MATERIALS REMOVAL MECHANISM OF ROTARY ULTRASONIC MILLING
Numerically controlled rotary ultrasonic milling is a process in which diamond abrasive grains are sintered on a tool head, using conventional mechanical rotary machining and tool axial ultrasonic vibration, and CNC programs are used to control the movement of x-axis, y-axis, and z-axis. To achieve three-dimensional contour processing, as shown in Figure 1.
Since the shape of diamond particles is generally irregular, there are many sharp corners. When the diamond abrasive particles act on the workpiece, the abrasive particles are like a small indenter that comes into contact with the working surface, resulting in a central crack and a transverse crack when the crack propagates to When the workpiece surface, it will fall off from the workpiece in the form of brittle fracture.
Figure 1 Schematic diagram of CNC rotary ultrasonic milling
Therefore, the removal of numerically controlled rotary ultrasonic milling materials is a combination of diamond abrasive grain grinding materials and conventional ultrasonic machining material removal. There are three ways to remove materials at the same time in processing: (1) Impact As the tool rotates, the abrasive particles on the tool face impact different parts of the machined surface; (2) The rotation of the abrasive tool and the feed motion of the tool make the abrasive The particles scratch a tiny groove on the surface of the workpiece; (3) Ultrasonic cavitation.
According to the indentation fracture mechanics, combined with the actual movement of diamond abrasive particles, the material removal process and cutting volume model for single-grain cutting hard and brittle materials are shown in Figure 2.
Figure 2 Single-grain pressure fracture mechanics model
In Figure 2, CL is the length of the transverse crack, Cr is the radial crack length, Ch is the depth of the transverse crack, w is the maximum penetration depth of a single abrasive grain, and d is the indentation length of the single grinding diagonal Fn is the maximum impact force of a single abrasive grain.
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