Up to date die drawings with accurate marked exposures is critical to a coating applicator.
Linetec defines an exposed surface (exposure) as the surface area indicated on a material shape that requires finish coverage. An exposed surface area, when assembled into doors, windows or other assemblies, is either viewable or in direct contact with environmental weathering.
When material is anodized, accurate exposed surfaces must be supplied even though the entire part is immersed in all the process tanks. Whenever possible, material is welded, clamped or racked on surfaces that are not exposed. Material is racked at an angle to help prevent gas-out onto exposed surfaces.
Square footage is calculated based on a parts total exterior perimeter. The square footage of a full load of anodize racked material is used to determine the time required in the anodize tanks to achieve a specific color. Inaccurate square footage can cause partial or complete job discoloration, which would require another production run and could decrease overall material thickness.
Calculation for an anodize exposure, per lineal foot, is calculated using the total perimeter of the shape. For non-extruded parts, all exterior surface dimensions are summed to determine the exterior perimeter.
Square footage is calculated by multiplying the exposure by the total lineal footage of the profile.
For hollow material, exposure and square footage calculations are based on the parts complete exterior surface. Interiors of hollow surfaces are not included in the exposure because the electrical current does not pass inside the hollow.