CNC turning is a subtractive manufacturing technology and refers to the process of removing material from a (typically) cylindrical stock piece of material — though CNC turning can also be performed on a wide range of stock shapes such as hex or square bar. The machine spins the workpiece while a tool moves to engage and remove material until the desired shape is achieved.
Turning machines can be vertical or horizontal, and the figure above shows the axes convention for vertical and horizontal machines (6 axes shown, although number of axes varies). Vertical CNC turning is typically used to machine large and heavy designs as the material’s center of gravity is aligned along the rotational axis.
Horizontal CNC turning has the workpiece mounted in such a way as to cause a cantilever effect. That cantilever setup may cause vibration in large, heavy pieces which can affect the machining quality, and also cause potential damage to the turning machine and tooling.
Vertical turning has its own set of drawbacks, however. One drawback is chip evacuation: if cutting chips are not effectively evacuated after being cut, potential issues like chip recutting and part scratching can result. Therefore, horizontal CNC turning is the most common setup.
The difference between a CNC lathe and a CNC turning center can be simply expressed as a difference in their capabilities, with a turning center typically being capable of multiple operations while a lathe simply turns. A lathe is a machine designed to cut a rotating workpiece while turning refers to the rotational cutting process in general.
Before CNC technology, lathe machines were similar and easy to identify. However, with advancements in technology, many new features have been added. So, we need to differentiate between simpler CNC machines that perform operations like the original lathes, and enhanced machines (CNC turning centers) that can perform turning cuts in additional ways.
Some companies differentiate the two based on the number of toolpath axes the machine can execute. CNC toolpaths can be classified as 2D, 3D, 4-axis, or 5-axis (this applies to both milling and turning-cutting processes). Lathes generally are 2-axis machines, while turning centers are typically 3-axis, 4-axis, or 5-axis machines. Other companies refer to machines that can perform turning cuts as well as milling and drilling operations as turning centers.
