Abstract: Gives out the mathematical model of the three segment base circle involute scroll profile,it adopts the bicircular arc interpolation to approximate and fit the scroll profile and programming by MATLAB software to calculate the coordinates of date points.Thus,the fitting of the combined scroll profile is realized,then the fitting error is analyzed.Through the processing and manufacturing module of Pro/E,the scroll plate is machined.By setting the parameters in the manufacturing process,the manufacturing process is optimized.Compared with the single arc algorithm,the results show that the fitting error is reduced by 90 %,the fitting notes reduced by 80 %,the number of machining arcs reduced by 74 %.The method is universal and practical.It has certain reference significance to the numerical control machining of the non-uniform scrolls.

Key words: curve fitting, three segment base circle involute, bicircular arc interpolation