Linear drive simplifies gantry building

Edited by the Engineeringtalk editorial team Apr 7, 2006

Modular linear drive unit with integrated position sensing can simplify the building of gantry and xyz handling systems

A type of modular linear drive unit from Copley Controls with integrated position sensing can simplify the building of gantry and xyz handling systems.

Using IP67 rated industrial linear motor technology, linear stages can be bolted together in minutes to produce a rugged multi-axis configuration.

The Servotube-based linear stage consists of an off-the-shelf unit with two parts, the forcer (the coils) and the thrust rod (permanent magnets).

Because direct drive actuation is used, a gearhead, servomotor and ballscrew do not have to be aligned and integrated, saving engineering time.

Backlash between a screw and nut and gearhead teeth are avoided using tubular direct drive technology, resulting in a repeatability of 12um.

Eliminating the mechanical drive train also improves speed to 10m/s, which is more comparable to belt drives, but delivers a more dynamic response reliably and with higher accuracy.

External position encoders require precise alignment, extra wiring and mounting area, occupying valuable machine space.

By using an in-built position sensor, mechanical integration is simplified; this also allows the IP67 rated system to be used in a dirty environment such as a bottling plant or food slicing machinery.

Saving space is another benefit of tubular direct drive technology.

Machine builders may find that they have to compromise on their design to accommodate a servomotor.

For example, an xy system of 1m square could require an additional 20mm for the servomotor and gearhead.

Whether affecting the external footprint or the internal operating space of the machine, eliminating this overhead is an advantage.

Large air gaps between the forcer and the thrust rod further simplify machine integration.

Alternatively, load-bearing x and y axes can be built from pre-assembled Servotube modules that typically use a single rail linear slide for support.

The rugged aluminium extrusion has Din standard T slots so that a load can be mounted directly onto the forcer.

Similarly, a z axis actuator can be bolted perpendicularly onto a z axis for instant configuration.

The Servotube requires no lubrication and a typical configuration is non-contact so it will not wear like gearheads and ballscrews.

The only maintenance that may be required is the lubrication of any external bearings added to improve radial load handling.

In addition to traditional moving forcer configurations, it is also made in a moving rod configuration called the Servotube actuator.

Often preferred for a z axis, the moving rod actuator uses a long life polymer bearing that requires no lubrication.

Servotube systems can be operated using standard sinusoidal drives, including their own range of drives such as the Xenus drive, which is matched to Servotube operation and provides plug-and-play multi-axis operation using Canopen.