An “indexing” operation within an automated manufacturing system is defined as “the starting and stopping of a device in precise intervals at precise locations.” As you can infer from that definition, “precision” plays an important role in an optimized indexing operation. But parsing down that search for precision reveals that being “precise” can take one of two forms: accuracy and repeatability, which are two entirely different things as they relate to an automation system.
Accuracy is measured via the act of positioning the indexer in the theoretically perfect position as it moves from station one to two, station two to three, etc. For DESTACO’s family of indexing products, (also found after this guide) the unit’s maximum margin of error between two consecutive stations is given as its stated level of accuracy. Repeatability, on the other hand, measures how exactly the indexer positions the tooling station back to position one in comparison with theoretical perfect position after it has completed all indexing stations within the specific automation process. In this case, the operator must be on the lookout for any small inaccuracies that may occur as the indexing cam makes its way through the process, whether it be clockwise or counterclockwise.
Before determining the ultimate level of accuracy and repeatability of the indexer/positioner, there are other operational variables to consider. Two of these are:
Both of these variables can be wide-ranging, which makes it imperative that they are noted before the system is designed, while realizing that systems that can achieve both high accuracy and repeatability even with heavier loads are a more robust and reliable system.
So, which is more important for the operator to focus on or optimize within the automation process, accuracy, or repeatability? End user indexer operation setup and desired automation process would determine the requirement.