Inspection Conditions

General Cosmetic Acceptance Criteria

Under the above inspection conditions, CNC machined parts should meet the following general cosmetic requirements:

• No obvious dents, cracks, deformation, or other defects that affect product quality on cosmetic surfaces.

• No obvious oil stains, contamination, or foreign matter.

• Surface finish color should be genera·lly uniform, with no obvious color variation on the same part.

• Surface textures, such as bead blasting, brushing, and machining marks, should be consistent without obvious irregular patterns.

• Unless otherwise specified by the customer, burrs and sharp edges that may affect assembly or normal use shall be removed.

Measuring Instrument

Based on the product application and cosmetic requirements, PCBWay classifies CNC machined parts into Standard Cosmetic and Premium Cosmetic grades, with production and inspection carried out according to the corresponding acceptance criteria.

Standard Cosmetic and Premium Cosmetic Requirements

The following standards define the cosmetic acceptance criteria for CNC machined parts.

Additional Notes：

1. During bead blasting, high-speed abrasive particles may deform thin-wall structures. For parts requiring bead blasting, a minimum wall thickness of 1.5 mm is recommended. If this requirement cannot be met, an alternative surface finish or no bead blasting is recommended.

2. During bead blasting, abrasive particles may remain inside threaded holes and affect assembly performance. We perform a secondary cleaning process to minimize the risk of residue. For blind holes or deep-hole structures, minor residue may still remain due to limited accessibility.

3. Small or lightweight parts (typically with a side length < 5 mm, weight < 1 g, or thin-wall structures) have limited fixturing contact areas and may become detached during bead blasting or anodizing due to blasting pressure or solution agitation. Therefore, bead blasting and anodizing are generally not recommended for such parts.

4. Surface finishing processes such as bead blasting and anodizing are influenced by factors including part size, wall thickness, structural design, and thread features. To achieve the best cosmetic quality, these factors should be considered during the product design stage.

Please select the appropriate cosmetic grade when placing your order. PCBWay will manufacture and inspect your parts according to the selected cosmetic standard to ensure the delivered quality meets your expectations.

If you would like to review your parts before shipment, please leave a note when placing your order. For Premium Cosmetic orders, product photos will be provided for confirmation before shipment.

Why Are Anodizing Rack Marks Unavoidable?

The anodizing process requires electrical current to form the oxide layer and produce the desired finish. Therefore, each part must be electrically connected to a fixture during anodizing. At these contact points, the oxide layer cannot form properly due to concentrated current flow, leaving small marks known as anodizing rack marks.

Because this is an inherent characteristic of the anodizing process, rack marks cannot be completely eliminated. However, their visual impact can be minimized by optimizing fixture locations, reducing contact area, and placing contact points on hidden or non-cosmetic surfaces whenever possible.

Common Anodizing Racking Methods and Their Characteristics