Thomas Roemer

Time-Cost Trade-Offs in Overlapped Product Development

Increasingly shorter product life cycles impel firms to design, develop, and market more products in less time than ever before. Overlapping of design and development stages is commonly regarded as the most promising strategy to reduce product development times. However, overlapping typically requires additional resources and can be costly.Our research addresses the trade-off between product development time and costs and introduces an algorithm to determine an appropriate overlapping strategy under different scenarios. The methodology developed was successfully employed at Rocketdyne Division of Rockwell International.

A Single-Product Inventory Model for Multiple Demand Classes

We consider a single-product inventory system that serves multiple demand classes, which differ in their shortage costs or service-level requirements. We assume a critical-level control policy, and a backorder clearing mechanism in which we treat a backorder for a lower-priority class equivalent to a reserve-stock shortfall for the higher-priority class. We show the equivalence between this inventory system and a serial inventory system. Based on this equivalence, we develop a model for cost evaluation and optimization under the assumptions of Poisson demand, deterministic replenishment lead time, and a continuous-review (Q, R) policy with rationing. We propose a computationally efficient heuristic and develop a bound on its performance. We provide a numerical experiment to show the effectiveness of the heuristic and the value from a rationing policy. Finally, we describe how to extend the model to permit service times, and how to extend the model to a multi-echelon setting.

Concurrent Crashing and Overlapping in Product Development

This research addresses two common tools for reducing product development lead times: overlapping of development stages and crashing of development times. For the first time in the product development literature, a formal model addresses both tools concurrently, thus facilitating analysis of the interdependencies between overlapping and crashing. The results exhibit the necessity of addressing overlapping and crashing concurrently, and exhibit general characteristics of optimal overlapping/crashing policies. The impact of different evolution/sensitivity constellations on optimal policies is investigated, and comprehensive guidelines for structuring development processes are provided. For the special case of linear costs, an efficient procedure is presented that generates the efficient time-cost trade-off curves and determines the corresponding optimal overlapping/crashing policies. The impact of key parameters and the robustness regarding their estimates is illustrated with a simple two-stage example.

Structuring product development processes

Abstract This paper proposes operational frameworks for structuring product development processes. The primary objective of this research is to develop procedures to minimize iterations during the development process which adversely affect development time and costs. Several procedures are introduced to restructure the development process. The computation of the corresponding product development times is facilitated by two Markov models addressing different types of learning. The methodologies are employed to identify a set of managerial concerns in restructuring the product development processes. The developed framework has become an integral part of a re-engineering project for the development of rocket engines at Rocketdyne Division of Rockwell International. Throughout the paper, the methodologies are illustrated with the help of this process.

Investigating the role of IT in customized product design

Realizing product customization as ‘just a mouse click away’ is the ultimate dream of many organizations and customers. To date though, mass customization is generally delivered through standardized products or custom-assembly of standardized components – often neglecting the product development aspect of customization through providing custom-designed products. In this paper we address this gap, and in particular investigate – both theoretically and empirically – the role of IT in product development-related customization. We revert to the automotive industry, which although it has long progressed beyond ‘any colour as long as it is black’, still offers only limited customization possibilities to its customers.

A note on the complexity of the concurrent open shop problem

The concurrent open shop problem is a relaxation of the well known open job shop problem, where the components of a job can be processed in parallel by dedicated, component specific machines. Recently, the problem has attracted the attention of a number of researchers. In particular, Leung et al. (2005) show, contrary to the assertion in Wagneur and Sriskandarajah (1993), that the problem of minimizing the average job completion time is not necessarily strongly NP-hard. Their finding has thus once again opened up the question of the problems complexity. This paper re-establishes that, even for two machines, the problem is NP-hard in the strong sense.

Configuration and coordination of activities within a supply chain: exploring the synergy between modularity and information technology

This research studies the impact of information technology-enabled coordination on product modularisation in the automotive industry. A structural equation model is tested based on 177 responses to questionnaires from 177 Korean first-tier automotive suppliers. The results provide support for the hypothesis that high quality of exchanged information enables better supply chain coordination, which in turn supports product modularisation.

The Traveling Salesman Problem with flexible coloring

This paper introduces a new generalized version of the Traveling Salesman Problem (TSP) in which nodes belong to various color classes and each color class must be visited as an entity. We distinguish the cases of the problem for which the colors are either pre-assigned or can be selected from a given subset of colors. We establish computational complexity and provide concise formulations for the problems that lend themselves to derive tight lower bounds. Exact solutions for special cases and a two-phase heuristic for the general case are provided. Worst case performance and asymptotic performance of the heuristic are analyzed and the effectiveness of the proposed heuristic in solving large industrial size problems is empirically demonstrated.