But many advantages come with the higher price tag. Flexibility is one of the biggest. Because they are controlled by programming, these cappers can be quickly changed over to run a different closure style and size. Specified application torques, which vary by closure, can be kept as “recipes” within the capper. Programmed torque specifications can be changed centrally for all heads on the servo-driven capper, eliminating the need to adjust each head individually. Instead of changeover time of roughly a minute per head on a magnetic clutch capper, a global changeover can be accomplished on a servo-driven capper with just a few keystrokes, even while the line is running.
Another key advantage of servo-driven cappers is their ability to deliver consistent application torque. A magnetic clutch capper has typical accuracy of +/-10%; with servo systems, this margin can go as low as +/-0.5%.
Because servo motors are digitally controlled, systems that use them can perform sophisticated monitoring and corrective functions on-line. These include torque testing, in which a chuck unscrews a cap, re-applies it and records the torque values; real-time feedback to verify that proper application torque was applied to each cap; and flagging of containers with cocked or cross-threaded caps for downstream rejection (or, in some cases, directing it back under a chuck for correction).
Another function at which servo-based cappers excel is in orienting caps before and during application. This is especially important with hinged caps, where it’s important to have the opening face front. But the closures may not have enough physically prominent features for the cap feeder/sorter to orient them as they flow to the capper.
For example, disc-top closures are essentially flat when closed; they are fed to the capping head, and the disc may or may not be oriented the way the brand owner intended when it reaches the container. Servo-driven cappers can be programmed to detect the caps that need to be rotated into the correct orientation prior to torquing.
Electronics also can address the problem of caps cocking. If the match between the closure and bottle threads is not ideal, there will be a strong tendency for the caps to cock as they connect with the bottles. When the servo-driven capper detects a cocked cap, it can apply removal torque to back the cap off and then apply application torque to the properly seated cap.
Rework is lessened because the problem is addressed in the moment, and waste is reduced because the faulty package is corrected before the container and/or closure are damaged. In addition, a separate sensor such as a photo eye is not required on the line to detect the cocked caps.
Finally, for filling applications in which cleanliness is imperative, servo-driven cappers provide a fundamental advantage. These cappers have significantly fewer parts than traditional systems and therefore have fewer lubrication points.F&BP