Interpolation

circular interpolation

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. 

Linear Interpolation

3- Circular interpolation

Circular interpolation enables machining of full circles or arcs, the CNC machine guides the tool along a circular arc.

Circular interpolation
plan selection

4- Helical interpolation

Combines circular motion with linear movement along a third axis.

Helical interpolation
Helical interpolation + pitch

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   
PositioningG00Rapid 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! 🛠️

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