Stamped parts warehouse (webs, tables and backplates)

In the stamped component group are included all the parts of the drum assembly that are manufactured via stamping procedures: all starts with a coil of metal sheet, that is used to feed the process. At the beginning, the sheet of metal is cut in several blanks of desired shape and dimensions; subsequently, the blanks are introduced in the stamping press, a machine made by a punch (an heavy duty piston that pushes on the blank, shaping the part) and a die (the constraint mould, on with it has been machined the desired geometry of the component), to be pressed and shaped in the desired configuration; at last, the parts are trimmed and stored, waiting for shipment to the customer.

In case of Continental, the process is performed by suppliers highly specialised in stamping processes. Every day, stamped parts (web, tables and backplates) are delivered to the assembly plant, and at the arrival they follow different ways: backplates are painted before being sent to assembly, while webs and tables are previously joined together and then painted, waiting to be glued to the lining.

Such a consistent flow of parts should be stored appropriately: the total available space for warehousing of parts consisted of around 470 square meters floor area, half for backplates, half for the remaining components, placed in two separated places of the facility.

The material is provided by metal containers for heavy duty applications. This kind of loading units has a unique feature, that essentially is the extreme resilience to intensive stresses due to high weight capacity, tough construction, and reutilization (containers can last for long periods before scrapping, some of them have faced a life cycle superior to twenty years, due to their robustness in application).

Parts are bulky loaded in the containers and shipped via full truckload to the plants.

At the plant, the containers are stored by counterbalanced forklift in a dedicated area in the middle of the factory: due to the lack in storage systems, the metal bins are stacked one on the other according to LIFO (Last-In First-Out) strategy (Figure 4.11): it means that the last stored part is the first one to be retrieved and sent to the workstations. The choice of that method is due to the low availability of space of the storage area, that does not allow neither to store goods in conventional ways nor to apply a FIFO method for retrieving, due to presence of constraints (wall boundaries) and intense passage of vehicles and operators nearby.

The first aspect concerning the poor efficiency of the system is that the warehouse layout has proved itself to limits the operability of the warehouse: in fact, stacks of loaded containers cannot reach elevated heights form the ground, due to safety issues concerning operators and risk of structural damages to the plant facility in case of fall; moreover, the capability of the space is not fully exploited, and the warehouse encounters an high risk of being stuck due to high saturation, especially during peak demand periods.

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Figure 4.11. Example of stacked metal containers for heavy duty application

The second aspect is related to the chain of actions carried out between incoming and storage.

The designer should think about the process to which parts undergo; once the loading units have been unloaded at the docks, they used to be stored in a waiting area, following the allocation in the storage. The main distance from the unloading dock to the storage is about 75 metres: the counterbalanced forklift transports two containers at a time, travelling on a driveway pretty close to assembly stations and walkways for operators (Figure 4.12).

Figure 4.12. Total travelled distance from dock to warehouse in the old layout: 75 metres

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To sum up, the system shows some drawbacks, that can be identified in:

- lack in proficiency for the LIFO system and the stacking.

- issues related to transportation of loading units from truck to storage area.

- long travelling distance by forklift.

The task of the designer is to think up a new strategy, able to proficiently dodge the setbacks that could occur from inadequate set up.

The solution built to overcome the distress is to think about a rearrangement of a disused area:

the space occupied by the small components warehouse nr. 2. Because of its embedding in a general warehouse for small components, it left a large portion of floor area available for storage.

The purpose is to set in the area a system based on static conventional rack system with aisles, to store the containers instead of stacking. The advantages are multiple:

- increased proficiency in material handling with respect to LIFO system.

- each loading unit can be associated to a storage bin allocation, so the units can be easily loaded on WMS and tracked along the internal supply chain of the plant

- avoided risk of damages or injuries due to net separation from assembly lines, driveways, or common areas.

To save space, it has been decided to adopt a trilateral side-loader turret truck, that thanks to the excellent performance in narrow spaces, allows to reduce the total width of the aisles, with respect to a conventional warehouse managed through counterbalanced forklifts.

The trilateral truck helps at maintaining very low floor space encumbrance: the new warehouse occupies an area of extent equal to 432 square metres, with a storage bin capacity increased to 840 locations: 2 bins per bay, 5 bays per row, 6 levels for each row, for a total of 14 rows.

Figure 4.13. Total travelled distance from dock to warehouse in the new layout: 35 metres

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The utilisation of the old components storage area is not random: an ulterior benefit comes from the reduced travelled distance performed by the forklift truck from the dock to the storage: 35 meters id the total path length to be travelled to bring loading units to the turret stacker, an improvement equivalent to half of the previously travelled distance (Figure 4.13).

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Figure 4.14 The proposed layout for the stamped components warehouse

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