ANALYSIS AND INSTALLATION OF A NEW LINE FOR ASSEMBLING HEAT EXCHANGERS
4 SIMULATION OF THE ‘TO-BE’ STATE
The simulation model of the ‘to-be’ situation reproduces a pilot assembly line that manufactures items of class M: this class includes the majority of items, the line therefore represents a modular model that can be used for the other classes too. The ‘to-be’ state of the line characterized by the following main aspects (fig. 5):
The assembly line is located in one building with reduced distances between work centers
Material flow is pull-based
One-piece flow
Assembling and packaging of different item families is managed by means of mixed-model
Component flow is managed by a kanban system
Several improvements were made in the new line. A supermarket kanban decouples feeding from assembling. A kitting system prevents waste due to lack of material, unnecessary in-line stocks and inefficient assembly operations. Small stocks are available long the line, thus reducing unneeded movements. Packaging operations are standardized. Visual management is applied in the line so that the assembly process is smooth and work-in-process minimized. The assembly line is ergonomically improved with benefits for the operators and their activity. Tasks are plainly assigned and distributed among the line workers, who benefit from a fair work balance;
still, the number of line operators has not changed making therefore possible the improvement of the line’s performance without additional resources. All
Figure 5: Model of the ‘to-be’ state.
Analysis and Installation of a New Line for Assembling Heat Exchangers
Several improvements were made in the new line. A supermarket kanban decouples feeding from assembling. A kitting system prevents waste due to lack of material, unnecessary in-line stocks and inefficient assembly operations. Small stocks are available long the line, thus reducing unneeded movements. Packaging operations are standardized. Visual management is applied in the line so that the assembly process is smooth and work-in-process minimized. The assembly line is ergonomically improved with benefits for the operators and their activity. Tasks are plainly assigned and distributed among the line workers, who benefit from a fair work balance;
still, the number of line operators has not changed making therefore possible the improvement of the line’s performance without additional resources. All these solutions were implemented in the simulation model and then tested.
The distribution of tasks allows a clear distinction of roles. A truck driver collects material from the central warehouse and feeds the supermarket; he delivers pallets of finished products to the shipping area. The supermarket operator replenishes, from the supermarket, in-line stocks by means of a kanban two-bin approach; he prepares assembly kits and loads the basic component of a product on a platform truck that is queued at the beginning of the line. The line operators perform the assembly tasks and the line set-up if needed. Items are assembled on the platform trucks and then moved to the packaging area. The packaging operator unloads the end-items from the platform trucks queued at the beginning of the area and puts them into a pre-assembled container. When the packaging contains all items reported on its packing list, the operator closes, straps, and labels it.
Time measurements were taken on the pilot line: results show that the reorganization of tasks positively affected production flow time and cycle time. In regard to class M, the following production rate increases were obtained:
72.7% for assembly (the average daily production rate increases from 55 pieces to 95 pieces)
60% for packaging (the average daily production rate increases from 50 pieces to 80 pieces)
The simulation shows a good distribution of work among the operators and 34.5% increase of utilization of assembly, which is the stage with highest value-adding activity (fig. 6 and fig. 7). It is worth noting that the truck driver, in this balanced configuration, uses 73.1% of time for feeding the assembly line (fig. 8).
The new configuration and layout of the assembly line were designed so that the areas for in-line feeding stocks were available, reducing movements and transports.
Figure 6: Summary of the simulation results (‘to-be’ state).
Figure 7: Resource states.
Analysis and Installation of a New Line for Assembling Heat Exchangers
Figure 8: Activity report of truck driver.
5 CONCLUSION
The reconfiguration of the assembly line, based on lean manufacturing principles and tools, brought significant improvements to the process performance. Simulation had a key role in the study, because it enabled to test possible solutions or changes on a model without the need to implement them on the actual line. Nonetheless, the final configuration of the new line was tested in the field, showing production rates that were in accordance with those produced by the model.
This opportunity encourages discussion about solutions, which can be immediately verified by means of the model, and their consequences on the system. Using this approach, possible problems or ineffective modifications to an existing line can be prevented, avoiding the introduction of errors in the design or realization stages.
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