EMG SORM

The new generation of the EMG SORM® is based on the confocal chromatic measuring principle and is suitable for both roughness and waviness measurements. This method utilises the effect that lenses have different focal points for different wavelengths of light. This property enables a very accurate, fast and non-contact distance measurement that can be used to create a surface profile. Based on this, EMG SORM® calculates the roughness values defined in DIN EN 10049 as well as the waviness parameters recorded in testing sheet SEP 1941, including the arithmetic mean roughness value Ra, the peak count value RPc and the waviness value Wsa. The maximum strip speed for Ra and Wsa measurement is 350 m/min. 

Thanks to the physical principle applied, EMG SORM® provides reliable roughness and waviness data over the strip length and width and can be used for all different surface structures (EBT, EDT, LBT, SBT, PRETEX ,...) without special adaptation.

So what is behind DIN EN 10049 and the SEP 1049 testing sheet?

DIN EN 10049 is a European standard that regulates the measurement of the surface roughness of cold-rolled flat steel products. It describes various roughness parameters that are used to assess the surface quality of cold-rolled steel flat products. The most important roughness values described in the standard are listed below:

Ra - Arithmetic mean deviation: The arithmetic mean of the absolute amounts of the profile deviations within the measuring section.

Rz - Averaged roughness depth: This is the mean value of the individual roughness depths Rz1, Rz2, Rz3, Rz4, Rz5 from five consecutive individual measurement sections.

Rz1max - Maximum roughness depth: The largest single value of the roughness depth from the five individual measurement sections.

RPc - Normalised peak count: The number of profile peaks that cross an upper and a lower cutting line in relation to a length of 10 mm.

Rt - Total height of the roughness profile: The height between the highest peak and the lowest valley of the profile within the measuring section.

RSm - Mean spacing of profile elements: The arithmetic mean value of the width of the profile elements of the roughness profile within the individual measuring section.

These roughness parameters are important for assessing the surface quality. In particular, the roughness parameters Ra, RPc and Rz calculated by EMG SORM® are critical parameters for material release and material yield and are used to ensure that the surface finish meets the required specifications.

The SEP 1941 testing sheet, on the other hand, relates to the measurement and assessment of waviness parameters in cold-rolled flat steel products. It contains specific instructions and parameters for assessing the surface condition. The testing sheet defines the filtering of the raw profile in order to determine the various specified waviness parameters that are used to evaluate the surface quality. These parameters are crucial for assessing the functionality and aesthetics of the steel products. Among them:

Wsa (arithmetic mean of waviness, also known as Wa): Analogous to Ra, Wsa denotes the average deviation of the waviness profile from the centre line over a specific wavelength range. It is a measure of the general waviness of the surface.

Wca (waviness height): This is the height of the waviness, measured from the highest peak to the lowest valley within the measurement distance.

Wcm (mean waviness height): The arithmetic mean value of the waviness heights within the measurement distance.

Wsm (mean waviness distance): The arithmetic mean value of the waviness distances within the measuring section.

The SEP 1941 testing sheet is therefore also an important document for quality control and ensuring the surface quality of steel products with regard to their waviness. EMG SORM® is able to determine the waviness parameter Wsa contactless and online on the running strip, making it an indispensable tool for quality assurance of strip products.

Conclusion

EMG SORM® is a state-of-the-art measuring system based on the confocal chromatic principle and is suitable for both online roughness and online waviness measurement of surfaces. It delivers precise, fast and non-contact roughness and waviness measurements calculated in accordance with the definitions of DIN EN 10049 and the SEP 1941 testing sheet. This makes EMG SORM® an indispensable tool for quality control and ensuring the surface condition of cold-rolled flat steel products. Thanks to its versatility, it can be used for different surface structures without adjustments and ensures reliable measurements at a production speed of up to 350 m/min.