Sharp-Corner 316L RHS for the Paddington Crossrail Canopy
The Paddington Crossrail connects Paddington Station with the Elizabeth Line, one of the most significant infrastructure projects in London in a generation. The historic legacy of the location and a number of listed structures required a design approach that respected the site’s character. On top of the whole structure, a 120-metre-long glazed roof canopy called ‘A Cloud Index’ was created by New York-based artist Spencer Finch, transforming the 2,300 square metre glass roof into an enormous cloud atlas displaying 27 different cloud types. The structural sections forming the canopy grid were specified as custom sharp-corner rectangular hollow sections in stainless steel 316L, polished by the customer after delivery. Montanstahl produced 180 bars totalling 56 tonnes in fixed lengths of 5,897 to 5,899 mm using a 5-axis laser welding robot, with zero length concessions and a weld surface free of splatter or defects to support the customer’s polishing operation.
Sharp-Corner RHS for a Glass Canopy at a Listed Heritage Station
The structural grid supporting the glazed canopy called for rectangular hollow sections with precise sharp corners — a geometry that standard hot-finished RHS cannot provide because the corner radius is inherent to the tube-forming process. A laser welded RHS, built by joining precision-cut flat plate strips, delivers true 90-degree corners at each edge consistently across the full batch. For a canopy at a heritage railway station in Central London, where the exposed structure is part of an artist’s design concept and will be mirror-polished by the contractor on site, the surface quality of the sections before polishing is as important as the dimensional accuracy. Any weld splatter or surface defect on the pre-polished section translates directly into additional polishing work and potential visual inconsistency in the finished installation. Montanstahl’s laser welded stainless steel structural sections are produced with the surface quality that downstream polishing operations require.
5-Axis Laser Welding Robot, Full Penetration, Zero Splatter, Fixed Length
The flat plate strips composing the RHS section were precision cut to width and length, then assembled by tack welding before the final structural weld was applied. Full weld penetration across the section wall was achievable only using Montanstahl’s 5-axis laser welding robot, which delivers the beam control and positional precision needed to achieve consistent full-penetration welds on a complex hollow section geometry without weld splatter. The 180 bars were supplied in fixed lengths of 5,897 to 5,899 mm with zero length concessions: the canopy module dimensions were coordinated, and any length variation outside the 2 mm window would have affected the fit of the glass panels in the roof grid. The surface condition of each bar on delivery was clean, splatter-free, and ready for the customer’s downstream polishing operation.
Application Context
This project sits within Montanstahl’s Architecture, Building & Construction segment, where laser welded sharp-corner hollow sections in stainless steel are specified for glazed canopies, curtain wall structures, and architecturally exposed applications where section geometry, surface quality, and dimensional precision are all part of the design specification. The Paddington Crossrail Canopy is one of several major public transport infrastructure projects in which Montanstahl has supplied custom stainless steel structural profiles to demanding architectural and engineering specifications. Custom RHS in any required grade, dimension, and length are produced to order and supplied to architectural projects worldwide.