Products Linear motion Actuators suit hovercraft steering systems


this combination is said to allow the position of the actuators to be precisely controlled by integration with a servo amplifier, allowing full proportional control of the props in forward and reverse pitch. The servo is connected to the hydraulic ‘beta’ valve of the airscrew in the centre of the prop hub and


The MINI 0 series of linear actua- tors from R.A. Rodriguez have been selected for a hovercraft steering system designed by systems engineers Carisbrooke Engineering (IW) on the Isle of Wight. The hovercraft is now in operation in South America. Framo Morat MINI linear actua-


tors use powerful coaxial motors to enable the required stroke force to be achieved using a minimum amount of space. In this application, two 24V DC


versions of the actuators are fitted to the two-off, 3m diameter aircraft type propellers of the hovercraft. These are IP65 rated and manufactured in stainless steel, which makes them suitable for use in harsh sea conditions. Complete with potentiometers,


is working in temperatures from -30˚C to +35˚C. Additional features include


thermostatically controlled heat- ing to augment the -20˚C manufac- turers’ stated minimum operating temperature; and a stroke of ±30mm about the centre of ram gives full movement of the beta valve with plenty of power available to cope with the low temperatures encountered. The range also has a thermally


protected motor, life-time lubrica- tion and integral safety switches. Mike Edwards, systems designer


at Carisbrook, is now working on a second system that incorporates the MINI 0 for a Canadian coast- guard craft. R.A. Rodriguez T: 01462 670044 www.rarodriguez.co.uk Enter 229


Production line manufactures up to 1000 nappies each minute


At one of Ontex Mayen’s plants, 11 lines manufacture all sizes and vari- ations of babies’ nappies, with between six and eight million leaving the factory every day. Each nappy production line is approximately 60m long and produces and packs approximately 1,000 nappies per minute. The throughput time for one nappy is around two seconds. Nappies differ depending on customer requirements and raw mate-


rials, percentages or compositions are used. Each nappy, however, must be easy to change, leakproof and gentle to babies’ bottoms! Line safety and flexibility must be guaranteed for production and


packaging, and every order or size changeover results in set-up times or adjustments. There are, on average, four changes in size per week per line; and three product changes, which makes at least 30 a day. Furthermore, the lines run round the clock seven days a week and, due to the process speed of up to 600m/min, the lines are also subject to high dynamic loads. During the manufacturing process, super-


absorber and cellulose are used which result in a relatively high level of dirt and dust. Super- absorber also behaves in a similar way to sand and contamination occurs through the effects of friction. drylin linear bearings from igus play a major role


here. Lubricant- and maintenance-free, insensitive to dust and dirt, corrosion-free, durable, quiet and lightweight, they are mainly responsible for positive adjustments such as in the adhesive application points. The adhesive application head must be moved reproducibly from A to B to C according to the respective product, a process which works reliably using linear guides. Primarily, different leadscrew linear units or tables are used in a


wide range of design sizes. They are often connected with leadscrew clamps to prevent unintentional twisting, position indicators for safe


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position setting and a handwheel for manual adjustment. Right- and left-hand threaded trapezoidal nuts are also used. This, for example, means the company has been able to combine a left- and a right-hand thread on one threaded leadscrew so that it is possible to adjust two positions at the same time around a virtual centre point. There are special format setting lists for every size or product changeover. When a line is retooled, staff are informed of the respec- tive parameters. Once set-up has been completed, it is 100% correct. The igus Easy Tube system, a compact linear unit for light adjust-


ment tasks, is also used on the lines. According to the company, this has a simple, effective and robust set up – a complete system is built using only a few components. The outer anodised aluminium tube guides the carriage while protecting the trapezoidal threaded leadscrew and nut from external contamination. The slides, torque compensator and trapezoidal threaded nut are made from a high-performance polymer which is lubricant-free combined with a low friction value and very good wear properties. Furthermore, RJUM linear plain bearings of differ-


ent design sizes substitute ball bearing guides in a range of different components. They are based on highly wear-resistant polymers specially developed for linear technology, and are tough and economical. Other special equipment for the nappy manufacturer includes a 2m high material handling crane which


brings the heavy rolls of raw material to the machine. Here, hybrid bearings modified from the drylin W range, which offer a combination of sliding and rolling, have been used. The igus lubricant-free linear solutions guarantee the complete


exclusion of contamination of the nappies during the whole process. igus


T: 01604 677240 www.igus.co.uk Enter 231 JUNE 2013 Design Solutions


Linear solutions for solar tracking


Harnessing renewable energy is one of the most effective solutions for reducing carbon dioxide, comments Markus Behn, global busi- ness development manager, SKF Renewable Energy, Solar Segment. To help, the company’s Solar Linear Actuator-CASD-60, and Solar Hub CRSD 290, provide single- as well as dual-axis movement that tracks the travel of the sun as it moves across the sky. According to the company, these contribute to the reduction of


CO2 emissions by increasing the energy production from one 58m2 solar panel by 5.8MWh/year. This equates to a reduction per solution


of 4.4 tonnes CO2/year according to the world power grid mix CO2 factor of 0.749 kg CO2e/kWh. Suitable for the harsh conditions in which solar panels operate, these


IP65 solutions are said to provide highly accurate movement and are virtually maintenance-free with an expected service life of 20 years, helping customers to achieve lower levelized cost of energy (LCOE). The technologies can be used with photovoltaics, concentrated


photovoltaics or concentrating solar power systems. SKF


www.skf.com Enter 230


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