Design Of DNC System Conversion Module Based On CAN Bus

With the development of computer technology,network technology and CNC processing technology,the Chinaese manufacturing industry has entered the development stage of informatization driven industrialization,and the network of CNC technology has become an important initiative for manufacturing enterprises to enhance their competitiveness.CNC machine tools as an indispensable processing equipment in the manufacturing industry,the number of its numerous.Due to the durability of the machine tool,the slow replacement,so in Chinaese existing CNC machine tools,both a large number of network communication interface,can be networked CNC machine tools,while there are also a large number of only RS232/RS232 C or RS485 interface CNC machine tools.This type of machine tool can not be directly networked,to the CNC machine tool network and manufacturing information management brings difficulties.In order to solve the problem of networking of CNC machine tools with only RS232/RS232 C or RS485 interfaces,this paper designs a conversion module and sets up a Distributive Numerical Control(DNC,Distributive Numerical Control)system through CAN(Controller Area Network)bus,so that a A computer controls multiple CNC machine tools,realising network processing and manufacturing information.In the DNC system,the host computer sends and receives data through the CAN interface and the CNC machine tool sends and receives data through the RS232/RS232 C or RS485 interface.The two communication protocols are inconsistent,so the conversion module is needed to complete the conversion of the different protocols to achieve the communication between the DNC host computer and the machine tool.The CAN transmission rate is much higher than the RS232/RS232 C or RS485 transmission rate,resulting in data overflow in the buffer of the machine tool;in DNC processing,the buffer of the CNC machine tool is usually only a few hundred bytes,resulting in frequent switching between CNC machines when the host sends the processing program,reducing transmission efficiency;to solve the above problems,it is necessary to add a To solve the above problem,a storage structure needs to be added to the conversion module,but as the CNC machine tools have to be processed in the order of the machining process,this paper uses the FIFO(first in first out)storage structure.In the DNC system,the two communication layers-host and conversion module,conversion module and machine tool-are kept relatively independent;the communication between the machine tool and the conversion module is controlled according to the handshake protocol,and there is a delay in the process of the conversion module receiving and responding to the machine tool’s commands,so a certain amount of program has to be set in the machine tool buffer.In the communication between the conversion module and the host,the conversion module sends a request to the host or stops sending data signals,and there is also a delay in the host receiving and responding.Therefore,this paper designs the upper and lower limits of data reception for the FIFO storage structure in the conversion module,and establishes a mathematical model to avoid communication conflicts,determines the size of the upper and lower limits of data reception and the parameters of the DNC system,and provides a theoretical basis for building a CAN bus-based DNC system.In this paper,the overall hardware implementation of the conversion module is determined from the design requirements and functional needs of the system,the software design is carried out,the CAN application layer is defined and the overall software design of the system is completed.The conversion module designed in this article can undertake data conversion between different protocols and store them.By building a simulation platform with two computers,experiments were conducted on the functions of the conversion module,and the experimental results verified the feasibility of the conversion module.