Assembly line control system

Details Assembly line control system Assembly line control system

2002-08-29

2004-10-05

Picard, Leo (Department: 2125)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Product assembly or manufacturing

C700S115000, C700S166000

Reexamination Certificate

active

06801821

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an assembly line control system and, more particularly, to an automotive assembly line storage and lot control system.
BACKGROUND OF THE INVENTION
In conventional assembly lines, and automotive assembly lines in particular, a continuous feed of partially completed assemblies, such as an automobile, is passed through, typically, a large number of assembly stations. Each assembly, or vehicle as the case may be, typically has an instruction or build sheet associated with the particular assembly. The build sheet includes instructions as to the processes that need to be performed, and the locations to which the assembly should be transported. The build sheet is typically a print out of a computer record for a particular vehicle that is attached, directly or indirectly, to the vehicle. A vehicle also has associated with it an assembly sheet. The assembly sheet identifies the various parts or components that must be installed for the particular vehicle to which the assembly sheet is associated. Consequently, the assembly sheet identifies the parts that are to be installed and the build sheet contains the instructions as to where and what processes are to be used in putting the parts identified on the assembly sheet together.
Recently the automotive industry has embraced two disparate manufacturing technologies: just-in-time (JIT) production and mass customization.
JIT production involves the co-ordination of parts supplies to the manufacturing plant and to “line side” (that is, locations physically proximate to the manufacturing assembly line making parts available for installation on/in the assembly) in an effort to reduce inventories and, consequently, costs. As is known in the art, JIT production may require several shipments of the same part, component or assembly, from the supplier (which may, for example, be another plant of the assembly manufacturer, another assembly line in the same manufacturing plant, or a separate or outside parts supplier, such as the Tier I suppliers to the large automobile manufacturers like Honda™). These parts shipments may and often are, due to manufacturing or delivery difficulties, delayed in their arrival at the manufacturing plant. As a result of these delays, and the associated low inventory problems, it is not uncommon for the delay in a single day's shipments or even a single shipment of parts to severely impact plant manufacturing and production schedules.
Mass customization is one of many terms to describe the process of building many variations of the same vehicle brand, such as a Honda™ Civic™, on the same assembly line, having the same platform or basic vehicle chassis. Moreover, other separate vehicle brands, such as the Acura™ 1.6EL™, which may share the same platform as another vehicle but require significantly different build sheets and instructions, may also be manufactured on the same assembly as the Honda™ Civic™ in order to reduce manufacturing costs. As a result of mass customization, it is not uncommon for a single platform to spawn thousands of variations amongst a number of different vehicle brands. These variations require a corresponding number of different parts to be made available to the assembly line in order to fulfil the build sheet instructions. It should be noted that the term “parts” is used very generically to include any type of component that may be affixed, applied or otherwise impact the particular vehicle manufactured. A “part” may include, for example, the fluids, the paint type, the paint colour, the wheel size, the exhaust system, the engine size and configuration, the transmission, the number of doors, the seat selection(s), etc.
To accommodate JIT and mass customization simultaneously typically requires a large number parts to made available at a single workstation, such as for example, the sound system (radio) installation station. However, due to physical limitations in line side space, many methods of manufacturing have been attempted to limit the number of parts changeovers. That is, a parts changeover is the removal from line side of one set of parts, such as economy sound system, with a replacement, at line side, of another set of parts, such as an upgraded or luxury sound system. To limit the number of changeovers, similar vehicle brands with similar configurations are, conventionally scheduled to be manufactured in lots or groups. That is, a production schedule is developed and implemented to group together those vehicles that have a similar vehicle brand and are configured or “optioned” by the customers in a similar fashion. In this manner, the number of different parts at line side required to manufacture the vehicles of a particular lot are significantly reduced. Nevertheless, the parts at line side, whenever there is a changeover from one lot to another, must be changed to accommodate the build instructions for the next lot of vehicles. For example, when a particular station completes its operations on the last vehicle of a first lot and is about to commence performing operations on the first vehicle of second lot, the line side parts located proximate to this station typically must be changed to accommodate the vehicle lot changeover.
Difficulties with the above described assembly line and method and often are encountered when a vehicle fails an inspection test and must be repaired or whenever part shortages or build changes must be implemented. As is well known in the art, partially completed vehicles, or vehicle assemblies, typically are inspected at one or more points during manufacture to identify defects. As a result of these inspections, a vehicle assembly failing inspection will, typically, be removed from the assembly line and the defect repaired. The repaired vehicle will then be re-inserted into the vehicle assembly line. As a result of the various inspections, removals from the assembly line, repairs and re-insertions, members of the lots of vehicles typically get “jumbled”. That is, a repaired vehicle may be inserted into an available position on an assembly line in the middle of a different lot of vehicles with vastly different build instructions from that of the repaired vehicle. Consequently, parts must be made available line side at the remaining workstations (that is, those workstations downstream of the insertion point) in order for the assembly of the repaired vehicle to be completed in accordance with the repaired vehicle's build instructions. This often results in the assembly line slowing down or stopping so that the parts control systems may provide the proper parts and components to the various workstations encountering this repaired vehicle. Moreover, some parts, such as paint colors and types, may require a significant delay due to any required flushing and cleaning of the paint system from the previous paint colour and type. For instance, if a repaired vehicle, which is to be painted white, is inserted into a lot of vehicles to be painted red, the paint system (paint lines, booths, nozzles, etc.) must be purged, flushed and cleaned of any residual red paint prior to the painting of the repaired, and to be white, vehicle. This cleansing process may be quite time consuming
Another difficulty encountered in the conventional assembly lines results from parts shortages. Should there be any difficulties in the JIT delivery system (which may, as aforementioned, result from the delay of as little as a single shipment of parts), the ability to perform a particular build instruction may be severely impacted. This may result in line stoppages or the removal of vehicles from the assembly line until parts are conveyed to the plant and, ultimately, line side.
Another further difficulty encountered in the conventional assembly line results from a required build instruction change. For instance, if production targets for a particular type of vehicle are not being satisfied it may be desirable to alter the order of the lots of vehicles on the production line. If the production targets are not being satisfied, an alternative

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