Form and roughness measurements with just one measuring system

Confovis aims aims at appropriate identification of customers' needs and employment of the most effective solutions. In addition to the confocal measuring technique, which was developed and patented as structured illumination by Confovis, focus variation is another measurement technique that is also available to customers. In the latest generation of measurement devices, Confovis also offers both measurement technologies in one measurement device. This provides the customer with the highest possible degree of flexibility and a considerable degree of added value. 

Extended 3D surface analysis by means of confocal microscopy and focus variation

Focus variation and confocal measurement technology based on the structured illumination microscopy (SIM) are not competing measurement technologies; on the contrary, they are complementary measuring technologies. With focus variation, micro geometries on tools can be measured very well because the technique can also capture structures with large acceptance angles.
However, it is often necessary to capture relevant sections on the surface with even more precision in order to determine roughness in accordance with standards, for example. This is necessary for tools, for example, to determine the chipping of the cutting edge. The confocal measurement is advantageous for roughness measurements because of its high axial resolution. Moreover, with structured illumination, even surfaces with a high degree of reflectivity can be captured.  

Wherever one measuring technology has reached its limits, the other one will take over. With this combined measurement technology, Confovis provides their customers with considerable added value.

Two measurement procedures in one measurement system

The functionality and lifetime of indexable inserts is essentially determined by the geometrical dimensions, especially the chipping of the cutting edge, and the roughness of the chipping surface. In order to measure these, reliable measurement data is captured with the optical 3D measuring technology by Confovis even for reflective and coated surfaces.

Sample: indexable insert

Determination of cutting edge parameters

  • R = 5.4 µm Radius of the cutting edge
  • ß = 67.9° Wedge angle
  • K factor = 1.08   This shows that the cutting edge has been protracted to the clearance surface.
  • Δr = 3.9 µm Distance from the point of the upper edge to the straight cutting point
  • Sα = 7.2 µm  Distance from the relief point of the clearance surface to the straight cutting point
  • Sˠ = = 7.8 µm  Distance from the relief point of the rake surface to the straight cutting point

This indexable insert was measured with the 2-in-1 scan module ConfoCam C1+. It is capable of switching between two measurement modes. This means that two measuring technologies are available in only one measuring device. The confocal measurement technology with structured illumination delivers precise resolution  — even for reflective surfaces. This is why it is used for roughness measurements and, in this case, for determining the Pt value (see below). The focus variation method is used to analyse the contour of the cutting edge. In particular, this measures surfaces with inclination angles of over 60° to 85° without any difficulty thereby allowing for evaluation of the cutting edge parameters (see above).

The chipping of the edge using high-resolution confocal measurement technology

The average profile of the profile series (25 individual profiles) depicts the chipping of the edge. (see above)
The parameter Pt can be drawn on as a measurement of chipping. >>

Measurement areas and data densities as needed

A further example demonstrates which added value the customer gets when using the high-precision confocal measurement method in combination with the focus variation predestined for steep edges.

For areas in the surface where the roughness should be measured, the confocal measurement technology  — and particularly structured illumination — is used. Here, the cutting edge was measured with a 50x0.80 NA objective lens. The high data density shows the cutting edge very distinctly as well as realistically. In this way defects of the cutting edge are made visible.

For the measurement and evaluation of steep edges, the measurements were taken with focus variation (objective lens 10x0.30 NA). Data was exported into Polyworks evaluation software. The point cloud shows the low data density. Therefore, a defect in the cutting edge is hardly visible. The measurement data, however, are sufficient for a contour measurement, that basically entails determining the angles, radii, distances.

In the global coordinate system, the measurement data of both measurment methods can be merged, and therefore also the point clouds.