Machine tool rigidity has a major impact on deep hole drilling because the less stable the foundation of the machine, the more vibration the head and table will generate, causing the tool to break down. For deep-hole drilling, features to look for include castings with uniformly thick walls to avoid heat distortion, box ways with a large surface contact area, a very strong head and a column that does not flex. A low-vibration spindle is also required.
Lack of stiffness in the machine tool causes the column to bend when pressure is put on the head from deep hole drilling operations. As a result, the drill may bend, decreasing accuracy and causing tool wear, eventually leading to a broken tool. With excessive pressure on the head, the drill enters at an angle and will miss the correct position.
Other features are also helpful. For example, a system for maintaining spindle speed as the load increases assures a constant chip load on the drill. If the spindle speed decreases during a cut due to tool load, the chip load will increase and risk breaking the tool. The spindle vector drive system on Fadal VMCs provides this function. Another feature found on these VMCs is dual spindle motor windings, providing low range speeds as high as 2,500 rpm and high range speeds of 2,500 to 10,000 rpm. This feature expands the capabilities of the vector drive spindle motor by doubling horsepower at high spindle speeds. Also useful in deep-hole drilling is Tool Load Compensation, enabling the programmer to designate a tool load that dynamically regulates the feed rate as cutting conditions vary.
What is Machine Tool Features
