a new method for measuring perforated surface by coordinate measuring machine (cmm)

nowadays cmm machines are widely used in surface measurement and inspection. as inspection results from cmm machine are obtained by the means of measuring surfaces with direct contact, they are more precise than non-contact method (like optical measurement). however, cmm machines give more reliable and accurate results rather than non-contact methods but also these results come with error when outer surface contains porosity spaces. this paper proposes a new method for measuring outer surface of porous objects. in this method the probe will be located above the porous area and doesn’t enter inside. the proposed strategy could be utilized whether cad model of object is available or not. if cad drawing of object exists, the probing stylus will not enter into the hole. on the other hand, if the cad drawing doesn’t exist a perpendicular plane to the surface will be virtually modeled and by this normal plane the outer surface of the object will be estimated. in addition in this research an effort has been made to reduce dependence on cad drawing.