Controlling Tolerence Stacks for Efficient Manufacturing

Datum-hierarchy (rooted) trees provide a highly efficient and sound basis for tolerance analysis and automated process planning. This paper builds on the previous work by the authors and shows that it is possible to optimise the structure of datum-hierarchy trees automatically. A process planner specifies an initial tree, which is improved upon by using an evolutionary algorithm and is checked against manufacturing and design constraints. A cost function that takes into account machine changes, datum changes and the sum of tolerance stacks drives the mutation process to generate "minimum cost" trees. Experiments were conducted on four industrial parts to demonstrate the feasibility of the approach. The results demonstrate that the method can reduce machine and datum changes and the sum of tolerance stacks. They also show that the order of priority of the cost criteria has a significant effect on the final shape of the trees.     

Die passive Realisierung vorgegebener Übertragungsfunktionen mit der Minimalzahl von Reaktanzen

Übersicht Die Arbeit befaßt sich mit der Verwirklichung der Übertragungsfunktion des RLCü-Zweitors mit gegebenen ohmschen Abschlußwiderständen durch eine Schaltung mit der geringsten Zahl von Reaktanzen. Dieses Problem wird in zwei Schritten gelöst. Zunächst wird aus der vorgeschriebenen Übertragungsfunktion eine das gesuchte Zweitor beschreibende Matrix vom minimalen Grad bestimmt. Sodann wird diese Matrix durch eine RLCü-Schaltung verwirklicht, die genau so viele Reaktanzen enthält, wie der Grad der berechneten Matrix vorschreibt. Es wird ausführlich die erste der beiden Teilaufgaben behandelt; bei der Lösung der zweiten wird auf bereits bekannte Verfahren zurückgegriffen.

---

Contents This paper presents the realization of the transfer function of an RLCu-two-port inbedded in ohmic impedances by a circuit with a minimum number of reactances. The problem will be solved in two steps. First from the given transfer function a matrix of minimum degree is determined, which describes the desired two-port. Then, this matrix is realized by an RLCu-circuit composed on a number of reactive elements identical with the degree of the determined matrix. The first part of the problem is presented in detail. Known procedures are referenced for solution of the second step.

---

---

Die vorliegende Arbeit entstand während der Zugehörigkeit des Verfassers zum Institut für Theorie der Elektrotechnik der Universität Stuttgart (Prof. Bader).     

Paradigm shift: unified and associative feature-based concurrent and collaborative engineering

With widely used concurrent and collaborative engineering technologies, the validity and consistency of product information become important. In order to establish the state of the art, this paper reviews emerging concurrent and collaborative engineering approaches and emphasizes on the integration of different application systems across product life cycle management (PLM) stages. It is revealed that checking product information validity is difficult for the current computer-aided systems because engineering intent is at best partially represented in product models. It is also not easy to maintain the consistency among related product models because information associations are not established. The purpose of this review is to identify and analyze research issues with respect to information integration and sharing for future concurrent and collaborative engineering. A new paradigm of research from the angle of feature unification and association for product modeling and manufacturing is subsequently proposed.     

Proactive supply chain management in the forging industry

Forging companies are nearly exclusively embedded into supply chains as suppliers and consequently have to accomplish strict requirements concerning their logistic performance. For providing products flexible and responsive to the market proactive supply chain management systems need to be introduced for a quick and reliable delivery to costumers in-time with low risks of failures. Therefore, this paper describes a comprehensive approach for the implementation of operative logistic risk management in the PPC within flexible supply chains. The method developed applies proven statistical fundamentals (e.g. trend analysis) to logistic risk management with the purpose of identifying potential logistic risks, estimating their impact and ranking them according to their importance. Hence, counter measures can be deduced and tested based on material flow simulation to counter balance the identified potential logistic risks.     

Selective Oxidation of 1- and 2-Propanol with Molecular Oxygen by Noble Metal Catalysis in “Supercritical” Carbon Dioxide

The selective oxidation of 1- and 2-propanol by molecular oxygen over supported platinum catalysts was investigated in supercritical carbon dioxide as an environmentally benign and safe reaction medium. The reaction occurs exclusively to acetone or propionic aldehyde and propionic acid in a single-phase region at 100–190 bar and at a mild temperature (40 °C). Compared to conversions in aqueous solution, catalyst stability is significantly enhanced in supercritical carbon dioxide and depends on the oxygen concentration in the reaction medium. Thus, at least a fourfold higher substrate/catalyst ratio than with water as a solvent can be used. Platinum catalysts with nanoporous silica (MCM-41, silicalite-1) as a support are also active for the oxidation of 2-propanol in supercritical carbon dioxide.     

A graph theoretic approach linking design dimensioning and process planning

The purpose of this paper and its companion (Part 2) is to present a rigorous graph theoretic model to link designing with process planning. This paper shows how to generate process plans from design dimension trees. It is the foundation for the companion paper, Part 2, which shows how part dimensioning (during designing) can be guided by knowledge of the datum-hierarchy tree structure underlying process plans. Design dimensions are represented as a design dimension tree, which is the basis for defining an ideal (optimal) datum-hierarchy tree of a process plan. The ideal datum-hierarchy tree, in turn, is used to define measures of process planning efficiency. These measures can be utilised to compare actual process plans and improve manufacturing processes. An example is presented to illustrate the concepts and method.     

Redimensioning parts for manufacturability: a design rewriting system

Both size and geometric dimension specifications contribute to the manufacturability of a part and must therefore be determined carefully to allow for efficient process plans. The presented approach is meant to systematically explore alternative geometric and size dimensions (as standardized in ANSI Y14.5) with the aim of improving the manufacturability of a design and how well-suited it is for a computer-based application.