Cleanliness Inspection and Analysis of Automotive Components

Effects of contamination on automotive components

Pistons in automotive engines repeatedly reciprocate with a clearance of only a few micrometres and are kept air-tight with engine oil. If a slight amount of metal contamination adheres to the side surface of a piston ring, repeated reciprocation will damage the inner wall of the cylinder liner, causing engine problems.
The importance of contamination analysis has increased with the number of automobiles equipped with high-capacity batteries, such as electric vehicles (EVs), as lithium ion batteries contaminated with metal components or other particles can generate heat, or even fire.
In addition to the complete cleaning of these components after manufacturing, cleanliness analysis in compliance with international industrial standards is also required.

International industrial standards ISO 16232 and VDA 19 for technical cleanliness inspection

Cleanliness standards were introduced in the early 2000s with VDA 19 issued in 2002 by the German Association of the Automotive Industry, followed by ISO 16232 in 2007. These standards have made measurement and composition analysis of foreign particles in compliance with quality requirements mandatory.
These standards define the management of technical cleanliness for oil and water related parts, such as tanks, pumps, valves, pipes, ducts, and casing, which are used in engines and transmissions. Particle contaminants generated in the manufacturing processes of these automotive components are removed as much as possible in the cleaning process. Hence, it is necessary to perform measurements and analyses to ensure that the technical cleanliness requirements defined in ISO 16232 and VDA 19 are satisfied.
Oil has an additional international standard for cleanliness inspection, ISO 4406, which requires the counting of particles per millimetre to define how contaminants are distributed in fluids.

Methods of cleanliness inspection and analysis

There are various methods of technical cleanliness inspection and analysis, and the following two methods are defined in ISO 16232 and VDA 19 as standard technical cleanliness analysis methods for the automotive industry.

Gravimetric method (gravimetric inspection)

This inspection is based on weight and is thus regarded as a relatively easy method, but analysis is conducted only using information related to the difference in weights.
With this inspection, it is impossible to investigate the size of each particle contaminant, the particle size distribution, and the properties of minute particles such as metals and fibres. That means you cannot obtain information useful for determining the cause of contamination or preventing its reoccurrence.

Light scattering method (light scattering analysis)

Optical microscopes are used for inspection and analysis. It is possible to determine not only the presence and volume of contamination but also the size of each particle, the particle size distribution, and the properties of particles (such as metals and fibres).
In the field of automobile manufacturing where contamination by minute particles may greatly affect the quality, performance, and safety of important safety components, technical cleanliness inspection using microscopes based on this light scattering method is most common.

Flow of extracting, measuring, and analysing contamination using the light scattering method

For technical cleanliness analysis of automotive components, inspection is not possible after assembly for components such as engines, which consist of complicated and important parts. Hence, the following procedure is used to conduct analyses for each component.

1. Wash the part (product) with a method such as pressure rinsing to extract foreign particles.
2. Filter the rinsed liquid through a membrane filter to trap foreign particles.
3. Analyse the used membrane filter as a sample using a microscope.

In measurement and analysis using microscopes, the number of particles (contaminant count), the particle sizes, and the type of foreign particles (such as metals and fibres) are measured, analysed, and compared under the same settings to prevent variation in measured values. Then, they are investigated in detail, including a determination of whether these items are risk factors in automotive components.
In ISO 16232 and VDA 19, various standards are defined, from methods to extract foreign particles to the minimum particle size for which analysis is required. For automatic measurement, they also define the pixel count and how to extract foreign particles. Furthermore, reports must be created in the format compliant with these standards.

Easy and accurate cleanliness inspection compliant with ISO 16232 and VDA

With the VHX Series 4K Digital Microscope

The VHX Series enables users to carry out cleanliness inspections compliant with the ISO 16232 and VDA 19 standards for the automotive industry. By analysing a high-resolution image with a deep depth of field taken with the 4K Digital Microscope, even targets with uneven surfaces can be measured with high accuracy.

Cleanliness inspection can be performed automatically with a few clicks. After the inspection is ran, the operator can use Detailed Analysis mode to further investigate particles and analyse their cause.

Automatic inspection settings improves results and speed

With the VHX Series 4K Digital Microscope

The VHX Series automatically reproduces imaging settings from past results, ensuring there is no variation due to inconsistent lighting, magnification, or white balance. The ability to automate the process not only educes work hours, but also eliminates different operators obtaining different values.

The high-resolution HR lens and motorised revolver enable a seamless zoom function that quickly switches lenses from 20x to 6000x magnification according to the size of contamination, eliminating the need for lens replacement. Additionally, the VHX Series automatically identifies the connected lens and records the magnification data with the captured image.
Finally, the VHX Series offers automatic calibration with just the click of a button, ensuring user results are accurate.