Information Technology for Manufacturing A Research Agenda (1995) / Chapter Skim
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4 Shop Floor Production
4 Shop Floor Production
Pages 84-108
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From page 84... ...
For a factory, the product delivered is a final product that can be sold to an external customer; for a work cell, the product delivered is a partially finished product that goes on to the next work cell, which regards it as a part or a raw material for that next cell. The demands made by factories on suppliers for components are the same as the demands made by an individual process to be carried out by a work cell.
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From page 85... ...
-related research needed to advance shop floor and production systems. SCHEDULING FACTORY ACTIVITIES Centralized Control The dominant issues in production planning today are achieving major reductions in manufacturing lead time and major improvements in honoring promised completion times.
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From page 86... ...
86 INFORMATION TECHNOLOGY FOR MANUFACTURING TABLE 4.1 Research to Advance Shop Floor and Production Systems Subject Area Example of Research Needed Equipment controllers Architecture and technology for shop floor equipment and data interfaces Open architecture for control systems Appropriate operating systems, languages, data structures, and knowledge bases Human-machine interfaces to permit people to interact effectively in a modern manufacturing environment Design for repairability and the ability to work around equipment crashes, including diagnostic software Better real-time control Wireless communication Sensors Dynamic (real-time) scheduling Intelligent routing systems Standardized interface connections Manufacturing control architecture Dynamic shop floor models with high-speed recomputing time and the ability to handle numerous variables Real-time planning and scheduling tools for the flexible factory and the distributed factory Techniques to ensure graceful degradation of production operations in the event of local problems Tools to facilitate situation assessment and scheduling by the factory manager and operations team Multilevel understanding of large-scale systems Means for identifying the relevant measures and quantifying the relative performance of alternative systems Tools to support the brokering of priorities and obligations among cooperating entities, based on minimizing overall transportation, material handling, inventory, capital, and labor costs Identification of appropriate interfaces among product design, product engineering, manufacturing engineering, and factory floor procedures as they emerge in computeraugmented work groups
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From page 87... ...
Modeling of manufacturing systems Rapidly reconfigurable production systems Resource description models Knowledge bases for new process methods Demonstration of the resilience of intelligent routing systems with respect to the vagaries of factory conditions Practical open standards for recording and communicating data among parts, assemblies, subsystems, and their network of makers and maintainers Mechanisms for cost-effective embedding of information and for ensuring access throughout the life of a part Ways to efficiently manage large amounts of related data spread over many machines and locations Ways of specifying complex data relationships Ways of ensuring interoperability of design process tools Better ways of encoding and decoding data Improved data retrieval methods, including human interfaces Development of agility in the face of rapid change in a number of important product or process variables Investigation of the feasibility of developing a reasonably universal Product configuration language and methodology Assessment of the feasibility of using programming languages to represent manufacturing operations in the same sense that design languages represent designs Development of systems that simulate the operation of a given manufacturing configuration under a variety of conditions to optimize configuration Development of schemata and models to represent manufacturing resources and their interconnection Development of a robust and flexible system that can model efficiently nearly any process that may be developed
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From page 88... ...
Once determined, the sequence of activities is passed down a control hierarchy that is often organized around equipment (e.g., numerical control machining centers, robot systems, automated ground vehicles, or any other computer-controlled manufacturing equipment and related tooling resources) , workstations of interrelated equipment, and cells of interrelated workstations.
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From page 89... ...
; · Capabilities to deal with the stochastic and sometimes reentrant nature of shop floor events. Within the MRP/MRP-II paradigm, inputs are deterministic estimates of the times for various shop floor operations that are obtained by time and motion studies.
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From page 90... ...
· Techniques to ensure graceful degradation in the event of local problems. Many production operations today are brittle, in that a problem in one crucial location can halt an entire production line.
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From page 91... ...
Research in this area would address diagnosis of plan failures, plan repair, and planner modification, as well as analysis of material handling. · Tools to facilitate situation assessment and scheduling by the factory manager and operations team.
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From page 92... ...
At least two aspects of decentralized control seem worth exploring, autonomous agents and work and logistics flow. Autonomous Agents The use of autonomous agents may offer some potential as a means to handle complex dynamic environments.
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From page 93... ...
· System stability. For sensible decision-making capabilities, autonomous agents must understand how to resolve conflicting goals.
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From page 94... ...
Planned maintenance regimens may also be recorded within the part, automatically trig gelling requests for maintenance. To realize intelligent routing systems, research is needed to identify appro 4 Even if no single agent will be able to demonstrate sophisticated behavior, the possibility remains that a collection of agents may be able to do so.
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From page 95... ...
For example, information technology enables the increased automation of traditional production techniques, as well as new techniques such as stereolithography and material deposition. In addition, many of the individual technologies and components of unattended machine tools and other fabrication and assembly equipment already exist as experimental devices in the laboratory or as commercial products, and in Japan, several "lights-out" factories (factories that operate with limited human involvement)
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From page 96... ...
Controllers are used in many aspects of shop floor operations; factories employ mill drive controllers, cutter controllers, controllers for variable-speed pumps, crane controllers, controllers for large AC/DC rectifiers, controllers for material-handling systems, and automated guided vehicle controllers. For simplicity, the discussion below focuses on tool controllers, although many of the issues discussed also arise for controllers of other types of equipment.
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From page 97... ...
machine industry will grow as market opportunities are expanded for sensor companies, diagnostic software developers, and all ancillary product suppliers. The following research and development areas should be addressed in order to achieve the vision of 21st-century control of factory equipment: · An open architecture for machine controllers.
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From page 98... ...
~ should include provisions not only far realtime control, but also far 1bc operation of accessory devices in co~uncdon Gil arc machining process, a more direct connechon to CAD/ CAM systems and a Oc~iblc inle~cc for user ~plicabons. Such a 1~guapc might also provide con~oHcrs Aim in~adon deeming Tic Cow being pc^~cd, rather 1ban Amply specifying me motion of ~ point ~roupb space (as ~ Tic case for most curing languagesf
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From page 99... ...
· Databases that pass and manage information about events and activities on the shop floor are needed to inform design engineers as well as shop floor workers handling successive shifts. Design engineers may not understand very well what is actually happening on the shop floor; expert system shells have been useful for presenting operators with theoretical best practices and capturing their immediate reactions, which are then routed instantly to engineers along with other information that explicitly defines the context of an operator's remark.
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From page 100... ...
. Desirable features for a factory HCI include: · A direct, easy-to-use interface into product design databases so that product specifications can be easily reviewed on the plant floor; · Support for unusual input/output options necessitated by the factory environment.
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From page 101... ...
But the trade-offs associated with wireless communications in a factory environment are complex, for example: · Trade-offs between the capital costs of fixed building wiring with very high bandwidth versus the facility costs of wireless transmitters and receivers that operate within a very restrictive bandwidth; · Trade-offs among broadcast power, geographical coverage, and multi station interference; and · The potential hostility of the factory environment to such communications (e.g., wireless communications in the presence of radiation-sensitive equipment)
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From page 102... ...
Additional dimensions of equipment controllers are discussed later in this chapter under "Facilitating Continuous Improvement" for reasons that are made clear in that section. Sensors To ensure the optimum performance of production processes, it is necessary to have information on what those processes are actually doing in real time and how those processes are affecting equipment, tooling, work zones, material handling, and workplace material.
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From page 103... ...
Sensors are key elements in the other enabling technologies of process control and process precision and metrology. A vast array of sensors are commercially available or under development in research laboratories; these sensors support unit processes through an extensive array of sensor technologies ranging
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From page 104... ...
Examples of more novel sensors include acoustic sensors to monitor and improve tool performance and surface finish or to monitor the relative location of parts in a finished product; photoelectronic and ultrasonic sensors that enable intelligent processing equipment to position and set functions; and bar code and radio frequency sensors that identify and report on the status and location of parts. In many cases, it is likely that relevant sensor technology will have been first developed for application in other fields.
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From page 105... ...
FACILITATING CONTINUOUS IMPROVEMENT When applied to the shop floor, continuous improvement refers to the continual monitoring of shop floor practice and how that practice is reflected in the products that result. Whereas traditional shop floor environments emphasize the desirability of procedures that are consistent and hence unchanging, continuous improvement suggests instead the incremental evolution of procedures to make products of ever-higher quality and timeliness.
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From page 106... ...
But they are discussed separately from the earlier discussion of equipment controllers in this chapter to underscore their importance in capturing information generated at the back end of the production cycle. CONTROLLING AND MANAGING PRODUCT CONFIGURATION Manufacturers often produce variants of a given product.
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From page 107... ...
The first is that of a single production facility whose internal operations can be modified substantially by software-based changes to machine controllers and schedulers.7 The second notion is that of a manufacturing operation that cart draw globally dispersed units providing specialized expertise and unite them temporarily to carry out a specific production task (e.g., to produce a specific product or product line) and then disband them when the task has been completed.
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From page 108... ...
· What is the trade-off between levels of detail required and the speed of response? · What characteristics and configurations of autonomous agents give rise to emergent behaviors, swarm stability, and divergent behavior?
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