The diversity of modern manufacturing machines can be overwhelming. This article will focus on the two most common machine categories and compare the use of milling machines and lathes.
What is a lathe?
A lathe makes cylindrical parts by rotating materials on fixed tools. Parts made with a lathe are called turning. The raw material is fixed in a high-speed rotating chuck - this rotating axis is called the c-axis. The tool of the lathe is mounted on the tool rest, which can move parallel to the c-axis (expressed as movement along the Z-axis) and perpendicular to the c-axis (movement along the x-axis). On the CNC lathe, by controlling the X and Z positions of the tool holder at the same time, the rotational speed of some features can be changed to turn complex cylindrical geometry.
More advanced lathes have automatic tool changers, part catchers for serial production, and power tools that allow certain milling functions. The material needs to be fixed in the chuck and, in some cases, its tailstock needs to be supported. Lathes are good at manufacturing cylindrical parts with very strict tolerances and repeatability. The lathe is not used for parts whose main features deviate from the axis. Without additional tools, parts with off-axis characteristics cannot be machined on the lathe. For example, the lathe can only drill holes on the central shaft by installing a drill bit on the tailstock; In standard turning operations, eccentric holes are usually not possible.
What is a milling machine?
Unlike a lathe, a milling machine holds the material in a fixture and cuts it with a rotary tool.
There are many different configurations of milling machines, but the most common is to allow the operator to move the parts left and right along the x-axis and move the parts back and forth along the y-axis. The tool moves up and down along the Z axis. CNC milling machines can simultaneously control the movement along these axes to create complex geometry, such as surfaces. This main type of milling machine is called 3-axis milling machine.
5-axis milling machines can cut more complex parts, and can process a wide range of parts, including many different functions that cannot work on the lathe. On the other hand, the setup and programming of the milling machine can be complex. A part may need to change its orientation several times to machine all features. Different settings are called milling operations. The increased milling operations increase the cost and expense of part manufacturing.
How to choose milling machine and lathe?
From the above summary, the lathe is most suitable for manufacturing cylindrical parts. The cross section of the parts must be circular and the same central axis must run through its entire length.
Milling machines are more suitable for machining parts that are not completely cylindrical, have flat, complex features, or have offset / inclined holes. The milling machine can process cylindrical features, but if the part is pure cylindrical, the lathe is a better and more accurate choice. More sophisticated machines, such as Swiss lathes, can cut planar features and drill vertical holes in the material. However, these machines are still more suitable for cylindrical parts.
