CONWIP
Encyclopedia
CONstant Work in Process (CONWIP) are pull-oriented production control system
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
. 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
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 WIPhttp://www.informs-sim.org/wsc01papers/122.PDF. CONWIP uses cards to control the number of WIP
s. 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 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 CONWIP system
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.
System
System is a set of interacting or interdependent components forming an integrated whole....
s. Such systems can be classified as pull and push systems (Spearman et al. 1990). In a push system
Push-Pull strategy
The business terms push and pull originated in logistic and supply chain management, but are also widely used in marketing.Wal-Mart is an example of a company that uses the push vs. pull strategy....
, the production order is scheduled and the material is pushed into the production line
Production line
A production line is a set of sequential operations established in a factory whereby materials are put through a refining process to produce an end-product that is suitable for onward consumption; or components are assembled to make a finished article....
. In a pull system
Push-Pull strategy
The business terms push and pull originated in logistic and supply chain management, but are also widely used in marketing.Wal-Mart is an example of a company that uses the push vs. pull strategy....
, 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
, also spelled kamban, and literally meaning "signboard" or "billboard", is a concept related to lean and just-in-time production. According to Taiichi Ohno, the man credited with developing Just-in-time, kanban is one means through which JIT is achieved.Kanban is not an inventory control system...
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 WIPhttp://www.informs-sim.org/wsc01papers/122.PDF. CONWIP uses cards to control the number of WIP
Work in process
Work in process 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...
s. For example, no part is allowed to enter the system without a card (authority). After a finished part is completed at the last workstation
Workstation
A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems...
, 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 CONWIP system
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.
See also
- Factory PhysicsFactory PhysicsFactory Physics is a book written by Wallace Hopp and Mark Spearman, which introduces a framework for manufacturing management. According to the book's preface, Factory Physics is "a systematic description of the underlying behavior of manufacturing systems...
- MRPMaterial requirements planningMaterial requirements planning is a production planning and inventory control system used to manage manufacturing processes. Most MRP systems are software-based, while it is possible to conduct MRP by hand as well....
- JITJITJIT may refer to:* Various meanings of Just In Time:** Just-in-time compilation - a technique for improving the performance of virtual machines in computing.** Just-in-time - a business inventory strategy.* Jabber ICQ Transport....
- kanbanKanban, also spelled kamban, and literally meaning "signboard" or "billboard", is a concept related to lean and just-in-time production. According to Taiichi Ohno, the man credited with developing Just-in-time, kanban is one means through which JIT is achieved.Kanban is not an inventory control system...
- C-VARWIP
Further reading
- Spearman, Mark L. and Michael A Zazanis, "Push and Pull Production Systems: Issues and Comparisons", Op. Res., Vol40(3), pp 521-532, May-June 1992.