CIRP Annals - Manufacturing Technology 58 (2009) 588–607 Contents lists available at ScienceDirect CIRP Annals - Manufacturing Technology journal homepage: http://ees.elsevier.com/cirp/default.asp Interaction of manufacturing process and machine tool C. Brecher (2)*, M. Esser, S. Witt Laboratory for Machine Tools and Production Engineering, RWTH Aachen University, Aachen, Germany ARTICLE INFO ABSTRACT Keywords: Analysing the machine tool and the machining process individually is necessary in order to tackle the Machine challenges that both have to offer. Nevertheless, to fully understand the manufacturing system, e.g. Modelling vibrations, deflections or thermal deformations, the interactions between the manufacturing process and Process–machine interaction the machine tool also have to be analysed. In cutting, grinding and forming there are important effects that can only be explained through these interaction phenomena. This paper presents the current state of research in process–machine interactions for a wide variety of manufacturing processes. It is based on the findings of the CIRP research group ‘‘Process Machine Interaction (PMI)’’ and on the international publications in this field. Cutting with defined and undefined cutting edges as well as sheet and bulk metal forming are the key processes. The emphasis is on understanding, modelling and simulating all modes of interaction. Additional needs of research in process–machine interaction are identified for future projects. ß 2009 CIRP. 1. Introduction and historical review first time a series of different projects on process–machine interactions during grinding. In 2004, Altintas and Weck [10] In an industrial context, production costs are often lowered by summarised a large number of the characteristics of the reducing manufacturing times. With this as the objective, machine regenerative effects during grinding, turning and milling. Research tools are continually being improved with respect to their speed, results for the various forming procedures are very sparse. To date, acceleration and process force. Moreover, processes are also there is no comprehensive compilation of the mechanisms of continually undergoing optimisation. Higher cutting and forming interaction for the different processes. For this reason, a vast range speeds, improved machine-tool concepts, wider contact and of different topics in the field of process–machine interaction have greater degrees of forming should enable processes to be carried been gathered together in the CIRP Working Group ‘‘Process– out more economically. The problem is that when optimised Machine Interaction’’. For the purposes of this paper, the topics manufacturing concepts are developed, the machines operate have been complemented, structured, generally summed up and particularly fast, but they either do not meet the requirements in evaluated. terms of part quality or else the machine components and tools Fig. 2 shows the possible interactions between machine and have short service lives. process, using a milling machine as an example. The continuity of interaction, i.e. the continuous and mutual influence exerted by 1.1. Motivation both machine and process, results in the often unpredictable effects of the interaction. In many cases, predictions can only be In many cases, the reason for such problems is not due to the made by means of complex simulations. incorrect planning of machines or processes, but rather due to The challenges arising from this were recognised many years additional effects that can only be explained by the interaction of ago, but were at first investigated only tentatively. machine and process. Fig. 1 shows the results of such effects, using various processes as examples. In research, these production–technical processes and the mechatronic structures involved, i.e. the machine tools have been dealt with separately up to now. However, in recent years it has been considered increasingly necessary to treat processes and structures in an integrated way, thereby overcoming the wide- spread independent treatment of such systems. Observations generally originate in details and certain specific mechanisms of the interaction. Recently, Biermann et al. [28] documented for the * Corresponding author. E-mail address: [email protected] (C. Brecher). Fig. 1. Motivation for PMI research. 0007-8506/$ – see front matter ß 2009 CIRP. doi:10.1016/j.cirp.2009.09.005 C. Brecher et al. / CIRP Annals - Manufacturing Technology 58 (2009) 588–607 589 describing the individual components of the overall system. This section is dedicated to achievements in the research of machine tools and processes as individual elements. Most of these have been summarised in keynote papers over the last few years. 2.1. Structural behaviour of machine tools The task of machine tools and their components is to generate the movements and forces necessary for executing a process. It is presupposed that the available forces are great enough and the movements fast and precise enough to complete the process successfully. However, disturbances that take effect during the process may negatively influence the behaviour of the machine. In general, such disturbances are forces, moments Fig. 2. Interactions between process and machine tool. or heat input. The relationship between the thermal load of the machine and the thermal drift of the cutting process is very complex. Due to the 1.2. History of international PMI research inaccurate knowledge of heat sources, thermal boundary condi- tions, mechanisms of heat transfer, etc., precise prediction of the The first work on interaction in cutting machines was carried behaviour of a standard machine tool at the design stage is very out as early as the 1950s. Some researchers found that chatter in difficult [202]. The research in this field has been summarised in turning and milling operations does not result from negative keynote papers by Bryan [53] and Weck et al. [202]. Some models damping of the chip formation process. Instead, they outlined self- offer a reliable correlation between thermal load and displace- excited vibrations with a force–displacement interaction between ment, but the metrological effort as well as the model complexity is the machine tool and the cutting process [119,143,181]. Based on high. this work, an effective circle of researchers formed within the CIRP- The correlations between force and displacement are easier to Ma group (today: STC M). From 1969 onwards, this group set itself handle because in general the force acts solely at the tool centre the goal of ascertaining the dynamic cutting force coefficients that point. The measurement of the correlation between force and describe the cutting process within this interaction [189]. displacement in static and dynamic cases has already been state- Ultimately, it was possible to predict the chatter phenomenon of-the-art for a long time. Nowadays it is also possible to simulate within certain limits [47,159]. Since then, modelling the range of the determination of machine behaviour. The relevant advances actions that includes processes and machines in a mutually were noted in 2005 by Altintas et al. [11]. Fig. 4 summarises the interactive system has become established as a possible means of possibilities of the computer-supported analysis, prediction and explaining complex behaviour. design of a machine tool. The broad application of this analysis concept resulted in a large Moreover, in the past few years many new challenges in the number of papers in all areas of cutting with defined and undefined analysis of machine-tool structures have been described. Here, we cutting edges. For some years, forming operations have also been must mention in particular the stringent requirements placed on viewed within the closed loop formed by process and machine. machine tools by high process speeds [190], the emergence of Since 2004, the (sometimes widely varying) research papers have parallel-kinematic structure [203], and the increased use of been summarised as one of the Priority Programs of the German adaptronic devices [151]. The fields of research mentioned and Research Foundation (DFG) (Fig. 3). the respective advances that have been made provide a solid At the international level, within the framework of the CIRP foundation with regards to the modelling of machine structures in General Assemblies and winter meetings, working sessions of the interactive systems. PMI (Process–Machine Interactions) Collaborative Working Group were held between 2003 and 2008. This group created a forum for 2.2. Cutting and grinding processes the presentation of very different papers, with the objective of comprehending and predicting such effects. The purpose of this In cutting and grinding, many parallel developments have been keynote paper is not least to summarise the research results carried out. The move towards faster processes may be one of the presented there. most important fields of research. Schulz et al. and To¨nshoff et al. have summarised these process developments for cutting and 2. Modelling of single phenomena grinding respectively [177,192]. Fig. 5 shows other important fields of research. Overviews of the Long before the interaction between machine tool and process various modelling approaches are given in [46,191] for grinding was treated, great advances were made in understanding and and in [139] for cutting. Fig. 3. History of PMl research. Fig. 4. Research on machine tool behaviour: virtual prototypes [11]. 590 C. Brecher et al. / CIRP Annals