2.3 Arc radius automatic compensation track
Whether the tool radius is compensated or not, is determined by G40, G41, G42 in the G command:
G40—The tool radius compensation is canceled, that is, the G41 and G42 commands are invalid after using this command.
G41—The tool radius left compensation, that is, the tool radius compensation when the tool is located on the left side of the workpiece as viewed in the tool movement direction.
G42———The tool radius right compensation, that is, the tool radius compensation when the tool is located on the right side of the workpiece as viewed in the tool movement direction.
Figure 7 shows the tool compensation process when using arc radius compensation.
The program format of the tool compensation in Figure 7 is:
G40__; Eliminate compensation;
G41__; radius compensation starting block;
__;
Figure 7 Tool Compensation Process
It can be seen from Fig. 7 that in the initial block, the tool gradually adds a compensation value during the movement. When the initial block ends, the tool arc center stays on the vertical line of the programmed coordinate point, and the distance is the radius compensation value.
3 Tool compensation calculation when CNC lathe does not have tool radius compensation function
When the CNC lathe does not have the tool radius compensation function, when machining the workpiece with the round turning tool, the calculation method is used to solve the tool radius compensation amount.
3.1 Programming the taper surface according to the imaginary tool tip
As shown in Fig. 8, if the imaginary tool tip moves along the workpiece profile AB, that is, coincides with AB and is programmed in AB size, the ABCD residual error in Fig. 8(a) is inevitably generated. Therefore, as shown in Fig. 8(b), the cutting point of the turning tool is moved to AB and moved along AB, so that the residual error can be avoided, but the imaginary tool nose trajectory and the contour are different by Δz in the Z direction.
Where: r is the radius of the tool arc; θ is the angle of the cone.
Therefore, the coordinate value of the imaginary tool nose trajectory can be directly programmed, and the Δz can be compensated in the x direction and the z direction.
3.2 Programming the arc according to the imaginary tool tip
When turning a circular arc surface, the situation shown in Figure 9 occurs. Fig. 9(a) shows a convex arc with a turning radius of R. Due to the presence of P, the circular path taken by the tool nose # point is not the arc shape required by the workpiece. Its center is "
", the radius is "R+r", at this time the programmer still programming according to the imaginary tool tip P point, regardless of the influence of the tool nose arc radius, but the Z direction and the X direction should be given to the tool compensation value before machining. Add a compensation amount r. Similarly, when cutting the concave arc, as shown in Fig. 9(b), reduce the compensation amount r in the X direction and the Z direction, respectively.
Figure 9 car arc knife repair diagram
3.3 Programming by the tool nose arc center path
The part shown in Figure 10 is composed of three-section convex arc and concave arc, which can be programmed with three equidistant lines as shown by the dashed line.
The radius of the circle is the radius of the circle, and the coordinates of the end point of the three-section arc are obtained by the equidistant tangent point relationship. This method of programming is relatively intuitive and often used.
Figure 10 Programming by tool nose arc center
4 Conclusion
The function of the tool compensation function is mainly to simplify the program, that is, to program the contour size of the part. Before machining, the operator measures the actual tool length, radius and determines the compensation sign, which is input into the CNC system as the tool compensation parameter, so that the tool size parameter changes due to tool change or tool wear, although the original program is used, It is still possible to machine parts that meet the size requirements. In addition, the tool compensation function can meet some special requirements of the programming and machining process.
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