With any rotating or indexing application whether it be mechanical or servo driven the drive torque required is a function of two quantities – angular acceleration, α, and moment of inertia, I. For many indexing applications it is desirable to minimize index time so that throughput can be maximized. Keeping index time as short as practical requires that angular acceleration be as large as possible. Since Torque = Iα, large accelerations require large torques and large torques require large drives which are more costly and can occupy considerably more space. If torque is to be conserved while maintaining a short index time, the designer has but one choice. – Minimize the load’s moment of inertia (I from the equation above).
What is indexing?
Whether linear or rotary, Indexing is the process of starting and stopping a device in precise intervals at precise locations. (more…)
Servo Indexers are more expensive than mechanical indexers.
Actually up until recently Servo Indexers (SI) were more expensive than mechanical indexers. However with advances in servo technology, cost has declined to the point where SI can actually be lower in cost than mechanical indexers. This is especially true in larger size units. In many large diameter applications mechanical indexers are removed from consideration because project cost won’t tolerate the expense. This is an ideal situation to consider SI. In general, as diameter increases the cost savings of using SI increases. With smaller size indexers the cost advantage is less dramatic and at first glance SI may appear to be more expensive. But when you consider the whole package, SI are a very cost effective solution. With SI there is no need for a home switch or an at-station sensor and no need for a mechanical overload device. These features come standard with SI. Some SI come fully assembled, wired and tested and therefore there are no assembly and wiring costs. And finally, what cost do you add for the home-adjust feature of an SI or the ability to add stations.