Papers by Keyword: Machine Tool

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: 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: 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: Classical lightweight construction in the field of machine tools is reaching its limits. New materials like fibre reinforced plastics are not widely used yet. The main reasons are the high material and production costs. This paper presents an approach for substituting a conventional component of the machine tool’s periphery by a structure made of fibre reinforced plastics. An easy and economic production process was used to enable quick fabrication.

Abstract: The current standards on the safety of machine tools are reliable sources for designers who need to know which materials and thicknesses are appropriate for safety guards on a certain type of machine tool. However, due to various possible designs of safety guards, information about requirements on their fixation is only provided for isolated cases. In this publication, a broad series of FE simulations and impact tests has been accomplished in order to provide quantitative values to machine tool guard designers. In addition, a method to validate FE simulation results and to determine their reliability is presented. This allows an integration of FE simulations in the dimensioning process of machine tool guards and significantly reduces required experimental impact tests.

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: Jet cutting with high-pressure CO₂ jets has the potential for a dry and residue-free machining of materials. However, a high-pressure CO₂ blasting plant as well as experimental expertise for the continuous jet cutting with high-pressure CO₂ at atmospheric conditions are not available. A pilot plant for the continuous jet cutting with liquid carbon dioxide was developed and realized at the Fraunhofer-Institute for Production Systems and Design Technology. Identical cutting tests were carried out in polyurethane blocks of different Shore D-hardness and density with high-pressure CO₂ and water jets. Based on the first results in polyurethane blocks the tests were extended to cutting carbon fibre reinforced plastic plates with the high-pressure CO₂ jet. Finally the possibilities and limits of the high-pressure CO₂ jet cutting were summarised.

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: This research studies the impact of maximum allowable stopping time for machining tools on the production-inventory policy under a variable tools lifespan and demand. A mathematical model is developed to determine the optimal maximal allowing stopping time, the inventory level, and the replenishment interval. A numerical example was conducted using an exhaustive searching method to show the implementation of our model. The results indicate that, compared to the traditional policy which only repairs and replace the broken tools, adopting a maximum allowable stopping time dramatically reduced the total production cost.

Abstract: The present paper work shows the efforts of the research group from University of Oradea on the introduction into the educational program at all the levels (bachelor, master and PhD) of the newest method of the machine tool study. By these methods is need to understand the educational stages ( engineering for constructive parts, the machining on CNC milling centre up to 5 axes simultaneous, machining of very complexes parts, the programming of the CNC units, the using of the most advanced CAM software, the programming of the robots into the flexible manufacturing cell, etc.). On the other hand we include here the research activity about the improvement of the performances of the entire flexible cell from University of Oradea laboratory by increasing of the technological experiences. It is necessary to mention that the UO-01 flexible manufacturing cell, based on the horizontal milling centre TMA-AL 550, both were developed by own efforts (retrofitting) at University of Oradea in our faculty (Faculty of Management and Technological Engineering) having the contribution of our research group. The entire concept of these new methods is based on virtual simulation into the 3D space of the functioning in real time of all the components at every technological case. For these targets all the components were modeled at 1:1 ratio in 3D space, including the movements of their movable parts.