Each month, Stainless Solutions from IMOA covers a different stainless steel issue with tips on design and specification, and links to technical resources. This month they are discussing specification decisions that affect apparent and actual stainless steel panel flatness.
Specifying Flat Panels
There are many reasons why an installed panel may not appear flat. Achieving flatness starts with appropriate specification and fabrication. The internationally recognized materials standards (i.e. ASTM, EN and others) include flatness requirements. They can vary with the specification, thickness and product form.
For example, if you are specifying wide cold-rolled coil for panels using ASTM, A480/A480M determines the dimensional tolerance requirements and has two flatness options – standard and “Stretcher-Leveled Standard of Flatness”. Table 1 shows the flatness requirement differences. For architectural and aesthetic applications, the project specification and the fabricator’s order should require, “ASTM A480/A480M stretcher-leveled standard of flatness”. If this wording is not included, then standard flatness can be provided. Some stainless steel producers obtain stretcher-leveled quality of flatness by tension leveling coils, which is acceptable.