Polyflex belt on a grinder.
Belt drives: offering alternatives for machine tools
David Clark explores the advances that belt drives present to users and designers of machine tools.
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www.engineerlive.com
hen designing belt drives for machine tools, the user is presented with a range of options, thanks to the new materials and processes available to belt manufactures.
For speeds of up to 60m/s, elastomer v-belts or
multi-ribbed belts are sufficient. Beyond 60m/s, Polyflex and Polyflex JB polyurethane v-belts are the best option. The key properties of these drives are the low specific weight of the belts, their high power density compared to other types of belt and their quiet operation, even in highly dynamic applications. Alongside the construction of the belts and the materials used, Polyflex belts incorporate a special wedge angle of 60°, which enables the drive to reach circumferential speeds of up to 100m/s. However, if the application in question involves a positioning drive that also runs at a high speed in the region of several thousands of revolutions per minute
(rpm), the solution lies with synchronous belts as friction drives are not suitable for this purpose. Increasingly, synchronous belt drives are being used instead of simple transmissions and chains, which are not designed for higher speeds, and are loud and require frequent maintenance. When selecting the right synchronous belt design for high-speed applications, the following principles should be considered:
Selecting a suitable tooth pitch and profile
Too small a tooth pitch will entail an increase in the construction space required as well as higher noise levels. Pitches that are too large, on the other hand, will necessitate larger pulley diameters, and will also result in high noise levels. The best solution is a belt drive combining the highest power density and the lowest possible tooth pitch. For high-speed drives and drives with power ratings up to 100kW, 8mm pitch belts with
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