The spindle system and feed system of CNC machine tools are very different. According to the working characteristics of the main drive of CNC machine tools, the early CNC machine tool spindle drive adopts the structure of three-phase asynchronous motor plus multi-stage gearbox. With the continuous development of technology, the machine tool structure has been greatly improved. This places new demands on the spindle system and varies from application to application.
The types of spindle drive system is DC spindle drive system and AC spindle drive system. The spindle drive system is selected according to the characteristics of these two types of spindle drive systems:
The high-speed, high-efficiency, high-precision control requirements of CNC machine tools make the FANUC DC spindle drive have the following characteristics compared to the usual speed automatic adjustment system:
(1) Wide range of speed regulation, CNC machine tools driven by FANUC spindle. In terms of mechanical structure, small machine tools usually adopt the structure of motor and spindle direct or belt shifting. Medium and large machine tools usually only set high and low speed. Mechanical shifting mechanism, therefore, the speed of the spindle motor must be controlled by the spindle drive. In order to ensure the processing range of the CNC machine tool, the machining process is relatively concentrate. The spindle drive must realize stepless speed change and have a wide adjustment range.
(2) Structurally, the FANUC DC spindle motor is a full cover structure.And use it in industrial environments where dust and cutting fluid splash.
(3) In the cooling system, in order to reduce the volume and improve the efficiency, the FANUC spindle motor uses a cooling system to dissipate the heat generated by the rotor to the outside.
(4) In the design of the magnetic circuit, in order to minimize motor heating, the FANUC spindle motor stator uses a unique additional magnetic pole to reduce losses and improve efficiency.
(1) The drive system is control by a microprocessor and modern control theory. The system runs smoothly with low vibration and noise.
(2) The larger power drive system uses the more difficult “feedback brake” technology. When braking, the motor energy can be fed back to the grid, which can save energy.
(3) The drive has D/A converter, actual speed/torque signal output, and electric spindle “directional stop”, which can be easily matched with various CNCs.
(4) The motor adopts a non-enclosure structure, and the stator silicon steel sheet is directly cooled by air, and can work safely and reliably in the case of floating dust and cutting fluid splashing.
(5) Compared with DC motors, spindle motors usually do not require maintenance because the AC spindle motors are structurally free of commutators.
(6) The cooling air of the spindle motor flows backward from the front end, which can effectively reduce the influence of motor heating on the accuracy of the machine.