CONWIP (CONstant

work in process Work in process (WIP), work in progress (WIP), goods in process, or in-process inventory refers to a company's partially finished goods waiting for completion and eventual sale, or the value of these items. The term is used in supply chain managem ...

) are pull-oriented

production control Within supply chain management and manufacturing, production control is the activity of monitoring and controlling any particular production or operation. Production control is often run from a specific control room or operations room. With invento ...

system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...

s. Such systems can be classified as pull and push systems (Spearman et al. 1990). In a push system, the production order is scheduled, and the material is pushed into the

production line A production line is a set of sequential operations established in a factory where components are assembled to make a finished article or where materials are put through a refining process to produce an end-product that is suitable for onward c ...

. In a pull system, the start of each product assembly process is triggered by the completion of another at the end of production line. This pull-variant is known for its ease of implementation. CONWIP is a kind of single-stage

kanban Kanban (Japanese: カンバン and Chinese: 看板, meaning signboard or billboard) is a scheduling system for lean manufacturing (also called just-in-time manufacturing, abbreviated JIT). Taiichi Ohno, an industrial engineer at Toyota, develope ...

system and is also a hybrid push-pull system. While kanban systems maintain tighter control of system WIP through the individual cards at each workstation, CONWIP systems are easier to implement and adjust, since only one set of system cards is used to manage system WIP.Marek, Richard P. et al., Understanding the fundamentals of Kanban and CONWIP pull systems using simulation, Proceedings of the 2001 Winter Simulation Conferenc

/ref> CONWIP uses cards to control the number of Work in process, WIPs. For example, no part is allowed to enter the system without a card (authority). After a finished part is completed at the last

workstation A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''workstat ...

, a card is transferred to the first workstation and a new part is pushed into the sequential process route. In their paper, Spearman et al. (1990) used a simulation to make a comparison among the CONWIP, kanban and push systems, and found that CONWIP systems can achieve a lower WIP level than kanban systems.

Card control policy

In a CONWIP system, a card is shared by all kinds of products. However, Duenyas (1994) proposed a dedicated card control policy in CONWIP and he stated that this policy could perform as a multiple chain closed queuing network.

References

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Card control policy

See also

References

Further reading