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Grotnes Expander/Roll Former Crafts Combustion Chambers for Water Heaters

Updated: Mar 28

The process of shaping combustion chambers for water heaters is intricate and demands high precision. Traditional methods often encounter issues with sizing accuracy, forming uniformity and operational efficiency.


Grotnes’ solution to these challenges is the advanced expander/roll former. The equipment is designed to accurately size the combustion chamber and form the upper and lower skirt regions. The essence of the system lies in its upward-extending forming head or tooling, which emerges from the machine’s working table to size the chamber’s entire width.

Grotnes Expander/Roll Former

Precision is at the heart of this tooling, which is crafted as a complete, pre-assembled set for each specific combustion chamber diameter. Flexibility is built into the system, as the expander/roll former accommodates adjustments in the chamber diameter if alterations in material or fit are necessary. The machine’s intelligent Human-Machine Interface displays cone expansion settings and enables the operator to tailor adjustments seamlessly.


Die expansion is executed through an electro-mechanical cylinder, while die rotation is powered by an AC motor. This motor utilizes an inverter for speed control, ensuring a smooth start and stop for the die set. Coupled with encoder feedback, the inverter precisely halts the die in alignment with any part load.


The machine boasts two independently activated forming rolls, each maneuvered by its elecro-mechanical cylinder. Their final stoke is adjustable, delivering just the right amount of travel for optimal forming and part removal clearance. Remarkably, the entire cycle time per machine is about 8 seconds, excluding handling; this rapid pace includes die expansion, rotation and retraction.

Sequence of Operation

The equipment operates in a synchronized sequence:


1.     An operator or optional  robot loads the chamber hoop.

2.     The die set expands to grip and size the hoop, initiating the forming sequence.

3.     Upon die expansion, sensors trigger the rotation of the die set.

4.     During rotation, two forming rolls progress to shape the part.

5.     Post-formation, the rolls and dies retract, and the part is ready for removal.

Changeover Simplicity

When it’s time to transition to a different part diameter or tooling height, Grotnes’ equipment is designed for minimal interference. Operators can easily access and manually switch over in approximately 8 minutes, streamlining the process without sacrificing productivity.

Comprehensive Customer Guidance

At Grotnes, the relationship with customers transcends mere transactions. Our team of experts offers thorough consultation services, guiding potential customers through the selection of the most suitable metal-forming solutions tailored to their distinct needs.


With a commitment to service and deep understanding of metal forming after more than 125 years of operation, Grotnes ensures each customer not only receives industry-leading equipment but also gains a long-term partner in manufacturing success. From prototyping to finished machine and ongoing support, Grotnes is your guide.


Connect with us today to learn more about our comprehensive line of metal-forming solutions!

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