Precision gearboxes offer lower prices

Edited by the Engineeringtalk editorial team Nov 19, 2007

ZF's latest innovation delivers accuracy and durability that is nearly as high as the WT range, at considerably lower cost.

The right-angle worm gear box takes advantage of one of the most basic mechanical principles.

Perhaps due to this simplicity, worm gear designs are typically selected for relatively simple applications such as conveyor control, where precision requirements have traditionally been low and their compact form makes installation straightforward.

Many gearboxes for these applications are built with cost as a primary driver.

They offer acceptable performance and durability for their purpose, but limited efficiency and high, unpredictable levels of backlash preclude their use in more demanding, high-precision applications.

Automation requirements are changing, however.

Today's flexible conveying and handling systems are expected to offer much higher levels of performance.

Conveyors must operate in both directions, at high, controllable speeds and with great precision.

To deliver the right kind of control, designers have been abandoning worm gearboxes for in-line solutions with higher efficiency, less backlash and more resistance to wear.

Along the way, they have also had to make expensive compromises in space efficiency in order to fit other gearbox designs into their equipment.

Now designers can exploit an alternative option.

High-precision, right-angle servo gearboxes offer durability and very low backlash for accurate control.

Historically, such desirable properties have come at too high a cost for less demanding conveyor control applications, but new designs mean that it is possible to select the right combination of precision, durability and cost for almost any application.

For challenging roles such as robot control, machine tools and very high precision handling, the ZF - WT range uses a hypoid gearbox designed and manufactured to the highest levels of precision.

In typical applications it can offer service life of 30,000 hours and backlash as low as two arc/minutes.

ZF's latest innovation delivers accuracy and durability that is nearly as high as the WT range, at considerably lower cost.

The SWG right-angled gearbox is one of the first worm-wheel gearboxes designed specifically for high-precision servo applications.

At the core of the new SWG technology is a computer-optimised profile that delivers 90% contact between worm and wheel.

Conventional designs only offer around 40% contact.

The broader contact area minimises wear, ensuring that the gearbox has a long life and that backlash levels remain constant and predictable.

A further benefit of the design is exceptionally low noise levels in use, less than 55dB.

The wheel itself is manufactured from a specially developed, highly wear-resistant bronze alloy.

This material is demanding to machine, but is far more resistant to wear and pitting than cheaper, softer materials.

Throughout the SWG gearbox, similar design details serve to increase capacity, durability and precision.

Large-diameter bearings offer increased load bearing capacity.

The worm wheel is securely mounted to the shaft with a press fit and multiple pins - a solution that is far more durable than the conventional keyed fit.

Most appealing for designers juggling demanding cost and accuracy constraints, the SWG gearboxes are available in three levels of accuracy.

The high-precision version of the unit has backlash of less than one arc/minute, the precision box offers three arc/minutes and the standard unit limits backlash to 10 arc/minutes.

The SWG units can operate at input speeds of up to 6000rev/min and output torques of up to 6900Nm.

They are available in rations from 5.2:1 to 90:1, in ten different sizes and with four output options for maximum flexibility.

Sizes 30-800 are available with dual-output shafts, making them particularly suitable for conveyors and handling systems.

The gearboxes are housed in a space-optimised aluminium -magnesium alloy case, which makes them highly suitable for weight-critical automated assembly and packaging systems.

The many configurations available in the range mean that off the shelf solutions are available for an extremely wide range of applications, offering designers the flexibility of a custom gearbox at the cost of a standard unit.

In use, SWG gearboxes offer service lives of around 25,000 hours.

This durability, combined with the units' efficiency and quiet performance makes them suitable for retrofit applications on existing conveyor installations.