By Andrew Christofides, P.E., Lead Engineer, Process Architecture and Technology – IPS
WIP is partially completed product either undergoing or awaiting processing. For OSD manufacturers, WIP accumulates between all unit operations and may represent a substantial percentage of a company’s total assets. Lean Manufacturing principles promote the reduction or elimination of WIP to minimize cycle times, inventory costs and waste, thereby improving operational throughput and profitability. In OSD processing, the effective management of WIP is especially critical because of the potential for cross-contamination, particularly in multi-product facilities.
Overlooking any aspect of WIP staging is a serious pitfall in the design of OSD facilities, which overwhelmingly feature batch processing. Undersizing a WIP staging area can constrict material flow and exacerbate a bottleneck. This could occur downstream of a manual dispensing area, where ingredients are pre-weighed in batch quantities and assembled in kits, to be delivered to a blending or granulation process. If dispensing is forced to stop until downstream staging is available, then the start of a subsequent batch may be delayed, jeopardizing production goals.
Improper design of WIP staging can also result in starving a critical process. If dispensing is the constraint, then it is critical to plan for adequate staging of raw materials upstream of dispensing, to ensure that the operation is never forced to wait for the delivery of components. Consideration must be given to material storage and handling methods and area adjacencies, as well as scheduling philosophy.
Oversizing is not the answer because WIP staging areas that are unnecessarily large could encourage the creation of excess WIP, which will drive up inventory carrying costs, make the material handling inefficient and increase the risk of cross-contamination.
OSD plant managers will feel the effects of poorly designed WIP staging areas long after the design firm hands over the keys to the facility. It is crucial that the facility designer and the manufacturing expert form a partnership at the inception of every OSD capital project to ensure that proper consideration is paid to WIP.
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