| As the main foundation part of the machine tool, the machine bed is the carrier ofmany important parts, so the design of its strength, stiffness and the dynamiccharacteristics plays a very important role in the machine design, and the static and thedynamic performance influence the machining precision of the machine tool directly. Thetraditional method of the bed design is to determine the intensity with the combination ofthe material mechanics and the simplified calculation. There is certain reliability of themethod but also some disadvantages such as the design cycle is too long and tooconservative. So it has important practical value to the optimization of machine bedespecially to large machine bed. This paper took the TH6918large NC floor type boringand milling machine as an example, by using of the finite element software HyperWorksthe machine bed model was crated, besides, the static and the dynamic performanceanalysis was also carried out, and on the basis the structure optimization research of themachine bed to lose its weight was carried on, and the main contents are as follows:(1) According to the drawing some features of the machine bed such as the anglepouring process hole were simplified, and the simplified geometry model of the machinebed was created by Pro/E. First the static analysis to the machine bed was carried out andits stress distribution and the maximal displacement of deformation under the action of thegravity and the out loads were obtained. Then the modal analysis of the machine bed wascarried out by using the method of BlockLanczos, and its first six modes were extracted, sothat the optimization to the machine bed structure was improved through the static stiffnessand dynamic characteristic analysis.(2) The internal rib plate of the machine bed was devised and the unit structure that isthe rib box unit was extracted for analysis. With the research on the influence of the rib boxinherent frequency by the unit structure parameters, the best optimal parameterscombination was found out which provided the accordance for the whole structure dynamic optimization.(3) With the change of the shape and size of the machine bed sand holes, the thicknessof the rib plates inside and the thickness of the machine bed the research was carried out toanalyze their influence on the machine bed dynamic characteristics, and based on this, fourkinds of machine bed weight optimization schemes were put forward, and the most properplan was chosen through the contrast analysis.(4) On the basis of the machine bed dynamic optimization, the density distribution ofthe machine bed material in the action of the outside load and the restraint was achieved bythe topology optimization to the machine bed structure with the variable density method.By the analogy of the similar machine tools two improvement plans were put forwardreferred to the machine bed structure improvement based on the topological optimizationdata. According to the actual working conditions and the stiffness and the dynamiccharacteristics of the machine tools the feasibility of the two schemes were verified, thenthe finite element analysis of the schemes were carried out and the machine bed optimizedscheme based on the topological optimization was determined.(5) The final machine bed weight light scheme was proposed on the basis of the unitstructure optimization and the topological optimization. |
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