The simplification of materials management is a tremendous potential benefit of continuous processing over traditional batch OSD manufacturing, which requires work in process (WIP) staging between discrete, de-coupled unit operations. The following table illustrates the elimination of WIP in a continuous process that includes gravimetric feeders, continuous blending, granulation, and compression:
Conventional batch dispensing operations, which typically feature labor intensive weighing and material handling tasks, are replaced by gravimetric loss-in-weight feeders, which precisely meter ingredients into the process at a constant weight per unit of time.
WIP is virtually eliminated in the continuous process, at least through compression. Eliminating post-compression WIP in a coated tablet process is challenging because tablets typically require relaxation time prior to coating, and truly continuous coaters are generally not available at the low throughput rates typically seen in continuous pharmaceutical processes.
Process Analytical Technology (PAT), integral to continuous processing, affords opportunities to reduce or eliminate in-process sample collection and associated off-line quality tests and material holds inherent to batch production. PAT creates the potential for Real Time Release Testing (RTRT), which greatly simplifies materials management by eliminating product quarantine prior to release.
The elimination of bins in the continuous column of the table above has desirable WIP implications in cleaning operations, where dirty and clean IBC staging areas are no longer required. Sizing these areas is typically an ambiguous exercise, based on a multitude of assumptions regarding scheduling, cycle times, and batch size—to name a few. Eliminating potentially large and heavy IBCs also has favorable safety implications.
In addition to improving product quality and process robustness, continuous manufacturing has the potential to drastically reduce space requirements and inventory carrying costs, improve safety in material handling operations, and vastly simplify and streamline overall materials management for OSD suppliers.
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