Chromatic sensors – Multipoint measurement for e-mobility

Fuel cell stacks made from bipolar plates, such as those used in motor vehicles, enable emission-free vehicle operation. Two half plates (anode and cathode) are joined together to form a bipolar plate. These are used to supply gas or liquid on the one hand and as electrodes on the other, which are used to generate electricity from the oxidation of hydrogen by means of a chemical reaction. The ScopeCheck® FB is suitable for measuring the plates.
These and the associated stamping dies are measured using a VideoCheck® HA (High Accuracy) at a renowned automotive supplier, for example.

Measurement of the tools

The production time for stamping dies is around 80 hours. In order to avoid product rejects, a 100 % inspection with tolerances between 3 µm and 10 µm is required. For this purpose, the entire tool is automatically scanned with the Werth image processing sensor in the patented Raster Scanning HD mode. By superimposing many single images taken during the movement, an overall image of the tool is created. This allows all visible two-dimensional geometrical characteristics to be evaluated very quickly.
As the wave profiles of the tools have very small radii of 0.1 mm, conventional probes are unsuitable for measurement. The patented Werth Fiber Probe® 3D with up to 20 µm small, glass sensing spheres or the non-contact measurement Chromatic Focus Point CFP can be used for highly accurate and fast measurements. Area measurements are possible with the Chromatic Focus Line CFL. The line sensor allows the entire surface of the workpiece to be captured at 10,000 points/mm2. This can be used to determine surface profile deviation, line profile deviation, embossing depth, flank angle and pitch. According to the measurement of the tool center offset, a virtual pairing of the upper and lower tool plates is possible.

Non-contact measurement of bipolar plates

Since conventional probes would lead to deformation of the thin-walled plates, the Werth Probe® or an optical distance sensor are also ideal for these measurements. The CFP 1000 offers an optimum ratio between the measuring range of around 1000 µm, the large working distance to the workpiece surface and the aperture for recording the light reflected from the surface. This enables fast scanning without moving the sensors relative to the workpiece surface with a low risk of collision. If there are too few points available on the flank despite the large aperture, the CFP can be brought into the optimum alignment for the respective flank side using the Werth tilt joint. In this way, the flow field can also be analyzed in individual sections: Line profile shape, channel depth, mold center offset and embossing angle can be measured. Deformations in the port area at the inlet and outlet openings for the gases and the sealing lips can also be measured.
The bipolar plates are uniquely identified with the CFP via data matrix code (DMC) capture and the flatness is measured. The CFP on the tilt joint can also be used to measure the offset from the welding of two half plates. In addition, the chromatic sensors enable coating thickness measurements for testing the sealing lips.