Engineering a Rectangular Bellows Around the System

A marine hydrogen fuel-cell developer needed a flexible connection capable of accommodating movement and vibration within a constrained rectangular space. A conventional circular bellows would have done the job, but a rectangular design offered the potential to make better use of the available space. The challenge wasn't simply changing the shape. It was achieving the required flexibility and performance within a different geometry. The developer brought the problem to Truform, who combined more than 20 years of bellows experience with additive manufacturing to design a bespoke bellows around the application, rather than a standard shape.

Why Shape Can’t Just Be Scaled Up

A rectangular bellows offered a way to make better use of the available space, but it couldn't simply be treated as a square version of a round component. Geometry affects stiffness, wall thickness changes how it moves, and the material sets how it performs. All three change with the shape.

Truform started with the application rather than a preferred way of making it. The starting questions were what the connection had to do, and how best to produce it once that was clear

A Small Part with a Wide Influence

The customer develops hydrogen fuel-cell technology for marine applications, where packaging, reliability, and system integration all matter.

In a marine fuel-cell system, space and weight are tightly constrained, so a connection that wastes the volume around it is a real cost. A flexible connection can look like a minor part of the system, but its geometry and movement influence everything around it.

Changing the Shape Changes the Engineering

Circular metallic bellows are proven across some of the most demanding engineering. Put a circular component into a mostly rectangular space, though, and some of that space goes unused. A rectangular bellows could recover it.

Making one perform is the harder part, because changing the geometry changes how it moves, how stiff it becomes, and where the stress goes. The customer's dimensions also differed from earlier rectangular bellows work, so scaling an existing design wasn't enough. The bellows had to be engineered around this particular connection.

From a Different Shape to a Different Approach

Truform wasn’t starting from scratch. A rectangular metallic bellows had already been designed, additively manufactured and tested in earlier development work, validating the concept. The challenge was adapting that proven starting point to the customer's specific requirements.

Engineering analysis explored geometry, wall thickness, stiffness, and movement, while stainless steel laser powder bed fusion was assessed as a potential manufacturing route. That raised a bigger question, one that reached past the bellows altogether. Transitions, flanges, and other interfaces are normally made as separate parts and joined together, but additive manufacturing offers the potential to integrate them into a single component. That could eliminate selected joints, welds, and assembly steps, while reducing potential leak paths.

By then the project had stopped being about the shape of a bellows at all. The real opportunity was a flexible connection designed around the system.

The interesting part isn't whether you can 3D print a bellows. We already know you can. It's what happens when you stop assuming what the bellows has to look like in the first place. Sometimes a conventional metallic bellows will absolutely be the right answer. But sometimes the application gives us a reason to do something different.

Ian Scutt, Founder & Managing Director, Truform

A Route Forward, and a Wider Opportunity

The work established how the existing rectangular concept would need to evolve around the customer's application, and identified a credible route for taking the engineering further.

It also opened up a wider possibility. Rather than treating the bellows as an isolated component, the flexible element and the interfaces around it could be considered together, reducing separately manufactured features and allowing greater integration. That’s a very different starting point from simply asking a supplier to quote for a bellows.

Key outcomes:

A bespoke rectangular bellows design developed around the customer's application requirements
Geometry, wall thickness, stiffness and movement investigated
Stainless steel laser powder bed fusion assessed as a potential manufacturing route
A credible path identified for continued development
Opportunities identified for future integration of adjoining features, with the potential to reduce part count and potential leak paths

Letting the Application Lead

Start with the application. Geometry, material, and how a part is made should follow what the component has to do, not the other way round.

Shape is only the beginning. A rectangular bellows still has to deliver the right movement, stiffness, and performance. Changing the outline doesn’t change the physics it has to satisfy.

Look past the single part. The larger gain can come from integrating features that would otherwise be manufactured and joined on their own.

Don’t assume additive is the answer. Where established technology is the right solution, Truform can supply conventionally manufactured metallic bellows.

The Answer Doesn’t Have to Be Unusual

Truform brings more than 20 years of bellows experience together with wider manufacturing capability and innovation, from conventionally manufactured metallic bellows where they’re the right solution to additive alternatives in metal, polymer, or high-performance polymer where the application calls for something different.

If a conventional bellows is right for the application, Truform can supply it. If it isn’t, that’s where the conversation gets interesting.