I. Overview

From the perspective of its hardware structure, the CNC device can be divided into the following categories according to the number of CPUs it contains:

Stand-alone system: The entire CNC device has only one CPU. It centrally controls and manages the entire system resources, and realizes various NC functions through time-sharing.

In the master-slave configuration, only one CPU (called the master CPU) in the system has control and usage rights over the system resources. Other functional components with CPUs can only accept control commands or data of the master CPU or send request information to the master CPU to Get the data you need. That is, it is subordinate, so it is called the master-slave structure.

Multi-machine system: There are two or more CPUs in the CNC device, that is, some of the functional modules in the system also have a CPU. According to the mutual relationship between components, they can be divided into:

Multi-master structure: There are two or more module parts with CPU in the system that have control or use rights to system resources. Tight coupling between modules, a centralized operating system, through the arbiter to resolve bus contention issues, through the public memory for information exchange.

Distributed architecture: The system has two or more functional modules with CPUs. Each module has its own independent operating environment. The modules are loosely coupled and use communication methods to exchange information.

Second, the function of stand-alone or master-slave structure module

The CNC device is constructed in a modular design

Modular design method: The control system is divided into several functional unit modules according to their functions and equipped with corresponding driving software. In the system design, different functional modules are selected according to the requirements of the function and inserted into the control unit motherboard to form a complete control system. The unit mother board is generally a passive mother board of a bus structure, and it provides a signal path for interconnection between modules.

The condition for implementing the modular design of the CNC system is the bus (BUS) standardization. When using a modular structure, the CNC system design work can be attributed to the rational selection of functional modules.

1, computer motherboard and system bus (motherboard)

The computer motherboard is the core of the CNC device.

Functional structure:

CPU and its peripheral chips; memory unit and its peripheral chips; communication interface (serial port, parallel port, keyboard interface). Soft and hard drive interface.

The main role of computer motherboards:

Corresponding arithmetic and logic operations are performed on various data, information (part machining programs, various I/O information, etc.) input to the CNC device. And according to its processing result, it sends out the control command to each function module, transmits the data, causes the user's instruction to carry out.

System bus (motherboard): A group of physical wires that carry digital information. It is the channel through which data or information is exchanged within the computer system:

Data bus: 8 data lines, bus width 8 bits; address bus: 16 address lines (direct addressing 64k);

Control bus:

The bus motherboard of an industrial PC is an independent passive four-layer board (a trace plane, a component plane, a power plane, and a ground plane), and its reliability is higher than that of a two-layer board. Its specifications are 6 slots, 8 slots, 12 slots, 14 slots and so on.

2, display module (display card)

The main function of the display card:

Receives control commands and data for display from the CPU, modulates with the scan signal of the CRT, generates the video signal required for the CRT display, and generates the desired picture on the CRT.

In the CNC device, the CRT display is a very important function, it is an important medium for human-computer communication, it provides the user with an intuitive operating environment, allowing users to quickly become familiar with the operation process.

The display card is a very versatile module. It is not only readily available on the market, but it also has very rich support software, so it does not require users to develop it.

3, input / output module (multifunction card)

It is an interface board for exchanging data and information between the CNC device and the outside world, that is, the CNC device can obtain data from the input device through this interface, and can also send the data in the CNC device to the output device.

This module is also a standard PC module and generally does not require the user's own development. If the computer motherboard is a standard motherboard, this board can be omitted.

The above three parts (computer motherboard, video card, input/output), and keyboard, power supply, and chassis are actually a general-purpose microcomputer system. It is the core of the CNC device. In a sense, CNC The grade and performance of the device are determined by it. Therefore, the rational selection of computer systems in CNC devices is crucial.

4, electronic disk (storage module)

The electronic disk is a unique memory module of the CNC device. It is used to store the following data and parameters in the CNC device:

System software, system intrinsic data; system configuration parameters (number of feed axes that the system can control, axis definition, system gain, etc.); user's part program.

There are three types of memory devices used in the computer field:

Magnetic storage devices, such as: soft/hard disks (read/write). Optical storage devices, such as: Optical disks (read-only). Electronic (semiconductor) memory devices such as RAM, ROM, FLASH, etc.

The first two types are generally used as external memory, which is characterized by large capacity and low price.

Electronic storage devices are generally used as internal memory and are more expensive than the first two types. According to its reading and writing performance, it can be divided into three categories:

Read-only memory elements (ROM, PROM, EPROM, E2PROM); volatile random read-write memory elements (RAM). Non-volatile read and write memory elements.

Such devices include:

E2PROM; FLASH; RAM with backup battery.

In CNC devices, electronic memory devices are often used as external memory, mainly considering that the working environment of CNC devices may be subject to electromagnetic interference, and the reliability of magnetic devices is low, and the anti-electromagnetic interference capability of electronic memory devices is relatively stronger. .

Because the storage unit composed of electronic devices is managed by the disk, it is called an electronic disk. The electronic disk specifications are: 1.44MB, 2.88MB, 6MB, 12MB, etc.

5, PLC (Programmable Logic Controller) module

PLC module: A module that implements sequential control of a CNC device.

The role of the PLC module: receiving signals from the operation panel, the various trip switches on the machine, sensors, buttons, relays in the power cabinet, spindle control, and magazine control. After processing, the output controls the operation of the corresponding device.

There are three types of information exchanged between the CNC device and the controlled device:

Switch signal, analog signal, pulse signal.

Because of the type, level, power, and anti-jamming, the above signals cannot generally be directly connected to the CNC device, and an interface is required to transform these signals.

The PLC module transforms its purpose:

Meet the CNC system input and output requirements. Signal conversion mainly includes several aspects:

Level conversion; A/D, D/A conversion; digital and pulse quantity conversion; power matching; blocking external interference signals into the computer, electrical isolation of CNC devices and external signals to improve the CNC device operation The reliability.

PLCs for CNC machine tools generally fall into two categories:

Built-in Type PLC (or integrated, built-in). Stand-alone Type PLC (or Universal)

6, the position control module

The position control module is an important part of the feed servo system. It is an interface module that connects the CNC device and the servo drive system when the track control is implemented.

Commonly used position control modules are:

Open-loop position control module: Interface between CNC device and stepper motor drive power supply; Closed-loop (including semi-closed loop) position control module: Interface between CNC device and DC and AC servo drive device.

7、Function interface module

Interface board that implements user-specific function requirements, examples:

Profiling controller interface; laser processing focus auto tracker interface; signal acquisition interface board in tool monitoring system.

Third, the numerical control system (hardware) Introduction

China's CNC system is one of the high-performance CNC systems with its own copyright. It is based on a general-purpose industrial PC and adopts an open architecture that guarantees the reliability and quality of the system. It is suitable for multi-coordinate (2-5 axis) CNC boring and milling machines and machining centers. After adding corresponding software modules, it can also be applied to other types of CNC machine tools (CNC grinders, lathes, gear processing machines, etc.) and special machine tools ( Laser processing machines, wire cutters, etc.).

Fourth, multi-master structure of the CNC system hardware

In a multi-master CPU architecture, there are two or more CPU components. Components are tightly coupled. There is a centralized operating system. Bus arbitrators (composed of hardware and software) are used to solve bus contention problems. Memory for information exchange.

1, the characteristics of multi-master structure:

It can achieve true parallel processing, processing speed, and can achieve more complex system functions. Fault-tolerant ability, after a module fails, can continue to work through system reorganization

2, the structure of multi-master structure:

Shared bus structure type; shared memory structure type.

Structure:

The functional modules are divided into a master module and a slave module (RAM/ROM, I/O module) with a CPU, centered on the system bus, and all master and slave modules are plugged into a strictly defined standard system bus. A bus arbitration mechanism (circuit) is used to determine the competition problem of multiple modules requesting the use of the system bus at the same time.

Shared bus architecture advantages:

Simple structure, flexible system configuration, relatively low cost and high reliability;

Disadvantages of the shared bus architecture:

The bus is the system's “bottleneck”. Once the system bus fails, the entire system will be affected; because the use of the bus is arbitrated, the information transmission rate is reduced.

Structure:

Designed for common memory, that is to use multi-port to achieve the interconnection and communication between the main modules, using multi-port control logic to solve the contradiction of multiple modules access to multi-port memory conflicts at the same time.

Because the multi-port memory design is more complex, and more than two main modules may cause blocking of memory transmission information due to contention for memory, this structure generally uses dual-port memory (dual-port RAM).

Main USES this series of machine tools is mainly used for groove grinding of Self-aligning roller bearing.1, CNC ac servo control system (PLC or CNC system), color screen display, "man-machine dialogue" and with fault self-diagnosis function.Equipped with electronic pulse handwheel.2. Adopt cross guide rail.3. The work-piece feed pallet and grinding wheel running pallet are driven by servo motor.4. External cylindrical cutting grinding of grinding wheel.5, electromagnetic centerless fixture, remote control control demagnetization controller, in the operation panel to adjust the size of the magnetic force.6. The workpiece shaft adopts sleeve workpiece extraction.Frequency control of motor spee.

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Xinxiang Sunrise CNC Bearing Equipment Co., Ltd. , https://www.cncsunrise.com