Swiss Watchmaking Manufacture

In a context of production processes being brought on lines, we were led to set up the Conwip, a simple and powerful method to control our work in process and our manufacturing lead times.

The simulation of the lines was made thanks to the WipSim software, which allowed us to confirm our means dimensioning, but also to target very easily the flow bottlenecks and to establish a roadmap of the various improvement projects to be carried out on the line to improve its capacity.

The WipSim tool is also very educational because it allows to appreciate the changes of parameters (batch size, number of batches, set-up time/cycle …) in an instantaneous and visual way and makes it an efficient means of communication to the impacted teams.

Expectations

In order to improve the performance and the service rate of the cogs manufacturing, an organization project was launched on the mainsprings and wheels.

Based on macro routings describing the various stages of manufacture of these pieces, a process of putting online was decided.

This led to a complete rethinking of the manufacturing of the Cogs perimeter: reduction of batch sizes, control of queues and transfer times, reduction of stocks, optimization of the number of equipment, development of HR versatility, elimination of bottlenecks, visualization and fine scheduling of operations, organization in products rather than in businesses.

Solutions

CONWIP (CONstant Work In Process) was chosen as the workshop management method to control the wide variety of pieces manufactured at the Cogs in a pull-flow mode, while remaining compatible with planning, which is not possible with the classic Kanban.

A very efficient visual management control panel has been set up in the workshop to control the flows in real time according to the Conwip principle (no new production order enters the line as long as none leaves) and above all to indicate the priorities according to the advancement of the work in progress.

This table is used on a daily basis because all the information is centralized and visible to everyone at a glance. The work is made easier, and the work-in-progress is totally controlled despite the great diversity of parts to be produced.

The dimensioning of the labels on the control panel was done with the WipSim simulator.

Project approach

With the help of the WipSim flow simulator, the first 4 months of the project were devoted to an in-depth study of the workstations and operations (analysis of the cycle times compared to the set-up times, choice of equipment, definition of the SMED site priorities, duplication of tools, etc.) in order to ideally dimension the future production lines.

Then, training sessions were conducted with the Conwip serious Game (Jeu du conwip) for all the employees concerned, in order to explain the project’s objectives and the changes to come.

Finally, the Conwip management solution has been deployed in the field.

Results

The first pilot project on hand-held cogs was a success as soon as we switched to Conwip mode:

the lead times have been divided by 5,
the service rate has improved significantly,
Planning was greatly facilitated because manufacturing became much more responsive.

Since then, the approach has been progressively deployed throughout the production of the cogs.

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