What is CNC Milling?    Everything You Need to Know About CNC Milling

CNC milling is a manufacturing process that uses a cutting tool mounted on a rotating spindle to selectively remove material from a block of raw substrate.    The workpiece is rigidly mounted to a table, and this table moves or rotates on different planes so the tool can work at many angles.    Sophisticated CNC milling machines can have 5 or more axes of independent motion to make more complex shapes or to avoid having to move the workpiece to a separate machine.

 

The axis of motion for a CNC milling machine are based on an X-Y-Z coordinate measuring system.    All machinists refer to this when describing the basic movements of the mill, relative to an operator facing the machine.    A standard CNC mill for example has three axes.    The milling spindle represents the Z-axis, moving up and down.    The X-axis is left-to-right, and the Y-axis is front-to-back.

Rotary tables can be added to CNC milling machines to provide additional movements, while 5-axis machines already have rotating work tables built-in.

 

All of these movements of CNC mills rely on Computer Numeric Control, which is a computer program derived from a 3D digital file of the desired finished part.

Early automated machine tools relied on punch cards to control their basic movements in a systematic fashion.    This technology worked but it was a slow and cumbersome system and punch cards could not be modified once made.    These were later replaced by magnetic tapes, disk drives and now fully digital instructions in G-Code.

 

 

Making a finished part from a block of material requires many different tools, each of them performing a very specific CNC machining function.    Changing these tools one at a time by hand would be prohibitively time-consuming and inefficient.

To counter this, CNC milling machines have rotating carousels where all the needed tools are pre-loaded on separate holders.    When needed, these CNC milling and machining tools can be exchanged automatically on the spindle within a few seconds.