Error compensation technique is a recognized and cost-effective method to improve machining accuracy of machine tools. In this article, a new compensation method for geometric error is proposed based on Floyd algorithm and product of exponential screw theory. Based on topological structure and measured data, volumetric geometric error modeling is established by product of exponential screw theory. Then, the improved Floyd minimum-distance method was used to establish an error compensation model by adjusting weight unceasingly. In order to verify the effectiveness and generality of the method proposed in this article, two experiments were designed. A total of 5 five-axis machining centers of the same type with different use time were selected to carry out the simulation experiments. Results show that the Floyd method can provide higher compensation precision, that is, Floyd algorithm compensation method can keep positioning errors within the range [28 mm, 9 mm]. In addition, roundness error, coaxial error, and surface roughness were reduced in the actual machining experiments of two machined conical tables. Therefore, it can be seen that the proposed compensation method is effective to improve machining accuracy of machine tools.
The geometric errors have a significant effect on the machining accuracy of multi-axis machine tool. Because of their complex inter-coupling, the process to control these geometric errors and then to improve the machining accuracy on this basis is recognized as a difficult problem. This paper proposes a method based on the product of exponential (POE) screw theory and Morris approach for volumetric machining accuracy global sensitivity analysis of a machine tool. When a five-axis machine tool is chosen as an example, there are five screws to represent the six basic error components of each axis (in an original way) according to the geometric definition of the errors and screws. This type of POE model is precise and succinct enough to express the relation of each of the components as the Morris method is based on the elementary effect (EE). The method can compare incidence of these errors and be used to describe the nonlinear relationship by less calculated amount in a global system. Based on the POE modelling, the Morris method is adopted to identify the key geometric errors which have a greater influence on the machining accuracy by global sensitivity analysis. Finally, according to the results obtained from analysis, suggestions, and guidelines are provided to adjust and modify the machine tool components to improve the machining accuracy economically.
Geometric error has significant influence on the processing results and reduces machining accuracy. Machine tool geometric errors can be interpreted as a deterministic value with an uncertain fluctuation of probabilistic distribution. Although, the uncertain fluctuation can not be compensated, it has extremely profound significance on the precision and ultra-precision machining to reduce the fluctuation range of machining accuracy as far as possible. In this paper, a typical 3-axis machine tool with high precision is selected and the fluctuations in machining accuracy are studied. The volumetric error modeling of machine tool is established by multi-body system (MBS) theory, which describes the topological structure of MBS in a simple and convenient matrix form. Based on the volumetric error model, the equivalent components of the errors for the three axes are established by reducing error terms. Then, the fluctuations of equivalent errors and the machining accuracy in working planes are depicted and predicted using the theory of stochastic process, whose range should be controlled within a certain confidence interval. Furthermore, the critical geometric errors that have significant influence on the machining accuracy fluctuation are identified. Based on the analysis results, some improvement in the machine tool parts introduced and the results for the modified machine show that the prediction allow for reduction in errors for the precision and ultra-precision machining.
Abstract. As the world industrial production requiring higher and faster efficiency, a series of manufacture processes is facing new challenges. Especially, there are two main parts according to potential profitability during each process steps. One has potential profitability that is logistics step and another is un-logistics. In this paper, there is a higher efficiency logistics system and about loading platform, material distribution and storage for shipment. The Floyd method would be an important role for planning the material distribution. An example is making the thought coming true. From the result, the production cycle that is from unloading materials to storage for shipment has be decreased with 10% to 20%. It has higher efficiency and better benefit for the factory. With the rapid development of industrial process, the higher efficiency means for that the industry holds importance position in the world.
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