CMM, one of precision measuring instruments, is an important component of advanced manufacturing technology. Nowadays, CMMs are widely used in the fields of machine-building, automobile manufacturing, aerospace, flexible manufacturing system and computer integrated manufacturing system due to the advantages of strong versatility, high degree of automation and high precision.
However, CMMs have some weaknesses. They are large, expensive and not portable.
In comparison with traditional CMMs, AACMM offers many advantages such as large workspace and ease of use, high degree of freedom, portability and low cost. However, it also reveals some drawbacks due to its many articulated arms like bigger accumulated errors and lower measuring precision than CMMs.
In an attempt to improve the measurement accuracy of AACMM and reduce its manufacturing cost, Rim Chang Hyon, a researcher at the Faculty of Mechanical Science and Technology, has performed an error analysis and an optimum tolerance allocation.
Firstly, based on the analysis of error source of AACMM, he constructed a systematic error model.
Next, he calculated by the analytical and numerical methods the position error of measuring probe due to the errors of each structural parameter and that due to the systematic error of individual rotary encoders.
Lastly, from the perspective of processing and assembly, he established a mathematical model that converts the perpendicularity error of the AACMM into the arm’s length error, and performed a calculation about the optimal tolerance allocation of each structural parameter and then verified its accuracy.
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