Flush rack-and-pinion drives for Item Line 8
11 February 2011
Also available in the UK from Machine Building Systems is the Item rack-and-pinion drive system, which offers a number of advantages over conventional bolt-on designs. The rack itself is unobtrusive, sitting entirely within the T-slot groove of any Line 8 aluminium extrusion, enabling compact linear slides to be constructed without an unsightly bolt-on driving mechanism. No part of the rack projects above the surface of the profile. Additionally, the groove ensures that the rack is aligned parallel to the guide mechanism without the unwanted 'snaking' that is often experienced with alternative racks.
Racks of varying length can be built up using any number of individual rack segments of 80mm length. These relatively short lengths ensure greater accuracy compared with longer lengths, where pitch errors can be significant, and they also reduce wastage. An end section is secured in place with a single dowel screw, and a spring clip secures consecutive pieces – no machining required.
The matching 18 tooth pinion is mounted via double ball-bearings in a housing which is neatly secured to the underside of the moving carriage plate. A coupling module is attached to the pinion housing and the pinion's keyed shaft engages with the coupling set contained within. The housing is adjusted to eliminate backlash before being fixed securely in position, and is machined according to how the drive motor is to be attached.
The system is designed for applications with a driving force of up to 1,000N, maximum motor torque of 23Nm and for speeds of up to 3m/s.
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