Analyzing the Surface of Steel After Spark Erosion

The decisive criteria for several applications in tool or engine construction is the strength of the material. Despite this, the harder the material, the harder its machining. Regardless, steel is most frequently used. Although it has a high strength, it is one of the most dynamic construction materials and can be indefinitely recycled.

EDT Process and Spark Erosion

Spark erosion is frequently utilized to create metal or steel surfaces with defined surface textures. This method is also known as Electro Discharge Texturing (EDM).

"As a rule, the electrically conductive workpiece to be machined (often metals) is processed in a non-conductive liquid (dielectric), usually deionized water or special oil. For this purpose, a likewise electrically conductive tool is brought into the vicinity of the material, which has a negative electrical voltage (typ. 40 to 150 V) compared to the workpiece. This leads to numerous small discharges between the tool and the workpiece. This leads to recurring sparks which primarily remove material from the workpiece."

This removal of material therefore roughens the material.

This process of roughening is utilized for the following components:

  • Cylinder surfaces in the automotive industry
  • Etching dies for minting coins or plastic surfaces
  • Structuring of the surfaces of rolls or sheet metal

Opposed to the traditional roughening process, the EDT process creates a rougher surface with a larger number of peaks. A small disadvantage is that the surface is prone to absorbing foreign particles and dirt because of the higher number of tips.

In turn, these can be removed in a cleaning process. Using light brushing with the roller brushing machine, the particles are cleaned and the roughness peaks are also lightly ground off.


Figure 1. Honing structure on a cylinder surface

Analysis of Mechanical and Functional Properties with Modern Surface Measurement Technology

Such structures are quantitatively analyzed to specify morphology, roughness, and texture of the surface by utilizing surface measuring tools. This is already required throughout the manufacturing process to ensure the intended process reliability.

By measuring the three-dimensional parameters bearing curve, roughness, and structure, the functional and mechanical features of such a structure, which is employed, for example, in deflection pulleys, can be consistently optimized throughout the production process.

The level of contamination and in turn the amount of cleaning of the used steel surfaces is also managed in this way.

Lastly, the destruction or wear of structured functional surfaces can also be measured in operation. Along with calculable wear, unforeseen damage can also harm the surface, for example when influenced by foreign materials during operation.

As such, the defects can additionally be accurately quantified by assessing the profiles, roughness and the structural heights. Among other things, important limit values for component performance can be discovered.

The MicroProf® Series

Different measuring tools and sensors from the MicroProf® series are utilized in these applications.

The choice of equipment is dependant on the requirements of the individual customer such as whether the measurement is to take place in the production line, during the process or in the laboratory. The outcomes are fully integrated into the standard documentation and is traceable within the scope of quality assurance.

The measuring tools of the MicroProf® series provides the feature of double-sided sample inspection. This enables simultaneous measurement of the top and bottom of the sample to determine the thickness of the sample.

This creates the ability to discover the total thickness variation (TTV) of the sample along with surface parameters such as the flatness and roughness of each side.

The Advantages of Optical Measurements

Another huge benefit of optical surface metrology is its efficient measuring time. Measurements can be completed with optical sensors in a few minutes, where tactile systems often need several hours. Lastly, the optical measurement is non-contact and non-harmful and can be fully and automatically integrated into production processes.

Further information can be found here.

For further comments or questions, please contact FRT, where the experts will be pleased to provide solutions to measuring tasks.

This information has been sourced, reviewed and adapted from materials provided by FRT Metrology.

For more information on this source, please visit FRT Metrology.

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