Alessandro Selvaggio

Extrusion Benchmark 2011: Evaluation of Different Design Strategies on Process Conditions, Die Deflection and Seam Weld Quality in Hollow Profiles

In the paper experimental investigations aimed at allowing a detailed and accurate comparison of different FEM codes were presented and discussed. Two hollow profiles within the same die were characterized by different thicknesses within the profile, two welding chambers and critical tongues (one fully supported and one partially supported). The material flow balance was performed by means of feeder size and position on a profile and by means of bearings on the other one. Accurate monitoring of process parameters was carried out by using a self-calibrating pyrometer for profile temperature, six thermocouples for die thermal monitoring, a laser velocitymeter for profile speed and two laser sensors for die deflection on critical tongues. AA6082 alloy was used as deforming material, while H-11 hot-work tool steel was selected for the die material. The experiments were repeated at least three times under the same conditions in order to provide a nearly steady state statistical distribution of the acquired data. These are used as a reference for the 2011 edition of the extrusion benchmark.

Curved Profile Extrusion

Curved profiles are essential components in lightweight constructions. Besides weight reduction, the preservation or even the improvement of functions in the component are pursued. Space-frame concepts are an option to achieve these aims, in which straight and curved extruded profiles are applied. With regard to design aspects, curved profiles gain in importance. Conventionally curved aluminum profiles are manufactured by the process chain including straight bar extrusion, stretching and bending. In comparison to conventional bending processes, the innovative curved profile extrusion offers great advantages concerning a precise, flexible, and cost effective production as well as the possibility to use innovative lightweight materials, such as magnesium or reinforced alloys. Besides the process principles and advantages, several results of investigations of fundamental and application-oriented research in the field of curved profile extrusion are presented in this paper.

Extrusion Benchmark 2013 - Experimental Analysis of Mandrel Deflection, Local Temperature and Pressure in Extrusion Dies

A bridge die was designed for the simultaneous extrusion of two rectangular profiles and used in a strictly monitored aluminum extrusion process. Experimental investigations aimed at the measurement of the mandrel deflection, the local die temperature, and the pressure inside the welding chamber by means of special measurement equipment. AA6082 alloy was used as extrusion material. The influence of the extrusion speed on the aforementioned objectives is reported. The experiments were repeated at least three times under the same conditions in order to achieve a statistical validation of the acquired data. These data are provided as reference for the 2013 edition of the Extrusion Benchmark.

Towards the flexible and near-net-shape production of three-dimensionally curved extrusion profiles

The present paper describes the new developments in continuous extrusion of curved profiles by a flexible production method which is composed of a short process chain starting with the extrusion press, a deflection tool, one robot for the flying cutting of the profile and another robot for supporting and handling the profile. Because of the flexibility of this complete system according to the profile curvature it is convenient for small-volume production. In order to reach high profile accuracy all kinematic systems in the process chain have to be synchronized with the profile speed caused by the extrusion process. The results of the investigation of different existing synchronization methods identify the need for an additional measuring system to compensate the large deviation of the cut profile length. By adjusting parameters of the synchronization the accuracy of the profile length could be strongly improved. Furthermore influencing parameters like die deformation during the extrusion process are measured and combined with the results of the cut profile length over the process time.

Increasing the production accuracy of profile bending with methods of computational intelligence

Important quality criteria for profile bending are an accurate profile contour and an accurate cross section. During the bending process, torsion of the profile, deformation of the cross section, and deviations at the profile contour can occur. If these undesired effects are too large, the bent profile is not usable. Critical causes of profile cross section deformation are thin wall thicknesses with hollow sections. The profile torsion is favored by asymmetrical profile cross sections. These effects can be minimized by a production-correct profile design, whereby a trade-off between a production-correct design and the boundary conditions exists. Furthermore, undesired variations in the profile material properties and the profile cross section lead to deviations in the profile contour. These deviations cannot be reduced by design but by usage of a closed-loop control during bending. In this article, a software system for three-roll bending is presented that minimizes undesirable effects during bending by structure optimization of the profile cross section and application of closed-loop control. The structure optimization is based on an evolutionary algorithm and the process control uses a neuro-fuzzy controller. The structure of the software system and results of experiments are presented and discussed.1

Prozesskette zur flexiblen Herstellung leichter Tragwerkstrukturen: Steigerung der Qualität und Zuverlässigkeit

Kurzfassung Im Rahmen des Sonderforschungsbereich Transregio 10 (SFB/TR 10) „Integration von Umformen, Trennen und Fügen für die flexible Fertigung von leichten Tragwerkstrukturen“ wird eine Prozesskette zur produktflexiblen Kleinserienfertigung von Space-Frame-Rahmenstrukturen aufgebaut. An diesem Forschungsprojekt sind Institute der Technischen Universität Dortmund, der Technischen Universität München und der Universität Karlsruhe (TH) beteiligt. Um bereits frühzeitig die Qualität und die Zuverlässigkeit der Prozesskette zu verbessern, wurde in einem standortübergreifenden Qualitätsarbeitskreis eine System-FMEA Prozess für die einzelnen Teilprozesse durchgeführt. Mit dieser konnten projektbegleitend potenzielle Fehlerschwerpunkte ermittelt und gezielt Gegenmaßnahmen eingeleitet werden. Im folgenden Artikel werden die eingeleiteten Fehlervermeidungsmaßnahmen für die am SFB/TR 10 beteiligten Prozesse und Verfahren beschrieben. Die Prozesse sind im Einzelnen: Das mehrachsige Runden beim Strangpressen sowie das darauf folgende fliegende Abtrennen zur Herstellung der Rahmenelemente, eine flexible und intelligente Greiftechnik in Kombination mit einer Handhabungs- und Bearbeitungskinematik zur spanenden Bearbeitung sowie als letzte Schritte die Verfahren Innenhochdruckfügen, Rührreibschweißen und Laserstrahlschweißen zum Fügen der Einzelteile zu einer Rahmenstruktur.

Development of a tele-operative control for the incremental tube forming process and its integration into a learning environment

A deficient access to experimental equipment leads to the usage of remote labs to improve engineering education and open experiments for every student location - and time - independent. The usage of a tele-operative controlled industrial bending process in lecture combines theoretical learning contents with practical experiences. Lecturers can make experiments in interaction with the students, who are able to assist in choosing the process values. The chosen and presented bending process is the incremental tube forming process that uses in contrast to many ordinary bending processes targeted the superposition of stresses. By superposing of stresses, in this process for example a tube bending and a tube spinning process, several fundamental process characteristics can be observed and integrated into lectures to visualize the theoretical fundamentals behind. Incremental tube forming combines the tube spinning process, which affects the diameter of the tube all along the tube and creates a compressive stress, and a bending process. The understanding of superposition of stresses and the process phenomena are ambitious, so that experimental experience is very useful. By using a tele-operative control, the experiment is location- and time-independent available for lecturers and students all over the world. They can interact with the process like stopping it, influencing it during the process or laying it up. The possibilities for a usage in learning environments are described and pointed out.

Lightweight Construction by Means of Profiles

This paper shows some product and process developments at the Institute of Forming Technology and Lightweight Construction of the TU Dortmund University supporting the lightweight construction. It presents the manufacturing of lightweight profiles by hot extrusion and their benefits as well as their design, material, and manufacturing potential for lightweight construction. Examples of process extensions in hot extrusion like curved profile extrusion, twisted profile extrusion and manufacturing of functional graded profiles and profiles with variable cross-sections during extrusion are shown. These procedures allow a flexible change of the profile geometry or contour in longitudinal axis and, therefore, support the shape lightweight construction. Other extensions like composite profile extrusion and energy efficient extrusion of profiles from scrap materials like chips support the material lightweight construction. The manufacturing and use of these profiles allow the realisation of diverse lightweight construction principles and promise to become a pillar of lightweight construction in future.

Demonstration of deep drawing experiments in a remote lab environment

Understanding fundamental process limits is a crucial skill for all types of engineers. In mechanical engineering, this especially applies to the field of metal forming. To have the students understand the different limits of the commonly used deep drawing process, e.g. the influence of the clamping force, a tele-operative testing cell was developed at the Institute of Forming Technology and Lightweight Components of TU Dortmund University. The live experiments that can be conducted using this testing cell are included in different lectures as well as in remote labs which are accessible online for students around the world. In either case, the experiments are used to have the students realize on their own what different types of limits exist and when they occur.

Advanced extrusion processes

Abstract This paper focuses on new extrusion processes for the improvement of product quality, the reduction of process chains and the saving of our available resources. The presented and discussed technologies cover the extrusion of reinforced profiles, curved profiles and twisted profiles. Besides, the process principles and advantages, several results from numerical and experimental investigations are given in order to show the motivation for fundamental and application oriented research in the field of extrusion technology.