Part cleaning & general finishing

Published on Friday, 11. February 2005

In CNC machining, part cleaning and finishing are critical steps to ensure part quality and performance. Below are the standards and guidelines for part cleaning and general finishing:

1. Part Cleaning Standards

The purpose of part cleaning is to remove oil, cutting fluid, metal chips, and other contaminants generated during machining to ensure smooth subsequent processes (such as surface treatment or assembly).

Cleaning Methods

Cleaning Method	Application Scenarios	Cleaning Medium	Precautions
Ultrasonic Cleaning	Small precision parts, removal of tiny particles and oil	Water-based cleaners, solvents	Avoid damage to fragile parts
Spray Cleaning	Medium-sized parts, removal of surface oil and debris	Water-based cleaners, alkaline cleaners	Ensure compatibility of cleaning agents with materials
Vapor Degreasing	High-precision parts, removal of stubborn oil and grease	Solvents (e.g., trichloroethylene)	Operate in a well-ventilated environment
Manual Wiping	Large parts or localized cleaning	Non-woven cloth, alcohol, acetone	Avoid using cloths that leave fiber residues
High-Pressure Air Blowing	Removal of loose debris and dust	Compressed air	Ensure appropriate air pressure to avoid damaging parts

Cleaning Standards

Cleanliness Requirements: Determine cleanliness levels based on part usage (e.g., ISO 16232 or VDA 19 standards).
Residue Inspection: Use white cloth wiping or microscopic inspection to ensure no visible oil, particles, or residues.
Drying Requirements: Ensure thorough drying after cleaning to avoid moisture-induced corrosion.

2. General Finishing Standards

Finishing is performed to improve dimensional accuracy, surface finish, and functionality of parts.

Finishing Methods

Finishing Method	Application Scenarios	Machining Accuracy	Surface Roughness (Ra)
Precision Turning	Cylindrical or rotary parts	IT6–IT7	0.8–3.2 μm
Precision Milling	Flat surfaces, curved surfaces, or complex geometries	IT7–IT8	0.8–6.3 μm
Grinding	High-hardness materials or high-precision parts	IT5–IT6	0.1–0.8 μm
Polishing	Appearance parts or parts requiring high surface finish	-	0.025–0.4 μm
Lapping	Ultra-high-precision parts, such as optical components or precision molds	IT4–IT5	0.012–0.1 μm

Finishing Standards

Dimensional Tolerances: Based on drawing requirements, typically referencing ISO 2768 or ASME Y14.5 standards.
Surface Roughness: Select appropriate roughness levels (e.g., Ra values) based on part functionality.
Geometric Tolerances: Includes flatness, roundness, cylindricity, etc., complying with ISO 1101 or ASME Y14.5 standards.

3. Inspection After Cleaning and Finishing

After cleaning and finishing, strict quality inspections are required.

Inspection Item	Inspection Method	Standard
Cleanliness Inspection	White cloth wiping, particle counting, microscopic inspection	ISO 16232, VDA 19
Dimensional Inspection	Use calipers, micrometers, coordinate measuring machines (CMM)	ISO 2768, ASME Y14.5
Surface Roughness Inspection	Roughness tester	ISO 4287, ASME B46.1
Geometric Tolerance Inspection	Coordinate measuring machines (CMM), projectors	ISO 1101, ASME Y14.5

4. Precautions

Material Compatibility: Cleaning agents and machining fluids must be compatible with part materials to avoid corrosion or chemical reactions.
Environmental Control: Maintain a clean environment for cleaning and finishing to avoid dust and contamination.
Process Sequence: Cleaning is typically performed after finishing, but intermediate cleaning may be required in some cases (e.g., before polishing).
Tool Selection: Choose appropriate tools and parameters during finishing to ensure surface quality and accuracy.

Tagged: Cosmetic standards Surface finishing

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