The world has transitioned to a buyer’s market, so manufacturers have to fulfill an increasing number of customer requirements. To remain competitive, manufacturers need the agility to cater to market changeability and uncertainty. On top of this, market globalization increases cost pressures. So production systems have to be highly economical—during the entire product cycle.
Fixed assembly systems with high degrees of automation are only economical during the short period of the product cycle and can’t easily be adapted to different products. These systems are bound to wilt under constantly fluctuating customer orders and increasingly diverse product portfolios that are expected with the advent of mass customization.
To achieve assembly lines with an adaptable degree of automation, suitable for varying lot sizes and capable of assembling multi-variant products, we need assembly line concepts that are extremely flexible and changeable.
Welcome the reconfigurable manufacturing system (RMS).
In an RMS, scalable, low-cost, reusable, redeployable, standard flexible assembly cells, or modules, are employed to make products at low cost and risk. An RMS uses dynamically configurable lines that many people compare to Lego blocks.
Desired attributes in an RMS are modularity, scalability, convertibility, mobility and the ability to automate.
With flexible assembly cells, smaller is better. That allows for movability and rapid reconfiguration.
An RMS is typically built to assemble products within a product category since comparable workpieces, processes and tools are essential for the adaptability to changed requirements. Designing a reconfigurable line for assembling completely different categories, such as big automotive parts and light electronic components, will not be efficient.
In a dynamic production environment, an assembly line configuration and product sequence may need to be revised each time demand changes to keep the line efficient. Since frequent or radical reconfiguration could be costly, efficient capacity management and production-planning strategies to optimize line configuration and product sequence are also required.
In some scenarios, products are produced in lot sizes that are big enough to last for at least one shift. In other scenarios, variant changes occur more frequently. Then, the system needs more built-in adaptability so reconfiguration will not be necessary between product variant changes.
Reconfiguration can be performed by the switch, exchange and/or reprogramming of process modules. The target is to do this within a few hours.
With high-flexibility modular cells, automation can be more effectively implemented in assembly systems producing high mix variations. Automating key processes provides uniformity in the final product. With in-process verification, problems are immediately caught and addressed.
Three common times when modular assembly lines need reconfiguring:
Product variant changes: Cell flexibility provides the ability to reconfigure a given fixed system by redeploying at least 90% of capital from one product variant to a different product variant. The assembly operations of the old and the new must be compared. If different operations are involved, modules will need to be switched or exchanged.
Rise or fall in demand: Reconfiguration will be necessary to adapt the production line to volumetric changes in a product life cycle. Changing customer demand can only be met by changing the target cycle time. One approach is to redesign the line by exchanging modules, rebuilding old modules and/or assembly devices and adding new stations.
New product type introduction: All existing components of the former assembly line have to be examined to see if their technical conditions allow further usage in the manufacturing of the newly introduced product.
There are commonly benefits and drawbacks to both dedicated and reconfigurable assembly lines. So it is wise to plan for their co-existence.