Novel Use of Cognex Vision System for on-Line Level Monitoring/Control in a Continuous Direct Compression Manufacturing Process

The continuous direct compression manufacturing process consists of several loss-in-weight (LIW) feeders, a horizontal mixer, a surge hopper, and tablet press equipped with a near infrared (NIR) probe at the die-filling station of the tablet feed frame. The surge hopper atop the tablet feed frame helps both dampen upstream flow fluctuations and maintain a consistent head of powder above the feed frame so as not to starve the tablet press of powder.  Use of a Cognex Vision system allowed for a novel means of measuring level in the surge hopper to gauge the mass balance of material flowing into and out of the surge hopper.  With the Cognex Vision system (or comparable level sensor) measuring fluctuations in surge level, the tablet press rotor/turret speed can be adjusted and has been shown to have minimal impact to tablet properties through monitoring of the force control on the main compression stage.  Additionally, measurement of the surge level enables application of a reduced system model which, in part, would forecast when an upstream disturbance in API concentration would reach the feed frame and when that disturbance would clear the feed frame.