How to reduce friction on conveyors with a nosebar (knife edge)

How to reduce friction on conveyors with a nosebar (knife edge)

Conveyors with one or two nosebars (knife edges) consume more power than conveyors with bearing pulleys. That’s a given. But we also regularly receive questions about a drive that slips, or motors that overheat and turn off. These problems may be caused by friction between the static nosebar and the tensioned belt. To deal with this, we need to know how friction occurs. There are several factors to look at:

  • The nosebar material
  • The nosebar radius
  • The arc of contact with the nosebar
  • The belt strength
  • Friction between the belt and the nosebar
  • The tension in the belt

Here are our recommendations for reducing friction:

  1. Nosebars should be made of hard, smooth material like stainless steel with a polished surface, or bright chrome-plated steel
  2. When possible, the nosebar radius should be limited to a minimum of 3 mm and a maximum of 6 mm
  3. The arc of contact should be kept as small as possible. The smaller the arc of contact, the less friction will be created
  4. Taking a belt with a low k1% value, for small belt widths, it’s preferable to use 1-ply belts. For wide belts, a 2-plies belt may be necessary to ensure the lateral stability required to avoid overlapping of the belt in the center. In general, belts with lower strength should be used, in order to keep down the force against the nosebar
  5. Belts should have a low coefficient of friction on the running side. It’s useful to remember that impregnated fabric gets damaged less quickly than non-impregnated fabric. When fabric is damaged it becomes fluffy and the coefficient of friction is considerably higher than with a new belt. Also, never use a steel drive pulley with grooves or knurling, as this will lead to excessive wear on the running side of the belt
  6. Since the tension in the belt is a factor that causes friction between the belt and the nosebar, it’s advisable to set a lower tension than used as standard. To make this low tension possible without slippage on the drive pulley, the drive pulley should be covered with an abrasion-resistant elastomer, which will double the coefficient between the belt and the drive pulley. The arc of contact with the drive pulley is also important. Using an arc of contact of 204°, the power transported is almost twice as much as with an arc of contact of 180° (based on Eytelwein’s formula).We’d be glad to help you calculation the best arc of contact for your application
Note that the diameter has no influence on the transmittable peripheral force

 

If you have any questions about this topic, please contact us for personal support.

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2018 November 30  |  Posted by

René Grevengoed

René Grevengoed is an Application Engineer who has worked at Habasit in the Netherlands since 1996. He speaks native Dutch and he is also fluent in English. Grevengoed specializes in general conveying, including fabric conveyor and power transmission belts. His expertise is applicable in several industries, including food, material handling, as well as printing and paper applications. Grevengoed’s experience began in workshops and onsite fittings where he was able to acquire the necessary special skills in order to progress to where he is today.

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