March 29, 2024

Research on Numerical Control Production Error and Regulation

The function relationship between the machining error and the influencing factors in the three-axis CNC end-end milling process of the spherical knife can be concluded from the above derivation: 1 The machining error of the spherical-blade three-axis linkage CNC end-milling processing is straight line approximation error and method It is composed of two factors: vector rotation error; 2 machining error is related to machining surface curvature, tool radius and interpolation length, and is proportional to the square of interpolation length L; 3 the maximum machining error in the interpolation section occurs near the midpoint The 4 normal vector rotation error is caused by the rotation of the machining surface normal vector along the interpolation straight line and is proportional to the tool radius.

Influence and control of other factors For high-speed machining, the numerical control system also has lifting speed error and servo system hysteresis error. Lifting speed error In high-speed machining, due to the inertia of the control system, the drive system and the electrical and mechanical systems of the controlled object, dynamic errors such as shock, oscillation, overtravel, and out-of-step may occur under high acceleration. Therefore, in terms of system accuracy requirements, the CNC system must have an automatic speed-up function. The automatic lifting speed is automatically realized by the software function of the numerical control system. The basic requirement is that the selected lifting speed law should ensure the trajectory accuracy and positional accuracy, ensure the rapidity, stability and stability of the lifting speed process, and the control algorithm should be as simple as possible. Easy for computer implementation.

Conclusion (1) The normal vector rotation error can be compensated by the method of correcting the position of the core. The concave surface does not need to be compensated. When the system has no automatic compensation function, it is controlled by reducing the tool radius and reducing the error. (2) The linear approximation error is determined by the interpolation chord length. The interpolation chord length is related to the interpolation period of the CNC system and the tool feed speed. Selecting the numerical control system with a small interpolation period or reducing the feed rate can control the linear approximation error. . (3) The residual height error of the cutting line is the main factor affecting the surface roughness of the workpiece in the surface machining. By selecting the reasonable cutting line width process parameters, the error can be controlled.

The lifting speed error is the error form that exists in high-speed CNC machining. The speed of the lifting speed is controlled to a minimum by selecting a reasonable lifting speed law and setting the interpolation processing after the first speed up and down processing. The servo system hysteresis error also exists in high-speed machining, and the influence of the error on the machining accuracy of the product is eliminated by the forward-looking control function of the numerical control system. The error in NC machining is absolute. The technical research to reduce or eliminate the error is endless. Only by analyzing the mechanism of the error, can we take measures to control the machining error and improve the processing quality.

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