Milling

Milling: A Machining Process

Milling

Milling is one of the most basic of machining processes. A mill holds the part firmly in place and moves it under a sharp, spinning tool that removes unwanted material in tiny chips. Mills are primarily used to make linear cuts in a part and to create flat areas, but a mill can also make holes in a part by guiding a drill bit, and make slots or threads in a part by guiding specialized tools called broaches and taps. Cutting parts on a mill is referred to as milling.

There are several types of milling machines on the market stemming from three basic types. These are:

1. Knee and column
   • Vertical spindle
   • Horizontal spindle
2. Bed type
3. Planer type
   • Vertical spindle
   • Horizontal spindle

Each style has unique advantages and limitations. Several types of milling cuts can be made by either the horizontal or vertical spindled machines. Often the choice of the machine type will depend on the depth and width of the desired cut, the power required, the preferred style of cutter and the time allotted for setup.

A traditional mill is generally assumed to have four axes:

1. Table x.
2. Table y.
3. Table z.
4. Milling Head z.

A five-axis or a six-axis CNC machine has extra axes for the horizontal milling head. This gives extra flexibility to the machine. Here are some examples of the cuts performed by the vertical and horizontal milling machines:

• Slots & Steps
• Keyways
• Half-round slots
• Pocket Milling
• Face milling

CNC Milling

The addition of Computer Numeric Control (CNC) to mills has enabled the milling process to achieve new heights in productivity and in the creation of highly precise parts. CNC mills are equipped with a computer consisting of one or more microprocessors and storage units, a user interface for programming and other interfaces that enable the CNC milling machines to work in conjunction with CAD/CAM software systems. All of this enables a CNC machinist to instruct the CNC milling machine to execute the exact movements necessary to create the precision milled part. Productivity has been further enhanced by the addition of two additional axes and live tooling.

CNC milling can be an economical manufacturing process because it requires very little time or attention from a CNC machinist once the machine, program and tools have been set up. With the addition of part loading and unloading systems, operators only need to load make any adjustments to the design parameters in order for a CNC milling operation to run semi-unattended for a certain period of time. CNC milling is an efficient and quick way to precisely produce detailed parts.