Improvement of the quality of the TCI hammer bits demanded by Russian mining industry requires improvement of the accuracy cylindrical TCIs’ diameter measurements, which are being cold-pressed into the sockets of the bit’s body during its selective assembly, since sending a TCI into wrong bin leads to the violation of the recommended interference fit value and hammer bit premature fault. The purpose of the research is to ensure required accuracy of the automatic non-contact measurement of the cylindrical TCIs’ diameters prior to the hammer bits’ selective assembly. A pneumo-electronic gauge is proposed, which performs a temporal conversion of the linear quantity into time interval, during which the measurement chamber containing the compressed air discharges into the atmosphere through the restrictor formed by the surface of the target part, located in the channel of a V-block, and the measuring nozzle exit section, contained by one of the channel’s faces. Experimentally established measurement error of the gauge is ±0,27 μm in the measuring range of 6…6,22 mm and ±0,45 μm in the range of 10…10,22 mm, allowing it to be used as a measuring device of an automatic sorting device for hammer bits’ selective assembly and for cylindrical parts’ diameter gauging in other industrial areas. Paper also covers a computational model of the temporal conversion, which allows evaluating the proposed gauge’s transfer function and measurement error depending on its design and operational parameters with respect to the transitional mode of air flow in the restrictor formed by the exit section of the measuring nozzle and the surface of the target part. Experimentally established adequacy of the model allows using it during the designing stage of such gauges.

Keywords

Linear measurement, diameter measurement, pneumatic device, temporal conversion.