Illustration: Profile of Surface control is applied generally for non regular shapes of castings, forgings or Pressed components. Here upper segment is depicting specification for compete pattern shifting of contour i.e. 0.5 mm Whole pattern can move in a band of 0.5 mm in any direction w.r.t datum A
Lower segment is controlling surface error within band of 0.1 mm. All high points and low points on the surface should lie between band of 0.1 mm. Both these phenomenon are illustrated in following figures.
Upper segment is also known as Pattern Locating Tolerance Zone (PLTZ) and Lower segment is known as Feature Relating Tolerance Zone (FRTZ)
PLTZ will have impact on wall thickness of subject casting, forging due to shift in above case and FRTZ will have impact on overall thickness and wall thickness due to high & low points on curvature (feature) which is within band of 0.1 mm
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