MATERIAL RACKING OPTIONS

Racking is a critical step in the paint process, as it assures good coverage to the exposed areas of the parts. All material processed through the paint line requires some method of racking. Whenever possible, marks left from racking will be in unexposed areas – identification of where your aluminum parts can be racked must be noted on prints.

Always let the applicator know if touch-up of rack marks are acceptable when it is required to rack on an exposed surface. A one half inch border is required for racking of flat sheets. Clipping or hole punch are other options for racking of sheet material. The half inch border must be along the long side of the sheet when the dimension is greater than five feet.

PRINTS & EXPOSURES

Linetec does not intentionally inspect customer material for flaws in metal or workmanship. It is the responsibility of the customer to control and approve manufacturing tolerance on their material.

Linetec will notify the customer of any obvious visible damage to bundles, skids or boxes that may be related to transfer or freight process.

If questionable damage is identified during processing, the customer will be notified as soon as possible. It is the responsibility of Linetec personnel to determine if the material should continue in the process or be held for customer determination.

square footage

Square footage, in most cases, is calculated based on a parts indicated exposed surface.

calculation of a painted exposure

Calculation of a painted exposure, per lineal foot, is calculated using the exposed surfaces indicated on the print.

Exposed surface calculation may vary depending on the type of exposure, such as a single adjacent exposure on one profile or multiple non-adjacent exposures on the same profile. Exposed surface calculation may also vary depending on the material profile or type. Exposure calculations are subject to established minimums.

Primary exposure

Primary Exposure is the exposed exterior and interior surface that must withstand the effects of the environment and normal use and wear. The primary surface must comply with all applicable AAMA specifications.

secondary exposure

Secondary Exposure is the semi-exposed areas requiring paint coverage, but which are not exposed to the direct effects of the environment or use and wear; this would include recessed channels and tracks. Semi-exposed or secondary exposures, requiring paint coverage do not have to be in compliance of the AAMA specification. Minor blemishes such as runs and bubbles may be present and will not be rejected or touched up. Rack marks may be evident in secondary exposure areas and will not be touched up.

faraday cage effect

Faraday cage effect is the electrostatic force that prevents charged particles from penetrating into recessed areas.

Charged paint particles are attracted to the closest grounded surface, as shown. Limitations due to an electrostatic painting system might make it impossible to achieve minimum recommended dry film thickness on all areas of an extrusion. Areas subject to the faraday cage effect are inside corners and recessed areas such as channels and cavities.

The following criterion defines Linetec’s acceptable quality level resulting from faraday cage effect.

• If recess depth is from 50 – 100% of the width, there will be color coverage within the recess, but less than the specified dry film thickness.
• If recess depth is from 100 – 200% of the width paint will be present, but the substrate may show through in some areas. The deeper the recess, the lighter the coverage will be within the recess. The substrate exposure will be less noticeable on pastel and light colors, and most noticeable on dark colors.
• Recess depths greater than 200% of the width may not have any paint coverage at the bottom of the recess.