Cosmetic standards

In CNC machining, surface treatment standards are established to ensure that parts meet specific functional, aesthetic, or durability requirements. Below are some common surface treatment standards and their applications:

1. Surface Roughness Standards

Surface roughness is a critical measure of the smoothness of a part's surface, commonly represented by Ra (arithmetic mean roughness) or Rz (maximum height roughness).

Roughness Grade	Ra (μm)	Rz (μm)	Application Scenarios
N12 (Rough Machining)	25–50	100–200	Non-contact surfaces, raw material surfaces
N11	12.5–25	50–100	General non-mating surfaces
N10	6.3–12.5	25–50	General mating surfaces
N9	3.2–6.3	12.5–25	Precision mating surfaces
N8	1.6–3.2	6.3–12.5	High-precision mating surfaces
N7	0.8–1.6	3.2–6.3	High-precision bearing surfaces
N6	0.4–0.8	1.6–3.2	Optical components, precision instruments
N5	0.2–0.4	0.8–1.6	Ultra-high-precision surfaces

2. Surface Treatment Methods

Based on the material, functional requirements, and operating environment of the part, appropriate surface treatment methods are selected.

Surface Treatment Method	Standard	Application Scenarios	Remarks
Anodizing	ISO 7599, MIL-A-8625	Aluminum alloy parts, improves corrosion and wear resistance	Can be colored
Electroplating	ISO 2081, ASTM B633	Steel, copper, and other metals, improves corrosion resistance and conductivity	E.g., zinc plating, nickel plating
Electroless Nickel Plating	ISO 4527, ASTM B733	Increases hardness, wear resistance, and corrosion resistance	Suitable for complex-shaped parts
Spray Coating	ISO 12944, ASTM D638	Improves corrosion resistance and appearance	E.g., powder coating, paint spraying
Passivation	ASTM A967, QQ-P-35	Stainless steel parts, improves corrosion resistance	Removes surface free iron
Polishing	ISO 1302, ASTM B46.1	Improves surface finish and aesthetics	Suitable for appearance parts
Sandblasting	ISO 8501, SAE J444	Cleans surfaces, increases adhesion	Suitable for pre-treatment before coating

3. Surface Hardness Standards

Surface hardening treatments are commonly used to improve wear resistance and service life.

Hardening Method	Standard	Hardness Range	Application Scenarios
Carburizing and Quenching	ISO 2639, ASTM E18	55–65 HRC	High-wear parts
Nitriding	ISO 9001, ASTM E18	60–70 HRC	High-precision, high-wear parts
Surface Hardening	ISO 3754, ASTM E18	50–60 HRC	Localized wear-resistant treatment

4. Surface Coating Standards

Coating treatments are used to improve corrosion resistance, wear resistance, or special functionalities.

Coating Type	Standard	Thickness Range	Application Scenarios
DLC Coating	ISO 20523, VDI 3198	1–5 μm	High-wear, low-friction parts
TiN Coating	ISO 23223, VDI 3198	2–5 μm	Tool and mold surfaces
CrN Coating	ISO 23223, VDI 3198	2–5 μm	High-corrosion-resistant parts

5. Surface Treatment Inspection Standards

After surface treatment, inspections are conducted according to relevant standards.

Inspection Item	Standard	Inspection Method
Roughness Inspection	ISO 4287, ASME B46.1	Roughness tester
Coating Thickness Inspection	ISO 2178, ASTM B499	Magnetic thickness gauge
Hardness Inspection	ISO 6507, ASTM E18	Hardness tester
Corrosion Resistance Inspection	ISO 9227, ASTM B117	Salt spray test

Considerations

Surface treatment standards should be selected based on the part's material, function, and operating environment.
Different industries (e.g., aerospace, automotive, medical) may have specific surface treatment requirements.
Ensure the part's surface is clean and free of oil, oxidation layers, etc., before surface treatment.

If more detailed surface treatment standards or industry-specific requirements are needed, please provide additional information!

Tagged: Cosmetic standards

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