The main motion requirements of CNC lathe machining:
- (1) The spindle speed is continuously adjustable within a certain range.
- (2) The spindle has sufficient drive power.
- (3) Spindle components have high rotation accuracy and stable operation.
- (4) The main shaft component has sufficiently high rigidity and shock resistance.
The main transmission system of the economical CNC lathe is almost the same as the basic structure of the ordinary lathe, that is, the gear shift is mainly used. In order to meet the requirements of automatic shifting of CNC lathes during processing, electromagnetic clutch shifting or double-speed motor shifting is generally used in the transmission. There are also some economical CNC lathes that use a handle shift fork for manual transmission. Economical CNC lathes generally have 4-8 speeds, which is somewhat lacking in high-level automatic processing, but can meet general processing requirements.
The main drive system of the standard CNC lathe adopts a DC or AC stepless speed regulation spindle motor, which is driven by a belt to the spindle box to drive the spindle to rotate, thereby achieving automatic stepless speed regulation and constant high speed cnc machining control. In order to increase the speed adjustment range and ensure that the spindle motor speed is not too low, sometimes two sets of variable speed gears are set in the spindle box, and the spindle speed range is divided into high speed and low speed. The hydraulic cylinder is used to push the slip gear to realize the gear transposition, or the electromagnetic clutch is used to turn on or off the transmission of power.
Standard type CNC lathe spindle speed is automatically performed in accordance with the processing program instructions. In order to ensure the accuracy of the main drive of the lathe, reduce noise, and reduce vibration, the main drive chain should be as short as possible; in order to ensure that different processing technology requirements are obtained and the best cutting speed can be obtained, the main drive system should be able to continuously change the speed in a wide range ; In order to ensure the productivity and machining quality of the turning end face, it should also be able to achieve constant cutting speed control. In addition, on the full-function CNC lathe, the spindle should be able to cooperate with other components to achieve automatic clamping of the workpiece.
There are two types of pulse signal generators used in spindle motion: photoelectric and electromagnetic. The spindle encoder on the CNC lathe uses a photoelectric pulse generator synchronized with the spindle. The pulse signal generator can be synchronized by a 1:1 belt drive installed on the intermediate shaft, or by a pair of gears, or it can be installed coaxially with the main shaft through an elastic coupling. On the high-level CNC lathe (cnc turning center), the C axis (that is, the rotating coordinate axis around the main axis) must also be controlled. The main transmission system of the turning center is basically the same as that of a general CNC lathe, except that the C-axis coordinate function of the spindle is added to achieve spindle-oriented parking and circumferential feed, and the C-axis and Z-axis linkage interpolation is controlled under the control of the CNC device , Or C axis and X axis linkage interpolation. In this way, drilling, milling, threading and curved surface machining can be performed on any part of the cylindrical surface or end surface of the rotating body. The rotation (ie feed) or indexing movement of the C-axis is achieved by the C-axis servo motor through a precision worm pair or sliding gear pair, and the indexing gear.