I posted last week on Volkan Alkanoglu’s sculptural installation for Cedar Rapids, IA. This week we continue with progress shots of fabrication.
After braking and indexing, the pieces were TIG welded to the backer plates which mount on the wall. The alloy used is 5052-H32 Aluminum which is known for superior ductility and weldability, and that has held true for this project.
In 5000 series Aluminums, Manganese is the second most abundant metal, imparting good ductility and workability. This contrasts with pure 1000 series aluminums, and the 4000 series, which is alloyed with Silicon. Both these series are lightweight and easily welded, but have poor mechanical properties, and will crack when bent. 2000 (copper), and 6000 (magnesium) series Aluminum is easily bent or formed, however it requires a more costly and time intensive pre and post weld processing period to achieve stable mechanical properties. 7000 series are difficult to form and require extensive post hardening, but find widespread use in aircraft components, as the Zinc alloy imparts superior mechanical properties. Each alloy is suited to a variety of tasks, but no alloy will perform all of them, and many can perform passably in more than one area.
Through the careful investigation and specification of this alloy, I was able to ensure that we would minimize the occurrence of stress fractures in these welds while maintaining an easily formable material.
Welding Aluminum, even the friendlier alloys, is a difficult, time consuming, and precise process. For comparison, 5052 Aluminum has a heat capacity of 0.21BTU/ lb - °F, while 304 Stainless Steel has a heat capacity of 0.12 BTU/ lb - °F. Aluminum also exchanges heat much more quickly, at 960 BTU-in/hr-ft²-°F, versus 112 BTU-in/hr-ft²-°F for 304 Stainless. Additionally, steel has an (essentially) unlimited working temperature, whereas Aluminum must be kept in a range of 500-900 °F. The capacity of Aluminum to hold nearly twice as much heat as Steel, while exchanging that heat nearly 800% more quickly, and the narrow working temperature, makes it one of the more difficult commonly used materials to work with. It is no surprise that aluminum extrusions, window sashes, and storefront components are rarely welded, but frequently seen with adhesive or mechanical fasteners.
Following braking, welding, and assembly, the 150 unique elements were arrayed on a full-scale print of the mounting plate layout, enabling the inspection and fine adjustment of every piece before they are sent off for paint. The smooth, uninterrupted plane along the edge of the “gems” is crucial to a correct reading of the piece, and it is during this mock-up that we checked and adjusted every element in preparation for installation.
A blog covering the various processes, methods, and pitfalls involved in designing, producing, and fabricating large scale sculptural and architectural features.