WCA May 2009

systems

Drive nuts for measuring machines When developing its drive nut, Uhing conceived a non-positive linear feed element that is successful as a drive element in measuring machines. “The secret is its lack of play, a feature that is fundamentally inherent to the construction of the drive nut,” explains Uhing’s head of marketing, Wolfgang Weber. Drive nuts have three or four rolling rings being alternately pushed against the surface of a plain shaft by spring force. These rings connect to the shaft by friction.

Test system for titanium rod

Magnetic Analysis Corporation, a designer and manufacturer of nondestructive test systems for over 80 years, recently supplied a multi-test eddy current/ultrasonic system to inspect small diameter titanium bars and rods (2.54mm to 31.75mm). Testing criteria was AMS-2631B, Class AA for the ultrasonic test (aerospace specifications) and typical eddy current inspection standards for the eddy current test. By combining eddy current and ultrasonic technology in a comprehensive inspection sys- tem, superior test results can be obtained as each technique is used to detect the conditions that it is best suited to find. This particular system incorporates Echomac ® FD-4 ultrasonic instru- mentation, an Echomac Rotary which spins the transducers and water couplant around the bar, and a MultiMac eddy current instrument and test coil. The UT test uses one normal incidence and two shear wave transducers to inspect for surface and near-surface defects such as seams, spiral seams and light cracks as well as inclusions and deep voids. The eddy current single channel test complements the UT test by detecting some very small surface seams or pitting that are poor reflectors of sound. The test system also includes air operated dual pinch stands designed to drive and position the test material accurately, a slide and elevate platform to adjust the UT Rotary, a water recirculation system for the couplant, and automatic markers. The system is mounted on a welded test bench and ‘learn controls’ are included to automatically adjust the timing based on the initial test piece. Magnetic Analysis Corp – USA Fax : +1 914 699 9837 Email : contactus@mac-ndt.com Website : www.mac-ndt.com

Uhing drive nuts for measuring machines ❍ ❍

Skewing the rolling rings results in their rolling off on the surface of the rotating shaft at their pitch angle, thus generating a linear movement. This results in drive nut and shaft acting like a nut and threaded spindle, but without threads. The spring force required to produce the frictional connection automatically reduces the theoretically existing play to zero, so there is no detrimental effect. The drive nut instantly translates the smallest back and forth rotation of the shaft into a movement to the left or right because there is no system-inherent play to overcome. The pitch of the drive nut varies in relation to the actual shaft diameter, which is never constant over the entire stroke because the feed distance per shaft revolution depends on the shaft diameter and the pitch angle of the rolling rings. This is why there is no innate accuracy. For this reason, the actual position of the drive nut must be monitored with a precise length scale in a measuring machine, which is standard equipment in such machines. “A release option, operated manually or pneumatically, is an additional advantage for tool adjustment devices,” advises Wolfgang Weber. “Once the drive nut has been uncoupled from the shaft, literally meaning the shaft has been released, the tool or measuring instrument is quickly moved by hand. This prevents damage to delicate components during test sample exchange, and measuring as such is speeded up.”

The Uhing drive nut is quiet when running and requires little maintenance.

Joachim Uhing KG GmbH – Germany Fax : +49 4347 90640 Email : info@uhing.com Website : www.uhing.com

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Wire & Cable ASIA – May/June 2009