7th International & 28th All India Manufacturing Technology , Design and Research Conference 2018 Anna University, Chennai – 600 025, India 13th -15th December 2018 AIMTDR 2018 CATEGORY: MACHINING Evaluation of Circularity and Sphericity from Coordinate Measurement Data G.L. Samuel¹[ ORCID Number] and M.S. Shunmugam1*[ORCID Number] 1Manufacturing Engineering Section, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai - 600 036, India shunmugam@iitm.ac.in PAPER ID: 19919 INTRODUCTION RESULTS AND DISCUSSION Table 1. Results The Computer Aided Inspection (CAI) procedures have gained a prominent role in the field of inspection. The coordinate data from CMM combines the information on form as well as size and a suitable transformation. In this paper, appropriate methods have been presented to handle the two and three-dimensional coordinate. Sl. No. xi mm yi mm 1 70.0150 50.0000 2 68.7900 58.4734 3 65.4060 65.9372 4 59.5675 72.7493 5 51.3791 77.7452 6 44.7944 79.6013 7 40.8903 79.9958 8 32.0312 78.9306 9 27.2296 77.1385 10 20.3993 72.7076 11 16.1556 68.2304 12 12.7184 62.4905 OBJECTIVES Fig. 1. Circularity error Fig. 2. Sphericity error To propose the methods for handling CMM and transformed data. To validate methods using the data available in literature. To evaluate various form errors Fig. 3. Circularity error OBSERVATIONS The ANSI Dimensioning and Tolerance Standard Y14.5 [1] defines form tolerances of a component with reference to an ideal geometric feature and ISO standards [2] recommend the form to be evaluated based on the minimum zone concept. The Data Sets in Table 1 shows the CMM data for circularity and sphericity features respectively. These data sets are taken to bring out the differences in ap-proaches to be followed for processing CMM data and transformed data. The International Standard ISO 1101 [1] defines circularity error as the radial dis-tance between two concentric circles separated by minimum possible distance and containing all the measurement points on the given profile as shown in Fig. 1. How-ever, sphericity evaluation is to be done with reference to two concentric spheres con-taining all points of the data set and having the minimum separation as shown in Fig. 2. The deviation of a point is expressed with reference to the limacon and limacoid (Ref. Fig. 3 and Fig. 4) METHODOLOGY In this paper, appropriate methods have been presented to handle the two and three-dimensional coordinate data obtained from CMMs. Methods to directly arrive at the error value using CMM data have been suggested. While evaluating the circularity error using CMM data directly a circle is considered as the assessment feature and while using the transformed data a limacon is considered. Fig. 4. Sphericity error CONCLUSIONS REFERENCES The CMM data contains both size and form information and hence circle/sphere is used as assessment feature and the normal deviations are to be considered. The co-ordinate measurement data can be converted suitably by applying appropriate trans-formations and it can be further processed to evaluate the form errors. As the size is suppressed and the profile is distorted while transforming, limacon/limacoid is used as assessment feature and linear deviation are to be considered. By applying appropriate methods, the value of form error remains the same for a particular profile wheth- er the coordinate data (CMM data) or the transformed data is used for processing. Murthy TSR, Abdin SZ (1980) Minimum zone evaluation of surfaces. International Journal of Machine Tool Design and Research, vol 20(2), pp 123-136. doi.org/10.1016/0020-7357(80)90024-4 Samuel GL, Shunmugam MS (2000) Use of limacon and limacoid in evaluation of circulari-ty and sphericity errors. In Proceedings of the All India Manufacturing Technology Design and Research Conference, Chennai, India (pp. 539-545). Jin L, YoshizawaT (2009) Handbook of Optical Metrology: Principles and Applications, 263. Kanada T, Modern Metrology Concerns, InTech, (1995) 281 – 289.