Interpolation is used in CNC programming, to define the path and speed of the cutting tool as it moves along the workpiece. The CNC machine interprets the code and generates the appropriate signals to control the motors and drives that move the axes.
1- Rapid positioning
Rapid traverse motion, sometimes called a positioning motion, is a method of moving the cutting tool from one position to another position at a rapid rate of the machine. The maximum rapid rate is determined by the CNC machine manufacturer and takes place within the travel limits of the machine.
2- Linear Interpolation
Moves the tool in a straight line between two points.
3- Circular interpolation
Circular interpolation enables machining of full circles or arcs, the CNC machine guides the tool along a circular arc.
4- Helical interpolation
Combines circular motion with linear movement along a third axis.
5- Thread Interpolation
Synchronizes spindle rotation with linear motion for threading.
6- Parametric (Spline) Interpolation
Machines complex curves (e.g., Bézier splines, NURBS) using mathematical models. Spline interpolation is the most sophisticated type. It allows for the creation of very complex, smooth curves by defining a series of points (spline points). The CNC control then generates a smooth curve that passes through these points. Different types of spline exist (e.g., B-splines, Bezier splines), each with its own characteristics.
Conclusion
Comparison Table
| Type | G-codes | Use Case |
|---|---|---|
| Positioning | G00 | Rapid traverse positioning motion |
| Linear | G01 | Straight cuts, drilling |
| Circular | G02, G03 | Arcs, holes |
| Helical | G02/G03 + Z-axis | Threads, helical paths |
| Parametric | G05, G06 | Complex curves (NURBS) |
| Thread | G33, G76 | Thread cutting |
Choosing the right interpolation method depends on the part geometry, required precision, and CNC capabilities. While linear and circular interpolations are standard, advanced techniques like parametric or helical unlock complex designs. Always consult your machine’s manual for supported G-codes and compatibility. By mastering these methods, you can optimize tool paths for efficiency and surface quality.
Happy machining!