Investigation on Thermal Deflections and Flatness on a Ground Surfece
Date Issued
2011
Date
2011
Author(s)
Wang, Jin-Jen
Abstract
Grinding is a common process used for high quality part production. The dimensional and geometrical precision is the major concern to such parts. In metal grinding, enormous heat is generated due to the material removal and friction as well, this usually leads to prominent temperature rise on a ground surface. The thermal deformations on the ground surface usually lead to concave distortion. The cutting forces also cause elastic deformations on wheel and workpiece surfaces, which will recover gradually if there is no increase in depth of cut. The elastic recovery is also used to improve the dimensional accuracy in some grinding process, and such process is called spark-out.
In this study, an analytical model is proposed to simulate the distortions in dry grinding by taking both thermal deformation in workpiece and elastic deformations on wheel and workpiece into consideration. The thermal deformation usually causes overcut and the elastic deformations will decrease the depth of cut. In the simulations of spark-out process, the cut will be made only when the sum of the thermal deformation and elastic deformations are greater than the cutting depth made by previous passes, and then the new cutting depth is found. By this mechanism, the surface profiles after grinding and spark-out will be found.
The grinding experiments were also conducted for the depth of cut of 10μm and 20μm for up to 4 rounds on a surface. The experiments for spark-out were conducted with different depth of cut, wheel types and coolant application methods. The results were compared with the analytical results, and it showed the analytical prediction was only good for the profiles along the grinding direction and with larger depth of cut. The experiments showed the smallest concavity was obtained after 8 spark-out passes when small depth of cut and a softer wheel were used. It also showed the distortion on ground surface were concave in dry grinding and might turn convex after 4 spark-out passes in wet grinding. Thus, the best flatness in wet grinding may be achieved for 4 spark-out passes.
Subjects
Grinding
Spark-out
Surface Deformations
Thermal Deflections
Type
thesis
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