Numerical control device is the core of the whole numerical control system, and its hardware structure can be divided into big plate structure and functional module structure according to the plug-in mode of PCB in CNC device.
(1) CNC device with large plate structure can be composed of main circuit board, position control board, PLC board, graphic control board and power supply unit. The main circuit board is a large PCB circuit board, and other circuits are small PCB circuit boards, which are inserted into slots on the large printed circuit board to form a CNC device together.
(2) Functional modular structure divides the whole CNC device into modules according to their functions. The design of hardware and software adopts modular design method, that is, each functional module is made into a printed circuit board (called functional template) with the same size, and the control software of the corresponding functional module is also modular. From the point of view of the design purpose of this system and the user’s use, this design selects the large plate structure. Plate structure design is as shown in the figure.
Hardware structure design of numerical control device on PCB
Main circuit board structure Tu Tu 3-1 main circuit board structure diagram
The main circuit board (PCB) in the figure has control core circuit, position control circuit, paper tape reader interface, speed control output interface, hand pulse generator interface, I/O control board interface and five small PCB slots. The core circuit is a basic microcomputer system, which consists of CPU, memory, timing and interrupt control circuits. The memory includes ROM and RAM,ROM (EPROM) is used to solidify CNC system software. RAM stores variable data, such as stack data and temporary data of control software. It has power-off protection function for variable data storage areas such as CNC machining programs and system parameters. The five slots can be respectively inserted with a magnetic bubble memory board, an LCD display control board, an I/O interface board, a stepping motor control board, etc. for protecting the NC machining program.
In addition to the main circuits mentioned above, the CPU board also includes some circuits such as reset and STD bus buffer/driver.
