Nexen’s Rotary Indexers and Inertia

In many rotary motion control applications, settling time and settling accuracy are very important. Managing what is called inertia mismatch or inertia ratio is required in these applications. Often, control engineers like to see a relationship of 10:1, where the translated inertia can be up to 10x greater than the servo motor inertia. The higher this relationship value is, the longer the system takes to settle on a given target location. Gearboxes are typically used to reduce the inertia ratio by taking the inertia from the output system and dividing it by the ratio of the gearbox squared.

Nexen Rotary Indexers assist in reducing the overall inertia translated back to the driving system(motor). All Nexen Rotary Indexer products utilize gear ratios to get the driving speed (motor) and mismatch to where the control system can be efficient. When sizing a Nexen Rotary Indexer, it is important to remember that if using the Indexer with a gearbox, it is two gear ratios in series. The inertia from the output is divided by the indexer ratio squared, then gets divided by the gearbox ratio squared.

Nexen also offers high gear ratio Motor Ready indexers, where an additional gearbox is not always required. In comparison to other direct drive system products, it has the advantage of an internal gear ratio to assist with inertia mismatch. It allows for efficient, zero backlash direct driving with a motor. For applications requiring zero backlash where a larger ratio advantage is required;  an Indexer with Nexen Harmonic Gearhead (HG) is available.  Starting at 50:1 and going up to 120:1 in ratio, the HG version of Nexen's Rotary Indexer line is a great option to decrease mismatch while maintaining zero backlash.