Hard milling uses a combination of several key technologies that can be categorized into components. These components are defined as the machine tool, the CAD/CAM system,

the tool-holders, the cutting tools and the know-how. To be successful at hard milling, these components must come together in what can be called The Circle of Technology . Each component will be examined within the circle so that a clear understanding can be developed to facilitate successful hard milling of small- to medium- sized parts.

Machine Tool
 Although all of the components of the circle are important, the machine tool component is, by far, the most significant. The machine must be designed for hard milling and have some of the same characteristics found in a HSM center. The base construction and the individual components of the machine such as the drive train, the spindle and the CNC control, etc., must be capable of handling all the demands of hard milling.

The base construction of the machine must be extremely rigid and have a high degree of damping abilities. These characteristics are commonly found in machines constructed from polymer concrete. Machines constructed from polymer concrete typically have six to ten times the damping characteristics over machines constructed from cast iron.

Polymer concrete also has excellent mechanical and thermal characteristics. The drive train should consist of digital drive technology for optimum acceleration and deacceleration. This technology provides the CNC control with the ability to perform a high degree of contouring accuracy encompassed with excellent dynamics capabilities. These characteristics will help minimize cutting tool wear.

Spindle
Another important aspect of the machine is its spindle. The spindle should be a vector-controlled motorized spindle. Vector-controlled spindles provide a great deal of flexibility, offering high torque at low rpms and maximum power for large speed range. The HSK interface between the tool holder and spindle should be used. This will provide minimal runout and excellent balancing at high speeds. Hybrid-ceramic bearing in the construction of the spindle will offer some excellent benefits including increased spindle stiffness, accuracy and temperature stability.

CNC Control
 The performance of the CNC control is critical. A control with maximum block processing rate will ensure that the received data will be handled quickly and efficiently. This data should reside on a hard-drive located on the control. Incorporating numerical algorithm to calculate the velocity profile in the control will assist in smoothing machine motion.

Additionally, all servo systems on a CNC machine exhibit a characteristic called servo lag. Servo lag is the actual amount that the machine position trails the position commanded by the control. In hard milling, any motion that is not continuous with the programmed path will create excessive stresses on the tool, causing the possibility of premature failure. Therefore, it is essential that the control have the ability to handle and control servo lag.