotation.

  • Independent Forming Rolls: Actuated by electro-mechanical cylinders with adjustable final stroke.

Sequence of Operation

  1. The chamber hoop is manually loaded or by an optional robot or similar mechanism.

  2. The die set expands to grip and size the chamber hoop.

  3. Sensors detect when the dies have expanded, starting the run sequence.

  4. While rotating, two forming rolls advance and form the part.

  5. The rolls retract once forming is complete.

  6. The rotation stops, and the dies retract.

  7. The finished part is removed from the machine.

Near Net Shape Roll Former

Near Net Shape (NNS) roll formers are unique in their ability to displace material both axially and radially during the cold rolling process. This method produces near net shape parts from rings with simple cross-sections, significantly reducing or eliminating the need for machining. This process is particularly beneficial for using high-value materials, when ensuring minimal waste is a must.


  • Aerospace Industry: NNS roll formers enlarge the diameter and width of rings, rolling symmetrical profiles into a ring. They process thick-walled rings into near net shape rings, minimizing or eliminating the need for further machines.


  • Material Savings: Offers substantial material savings, especially important for expensive alloys.

  • Efficiency: Saves at least 25–75% of material compared to conventional machining.

  • Enhanced Quality: Improves material hardness and grain structure.

  • Precision: Forms profiles to precise tolerances, accommodating a wide range of profiles.

How Grotnes Can Help

Grotnes is committed to providing customers with the most suitable metal-forming solutions for their manufacturing challenges. Our expert team offers comprehensive consultations, troubleshooting and training to ensure our clients achieve optimal results with our roll formers. Whether you need assistance with design, setup, maintenance or process optimization, Grotnes is here to help.

Contact us today to learn more about how we can support your manufacturing needs and help in driving your success. 

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