Design And Implementation Of Artificial Synthetic Diamond Control Syste

Diamond is not only the hardest substance in nature,but also has excellent optical,thermal and electrical properties,which broadly applied in industrial area,especially high-tech fields.However,natural diamond is expensive and difficult to mine,and it is a non-renewable resource,which limits the application of diamond to a large extent.Therefore,synthetic diamond technology has become a research hot spot.At present,the chemical vapor deposition(CVD)method can synthesize high-quality diamond films at lower production costs,Microwave Plasma Chemical Vapor Deposition(MPCVD)has become the most ideal method for preparing high-quality diamond films due to the advantages of no electrode contamination.In the process of synthesizing diamond by MPCVD method,the growth of diamond is affected by various factors such as carbon-containing gas concentration,substrate temperature,vacuum chamber pressure,microwave power,etc.Only by comprehensively considering and controlling these process parameters can high-quality diamonds be produced.On the basis of in-depth study of the principle of MPCVD method,the thesis designs and develops a synthetic diamond control system based on this method.The system selects Siemens’ new PLC with excellent performance as the controller,and selects the microwave generator,mass flow controller and pressure controller with high precision and good stability as the actuator,to realize automatic control of process parameters such as gas concentration,temperature,pressure and microwave power through program design.The control system designed in this thesis has fast adjustment speed and high operating efficiency,and improves the automation degree of the artificial diamond production process.The main work of the thesis consists of the following aspects:(1)By studying the process principle of MPCVD synthetic diamond,we formulate the production process flow of artificial synthetic diamond,design the synthetic process parameters,and propose the overall design scheme of the system.(2)Hardware design and software programming is carried out for synthetic diamond control system.The new 1200 series PLC of Siemens is selected as the controller,and the new digital instrumentation equipment with control function and communication function is selected to realize the measurement and control of process parameters.The system is programmed according to the artificial synthetic diamond process flow,and the communication program design of PLC and digital instrument,and the program design of startup preheating process,heat preservation process and shutdown cooling process is completed by using Siemens TIA Portal software platform.Especially in the heat preservation process stage,the system has designed a formula control scheme,which can automatically adjust the process parameters according to the temperature measurement value,the matching relationship between microwave and pressure,and the existing experimental data.(3)The host computer monitoring system is developed.It consists of two parts:local monitoring system and remote monitoring system.The local monitoring system is designed through the SIMATIC WINCC integrated by TIA Portal software,which realizes the functions of data monitoring,modification,alarm and data recording of the on-site production process;The remote monitoring system is designed by using the.NET operating platform provided by Microsoft and using the Visual Studio C# programming language to realize the function of remote monitoring equipment status information without the aid of an intelligent gateway.