Fabrication of

complex structures

Fabrication of aluminum roofs for the metro cars of a major Canadian city

In 2014, SBB was retained by a major OEM to help them fabricate the components for a light train system designed for the Canadian market. SBB had to fabricate the aluminum roofs for each of the wagons. A total of 102 roofs were part of Phase I, with another 38 in Phase II.

Mandate

These roofs are 2.5m/8 ft wide and vary in length between 10m/33 ft and 11.5m/38 ft. Each roof weighs 1300Kgs/3000 lbs and is made of several extrusions that must be machined, welded using FSW technology (Friction Stir Welding), then again using MIG and TIG technology and finally liquid-paint coated.

Specifications

All the above operations are complex because regular methods had to be adapted to the unconventional size of the roofs. For example, given the size of the components, the heat generated by regular welding methods could have an impact on the flatness of the structure.

To successfully overcome these specific challenges, SBB decided to partner with the University of Quebec in Chicoutimi (UQAC) and use Friction Stir Welding (FSW) technology. This method has the advantage of reducing heat generated by regular welding methods, therefore avoiding deformations.

Although FSW has been used in Europe for many years, it had never been used in North America so there were no existing parameters or data to help us. SBB was indeed the first company in North America to use FSW for a real production and had to generate its own parameters through many trial and errors.

Challenges

Tests and Adaptability of SBB

 

In order to successfully complete this project, SBB created a team exclusively dedicated to this project, with engineers and welding experts who worked for over a month to determine parameters such as welding speed, rotation speed, pressure, flexion and geometry of the welding tools and heads.

SBB also had to modify many of its North-American processes in order to adapt them to the customer’s European processes and standards.

Finally, in order to ensure the roofs 100% compliance with customer’s tight specifications, SBB had to conduct on a regular basis inspections such as radiographic inspection, ultrasonic inspection, magnetic particle inspection and liquid penetrant inspection.

SBB never compromised on quality and attention to detail given the importance of such values in the land transportation industry and their fit with SBB’s core values. We are very proud to say that none of the tests mentioned above failed during Phase I of the above project, that was completed by the end of 2017.