MANAGE YOUR WORKSHOPS WITH CONWIP PULL SYSTEM
A custom support by our experts
A custom support by our experts
The CONWIP (CONstant Work In Process) method is your ally to efficiently manage your production
Reduce and stabilize your lead times
Use the WO from the net requirement calculation
Serves as a support to the workshop management
Helps to dynamically allocate capacity
Allows to stretch the flows and to detect the pitfalls that block it
Starts with the existing work in process, without production jolt
Gives autonomy and sense for the team’s work
Suitable when the line cannot be used with Takt because of a high routing times versatility
CONWIP is also very efficient to manage repair lines
Is CONWIP really a pull system?
The CONWIP method was immediately presented by its MIT theoreticians as a pull system, in the funding scientific article in which they established its main principles: “Spearman, M., Woodruff, D. and Hopp, W. (1990) CONWIP: a pull alternative to kanban. International Journal of Production Research, vol. 28.”
It is also presented as pull system in many other articles, such as:
Hopp, Wallace J., and Mark L. Spearman. “To Pull or Not to Pull: What Is the Question?” Manufacturing & Service Operations Management 6, No. 2 (April 1, 2004).
Roser C., « The (True) Difference Between Push and Pull ». http://www.allaboutlean.com/push-pull/ (June 2, 2015).
If we consider a pull system as a system in which the production input of a new work order is conditioned by the physical output of pieces, then CONWIP, as Kanban, square Kanban or POLCA are all pull systems.
Indeed, all these systems comply with the same objective assigned to the pull system: contain the stock or work in process level.
Can CONWIP be combined with MRP?
The CONWIP management solution is compatible with the MRP net requirements calculation: the work orders are calculated by MRP according to the forecast or effective customer orders, and the CONWIP system takes the lead in the workshop to avoid launching to many work orders at the same time.
It is hence MRP which calculates the reference to produce and its quantity, and CONWIP which regulates the workshop inputs according to the output rate.
Is it possible to manage several items on a same CONWIP?
CONWIP is a good management solution for a line with high product mix, variable routing times and different routing paths. As an implementation condition, the production have to follow a consistent and stable process, which is usually the case (for example cutting – machining – heat treatment – quality control). All references moving along all workcenters isn’t a requirement. Some of the routing may skip operations. It is also possible to design a routing in which the references moves several times along the same workcenter: in that case there will be several columns for this workcenter on the CONWIP control panel.
Does CONWIP know how to manage WO with different loads?
A single workshop might have to process work orders with many different loads. The important thing is to consider the load of these WO comparing to the line’s bottlenecks. CONWIP knows how to manage this variability in two ways:
This second method is much easier to set up in the field with a digital CONWIP, that will automatically allocate several CONWIP tickets regarding the load rules.
What would be the delay to implement a CONWIP?
A CONWIP project takes approximately 2 months to deploy, taking into account the line dimensioning, the design of the visual management, the training of future users and the workshop go-live.
These 2 months are an average lead time of all the previous projects we did. We are not talking about 2 month in full-time job, but a calendar time, as the project is progressing when the workhop is available, taking into account the production requirements.
We also managed CONWIP project in accelerated mode. In this case the project lasts one week.
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