Why do timing belts need guidance?

Why do timing belts need guidance?

Most people understand that fabric belts need guiding mechanisms to keep them running true. But I’ve noticed that not all our clients know that timing belts also need tracking guidance. This may be because sturdy thermoplastic urethane timing belts are so clearly rigid and look very strong. Why wouldn’t they run true on a conveyor?

Timing belt cordsThe truth is that every timing belt pulls to the left or the right. This is because of the steel or aramide tensile members, or cords, in the belt. Since the filaments making up these cords are twisted either left or right (S or Z), they produce a force that pushes to the left or right. To reduce the effect of this, during fabrication the tensile members are laid down in an alternating SZSZ (left, right, left, right) pattern to balance out these forces. Unfortunately, however, this effect can not be entirely prevented. So timing belt guidance is always needed to keep the belts tracking straight.

Another important point: since side loading or unloading onto timing belts places a lateral shift on the belt’s direction of travel, it’s essential to use a tracking mechanism to counteract this.

What mechanisms are available for timing belt guidance? There are two main methods, which are very different from those used for fabric belts.

Pulley flanges

A very common solution to the problem of timing belt mistracking is to place pulley flanges on the pulleys. While often successful, there can be problems with the conveyed product using this method, since the discs are usually higher than the belt thickness. In situations where the product e.g. a board, is transferred between two belts, it can hit the pulley flanges. The solution here is to make the belt thicker, so the product sits higher on the timing belt and cannot hit the pulley flanges. But the trouble with this is that if you make the belt thicker, it can affect the overall belt construction, and you may need a larger pulley diameter. Changing belt properties has to be done with great caution.

Tracking guides

If pulley flanges on the pulley or a thicker belt are unsuitable, tracking guides mounted on the belt’s tooth side are an excellent alternative. These are either welded onto the belt, or can be integral to the belt and extruded during manufacture. Tracking guides come in a vast array of forms, the most popular of which are U-shaped with boards left and right, or with a V-shaped groove in the middle.

Which form of tracking guide to choose?

As ever, it depends on the application, how the conveyors are set up, where the goods are loaded, and if there are transfers to other conveyors. For example:

  • U-shaped tracking guides with side walls are used in many standard conveyor designs.
  • V-shaped tracking guides with a trapezoid groove support a flat or flush conveyor design without boards between parallel running belts, with no need for pulleys with flanges. Note, however, that this solution requires pulleys with a groove.
  • In cases where maximum flexibility is called for, a timing belt with a centered groove running on a tracking guide with a strip can be an option.
  • If the belt is not running 100% flat, but at 90 degrees, a tracking guide with a groove delivers the best results.

All industries and applications

HabaSYNC timing belts are used today in almost every industry, and in a diverse and growing number of applications. Tracking guides deliver support for every situation, meeting the challenges of reduced friction, side loading, transfers, belts at an angle or upended, and helping to ensure that your timing belt runs not only precisely and reliably, but also true. Be sure to ask us for advice on timing belt guidance from the start of your planning process. We’ll be happy to help.

2019 January 31  |  Posted by

Andreas Ebhart

Andreas Ebhart is a Product Manager for HabaSYNC and HabaCHAIN in Wien, Austria. He has been with Habasit for the last five years. His expertise is timing belts in wood, tire and MH. Fluent in both German and English, Ebhart is always eager to answer any questions you might have!

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