DIN EN ISO 21920: Surface Roughness Measurement

The DIN EN ISO 21920 is an international standard that addresses the surface texture of components. It does not define specific tolerances or surface requirements but rather establishes the methodology and terminology for surface description. For example, it determines how roughness is measured and specified, and which symbols should be used on technical drawings.

The DIN EN ISO 21920 is widely used in various industries such as mechanical engineering, electronics, and the automotive industry. It enables consistent communication regarding surface quality requirements between manufacturers, suppliers, and customers. The standard contributes to the improvement of quality and comparability of surface specifications.

Surface texture plays a crucial role in various applications, whether in the automotive industry, medical technology, or the optical industry. It affects the function, durability, and aesthetics of components and workpieces, influencing factors such as friction, sealing, adhesion, lifespan, and optical properties of a product.

Surface roughness describes the microstructures and irregularities found on a surface, which can include grooves, scratches, or unevenness. The roughness depth indicates how deep the grooves or protrusions on the surface are. DIN EN ISO 21920 specifies how these parameters should be measured and indicated.

Adhering to the surface specifications according to DIN EN ISO 21920 is of great importance to ensure that the manufactured components meet the required standards. This allows for a consistent evaluation and comparability of the surface quality of different products, facilitating quality control.

In practice, surface texture can be influenced by various factors, such as the applied manufacturing process or changes during machining. However, DIN EN ISO 21920 provides clear guidelines for measurement conditions and the indication of surface specifications to ensure a consistent assessment.

Various factors can influence the results of roughness measurement. These include the chosen measurement length, the direction of the grooves on the surface, and the method of data evaluation. Additionally, environmental conditions such as temperature, humidity, and the surface condition can affect the outcomes. It is important to consider these factors to achieve reproducible and comparable measurements.

According to DIN EN ISO 21920, the measurement length must be determined before roughness measurement. Measurement length refers to the area of the surface where the roughness is measured. It should be selected to be representative of the entire surface and cover all relevant areas. The standard also provides instructions for determining the filtering. Special care must be taken here, as different nesting indices (cut-off wavelengths, filter values) can lead to different test results.

For the individual steps of surface roughness measurement, DIN EN ISO 21920 provides guidelines to ensure a consistent and precise execution:

• Preparation: Ensure that the measuring device is calibrated and ready for use according to the manufacturer's specifications. Thoroughly clean the surface of the workpiece to remove any contaminants. Position the measuring device according to the manufacturer's instructions.
• Measurement: DIN EN ISO 21920 does not specify a particular measurement speed. However, it is important to maintain a constant and uniform measurement speed to achieve reproducible results. Perform the measurement along the defined measurement length, with individual measurements close enough to allow a reliable analysis of the roughness.
• Evaluation: Use appropriate software or evaluation methods to filter and analyze the measurement data. Also, consider the specified symbols and signs according to the standard to ensure a consistent and comprehensible representation. The indication of the groove direction, if relevant, should also be made according to the standard's specifications.

This standard plays a significant role in metrology and quality assurance. It enables consistent communication about the required surface quality and improves the quality of components. The DIN EN ISO 21920 provides clear guidelines for describing and evaluating the surface texture of components. It defines key parameters such as roughness and establishes methods for measuring and specifying surface characteristics.

Standardized measurement conditions are essential for achieving reliable results. Determining the measurement length and individual measurement length, and considering manufacturing processes and machining allowances, are crucial for surface quality and are therefore also part of DIN EN ISO 21920.

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