Limitations of traditional CNC machining

September 13, 2022

Since the 1980s, large-scale gantry 5-axis linkage CNC milling machines have been used to process aircraft structural parts. The table, beam and spindle components of the gantry machine realize the movement of the X, Y and Z axes, plus the pendulum or universal spindle head to realize 2 rotary motions of the A axis / C axis or the A axis / B axis , constitute a 5-axis linkage CNC machine. The operation of the aircraft structural parts processed by the gantry CNC machine tool is shown in the figure.

Aircraft structural parts are processed on gantry CNC milling machine

The advantage of the split-fork or universal spindle head is that the spindle has a large deflection angle and can realize 5-sided machining of rectangular parts. However, although the spindle head can achieve very high rotational speeds and accelerations on a single axis. However, the orientation speed of the tool space is still low, because the two rotary motions of the spindle head are connected in series and cannot be rotated at the same time. The compensation motion of the X, Y and Z axes of the machine tool cannot be reflected in time. This congenital defect in kinematics makes the gantry CNC machine not fully suitable for machining aircraft structural parts, or the machining efficiency is not ideal.

In addition, regardless of the split-fork spindle head or the universal spindle head, there are three motors inside the spindle head. Each electric cable is connected to cables or pipes such as power supply, cooling, lubrication and position detection, and there is positional rotation between them. The connection and sealing structure are very complicated. In addition, the tool clamping device needs to be arranged inside the spindle motor, resulting in dozens of cables and pipes at the end of the spindle head, which is extremely inconvenient to maintain, as shown in the figure.

Schematic diagram of the fork-type spindle head

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Ms. SU LAN RONG

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