Blum: Combining digital and analogue

Until now, commercially available touch probes have relayed a digital signal to the machine control. In Blum touch probes this is generated via a state-of-the-art, rotationally symmetrical measuring mechanism and the shadowing of a miniature light barrier. As soon as the machine control detects this switch signal, it reads off the position of the axes and from this calculates the position of the measured point in the machining area.
Following consultation with customers, Blum has now refined the current technology. The idea is simple yet brilliant: if you can measure the start of the shadowing of the light barrier, it must also be possible to analyse the percentage increase in the shadowing which occurs when the stylus is deflected ever further. This enables an analogue signal to be generated that greatly extends the range of application of touch probes in the machining centre and can also save a great deal of time. When mechanically connected, the TC76-DIGILOG touch probe is compatible with typical 25 mm touch probes with an M16x1 fastening screw thread – and, of course, digital measurement continues to be possible without restriction.

Analogue measurement always offers advantages when surfaces or lines are being assessed, for example when a workpiece surface has to be checked for machining errors. When a switching digital probe is used, in such a case a very large number of points has to be measured to achieve an adequate resolution, whereas an analogue probe can be moved in ‘scanning’ mode over the surface and records more points in a fraction of the time. Astonishing speeds are reached; up to 2 m/min are possible with outstanding accuracy.

It’s not just Blum’s specialists who regard the ability to use a touch probe on the machining centre in switch mode, i.e. measuring digitally and now also in analogue mode, as a revolutionary step. Coining the ‘technical sounding’ word ‘digilog’ for this combination of technologies therefore seemed natural. The additional costs compared with a purely digital touch probe are also limited and Blum-Novotest is even contemplating retrofitting analogue capability in its other digital touch probe models; a cable-free model that can simply be
exchanged from the tool magazine is due to come onto the market soon.
Practical examples of the use of the TC76-DIGILOG involve the measurement of very large gear wheels, which previously were only tested randomly but are now tested fully for quality. Or the inspection of valve seats in car cylinder heads, in which annular beads with a height of a few micrometers were previously detected only at a later stage, but today the profile of each valve seat is shut down immediately after the reaming process using the digilog touch probe.