Studies on Uncertainty Evaluation in Straightness Measurement
Sanjay Yadav*,**, Jiro Matsuda* and Lalith Prasantha Liyanawadu Chitarage*,***
*Dimensional Standard Section, Division of Lengths and Dimensions, National Metrology Institute of Japan (NMIJ) and National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 3 Tsukuba, Ibaraki, 305-8563, Japan
**Pressure and Vacuum Standards, National Physical Laboratory (NPL), Dr. K.S.Krishanan Road, New Delhi-110012, India
***Standard/Testing Officer, Division of Metrology, Sri Lanka Standards Instruction (SLSI), 17, Victoria Place, Elwitigala Mawatha, Colombo 8, Sri Lanka
The evaluation of uncertainty associated with measurements of geometrical forms is a subject of considerable interest these days in machine design. In the present study, a straightness measuring machine that was developed at National Research Laboratory of Metrology (NRLM), Japan is investigated to evaluate various uncertainty components associated with measurements over a length of 500mm of a datum cylinder. Investigations on the heating effect of the measuring machine due to heat generated by an electric motor, the effect of the stability and shape of the probe head, the effect of bending of the carriage bed and the effect of angular movement of the carriage i.e., yawing and pitching, are carried out, with consideration of the magnitudes of the uncertainty components. The studies have broken the 200mm limit in straightness measurement range imposed by the non-availability of good reference standards beyond this range and would lead to manufacturing of reliable, accurate and precise commercial straightness measuring machine.
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