n MACHINE BUILDING to support a load, rather than line contact, they produce less friction. This means that ballscrews typically operate with an efficiency of at least 90%, plus they run cooler and produce much smoother movements. Because the recirculating balls support the load, ballscrews have a higher load capacity than leadscrews of a similar size. Ballscrews are also more versatile than leadscrews. They are available in higher accuracy grades for higher positional accuracy, and can be adjusted to increase/decrease preload. But there are some drawbacks. Obviously, cost is one, which is further increased by the need for braking mechanisms to eliminate the risk of back-driving. This occurs when the motor shuts off and the ballscrew free-falls as a result. Brakes must be fitted as a safety precaution to guard against this. They are particularly pertinent when loads are carried vertically. With balls moving within the mechanism, ballscrews are likely to be noisier than leadscrews, and also require regular lubrication to ensure the balls move freely. Furthermore, the total size of a ballscrew is larger than a comparable leadscrew due to the need for the balls to be recirculated. What to use where While a definitive answer on whether to use leadscrews or ballscrews isn’t practical – each application will have other factors and tradeoffs that may need to be taken into account – in general, leadscrews are more suitable for transfer applications for which speed, accuracy, precision and rigidity are not as critical. Most leadscrews are not well suited to high-throughput, high-speed applications or those with continuous or long cycle times. Typically, you will find leadscrews in fluid handling, data storage and life science equipment applications. Ballscrews, on the other hand, are usually used for higher precision applications where accuracy and control are critical. They are also a good option for high-load applications and where thrust force is needed to move loads smoothly, while maintaining speed. Examples of applications include 3D printers and automotive and aerospace manufacturing. A recent real-world example of ballscrews in action can be found in a CNC corner transfer machine for UPVC double-glazed windows built by Rugby-based Pernamatic Engineering. Matara supplied an XY linear system with compact linear rails and guides, and precision ballscrews. The 20mm ballscrews, machined in-house by Matara, are highly efficient and have a high load capacity at fast speeds, making them ideal for this application where each UPVC window frame has welds cleaned from it automatically in just 80 seconds. While both ballscrews and leadscrews perform the same task of converting rotational motion into linear movement, the way in which they do this and the end-result you achieve are markedly different. n +44 (0) 1923 853434 | info@pes-group.co.uk | www.pes-group.co.uk PES Group are the largest distributor of Moxa products across the UK & Ireland. This includes Ethernet Switches, Fieldbus Gateways, Remote I/O and Serial to Fieldbus Converters. The full range of Moxa products are now available from all PES Group locations. Please email info@pes-group.co.uk for any Moxa requirements. Ballscrews operate with higher high efficiencies than leadscrews and run more smoothly, but cost more and are noisier
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