A novel pseudo-tactile 3D zero indicating probe for nano metrology |
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| Albert Weckenmann, J. Hoffmann |
- Abstract:
- Today several coordinate measuring machines for the measurement of microparts have been developed, some of them are commercially available already. State of the art are axes resolutions of a few nanometers at a measuring volume of a few cm³, what can be achieved by laser interferometry or scale based length measuring systems. However, the most critical part of a conventional CMM, the usually tactile probing system, is difficult to be scaled down for the measurement of microparts. Due to the small contact area between a micro tip ball of e. g. 0.1 mm diameter and a workpiece, Hertzian stress can get significant even at very low static contact forces. Depending on approach velocity and moving mass of the probing system, dynamic reactions during deceleration of the probing element upon contact may exceed the yield stress of the probed component and cause damages. When using very small probing elements this can only be avoided by drastically reducing static and dynamic probing forces.
To achieve this, a novel 3D probing system (patent pending) was designed, which detects and measures vicinity to the work piece surface without actually touching it by the means of tunneling current measurement. Therefore a highly stabilized bias voltage is applied between a conductive work piece and a special probing element that leads to a weak, but measurable current flow if the separation between these electrodes is in the order of a few nanometers. Due to the exponential dependence of the tunneling current from separation, a radial resolution far below 1 nm could be achieved. The system has been set-up, integrated into a long range nano positioning system and tested. It is capable of conventional 2.5D STM measurements with a maximum measuring range of 25 mm x 25 mm x 5 mm, but also coordinate measurements of true 3D geometry. - Keywords:
- micro/nano-metrology; scanning tunneling microscopy; coordinate metrology; micro probing system
- Download:
- IMEKO-TC14-2007-31.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC14
- Event name:
- TC14 ISMQC 2007
- Title:
9th Symposium on Measurement and Quality Control in Manufacturing
- Place:
- Chennai/Madras, INDIA
- Time:
- 21 November 2007 - 24 November 2007