The Research On Inspection And Analysis Method Of Geometric Feature Applied Maximum Material Requirements

Under the datum of the measured elements subjected to the MMR/LMR, the border of designdatum and measurement datum are not coincided, and resulted in the floating range of design datumcan be resulted by the different borders. In order to solve these problems, based on geometrycharacteristice factor and the concept of datum refrence frame (DRF), a general representation andcompensation method of datum’s deviations is proposed.The researched mainly include the following aspects:(1) The establishment method of datum feature simulator. Based on the concept of datumfeature simulator and VC++6.0, the calculation function of measured element’s DRF are establishedand stored in the information list of datum.(2) The establishment method of movement relationship of the Datum Reference Frame.According to the concept of Datum Reference Frame and geometry characteristice factor, therelative position between the datum simulator at actual condition and the datum boundary atMMC/LMC is dedetermined, and the relative position between design DRF and measurement DRFare obtained. The relative position boundary between design and measurement DRF is described bythe combined mechanism of crank-guide bar and oscillating bar.(3) The deviations of datum are represented by the crank length and the oscillating angle of theoscillating bar, and the crank length is the increment of the tolerance value of the toleranced feature,the oscillating angle is used to modify and enlarge the tolerance zone of the toleranced feature.On the platform of UG NX7.5, under MMC/LMC the functional requirements of CAT arerealized by using the VC++6.0and UG/OPEN API modules. The annotation and associaled featureinformation of modles can be extracted in UG based on the UG/OPEN API modules provided byUG NX7.5systerm.The example applied MMC is used to verify the influence of measuredelement’s DRF and the tolerance zone.