The Basics of CNC Machine Interpolation
The acronym “CNC” stands for Computer Numerical Control and is used to describe the use of computer controls to do the process of machining. In the machining process, a machine tool such as a lathe, drill press, or mill is used to shape and form a part from a raw material. CNC machines are capable of carrying out a variety of operations with extreme speed and accuracy due to their ability to interpret computer instructions and make precise movements in three-dimensional space.
At the heart of this system is a concept known as interpolation. This is nothing more than the ability to accurately and precisely follow the programmed instructions of a CNC machine and move the tooling accurately in three-dimensional space. This is accomplished by having two or more drives functioning independently of each other. These drives move the tool positioning in each of the three available planes (X, Y, and Z).
The first step in setting up a CNC machine and interpreting instructions is to define the coordinates. This is done by entering a code into the operator’s console that tells the machine what the zero position is. At this point, the machine will reference all other coordinates in relationship to the zero position, which allows it to move the tool in the desired direction. Once the machine has been programmed with coordinates, the operator can then give the machine instructions to move in a linear fashion or to do a motion called “circular interpolation”.
Circular interpolation is when the machine refers to three-dimensional coordinates; two linear axes and one rotary axes. This allows the machine to move in a circular fashion, that is, in an arc. In a CNC machine, this can be done either in a clockwise or counterclockwise direction. In order to perform a circular interpolation, a mathematical algorithm is applied that determines the number of steps that the machine tool needs to move at which angular velocity.
In addition to being able to use circular interpolation, CNC machine tools also have the ability to use linear interpolation. For this type of motion, the machine uses two linear coordinates and moves along a straight line from one point to another. The machine takes into account the curved nature of the line when computing the total path that needs to be followed. This type of motion is often used in locksmithing operations in order to drill precise holes for a lock cylinder.
CNC machines can also take advantage of another technique called helical interpolation. This is typically used to create screws, threads, or helical staircases. The difference between helical interpolation and circular interpolation is that helical interpolation is programmed to move in a clockwise or counterclockwise direction while changing the angle and distance of the tooling.
Overall, the concept of CNC machine interpolation is relatively simple. By understanding this technology and how it works, it is possible to create parts and components with extreme levels of precision. With the right tools and knowledge, any well-equipped machinist will be able to create highly precise shapes and objects quickly and accurately using a CNC machine.
