Master’s thesis is focused on optimization of the process of turning balls for ball valves, which has a problem of product inconsistency due to instability of the process. Its cause lies in limited rigidity of the machine, inadequate machining parameters and vibrations transmitted from the surroundings. Due to narrow tolerances for the diameter of the ball and surface roughness it was decided to use Statistical Process Control (SPC) for determining process stability and capability and Design of Experiments method (DOE) to determine optimal process parameters. With the use of DOE it was determined that spindle speed has the biggest effect on Ra and that feed and cutting depth have the biggest effect on Rt. With the use of optimal process parameters surface roughness of the balls was minimized and a stable process was achieved.
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