Requirements and Constraints for a Robotized Roll Hemming Solution
The objective of this study is the design of a new roller hemming tool. For this purpose, main parameters affecting the final quality of the rolled hemmed part have been studied in order to identify and outline the key factors in roller design as well as in roller hemming process stages. A preliminary set of experiments has been carried out to study the pre-hemming force and springback relation in an aluminium sheet. Experiments showed the required forces in first pre-hemming stage and allowed to calculate a stiffness coefficient based on the springback deformation angle.
Numerical analysis and experimental investigation of surface defects in die hemming process
Hemming is the main assembly process used for auto-body panels. Surface defects resulting from the hemming operation may significantly influence the appearance aesthetics of an automobile. The formation of surface defects can be forestalled, and the process can be optimized and compensated by the numerical simulation method during the process design stage. In this study, the hemming assembly of a fuel tank cap is chosen as the research object, and the specimen is made of DX54D + Z deep drawing steel sheet. Numerical simulation and forming experiments have been carried out. It was found that the surface defect index can be expressed as the weighted sum of the design variable effects by simulation and orthogonal design. In addition, the magnitude of each effect can be ranked from the most significant to the least significant. Using this information helps to obtain an optimal hemming process plan. However, process parameter optimization cannot completely eliminate surface defects. The surface compensation of tool geometry based on the continuity of curvature was used to eliminate the surface lows and the hemming test results indicated that the obtained component was of the required quality.
Ignition and burning rates of segregated waste combustion in packed beds.
Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results. Two successive stages of combustion were identified for both samples: the propagation of ignition front into the bed and combustion of the fuel above the ignition front. The burning rate of cardboard reached a peak of about 300 kg/m(2)h at the air flowrate of 936 kg/m(2)h and decreased at higher air flowrates. For waste wood, both the ignition and burning rates increased in the tested range of the air flowrate up to 702 kg/m(2)h, of which the values were very close to those for the cardboard. The model prediction was in good agreement with the test results for waste wood. However, the burning rate for cardboard was under-predicted due to strongly irregular shapes of the fuel.