Uwe Heisel

Reconfigurable Manufacturing Systems

Manufacturing companies in the 21st Century will face unpredictable, high-frequency market changes driven by global competition. To stay competitive, these companies must possess new types of manufacturing systems that are cost-effective and very responsive to all these market changes. Reconfigurability, an engineering technology that deals with cost-effective, quick reaction to market changes, is needed. Reconfigurable manufacturing systems (RMS), whose components are reconfigurable machines and reconfigurable controllers, as well as methodologies for their systematic design and rapid ramp-up, are the cornerstones of this new manufacturing paradigm.

Machine Tool Design Requirements for High-Speed Machining

Abstract The high speed machining process requests completely new demands for the mechanism of such processing equipment, as due to the process, path speeds exceeding 50 m/min can be achieved. In this field, potential capacities of manufacturing processes require a dynamic behaviour ten times higher than conventional machine tools and increased accuracy. This can be solved by the systematical evaluation of suitable machine kinematics, by the application of linear direct drives with high k v -factors as well as by mass reduction of the axis through light weight components of sheet metal.

Thermal Behaviour of Industrial Robots and Possibilities for Error Compensation

Abstract The fundamental differences between the kinematics of SCARA-, six-axes- and portal robots as well as tripod and hexapod machines are also reflected in their varying thermal behaviour This paper describes the sequential investigation of the thermal behaviour of industrial robots with a standardized experimental setup It includes a comparison of the results for the different robot types as well as conclusions regarding improvement possibilities in robot design. There are also suggestions for the compensation of errors due to thermal effects and for a correction of the spatial position of the tool center point (TCP)

Dynamic Influence on Workpiece Quality in High Speed Milling

Abstract The high speed milling process places completely new demands on the dynamic behaviour of machining centres. This paper describes the causes of vibrations in high speed milling. It includes a quantification of vibrations due to imbalances, accelerations and cutting forces. The effects on the quality of workpieces are simulated by a dynamic model of the machine. Therefore, also the mechanical structure and the axis control system are taken into account. The results of the simulation are verified by some cutting examinations. To improve the quality of workpieces suggestions are made to avoid vibrations or to compensate the effects on vibrations due to imbalance.

Vibrations and surface generation in slab milling

Summary In slab milling the quality of the machined surface is directly influenced by the dynamic behaviour of the machine tool. In addition to the cycloidical microgrooves, the dynamic relative motion between the workpiece and tool is superimposed on the machined surface. In general these vibrations cannot be directly identified by investigating the machined surface. By the application of a special purpose milling cutter, microgrooves are generated which are identifiable and from which the relative motions in the cutting zone can be determined by surface topography measurement. It is shown how the groove structure is produced as a function of the kinematics of the process and the relative motions in the zone of cutting. An example based on experimental investigation is used to illustrate the procedure used to determine these relative motions based on analysis of the workpiece surface.

Modular Modeling of Energy Consumption for Monitoring and Control

A prerequisite to achieve energy efficiency in production through optimization is the possibility to use simulation models to predict the consequences settings, decisions and actions have on the energy consumption and thus on the lifecycle cost of production machines. But today’s production systems are dominated by agile structures and rapid changes of general conditions so that predictive energy consumption models need to be adaptable. Therefore in the ECOMATION project the modular modeling approach for energy consumption prediction presented here is being developed, which facilitates re-use of energy consumption models and thus minimizes the cost of finding the optimal operational profiles.

Thermography-Based Investigation into Thermally Induced Positioning Errors of Feed Drives By Example of a Ball Screw

The following paper presents a method, based on thermographic measurements, to calculate the thermally induced positioning errors of feed drives in machine tools, here described with the example of a ball screw drive. Especially the effect of an uneven temperature distribution in the components on the total deformation is examined in this method. A transformation between the 3-D object space and the 2-D image space was created by means of digital image processing and photogrammetry as well as defined reference points on the structure of the feed drive with the surrounding machine components. The transformation enables the necessary identification of the defined structure points in the thermographic picture. With the help of the temperature information contained in the thermographic images, the respective thermally induced errors can then be calculated depending on the respective axial position by means of a temperature deformation model.

Process Analysis for the Evaluation of the Surface Formation and Removal Rate in Lapping

Abstract During the process of lapping, the mechanisms of surface formation and removal rate are decisively influenced by the movement type of the individual grains within the lapping abrasive. Two active movement types can be differentiated. These are the rolling and sliding of the individual lapping grains within the working gap in relation to one of the working partners as well as the passiveness of the grains, whereby varying surface topographies of the workpiece are created by active movement types. These can among others be influenced by some of the adjustable process parameters. However, the most important parameter is the significant grain form. On this basis, a simulation model for the analysis of the surface formation by the motion of grains is described in this paper, also considering collisions and break-ups of grains. It enables the quantitative specification of the individual movement types of the lapping grains under the influence of different process parameters. These are for example the lapping pressure, lapping speed, grain size, grain concentration etc as well as the qualitative estimation of these influences on the processing result.

Burr Formation in milling with minimum quantity lubrication

In milling, burrs are formed on entry and exit edges of the workpiece to be machined like in all material removal processes. In the subsequent production these burrs have to be removed. Understanding the influencing factors and burr formation mechanisms can help to avoid or reduce burrs. Another possibility for saving costs is to reduce the process materials, for example, cutting fluids. This can be realised by using minimum quantity lubrication or dry machining. The investigations show which influence both methods have on burr formation.

Prediction of Parameters for the Burr Dimensions in Short-Hole Drilling

The following paper presents a method for the determination of the burr dimensions to be expected in short-hole drilling, simultaneously taking the parameters into consideration which influence the burr formation. These parameters are yield stress, forces and the geometry of the inserts. The method is based on empirical cutting examinations and takes account into the correlation between different burr parameters and the machining conditions such as cutting speed, feed and tool geometry. Using Schaefers burr value g, it is possible to make a quantitative evaluation of the burr dimensions. The method was verified for the materials 16 MnCr 5 and Ck 45 in case of dry machining.