Gunning for perfection

Automated motor and drive systems are fast becoming the norm for a host of applications, from Arsenal’s under-pitch aeration system to super-cranes. Colin Carter reports.

It is widely accepted that more automated plant is fast becoming an economic necessity in today’s cut-throat global manufacturing environment. This applies to discrete manufacturing as well as the process industries.

But it is not just traditional engineering-type applications that exploit automated motor and drive systems — even going to watch your favourite football team is enhanced by the application of drives.

At Arsenal’s Emirates Stadium, for example, the turf is kept in tip-top condition by an automatic, and complex, under-pitch aeration system that helps to drain the soil and promote the healthy turf which has the advantage of keeping the ball on the ground.

The system uses a fan driven by an ABB industrial drive to feed air to or from a pipework system, which can extract moisture from a ‘permeable bed’ consisting of sand and gravel upon which the turf sits.

This works in two directions. In the forward direction it blows air into the gravel bed and into the root zone of the grass. In the reverse direction the system can be used to provide drainage from the root zone and pull moisture away from the playing surface, meaning that play is possible even after heavy rain.

The fan itself sits in a plant room and is powered by a large ABB motor and a 160kW ABB low harmonic drive. This low harmonic specification is necessary to minimise interference with TV filming and transmission equipment used at all matches at the ground.

Even the once-simple crane — whatever the size and capacity — is now automatically controlled. For example the world’s second largest overhead crane, used to transport molten steel at speeds of up to 8m/min at the Usiminas steel plant in Brazil, is a fully-automated device.

WEG Electric Motors has supplied a complete system including transformers, motors and frequency inverters for the control of the crane, which has a 260-tonne lifting capacity on its main hook, augmented by a 40-tonne capacity auxiliary hook for moving the molten metal. The crane itself is controlled by a Programmable Logic Controller (PLC) and digital frequency inverters all connected over a Profibus-DP network.

Also in the field of materials processing, the Italian plastics machinery builder, Ghioldi, will be running its next-generation direct drive plastic extruders using Parker torque motors. These direct drive motors are designed to replace gearbox-based systems on extruder systems rated at up to 320kW.

In addition to lower maintenance costs as a result of removing gearboxes from the system, the motors have the advantage of being low on vibration and noise, which helps with product consistency in plastics production.

Equipment that has to transmit large loads can also be specially manufactured to withstand extremes. For example Renold Gears has produced 25-tonne gearboxes, the heaviest produced in the company’s history, for use in steel mills in Asia.

These gearboxes feature a huge tooth thickness and can withstand in excess of 530,000Nm of static torque. They are destined to be used as part of an existing steel mill fitted to the main drives of a screw-down mechanism used to re-form steel billets into smaller section pieces.

The units, powered by 220kW motors, press the steel into the required widths using a worm gear design with a reduction ratio of 25.1:1 — hence the huge torques and the need for these super-size gearboxes.

The automated movement of parts around its plant was behind the recent announcement that DaimlerChrysler has ordered more than 800 drives from Control Techniques for use at its Sprinter van production facility in Ludwigsfelde, Germany.

The AC drives (the company has specified Unidrive SP drives for all applications over 1.1kW) are used for tasks such as the control of conveyor belts, scissor lifts, automated guided transport vehicles and advanced storage systems, as well as factory units for ventilation and air extraction through three main areas of the plant — body shop, paint shop and final assembly.

More than 200 drives are used in the body shop to move body shells and parts around or to position pieces in automatic welding cells. Some of the units communicate over ProfibusDP or CANOpen bus — a historical favourite of the automotive industry — especially for precision positioning.

In the paint shop more than 200 drives (rated up to 110kW) are employed for ventilation and extraction, blowers and pumps being controlled over an Interbus network by an array of PLCs. For the cathodic electro-dip coating plant the precise movement of the body shells, both through the dip and rotating within it, is controlled by drives connected together over a Profibus network.

Finally another 400 or so Unidrive SP drives are used in the final assembly area for moving the bodies around the plant, carrying parts such as the complete power transmission systems for the Sprinter to the plant floor via automated guided transport vehicles, and to power scissor lifts in the plant.

So whether these large drive and motor systems are used to move molten metal or car parts in manufacturing environments, or to improve our leisure by helping sports arenas become more hi-tech, they are increasingly touching our lives in every way.