The method for determining the parameters of taper in CNC turning

The parameter determination method of taper in CNC turning mainly involves taper calculation, programming parameter setting and adjustment during processing. The following are the specific key points:

Basic calculation of taper

Taper (C) is defined as the ratio of the difference between the diameter of the large head (D) and that of the small head (d) to the length of the cone (L), that is, C=(D - d)/L. Through this formula, as long as three of the values are known, the other one can be calculated. For instance, given that the diameter d of the smaller end of a cone is 16, the length L of the cone is 10, and the taper C is 1:5, the formula D=d+C×L can be used to calculate that the diameter of the larger end of the cone is 18.

Determination of programming parameters

R value calculation: In numerical control programming, the conical surface cutting cycle instruction (such as G90) needs to specify the "R" value, which is the radius difference between the starting point and the ending point of the conical surface cutting. If the x-coordinate value of the cutting starting point is less than that of the ending point, the R value is negative. The opposite is positive. For example, when processing external threads, if the tool moves from the big end to the small end, the R value is negative.

Thread taper calculation: Taking an external thread taper of 1:16 as an example, the variation per millimeter of diameter is 1/16 = 0.0625. The formula for calculating the small end diameter is d= reference large diameter - (reference length ×0.0625). The calculation formula for the large end diameter of the internal thread is D= reference diameter +(0.0625× reference length), and the calculation formula for the small end diameter is d= large end diameter - (0.0625× total thread length).

Parameter adjustment during processing

Relationship between Angle and taper: slope S = tan (alpha) / 2 = (D - D)/(2 l) / 2 = C, the cone Angle of alpha = 2 arctan ((D - D)/(2 l)) = 2 arctan (C / 2). When the cone length of the workpiece is short and the bevel Angle is large, turning can be done by rotating the Angle of the small tool rest. The approximate formula for calculating the rotation Angle β of the small tool rest is β(degree)=28.7°×K=28.7°×(D - d)/ L. This approximate formula is only applicable when the bevel Angle is less than 6°; otherwise, the calculation result error will be relatively large.

Accuracy verification: By measuring the difference between the diameters of the large end and the small end, and combining with the formula to infer the cone Angle or length, the processing accuracy can be verified. For example, given that D = 19, d = 18, and L = 20, it can be calculated that C=(19-18)/20=1:20.