Manufacturing plant and system for manufacturing rigid bodies

Details Manufacturing plant and system for manufacturing rigid bodies Manufacturing plant and system for manufacturing rigid bodies

2000-05-16

2003-01-07

Bryant, David P. (Department: 3726)

Metal working

Means to assemble or disassemble

Means to interrelatedly feed plural work parts from plural...

C029S791000, C029S430000

Reexamination Certificate

active

06502301

ABSTRACT:

This invention relates to an alignment-based rigid-body manufacturing plant, system and method.
Manufacturing systems and methods have heretofore been utilized in manufacturing plants. In an output-based organizing system manufacturing operations are categorized in terms of the types of outputs generated and the tools used in production. For example, the category “mechanical joining” has the following sub-categories: pressure/cold welding, friction welding, ultrasonic welding, explosive welding, etc. Therefore, the number of distinct competencies is arbitrarily large, since outputs and tools continue to evolve (e.g., due to changes in technology). Such manufacturing line operations are often specific to the type of product or component being produced. Each line produces one type of product (where that product may be a finished good, a subassembly, or a component). Both “line” manufacturing and “modular” manufacturing are fixed from this point of view, since in both cases, a line or cell is dedicated to a particular type of product, and therefore require re-configuration in order to produce a new product. Producing new products (or new models of the same product) requires different operations. Conventional manufacturing systems have low adaptability, since whenever a product or component is modified or added, a work center must be added or modified. This discourages plants or factories from producing multiple product lines, which restricts the capability of the manufacturing system to adapt to the changing needs of the marketplace (e.g., quickly switching to a more popular product line). In fact, in many industries, the biggest barrier to mass-producing a new product model is the high “first-time-through” or “launch” cost of modifying work stations to develop new products or components.
With conventional manufacturing systems, unplanned jobs and new products are handled as exceptions, or events that cannot be handled by a workflow. New products typically require a new manufacturing infrastructure, which typically requires approximately several months to become operational. Furthermore, there is a significant learning curve to achieve standard levels of performance for new products. This learning curve results in lost opportunity costs. When exceptions arise, operations are in flux, and require timely adaptation in order to respond to the exceptional event or crisis. However, conventional, rigid manufacturing systems have difficulty responding quickly and effectively to changes or unanticipated events (i.e., exceptions to the normal, expected workflow). One typical response is to form new departments to handle exceptions, which guarantees that exceptions will continue to exist, and that the bureaucracy will continue to grow (the stream of exceptions becomes the rationale for the existence of these new departments). Thus there results a significant capital investment since a product-specific manufacturing infrastructure is required (where that infrastructure includes work stations, devices for transporting work-in-process and finished goods, equipment, machines, etc.).
Also long learning curves are required for operators to manufacture new products which result in unplanned jobs. Learning is limited with conventional manufacturing operations, since operator expertise is linked to specific output types and tools. Therefore, operators typically require new training whenever products and components are added or modified. In addition classical progressive lines causes worker idle time. The classical, balanced progressive line (e.g., a conveyor-driven assembly line) regulates the rate of production and enforces a maximum rate of productivity for every operator which cannot be faster than the slowest operator's rate of productivity. Therefore, all other operators must wait, in varying amounts of time, depending on their own productivity rate. Operators try to complete a job (e.g., install a part) within a fixed time interval. If they cannot perform the job within the allotted time interval, then it is finished at subsequent work stations. This has the advantage of guaranteeing a certain sustained rate of production. However, the disadvantage is that some workers will inevitably exceed the standard rate of production, and must wait, since no worker can go faster than the regulated production rate. Typically, there is a great deal of slack in standard production rates, which are often set below the productivity capacity of most workers (so that the great majority of, if not all, workers can achieve the standard rate).
Conventional operations also make achieving quality costly and increases cycle time. Steady inspection is required to maintain quality. A given individual (or group) would be responsible for all operations pertaining to a given component. In addition, these complex operations often contain common (therefore redundant) sub-operations, which makes it very difficult to modify operations in a coherent fashion. For example, using a conventional manufacturing system, there are separate work centers for manufacturing the various components of the final product. Unfortunately, such operations contain many redundant sub-operations that are performed at multiple work centers. When a process is modified at one work center, it should also be modified at the other work centers, in order to ensure consistent quality.
Ensuring consistent quality across redundant operations can be accomplished only using quality control techniques that are external to the operations themselves (e.g., statistical process control) and an additional management layer, which adds to the bureaucracy. In addition, redundant operations may compete for common resources (e.g., machines, or even human expertise), thereby introducing unnecessary resource sharing and scheduling problems. These difficult scheduling problems create large work-in-process queues at most activity centers, resulting in increased cycle time. Modular manufacturing exacerbates the fundamental limitations of line manufacturing. Modular manufacturing uses smaller production lines, which creates unrelenting quality concerns due to the greater vulnerability of these lines to absenteeism and sub-standard individual performance.
In recent years, the concept of “lean manufacturing” has gained popularity. The fundamental essence of lean manufacturing is its “backward-chaining”, or goal-driven (pull) operation, where reasoning starts “backward” from the goal (in this case, the demand pull). All other lean manufacturing characteristics are derivable from this fundamental lean axiom. Implementations of lean manufacturing employ the principle of “production leveling”, which generates production plans relative to a “batching” time interval (this time interval is typically about one month). Since planning production over small time intervals (for example, daily, or even hourly intervals) is considered to be infeasible due to its complexity, production leveling is considered to be necessary in order to make lean manufacturing practical. Unfortunately, the practice of production leveling constrains the ability of the factory to respond quickly to change (i.e., within a very small time interval), on a systematic basis (i.e., without expediting). (A capability for rapid response to change would promise to increase sales by rapidly adjusting production to satisfy demand spikes.) “Flexibility” associated with lean manufacturing is based on various ways of re-shuffling personnel. Cross-training enables personnel to be re-assigned to a variety of production lines (to respond to demand fluctuations). However, there is typically a significant learning curve when operators begin work on a new production line. Overtime increases the capacity of a production line (to respond to increased demand). Layoffs reduce the capacity of a production line (to respond to reduced demand). Lean manufacturing, however, does not overcome the fundamental rigidity of conventional manufacturing, as lean production lines are still “fixed” in the sense that they are dedicated to a spec

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