Coordinate measuring machines for two-dimensional measurements

If the measuring objects are not too large or the accuracy requirements are not too high in relation to the measuring range, such parts can be measured completely "in the image". Special machines for this purpose are sometimes mobile so that they can be moved between different locations in the company as required. Telecentric lenses and high-resolution cameras (up to 16 megapixels, as of 2019) are used. Measuring ranges from a few millimetres up to approx. 250 mm with length measurement errors down to a few 0.1 µm can be achieved (Werth QuickInspect series).

If higher accuracy is required for larger measuring ranges, it is more economical to use lenses with high magnification and a small field of view. The workpieces placed on the measuring table can be automatically aligned and captured by "Raster Scanning HD" using mechanical axes. For measuring objects of different thicknesses, such machines are equipped with a focus function in the measurement software or a CNC-controlled positioning axis. If large measuring ranges of over 600 mm are required, the 3D measuring machines described can also be used in principle for 2D measurements with "Raster Scanning HD". The third measuring axis is required at least for focussing due to the varying workpiece thicknesses. However, this solution is not user-friendly and is relatively expensive. By arranging the image processing sensors under the glass plate for supporting the measuring objects, on the other hand, the measuring plane is always at the same height and the disadvantages mentioned are avoided.

The short measuring time of the 2D measuring machines described here fulfils this requirement (approx. 1 s for "in the image" measurement with QuickInspect, a few 10 s for FlatScope® with "Raster Scanning HD"). Due to the proximity to the production process, time-consuming manual programming during ongoing production is out of the question. A few sizes can simply be measured interactively.

When measuring many features, the programme must be created in advance using the CAD data. With the Werth CAD-Offline® software function, the test plans can be created in advance during the design phase (see Measuring with CAD data, p. 85 ff.). Simple operator guidance and the graphical output of the test report as a drawing with all sizes provide assistance during shopfloor measurement. Other fields of application for 2D machines include cable cuts, watch parts, punched parts and seals.