MANAGE YOUR WORKSHOPS WITH CONWIP PULL SYSTEM
A custom support by our experts
Control your work in process and lead times
The CONWIP (CONstant Work In Process) method is your ally to efficiently manage your production
Improve your OTD (On Time Delivery)
- Improve your lead times reliability,
- Upgrade the synchronizing of sub-assemblies’ arrival in the assembly line,
- Identify efficiently the Work Orders to prioritize,
- Increase the On-time delivery rate.
Generate more cashflow
- Reduce the works in process in your workshops,
- Lower your WCR (Working Capital Requirement),
- Ensure your new investments and your company’s development thanks to the cashflow gain.
Increase your productivity
- Efficiently assign your capacity according your workcenters’ load,
- Reduce the need in overtime and in load subcontracting,
- Gain time in the scheduling and management operations,
- Develop your teams’ autonomy and motivation,
- Make better use of versatility.
“The ConWip approach has been applied in the Thales’ workshops within the defense mission systems in a technical repair environment: small flows, high product mix, difficulty to develop versatility, erratic input flows, highly variable routing times…
In this context, Wipsim helped us a lot with the ConWip loops dimensioning, the environment and constraints are such unstable that it certainly was not easy.
Additionally, the WipSim tool’s asset is in its ability to quickly design the behavior of a ConWip working line and do so with sufficient precision and consistency to carry out parametric impact analysis of the line (change of resources, improvement of a routing operation variability, development of the versatility…).”
Translated from French
The ConWip approach has been applied in the AREVA Saint Marcel site. This site designs and manufactures the heavy equipment for nuclear power plants, namely reactor vessels, steam generators, pressurizers, etc.
The ConWip has been implemented in the welding and prototyping area. This area has several functions : it is the place where the welders do their qualifications, where the operating procedures are validated and where the control samples are manufactured to be tested in the plants.
The Wipsim simulator was necessary for the correct dimensioning of the work in process, and to ensure a risk-free transition between the initial situation and the lines management with the ConWip pull system »
Translated from French
In the context of a line set-up of the production processes, we have been led to work with the ConWip approach, simple and powerful method to control our work in process and lead times.
The simulation of the line has been done with the WipSim software, which allowed us to confirm our supply dimensioning, but also to easily target the flow bottlenecks and to establish a roadmap of various projects to run onto the line to improve its capacity. »
Translated from French
The advantages of the CONWIP approach
Stables lead times
Reduce and stabilize your lead times
MRP compatible
Use the WO from the net requirement calculation
Visual management
Serves as a support to the workshop management
bottleneck visualization
Helps to dynamically allocate capacity
Lean improvement tools
Allows to stretch the flows and to detect the pitfalls that block it
Smooth implementation
Starts with the existing work in process, without production jolt
Shared flow vision
Gives autonomy and sense for the team’s work
Compatible with high production mix
Suitable when the line cannot be used with Takt because of a high routing times versatility
In production or repair lines
CONWIP is also very efficient to manage repair lines
Expert trainings
- CONWIP approach trainings regarding skilled workers and management teams,
- Seminars about compared pull system management approaches (Kanban, generic Kanban, DBR, CONWIP, POLCA),
- General management Master class,
- Workshop situation simulation with the CONWIP serious game (Jeu du ConWip ®),
- Inter-company seminars.
Customized pre-study
- Analyze of your production to identify the best management solutions,
- Achievable performance and potential gains estimation,
- Deployment roadmap proposal
- Report writing and oral presentation.
Agile deployment
- Field support provided by our experts,
- Contribution of our experience on similar projects,
- Site implementation support,
- Go-live assistance,
- Support for durability.
Frequently Asked Questions about CONWIP
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:
- By adding the necessary buffers to avoid the queue hazard on the bottlenecks (way close to the DBR approach from the Theory of constraints),
- By allocating several CONWIP tickets to the WO with high load,
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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