Lars Penter

The advanced forming process model including the elastic effects of the forming press and tool

This article addresses process, stamping, and manufacturing engineers, as well as tool designers (prototype and series production tools), and press shop planners in the range of metal forming. The paper deals with methods of modelling and simulating the metal forming process and their application in product design, production, and forming process planning. In models usually applied major effects on the forming process are neglected. For instance, the elastic behaviour of presses and die tools is not considered in process and tool planning. Thus, reworking of tools is a consequence of this model oversimplification. The paper illustrates how interactions between forming press, tool and metal forming process can be modelled by enhancing conventional FE models. Several examples demonstrate the information value of the Advanced Forming Process Model (AFPM).

Advanced Forming Process Model - AFPM

This chapter discusses methods of modeling and simulating metal forming processes and explains their application in product design, production and process planning. In today’s Finite Element (FE)-based forming analysis, major effects on the forming process are being neglected. Based on the analysis of the elastostatic press and tool properties, a conventional FE process model was extended with the most dominant elastostatic influences. It is shown that complex elastic systems, such as die cushions and tool guidance, are quite easily implemented in FE process simulations by using discrete elements and other reduction methods, recently introduced in commercial simulation software. The benefit of the Advanced Forming Process Model (AFPM) is demonstrated by an experimental verification. Servo mechanical presses enable the manufacturers to establish high-speed processes in sheet metal forming. There, the dynamic press behavior has a much larger influence on the forming process than it has in the relatively static conventional deep drawing. As an example, a highly dynamic forming process is simulated and explained in the following.

Static compensation for elastic tool and press deformations during deep drawing

Although today’s deep drawing tools are thoroughly designed and calculated by means of computer-aided design (CAD), finite element (FE) simulation and computer-aided manufacturing (CAM), the sequence of operations to put a tool into production still encompasses manual and irreproducible labor. In particular, the die spotting is empirical and is almost entirely dependent on the toolmaker’s experience. This fine-tuning of the drawing tool consumes a large amount of time. In minimizing manual die spotting, a large potential to decrease time and costs exists. This article presents error compensation methods to create deep drawing tools, which require less manual die spotting in order to produce sound quality stampings. In FE simulations of deep drawing operations, it is general practice to assume rigid tool and press properties. The fact that die and punch design are based on these simplifications might be one of the main causes that empirical die spotting is still imperative. Therefore, the authors developed a methodology to compensate the tool face for effects of elastic press and tool deformations, which occur under applied process load. The authors demonstrate the static compensation with two examples. The first shows the static compensation for ram tilting caused by an unbalanced load, which can originate from asymmetric part design and/or eccentric mounted tools. The second example describes the compensation for elastic die deformation caused by local and global deflections. In either case, the compensated die face, under applied process load, deformed into the desired die face. This research work shows the potential and limits of a static compensation for effects of elastic tool and press deformations on the final shape of the stamping.

Das Presswerk auf dem Weg in das Cyber-physische Zeitalter

Kurzfassung Bereits heute sind Presswerke mit Sensorik, Aktorik, Datenspeichern, Datenverarbeitungs- sowie Kommunikationseinheiten ausgestattet und besitzen damit Merkmale eines Cyber-physischen Systems. Konkrete Beispiele im Beitrag zur Sensorik, Datenanalyse und Aktorik zeigen dies auf. Ein Anwendungsbeispiel in Form eines digitalen Zwillings demonstriert die Adaption der Ziehkissen-Zylinderkräfte, basierend auf Ergebnissen der Werkstoffprüfung. Nach Meinung der Autoren wird das Presswerk zukünftig als autonomes System in Echtzeit auf Parameterschwankungen reagieren und Korrekturmaßnahmen selbstständig einleiten können.

Hydraulic Die Cushions in Deep Drawing Presses: Analysis and Optimization Using Coupled Simulation

The scientific paper proposes a method to analyze and optimize the drawing press and the deep drawing process with a virtual model. It focuses on hydraulic multi-point die cushions since they offer a wide range of possible adjustments and a high potential to increase production quality and efficiency. The operator can apply individual die cushion cylinder forces to the blankholder which enables the control of the forming process and manual die spotting can theoretically be reduced to a minimum. Utilizing the virtual model can improve the drawing press’ behavior and significantly reduce the set-up time for drawing presses during try-out of new tools or when tool sets are transferred to a different machine.The paper presents a system simulation model of a deep drawing press including its mechanics, hydraulics, and control. It serves as a basis for developing an advanced control system which improves system performance with potentially higher slide speeds, and therefore, a more efficient production.Another aspect in the paper is the development of a coupled simulation consisting of the machine model and a process model. This includes the elasto-static as well as the dynamic behavior of the drawing press and allows for simulations with the highest possible level of detail. The model was used to determine individual set forces for the die cushion cylinders which allowed for the production of sound quality parts without manual die spotting.Copyright

Systemsimulation in der Umformtechnik

Kurzfassung Die Anwendung der Simulation in der Umformtechnik beschränkt sich bislang vor allem auf den Einsatz quasi-statischer Modelle zur Unterstützung der Prozessgestaltung. Durch neuere Entwicklungen in der Antriebstechnik stehen heute Pressen mit erheblich gesteigertem Bewegungsvermögen zur Verfügung, was zu angepassten Geschwindigkeitsverläufen und letztlich zu einer erhöhten Dynamik bei der Durchführung von Umformprozessen führt. Die vorgestellten Arbeiten untersuchen Wege zu einer durchgehenden virtuellen Analyse von Umformprozessen unter Berücksichtigung der statischen und dynamischen Wechselwirkungen zwischen Maschine und Prozess.