Tali Freed

The Limits of Reflexive Design in a Secrecy-Based Organization

Michael W. Stebbins et al. — Wed, 07 Dec 2011 11:49:48 PST

A Psychological Perspective on Service Segmentation Models: The Significance of Accounting for Consumers' Perceptions of Waiting and Service

Ziv Carmon et al. — Fri, 30 Sep 2011 14:16:08 PDT

We examine how service should be divided and scheduled when it can be provided in multiple separate segments. We analyze variants of this problem using a model with a conventional function describing the waiting cost, that is modified to account for some aspects of the psychological cost of waiting in line. We show that consideration of the psychological cost can result in prescriptions that are inconsistent with the common wisdom of queuing theorists derived according to the conventional approach (e.g., equal load assignments). More generally, our intention in this paper is to illustrate that aspects of the psychological cost of waiting can be accounted for in the analysis of queuing systems, and that this may have significant implications for the service schemes that are derived.

Work Flow Policy and Within-Worker and Between-Workers Variability in Performance

Kenneth Howard Doerr et al. — Fri, 30 Sep 2011 14:16:06 PDT

Work flow policies are shown to induce a change in average between-workers variability (worker heterogeneity) and within-worker variability in performance times. In a laboratory experiment, the authors measured the levels of worker heterogeneity and within-worker variability under an individual performance condition, a work sharing condition, and a fixed assignment condition. The work sharing policy increased the levels of worker heterogeneity and worker variability, whereas the fixed assignment policy decreased them. These effects, along with work flow policy main effects on mean performance times and variability are examined. This article represents an initial step in understanding effects that may be important in the selection of an operating policy, the ignorance of which may lead to costly misestimates of performance.

A Taxonomy of Scheduling Problems in Semiconductor Device Test Operations

Tali Freed et al. — Fri, 30 Sep 2011 14:16:04 PDT

Semiconductor device test facilities differ not only by production volume and tester brands. The complexity of the devices and the characteristics of the testers affect the scheduling methodologies as well. Goals and strategies vary from one firm to another, leading to a variety of objectives and performance measures. Due to random yield lot size is variable and lot priorities are common. Changeover times are oftentimes sequence-dependent. Since semiconductor device testing systems are very costly, scheduling methods that increase the throughput of the facility are financially significant. In this paper we describe a variety of semiconductor device testing environments, develop mathematical formulations for their scheduling problems, and suggest solution methods. The paper is intended to serve as a basis for the development of scheduling systems for a variety of semiconductor device testing facilities.

Proposed Scheduling Methods for Printed Circuit Board Assembly

Tali Freed et al. — Fri, 30 Sep 2011 14:16:02 PDT

The current practice in the assembly of electronic components on printed circuit boards (PCB's) is serial production, a process characterized by very long set-up times.

However. with the advent of efficient on-line process information, new production control methods are now possible. This paper proposes two new production methods - the Grouped Set-up (GSU) method and the Sequence-Dependent Scheduling (SDS) method, which can significantly reduce set-up times.

It is shown that the GSU always performs better than the SDS method in terms of total production flow (throughput). while the SDS performs better than the GSU method in terms of work-in-process (WIP) inventory.

A preliminary model for lot sizing In semiconductor manufacturing

Tali F. Carmon et al. — Fri, 30 Sep 2011 14:16:01 PDT

On Capacity Modeling for Production Planning with Alternative Machine Types

Robert C. Leachman et al. — Fri, 30 Sep 2011 14:16:00 PDT

Analyzing the capacity of production facilities in which manufacturing operations may be performed by alternative machine types presents a seemingly complicated task. In typical enterprise-level production planning models, capacity limitations of alternative machine types are approximated in terms of some single artificial capacitated resource. In this paper we propose procedures for generating compact models that accurately characterize capacity limitations of alternative machine types. Assuming that processing times among alternative machine types are identical or proportional across operations they can perform, capacity limitations of the alternative machine types can be precisely expressed using a formulation that is typically not much larger than the basic linear programming formulation that does not admit alternative resource types. These results have important implications for industrial practice, suggesting that in the case that processing times are nearly proportional among alternatives, the prevalent approximation that involves using a single, capacitated, artificial resource may be dropped in favor of our formulation incorporating the approximation that processing times among the alternatives are proportional. Another advantage is that the set of capacity constraints we formulate can be used to check the feasibility of suggested production schedules or demands simply by plugging them into the constraints, without need to develop values for allocation variables.

Scheduling Semiconductor Device Test Operations on Multihead Testers

Tali Freed et al. — Fri, 30 Sep 2011 14:15:58 PDT

Past attempts to devise scheduling methods for the device test operations of semiconductor manufacturing firms fail to address a significant characteristic of multiple-head test systems—the dependency of processing rates on the lots processed simultaneously on the testers. Since the problem has never been modeled accurately in the scheduling literature, feasibility and performance of previously proposed scheduling methodologies for multihead testers may not be accurately assessed. In this paper, we describe the multihead tester scheduling problem, present an enumeration solution procedure, and illustrate the problems of previously suggested tester scheduling algorithms.

The Benefits of Automatic Data Collection in the Fresh Produce Supply Chain

Ryan Charles Panos et al. — Fri, 30 Sep 2011 14:15:56 PDT

The potential for RFID based systems to improve the safety and efficiency of a supply chain with rapidly decaying products and strict health standards is creating pressure to adopt RFID in several agricultural industries. A handful of fresh produce industry leaders currently participate in mandated pilot projects, while the industry as a whole is still intimidated by the perceived cost of RFID. Therefore in this study we attempt to validate the correlation between performance and automated data collection, paving the way to economic justification of investment in data collection technologies, such as barcode and RFID.

The majority of product in this industry is identified and tracked using pallet barcode labels at the more progressive facilities, or facility-specific manual identification methods at the less advanced facilities. Most fresh produce facilities in the US have minimal information systems capabilities, and most of their logistics operations are documented on paper only.

Thus the form of Automated Data Collection (ADC) used in the more advanced facilities is Barcode-based. This study compares facilities that use ADC with those that do not. Significant advantages of using ADC are found in many areas, especially in product spoilage, administrative labor and space utilization.

In-house development of scheduling decision support systems: case study for scheduling semiconductor device test operations

Tali Freed et al. — Fri, 30 Sep 2011 14:15:55 PDT

Most manufacturing processes can benefit from an automated scheduling system. However;: the design of a fast, computerised scheduling system that achieves high-quality results and requires minimal resources is a difficult undertaking. Efficient .. scheduling of a semiconductor device test facility requires an information system that provides good schedules quickly. Semiconductor device testing-is the last stage of the long semiconductor manufacturing process, and therefore. is subjected to customer service pressures. The cost of an off-the-shelf computerised scheduling system may he prohibitive for many companies. In addition, many companies are taken aback by other characteristics of off-the-shelf scheduling systems, such as code confidentiality, maintenance costs, and failure rates. We draw upon the literature and our field case to discuss some of the"trade-offs bet\',:een in-house development and off-the-shelf acquisition of software: We describe the in-house design and implementation of a scheduling decision :support system for one device test facility. Using the design and implementation process of this system as a case study, we discuss how one facility uses in-house design of systems in a strategic way, as a competitive capability.

Group set-up for printed circuit board assembly

Tali F. Carmon et al. — Fri, 30 Sep 2011 14:15:53 PDT

The current practice in the assembly of electronic components on printed circuit boards (PCBs) is serial production. a process characterized by very long set-up times. However, with the advent of efficient on-line process information .. new production control methods are now possible. This paper proposes a different production method, called the group set-up (GSU) method, which can significantly reduce set-up times. The traditional and the GSU production methods are compared, and it is shown that the GSU always performs better than the traditional method in terms of total production flow (throughput) and labour time However, the traditional method performs better than the GSU in terms of work in process (WIP) inventory; and in some cases, in terms of makespan (lead time). A detailed analysis for a small number of PCBs is presented.

Set-up saving schemes for printed circuit boards assembly

Oded Z. Maimon et al. — Fri, 30 Sep 2011 14:15:52 PDT

Focusing on a basic printed circuit board (PCB) assembly line configuration characterized by very long set-up times, we examine two scheduling methods that can significantly reduce the set-up. Both methods -the Grouped Set-Up (GSU) method that has been recently introduced in the literature and the Sequence Dependent Scheduling (SDS) method, which has not been studied in this context -are based on component commonality among PCB types. Using the typical traditional scheduling method as a benchmark, the GSU and the SDS methods are compared in terms of three performance measures: line throughput, average work-in-process (WIP) inventory level, and implementation complexity. Guidelines for selecting the most appropriate method for a given production environment are proposed. The analysis is illustrated using real data from a typical production line.