SIMULATOR FOR ROUGHNESS MEASUREMENT WITH SPHERICAL PROBE

A measurement of surface roughness is commonly carried out with the aid of profilometers, but when measuring the roughness of a curved surface arise difficulties. A technical problem consists in a probe feed along the normal to a nominal surface and filtration followed to exclude a low-frequency constituent of a profile. That is why it is purposeful to use coordinate measuring machines which have a probe with a spherical tip. For the first time there is presented a simulator of a spherical probe flat contact and surface roughness. A contact model developed is based on the regulations of analytical geometry. With the use of a numerical algorithm one finds a contact point and the center of a probe circle. On the basis of the simulator there is carried out an investigation of the impact of a probe radius upon roughness parameters Ra, Rmax, Rq. As initial data were used measurement results of the profilometer and profiles modeled with the aid of Monte-Carlo statistical method. It is defined that with the increase of the radius of the spherical probe its penetrating capacity decreases. That is why height parameters of roughness are distorted. The application of the spherical probe with the radius of 5-50 mkm ensures satisfactory results.