Engraving machine In CNC machine tools, the electric spindle usually adopts the frequency conversion speed regulation method. At present, there are three main control modes: common variable frequency drive and control, vector control drive drive and control, and direct torque control.
The common frequency conversion is scalar drive and control, and its drive control characteristic is constant torque drive, and the output power is proportional to the rotational speed. The dynamic performance of ordinary variable frequency control is not ideal. The control performance is not good at low speed, the output power is not stable enough, and the C axis function is not available. However, it is cheap and simple in structure, and is generally used in grinding machines and ordinary high-speed milling machines.
The vector control technology mimics the control of the DC motor, and is oriented by the rotor field. The vector transformation method is used to realize the drive and control, and has good dynamic performance. The vector control driver has a large torque value at the beginning of the start, and the electric spindle itself has a simple structure and a small inertia, so the starting acceleration is large, and the allowable limit speed can be instantaneously reached after the engraving machine is started. This kind of driver has two kinds of open loop and closed loop. The latter can realize the feedback of position and speed. It not only has better dynamic performance, but also can realize C axis function. The former has poor dynamic performance and does not have C axis function. But the price is cheaper.
Direct torque control is a new type of high-performance AC speed control technology developed after vector control technology. Its control idea is novel, the system structure is simple and clear, and it is more suitable for high-speed electric spindle drive, and can meet high-speed electric spindle. High speed, wide speed range, high-speed instantaneous quasi-stop dynamic characteristics and static characteristics have become a hot technology in the field of AC transmission.
