Rachael Morling visits Mönninghoff, a Techdrives manufacturing partner based in Germany, to find out about its latest mechanical components
I have covered products and applications from Lenze and its Techdrives division frequently over the years, so when I had a call inviting me to visit one of Techdrives’ manufacturing partners in Germany I jumped at the chance.
So, at the end of January, with a small group of editor’s, I flew into Düsseldorf airport before making the short journey to the very cold, snowy, Bochum where Mönninghoff is situated.
A friendly, accommodating company, Mönninghoff was founded in 1916 to provide robust and reliable drive technology for the mining industry in the region. Since then, and with the gradual decline in the mining industry, the company has grown to become a developer and manufacturer of mechanical drive technology, producing such products as clutches and brakes, couplings, torque limiters and voice coil actuators, for a wide range of industries. Hence the link with Techdrives, which sells components for machine building to the UK and Ireland.
Products manufactured by the company are now part of a wide range of machinery. Examples include printing machines, textile machinery such as spinning machines, machine tools like drilling and milling machines, and those found within the food industry, such as baking and chocolate production machinery. Its components, however, can also be found in special purpose machines and in the aerospace industry. In fact the company is currently working on a component to drive aircraft landing gear directly, rather than via the engines, which could offer big energy saving benefits.
As well as manufacturing products, the company has a well equipped testing facility at the site – with 70-80% of products customised, it is essential everything is tested here to ensure quality and reliability.
Among the many products manufactured by Mönninghoff, and available in the UK from Techdrives, is a new bi-stable electromagnetic tooth clutch. The M1, which will be launched at the Hannover Fair in April, is engaged by applying a pulse of DC current and will only disengage when a second pulse of current is applied. Not only does this therefore save energy as an engaged clutch requires no applied current – a benefit for machinery powered by batteries – but it offers increased safety. In fact the product meets the EU directive 2006/42/EG clause 1.2.6 which refers to machinery where the drive must not disengage in case of a power failure. The M1 clutch cannot be released until a further pulse of DC current is applied.
There is a range of four sizes that suits torque from 50 to 500Nm and shaft diameters 20 to 50mm. Clutch engagement can be made statically or at low speeds with disengagement possible at any speed.
Another new product is the Hexaflex BlueLine shaft coupling which is designed to fit between the diesel engine gearbox and the propeller shaft
on boats, leisure craft, yachts and ships. The coupling is designed to accept the misalignment and vibrations along with any thrust from the propeller to give a drive that is both smooth and quiet.
It consists of an input adaptor dimensioned to fit the gearbox flange, a flexible disc and a hub for the propeller shaft, together with bolt fixings. All metal parts are stainless or corrosion treated. According to the company, the construction of the rubber flexible disc is important – the torque is not transmitted through the synthetic rubber alone, it is safely transmitted through a special arrangement of looped fibres located below the surface and giving a safety factor of ten. The strength of the flexible disc allows perfect centering of the drive even at high speeds and maximum misalignment.
The output hub connecting to the propeller shaft has a split clamp design that makes it easy to assemble and dismantle the coupling.
The corrosion-protected BlueLine is torsionally soft to dampen diesel vibrations and accept the misalignment from flexible engine mountings. Six sizes are available to fit most common engine gearbox configurations.
The 450 series of pole face clutches, meanwhile, covers torques from 400 to 2000Nm and has a ‘double flux crossed’ design. These are engaged by applying a DC voltage to a stationary coil which generates magnetic flux which travels into the rotor, a rotating plate that forms one of the two friction surfaces. The flux then crosses an air gap and pulls another plate, the armature, into contact with the rotor generating the torque by friction. The clutch is designed so that the magnetic flux crosses the air gap twice, which doubles the attractive force, increases the torque and leads to compact dimensions. In addition, the friction is achieved through steel-to-steel rubbing surfaces without friction material. This makes the clutches unaffected by minor contamination of oil or water.
These are suitable for mobile applications, particularly power-take-offs from diesel engines.
Mönninghoff is also introducing two moving coil actuators (or voice coil actuators) with a different internal structure to give alternative force/stroke characteristics. The single coil actuators in four sizes deliver lower forces up to 40N with strokes up to 50mm. The double coil actuators gives 30% higher forces at the same strokes as a result of higher flux concentrations. In both cases rated forces can be exceeded by a large factor with intermittent duty.
Moving coil actuators are generally integrated into machine designs with a position feedback device, linear amplifier and motion controller. They feature integral guidance of the moving coil assembly by low-friction plain bearings. Alternatively, customers can supply external support and bearings which can be connected to the end of the coil assembly or the guide pin. If the actuators act against a spring with a rising linear characteristic, they can be operated in open loop control with current as the control variable.
The combination of precise control with very fast operation gives advantages for machinery such as focussing of lasers and lenses, laser cutting, cameras, vibrating tables, medical machinery and micro-assembly, explains the company.
The above are just a few examples of new products from Mönninghoff. More information on these and other solutions is available from Techdrives.
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