In modern numerical control technology (CNC), interpolation control is the core link to realize high precision machining. It determines how the machine tool moves from one point to another in space, and ensures the smoothness and accuracy of the machining trajectory. This paper will discuss how to calculate interpolation control, and introduce its basic principle, common types and implementation methods.
First, the basic concept of interpolation
Interpolation refers to the process of calculating the coordinate data of the intermediate point in real time through the numerical control system according to the starting point, ending point and geometric parameters of the contour or trajectory of the part. The purpose of interpolation control is to generate a continuous and smooth trajectory, so that the machine tool can accurately move along the predetermined path during machining.
Second, the classification of interpolation
According to the different trajectory, common interpolation methods include:
1. Linear Interpolation (linear interpolation)
Linear interpolation is used to move in a straight line between two endpoints. The numerical control system calculates the coordinates of each intermediate point through a simple geometric formula to ensure that the tool moves along a straight path at a set speed.
2. Circular Interpolation.
Arc interpolation is used to cut arc contour. The system needs to calculate a series of intermediate points according to the center, radius and starting and ending points, and usually uses trigonometric function or vector method to calculate coordinates.
3. Spiral interpolation and spline interpolation (Spline/Curvature Interpolation)
The high-end CNC system also supports more complex interpolation methods, such as three-dimensional spiral interpolation and spline curve interpolation, which is suitable for high-precision machining of complex surfaces.
Third, the basic steps of interpolation calculation
1. Input parameter analysis
The CNC system first analyzes the interpolation instructions and related parameters in G code, such as target coordinates, feed speed, center position, etc.
2. Calculation of trajectory parameters
According to the interpolation type, the system calculates the length, direction and number of intermediate points of the whole trajectory.
3. Interpolation calculation point by point
In each interpolation cycle, the system calculates the position instructions of each axis at the current moment according to the set interpolation algorithm, which is usually updated with micron precision.
4. Speed planning and acceleration and deceleration control
In the process of interpolation, it is necessary to combine the speed curve (such as S-shaped acceleration and deceleration) for feed control to ensure the stability of machine tool movement.
5. Output control signal
The interpolation result is finally transformed into the control signal of the servo drive system, which directs the motors of each axis to move accurately.
Four, interpolation accuracy and performance factors
-Interpolation cycle: The shorter the cycle, the higher the interpolation resolution, but the higher the system processing capacity.
-Optimization of interpolation algorithm: Using efficient algorithm can improve calculation speed and reduce errors.
-Hardware performance: including processor speed, memory capacity, accuracy of feedback system, etc. affect interpolation quality.
V. Summary
Interpolation control is one of the key technologies for CNC system to realize high precision machining. By reasonably selecting interpolation type, optimizing interpolation algorithm and improving hardware performance, machining efficiency and surface quality can be significantly improved. With the development of intelligent manufacturing and Industry 4.0, the future interpolation control system will be more intelligent and adaptive, providing stronger technical support for high-end manufacturing.
—
Word count: about 820 words