O’zbekistоn respublikasi оliy va o’rta maxsus ta`lim vazirligi

Surface geometry
Machine parts are depicted in the drawings in the form of elements bounded by surfaces of a certain geometric shape. Real machine parts have deviations from the ideal shape depicted in the drawings. These deviations are called errors. Surface errors according to the criteria of the reasons for their formation and measurement methods are divided into macrogeometric errors, waviness and roughness.
Macrogeometric errors are deviations of the surface shape from the given one. For example, cylindrical parts may have deviations of the cylinder contour from the circle (ovality, faceting), non-parallelism of the cylinder axis generatrix (barrel shape, taper), axis curvature, etc. Such errors arise due to machine inaccuracies, poor workpiece setup, tool wear, etc.
Waviness is a characteristic of the surface, determined by a set of regularly alternating and similar in size elevations and depressions, which are formed during the machining of materials due to the uneven forces of the tool and vibrations in the machine-tool-product system.

Fig 3.1 Scheme of a wavy surface
There are (Fig. 3.1) longitudinal and transverse waviness - along and across the movement of the processing tool. The waviness parameters are: height ( H _B or H _O ) and step ( L _B or L _O ) of the waves.
The causes of waviness can be distortions in the shape of the cutter or grinding wheel, errors in the movement of the tool or workpiece, in particular, the imbalance of the grinding wheel.
Roughness is a set of surface microroughnesses. Roughnesses are present on the smoothest surfaces of solids: on the surface formed during the splitting of mica - up to 2 nm high, on a quartz crystal - 10 nm, on cleanly machined steel parts of machines - 0.05-0.1 μm, and on roughly processed up to 100-200 μm . The microroughnesses that characterize the roughness are smaller in size than the waviness and are located on a wavy surface.
If the part is cut by a plane perpendicular to the ideal geometric surface of the part, a profile is formed that characterizes the microgeometry of the part surface. profilogram surfaces -
graphical representation of the profile based on the results of roughness measurements. The surface at each point can be cut by a set of normal planes. Therefore, roughness is associated with one or another direction of the section. For example, the surface roughness of a machined part is called longitudinal in the direction of the main movement of the tool and transverse in the feed direction.