Advanced Materials Research Vol. 1018

Abstract: Thermally induced deviations become the limiting factor for the precision of machine tools. Structure-based finite-element models of high resolution can estimate these deviations with high accuracy but have also a high computational effort. With model order reduction (MOR) these models can be converted into structure-preserving reduced-order finite-element models (FEM-MOR-models) which can be solved very efficiently in MATLAB/Simulink®. To improve model matching selective thermography is used. Selective thermography is a measurement method providing high structural resolution and minimal instrumentation expense due to the use of thermography and photogrammetric methods.

Abstract: Thermal models of machine tools contain parameters whose values have a high degree of uncertainty and which can limit the accuracy of the model beyond applicability. Thus, the parameters have to be adjusted by means of measurements. At present, substantial time, effort, and expensive measurement equipment are required for adjustment, as well as in-depth expertise. For these reasons, we have studied the development of methods providing rapid, comprehensive, and low-cost adjustment. This objective can especially be achieved by methods that support the planning stage of the model-adjustment procedure. The paper demonstrates this based on methods for model and behaviour visualisation.

Abstract: This paper gives a short overview of the structure based correction of thermoelastic errors of machine tools. Measured load data of the machine control and structure based simulation models are used to calculate the error at the tool center point in thermal real time. The derived correction can be divided in modules, which are described on the example of a ball screw.

Abstract: Monitoring functions of machine tools are of increasing importance to enhance their productivity. They can also be complemented by several system identification approaches which provide additional information. To utilize these approaches, special requirements, e. g. adequate reactions to variant process excitations during the regular process have to be fulfilled. The paper deals with the identification of velocity loop parameters of numerical controlled (NC) axes on a state of the art machine tool and gives an insight on how to correspond to the given requirements. Mainly, this is done by implementing extending modules, of which the model error estimation is pointed out in particular. Experiments with data for a turning operation show the practicability.

Abstract: This scientific contribution presents a novel concept and design of a hydraulic inchworm feed drive based on an electrorheological suspension. This feed drive is ought to power Micro Machining Units (MMU) of Square Foot Manufacturing (SFM) modules. The transfer of energy is conducted by an electrorheological suspension, a field-responsive fluid that allows the use of small, rugged and simple micro valves. Both of the presented feed drive’s prototypes comprise electrorheological micro valves as primary actuators and flexible metal bellows as secondary actuators in two configurations. The combination of electrorheological micro valves with flexible metal bellows allows a very compact and sealed design that avoids dynamic seals and therefore leakages making the electrorheological inchworm feed drive suitable for a wide spectrum of motion solution including clean room applications.

Abstract: Machine tools for micro machining are so far not adapted to work piece sizes and process forces. They feature hardly any modularity and do not allow reconfiguration in a significant process change. One possibility to adapt the machines is to produce them from plastic or composite materials through generative methods. This “printed” machine is a reconfigurable, monolithic module, in which drives are integrated. By a cooperative motion generation, larger workspaces can be realized while the installation spaces decreases. This gives the possibility to use alternative drive technologies for example piezo-drives. Based on these methods, two small generatively produced machine tools are designed. These machine tools use two different drive principles. The first machine tool is equipped with ball screw drives which are cost efficient and space saving. The second machine tool uses piezo-actuators, which are very dynamic in motion generation. Further has to be examined, which tolerances and rigidities are needed at critical points and which parts can be produced generatively and which in a conventional way.

Abstract: The paper at hand introduces a 3D printing (3DP) process for additive manufacturing of inorganically bound sand moulds. The fundamental differences to 3DP with organic binders (which is state of the art) are explained and the quality relevant process parameters of the inorganic process are introduced. Since the inorganic binder system is thermally activated during the printing process the main focus lies on the heating procedure. The properties of printed specimens are measured by the quality features fluid migration and strength for which novel methods of moulding sand testing are used. Results show that the identified process parameters have a significant influence on specimen properties. The interaction of the attributes fluid migration and strength are also shown. By understanding the relationship between process parameters and quality features the properties of printed inorganic sand moulds can be tailored to fit casting specific requirements.

Abstract: Electric actuators are an important part of every manufacturing system. Often it is a problem to get a good motion control configuration which allows high performance tasks. This contribution shows how the mechanical load and the self-dynamics of the system associate. Based on this, it is possible to formulate an identification algorithm to estimate the mechanical load. Now all system parameters are known and the controller can compute automatically. Therefore we show the results in an experiment with a classic cascaded and a flatness-based controller.

Abstract: Robustness becomes a crucial feature of production systems. On the one hand, the systems are subject to many disturbances and on the other hand, a reliable production is demanded. A robust system shall be able to keep the working process on a good performance level despite occurring disturbances. To enable such a system’s behaviour, different actions have to be taken. The paper presents an approach to identify the best action to improve a system’s robustness on an operational and tactical level by investigating its disturbances and performance.

Abstract: In this paper an approach to assess the performances of the production structures is introduced. Key figures within this approach are the performance limit of the production structure and the control dependence of the production performance. These figures are visualised for different production structures in a production structure portfolio.