1. Preparation before machine tool transformation
Because the machine tool transformed by microcomputer can only improve the consistency of parts processing quality, the processing accuracy of parts is guaranteed by the transmission accuracy of the machine tool itself and the step distance accuracy of stepping motor. Therefore, the machine tool must be repaired before refitting.
(1) For machine tools that have been used for less than 5 years, the accuracy of each component has not been seriously worn, and the guide rail is scratched in a basically visible state, so overhaul is not required.
(2) For machine tools that have been used for 5-10 years, their parts are basically good. Only some vulnerable parts need to be repaired and replaced, and they can be transformed after passing the inspection according to the standard of lathe overhaul.
2. Modification process
Refitting of lathe transmission system for ordinary lathes, the main transmission system and feed system are both from the spindle motor, while the transformed CNC lathes, the main transmission system and feed system are separated into two unrelated systems.
The connection mode between stepping motor and ball screw is an important problem in the refit of machine tool, which requires reliable connection. The connection form between stepping motor and machine tool adopts gearbox connection. Connect the stepper motor shaft and the lead screw shaft with a box, and the center distance of the shaft hole can be accurately guaranteed, so that the gears mesh well, the transmission is stable, the noise is low, and it is easy to prevent dust. It is suitable for refitting lathes with good accuracy.
Measures to eliminate the gear clearance as a pair of gears are used between the stepping motor and the ball screw, the transmission clearance is introduced, and the stepping motor turns a step angle, which fails to make the ball screw turn a corresponding angle synchronously, thus reducing the machining accuracy. If this transmission gap is not compensated, the accumulated error of part processing may become larger and larger, resulting in dead zone and return error. On the one hand, computer software is used to correct the gear clearance, on the other hand, gapless gear transmission is used.
The hardware circuit of the reformed CNC lathe control system is generally composed of the following four parts: main controller, memory, bus and interface. The reliability of hardware circuit directly affects the performance index of CNC system, in which CPU is the core of CNC system.
Software design the software of the single chip microcomputer numerical control system adopts the modular design method, including the main module, subroutine module and interrupt processing module.
With the development of science and technology, the numerical control transformation of ordinary machine tools can greatly reduce the investment of technological transformation on the premise of meeting the same processing tasks, and has been widely used in practice.