Innovation Spotlight: A New Expansion Fixture
At Tummers, continuous improvement is part of our DNA. One of the latest examples is the development of a new expansion fixture for our Tubereel bundles. Designed in close cooperation between Engineering, the workshop, and graduating students, this new fixture brings greater accuracy, easier assembly, and the potential to significantly reduce production lead times.
Why a new fixture?
During the expansion process, tubes are mechanically expanded into the tube sheets and heads of a bundle. Accurate alignment is essential. Even small deviations can cause unwanted movement during processing and may lead to additional machining afterwards.
The previous setup relied on a heavy beam construction where plates had to be positioned and aligned manually using a crane. While functional, it required considerable adjustment and offered limited control over the alignment of the plates.
The new fixture was developed to solve exactly that challenge.
Designed for precision
The new fixture provides a robust and repeatable setup, making it immediately clear how components should be assembled. By controlling the alignment of the tube sheets more accurately, the bundle remains more stable throughout the expansion process.
The design also includes additional safeguards to prevent assembly errors. Special guide plates ensure that the correct holes are always selected during expansion. This helps avoid costly mistakes that could otherwise require tubes to be removed, replaced, and expanded again.
From concept to reality
The project started as an assignment for two graduating students, who delivered the initial concept. From there, the Engineering department further developed the design, working closely with the workshop team.
Together, they evaluated everything from ease of assembly and disassembly to structural strength, machining requirements, and long-term usability. Considerable attention was given to determining which surfaces needed post-weld machining and how bundles could be removed efficiently without unnecessary dismantling.
The result is a fixture that combines precision, strength, and practicality.
Reducing lead time
One of the main objectives is to eliminate the need for additional machining after expansion. Currently, expanded bundles are often sent to an external machining company for finishing operations. This adds cost and can extend the lead time of a machine by approximately one week.
Initial measurements indicate that the new fixture significantly improves accuracy compared to the previous setup. To validate the results, the expanded tube bundle is removed from the fixture, fitted with its headers and subjected to a hydrostatic pressure test. This confirms leak tightness while also allowing any residual stresses to settle.
The completed assembly is then fitted with bearings and rotated while measurements are taken at several points using a dial gauge. This process provides a clear indication of the bundle’s alignment and whether it meets the required tolerances. Early results are encouraging and demonstrate the potential of the new fixture to reduce subsequent machining operations.
Built for today and tomorrow
The fixture is currently designed for four- and six-metre bundle models, with dedicated beam lengths for each machine size. Future bundle sizes may require additional beam sets or end plates, but the modular concept provides a solid foundation for further development.
In true Tummers style, the fixture is finished in the company’s familiar anthracite and orange colours, making it instantly recognisable on the workshop floor.
Continuous improvement
Several improvements have already been implemented since the first use of the fixture, mainly focused on functionality and ease of operation. Further testing and measurements will determine the full impact on production accuracy and lead time reduction.
What is already clear, however, is that the new expansion fixture makes the work easier, faster, and more controlled. And that is exactly what continuous improvement is all about!
