Items between machines waiting to be processed.
Work in process (acronym: WIP) or in-process inventory includes the set at large of unfinished items for products in a production process. These items are not yet completed but either just being fabricated or waiting in a queue for further processing or in a buffer storage. The term is used in production and supply chain management.
Optimal production management aims to minimize work in process. Work in process requires storage space, represents bound capital not disponible for investment and carries an inherent risk of earlier expiration of shelf life of the products. A queue leading to a production step shows that the step is well buffered for shortage in supplies from preceding steps, but may also indicate insufficient capacity to process the output from these preceding steps.
Just-in-time (acronym: JIT) production is a concept to reduce work in process with respect to a continuous configuration of product. Just In Sequence (acronym: JIS) is a similar concept with respect to a scheduled variety in sequence of configurations for products.