G-networks with resets

Gelenbe networks (G-networks) are product form queuing networks which, in addition to ordinary customers, contain unusual entities such as “negative customers” which eliminate normal customers and “triggers” which move other customers from some queue to another. These models have generated much interest in the literature since the early 1990s. The present paper discusses a novel model for a reliable system composed of N unreliable systems, which can hinder or enhance each other’s reliability. Each of the N systems also tests other systems at random; it is able to reset another system if it is itself in working condition and discovers that the other system has failed, so that the global reliability of the system is enhanced. This paper shows how an extension of G-networks that includes novel “reset” customers can be used to model this behavior. We then show that a general G-network model with resets has product form, and prove existence and uniqueness of its solution.     

Implementing mass customization

Total Customer Satisfaction today can mean embarking on “Mass Customization”: giving every customer a product tailored specifically to his or her needs. In the past, manufacturing was usually “high volume, low mix”, characterized by keeping costs down with economies of scale, or “low volume, high mix”, incurring costs and time for changeovers and special handling. Today's mass customization, however, can result in a challenging manufacturing environment with both high volume and high mix, where customers expect individualized products at the same price they paid for mass-produced items. Meeting this challenge requires changes in the manufacturing processes. Equipment must be more flexible. Most important are the computer systems which support the manufacturing enterprise. Never has data been so essential to define, control, and monitor manufacturing as with mass customization. Motorola's product lines — from the pagers with millions of possible options, to the cellular phones and semiconductors — are all experiencing the move to mass customization. This presentation will describe some Motorola examples and the methods used to achieve world-class manufacturing under these conditions.     

A synopsis of industrial engineering methods utilized in designing for the environment

Environmentally Conscious Manufacturing and Designing for the Environment have become considerably important in the recent years due to the results of sustained high living standards and dynamic population growth. The scope of activity involved is immense. Physical products must not only proceed from “cradle to grave” but now must proceed “cradle to reincarnation”. Business practices must be altered and enhanced to address a multitude of items needed to produce products with less overall environmental impact. This paper presents both the physical product system and the business process system and identifies key areas where the competencies of industrial engineers can best be used.     

A heuristic for determination of optimal capacity of central storage

A system of one machine used to produce m products in batches and a central storage used for storing raw materials and finished products is considered. The system maintains enough finished products to assure no stockout will happen. The machine has a finite production rate greater than or equal to the demand rate for each product, and thus operates with periodic start-ups and shut-downs. For special case when set-up for each product requires time and every product is produced in every cycle, the best policy given limited storage space is determined, and total production cost as a function of set-up costs, carrying cost, storage cost, and material handling cost is presented. A heuristic is developed that determines “optimal feasible cycle time” such that production scheduling remains feasible, the capacity of the central storage is not exceeded, and the overall costs are minimized.     

Group technology applications in manufacturing operations through the computer system

The typical manufacturing facility is constantly developing new product designs and related manufacturing processes. The increased volume of new designs and processes causes rapid and inefficient construction of product designs and manufacturing processes. Many parts and manufacturing processes are developed over the life cycle of a production facility with no organized means of cataloging this past and present data. This procedure is extremely ineffective because there is no way to determine if a part or process has been previously developed. The constant “reinventing of the wheel” creates a tremendous waste of manpower and cost.

One approach to solving this problem is through the use of group technoogy. Group technology is the identification and grouping of similar parts and processes in order to take avantage of their similarities in the design and manufacturing process. Parts and processes can be grouped under a classification and implemented with a coding system. Concurrently, the number of parts and processes can be reduced by putting them in a “family.” This “family” has common characteristics such as shape, size, color, tolerance or production operations.

For handling and manipulation of this data, a computer system has been developed. The computer system would set up a reporting format that would classify, code and group the parts and processes, so the user can analyze if a previously designed process or part can be used in the current system and/or if a better layout can be feasible.

Many advantages such as reduced inventory cost, increased facility space and better utilization of manpower are but a few of the benefits from this system.     

Stability and performance analysis of mixed product run-to-run control

Run-to-run control has been widely used in batch manufacturing processes to reduce variations. However, in batch processes, many different products are fabricated on the same set of process tool with different recipes. Two intuitive ways of defining a control scheme for such a mixed production mode are (i) each run of different products is used to estimate a common tool disturbance parameter, i.e., a “tool-based” approach, (ii) only a single disturbance parameter that describe the combined effect of both tool and product is estimated by results of runs of a particular product on a specific tool, i.e., a “product-based” approach. In this study, a model two-product plant was developed to investigate the “tool-based” and “product-based” approaches. The closed-loop responses are derived analytically and control performances are evaluated. We found that a “tool-based” approach is unstable when the plant is non-stationary and the plant-model mismatches are different for different products. A “product-based” control is stable but its performance will be inferior to single product control when the drift is significant. While the controller for frequent products can be tuned in a similar manner as in single product control, a more active controller should be used for the infrequent products which experience a larger drift between runs. The results were substantiated for a larger system with multiple products, multiple plants and random production schedule.     

Justification of new technologies through the use of “cause and effect” analysis: Case of tile replacement at Kennedy space center

This paper presents a case of introducing new technology to a single stage in a maintenance operation composed of sequence of stages. The process - Thermal tile replacement - is a low volume, high value operation. A method for data collection at each stage, to estimate the variability in process quality, cost and duration is presented. The method involves: Identifying key product features, accuracy measure for each, rate of product rejection by feature and the associated probability density functions at each stage. The method relates accuracy variability by feature, “effect” to the contributing stage in the process “cause”. Simulation is used to justify the introduction of a new technology and to predict the percentage of product conformity in a “before” and “after” scenarios for the implementation of the new technology. The simulation model enables the quantification of technology impact on the product quality, overall productivity and the associated cost savings.     

Shelf life determination using sensory evaluation scores: A general Weibull modeling approach

Sensory evaluations to determine the shelf life of food products are routinely conducted in food experimentation as a part of each product development program. In such experiments, trained panelists are asked to judge food attributes by reference to a scale. The “failure time” associated to a product unit under test is usually defined as the time required to reach a cut-off point previously defined by the food company. Due to the destructive nature of these evaluations, one never knows the exact “failure time” of a given unit. Consequently, data arising from these studies are either left or right censored. This article deals with the problem of modeling such kind of data for shelf life determination and develops a general Weibull model (GWM). Simulations indicate a good performance of the parameter estimates obtained though the GWM. The modeling approach is applied to a real data set.     

Scheduling concurrent production over a finite planning horizon: polynomially solvable cases

The paper analyzes a manufacturing system made up of one workstation which is able to produce concurrently a number of product types with controllable production rates in response to time-dependent product demands. Given a finite planning horizon, the objective is to minimize production cost, which is incurred when the workstation is not idle and inventory and backlog costs, which are incurred when the meeting of demand results in inventory surpluses and shortages. With the aid of the maximum principle, optimal production regimes are derived and continuous-time scheduling is reduced to a combinatorial problem of sequencing and timing the regimes. The problem is proved to be polynomially solvable if demand does not exceed the capacity of the workstation or it is steadily pressing and the costs are “agreeable”.

Scope and purpose

Efficient utilization of modern flexible manufacturing systems is heavily dependent on proper scheduling of products throughout the available facilities. Scheduling of a workstation which produces concurrently a number of product types with controllable production rates in response to continuous, time-dependent demand is under consideration. Similar to the systems considered by many authors in recent years, a buffer with unlimited capacity is placed after the workstation for each product type. The objective is to minimize inventory storage, backlog and production costs over a finite planning horizon. Numerical approaches are commonly used to approximate the optimal solution for similar problems. The key contribution of this work is that the continuous-time scheduling problem is reduced to a combinatorial problem, exactly solvable in polynomial time if demand does not exceed the capacity of the workstation or the manufacturing system is organized such that the early production and storage of a product to reduce later backlogs are justified.     

Development of a complex mixed production system for plain paper copier machines

Manufacturers now face the challenges of increased product variety, the need for small-to-medium-quantity production, shortened product life cycles, and reduced costs due to changes in customer demand. Total factory automation, including the automation of assembly as well as indirect (overhead) functions, must be realized for these challenges to be met.

Ricoh's factory for the production of the Plain Paper Copier (PPC) has developed a new production system employing hardware, software and “humanware”. This system has an automated production support system (RINKS), assembly system, and physical distribution system. It is network composed of computer and terminals. This article discusses the development and implementation of Ricoh's system.     

Have we Forgotten the Fundamental it Enabler: Ease of Use

“I asked for a glass of water and got a hose in the face.” That's how one IT customer explained to his IS manager the latest and greatest e-mail system that their company installed. the system simply overwhelmed users with its myriad of functions. It seems that as computers and software grow more powerful, they are also growing too complex for most IT customers to use. This article is a reminder that using information technology should help people accomplish tasks and not be a task itself.     

Simulation and design of a dual-kanban production system

A procedure to evaluate system design parameters for “pull” production strategies is presented in this paper. The evaluation procedure is based on a cost function which includes the inventory carrying, storage, setup, stockout, and idle costs. A combined SLAM II/FORTRAN simulation model and electronic spreadsheets support the evaluation procedure. A “pull” production strategy using the dual-kanban production control method is modeled. The best design in terms of unit load size/number of kanbans is found to (a) satisfy daily production requirements and (b) minimize the cost function.     

Architectural requirements for rapid development of agile manufacturing systems

As product life cycle becomes shortened, high product quality becomes necessary for survival, and continuous and unexpected change becomes key obstacles in success, the need for a method of rapidly and cost-effectively developing products, production facilities and supporting software including design, process planning, shop floor control systems becomes urgent. The essence of this concept of manufacturing would be characterized by adopting a new term “agility”. Agile manufacturing can be successfully accomplished using various well-defined system architecture. This paper provides a primary sketch of architectural requirements for rapid development of agile manufacturing systems.There are several aspects of system architecture : control, function, process, information, communication, distribution, development, and implementation.In the past, the confusion of those architectures prohibited the successful construction of the automated CIM systems.     

The Wizard of OZ in Crmland: Crm's Need for Business Process Management

For several years now the focus of CRM has been to make it easier for companies to “reach out and touch” their customers, and vice versa. We have seen an explosion of technologies (wireless, chat, Web portals, voice recognition, analytics, and so on) that have made it convenient for customers to contact vendors, for employees to obtain information, and for companies to hone in on their most valuable assets - profitable customers. Over the last year, CRM company revenues have soared as the big get huge, and the small pick up sizable crumbs left over from the CRM table. Sure, the market is consolidating; but the CRM money machine rolls on.     

A computerized quality function deployment approach for retail services

Product and service quality can only be effectively improved when the most important needs of customers are satisfied. Quality Function Deployment (QFD) is an approach used to guide R&D, manufacturing, and management toward the development of products and services that satisfy the needs of consumers. The QFD operations are performed by way of a diagram called the House of Quality (HOQ). The HOQ contains information about the customers' needs (what), mechanisms to address these needs (how), and the criterion for deciding which “what” is the most important and which “how” provides the greatest customer satisfaction. A less familiar application of QFD is for the improvement of retail services. When QFD is applied to retail services, a computerized HOQ approach becomes integral to the process for providing continuous, iterative quality improvement. The objective of this research is to develop a formal QFD methodology for the retail industry and to build a computerized retail QFD system. The system provides a HOQ architecture for specifying and analyzing the customers' needs, deriving improvement strategies, and formalizing records of progress. Furthermore, two ranking methods that apply customer satisfaction theory are used to assist managers improve retail services. This system provides an integrated workbench for building retail HOQs and designing retail service strategies.     

A strategic decision support system for supply network design and management in the semiconductor industry

This paper presents a strategic decision support system (DSS) which has been conceptualized and designed by SEMATECH^* to assist the large semiconductor manufacturing organization in managing its extensive supply chain network. This DSS has been named “Manufacturing Enterprise Model” or “MEM”. MEM ties each factory and its primary metrics to the rest of the business enterprise to assess how changes in wafer fabrication affect other factories, the distribution system, and customer deliveries. The model is intended to be used to evaluate future factory concepts and to assist business planners in strategic decisions about product allocation and major resource/facility planning.     

A decision support system for production planning and bid preparation for a small job shop manufacturer

With the advent of the inexpensive micro-computer, small manufacturers have been able to automate many applications in their day-to-day operations. Under the auspices of the State of Missouri “Productivity Improvement Program” - a program to aid small manufacturing businesses in improving their productivity, a Decision Support System (DSS) was developed to assist a small metals manufacturing company in production planning and bid preparation.

The DSS was developed at UMR by a graduate student as part of his master's thesis; the work was funded by both the Productivity Improvement Program and the small manufacturer. After development of the DSS, the graduate student was hired full time for one year to assist the manufacturer in implementing the DSS and to train on site personnel in its operation.

This paper discusses the development of the DSS, its implementation, and its utilization.     

Approximate analysis of finite fork/join queueing networks

We perform an approximate analysis on the finite-buffered acyclic fork/join queueing networks under the “blocking before service” mechanism. This study, besides being able to handle a network with complex topology and with finite buffers, is more general than the existing ones of its kind in that two performance measures, the system throughput and the average number of customers in each buffer, are taken into account. For a simple two-sibling network, we propose in detail a decomposition algorithm in which each decomposed subsystem carries over the local fork/join/tandem structure. The extension of this algorithm to a more general system is also discussed. Experimental results are provided showing that the proposed algorithm yields accurate results on the two performance measures.     

Analysis of multi-stage production/inventory system with an acceptable response time

This paper describes a method to decide the inventory levels of semifinished and finished products so as to realize the target service rate by shipping the finished products within a specified time which we call the acceptable response time. We analyze the substitution relation between the acceptable response time and the inventory levels of semifinished and finished products. As a result, inventory levels required according to the length of the acceptable response time under the condition of satisfying the target service rate are obtained. The validity of our method is also demonstrated through simulation experiments with the conditions given by the analysis.