1 Manufacturing Engineering, Department of Mechanical Engineering, Technical University of Denmark2 Department of Mechanical Engineering, Technical University of Denmark
An investigation on the reproducibility of surface roughness in reaming was performed to document the applicability of this approach for testing cutting fluids. Austenitic stainless steel was used as a workpiece material and HSS reamers as cutting tools. Reproducibility of the results was evaluated with respect to different operators, workpieces and measured position in the reamed hole for different combinations of lubrication condition and cutting speed. The measurands were the conventional surface roughness parameter, Ra and the ability of a cutting fluid to ensure a surface which is a replication of tool geometry and path. 2D and 3D reference measurements were done to ensure traceability of the measurement. Moreover, surface profiles were examined under the 3D optical microscope. Measuring uncertainty evaluation using statistical methods was applied. Surfaces produced with a low cutting speed were generally reproducible when considering different operators, workpieces and measured position in the hole, unlike the surfaces produced with high cutting speed. These latter contain uneven, random surface profiles and vary considerably for different operators. However, it can be observed that a higher concentration of the oil in water-based cutting fluid (or when using a straight mineral oil) results in surface profiles that are more reproducible at higher cutting speed. Moreover, it can be seen that three cutting fluids (two water-based cutting fluids with different oil concentration and a straight mineral oil) used in connection with a low cutting speed result in "identical" surface profiles. Biggest uncertainty contributors were due to the process repeatability and repeatability around the hole circumference. This was however only in the case of high cutting speeds and low degree of oil concentration. High reproducibility of different operators, especially when low cutting speed was applied, was achieved. From the surface profiles, an identification of individual feed marks from the tool is possible, tool replication being most clear from the 3D reference measurements.