Research On Detection And Evaluation Of Bottom Dead Center Accuracy In Press Machine

In recent decades, the development of control technology and testing technology has promoted the rapid development of modern manufacturing, and users’ requirements for product performance is becoming more and more demanding. Bottom dead center(BDC) is an important performance index of press, but how to accurately measure and improve the accuracy of BDC is a technical problem faced by the press industry. The bottom dead center accuracy of press is constantly changing in the work process, and it will be insufficient enough to meet the needs of the market products. Therefore, how to control the accuracy of bottom dead center and keep it in good working condition has become a key issue to be solved for modern enterprises. This paper takes an enterprise slider-crank type of press machine as the research object, using the visualization platform of Visual Basic software and showing the measured curve of BDC in real time; it adopts the connecting rod length adjusting device to regulate and control press die height to achieve the control of BDC position, and makes an analysis of the results to improve its accuracy.(1) The analysis and simulation of the main component in press: analysis of factors and heat source influencing the accuracy of press, makes a calculation of statics, dynamics and heat generation to main heating components; using Pro/E4.0 to three-dimensional modeling of key components, importing the model into ANSYS to thermal load and stress load in order to calculate the temperature field and stress field of the crankshaft system, the maximum temperature and deformation is located in the joint of the crankshaft and connecting rod, the values are 62.092℃ and 0.0427 mm respectively. Therefore, it can be conclude that the temperature and load have a significant influence to the press die height, and eliminates the influence degree by the constructed control compensation model.(2) Build error compensation technology of press machine: measuring the temperature and the slider position of crankshaft system, the BDC position measurement device is designed; by measuring the bottom dead center fluctuation, connecting rod thermal expansion amount and data analysis, and proposing the dynamic compensation scheme of BDC positioning precision based on crankshaft connecting rod system, then designs a kind of connecting rod length adjusting device to regulate error. It uses pulse distribution to control the motor for the purpose of compensation.(3) Evaluation of bottom dead center position precision: it takes an analysis of experimental data and combines with analytic hierarchy process and fuzzy evaluation method, and constructs mathematical evaluation model; in the case of multiple parameters, evaluating repositioning precision of press bottom dead center, it provides the basis for enterprises to improve the accuracy of press.