Gas Flow Rate Monitoring And Controlling In Pyrocarbon Coating Furnace For Mechanical Heart Valve Prostheses

Artificial heart valve is designed for people whose heart valve can't work naturally, and it can be used to instead of natural heart valve. Artificial heart valve is made up of limb, flap frame and valve ring. The limb and flap frame of artificial heart valve components are made from graphite substrate, coated with a thin impermeable layer of low-temperature isotropic (LTI) pyrocarbon. LTI carbon containing silicon is fabricated by the co-deposition of silicon and carbide. Coating process for artificial heart valve by CVD is very complex, and there are many factors. Of these, argon, silane and propane gas flow is one of the main factors, directly affect the performance of pyrolytic carbon and structure, thus affecting the quality of artificial heart valves.To provide data support for study the quality of the gas flow and the relationship between artificial heart valves. In this paper, artificial heart valves pyrolytic carbon coating furnace gas flow monitoring and control system in order to achieve accurate control of the gas flow during deposition, the deposition process real-time monitoring and storage of traffic flow changes the value of the objective.The main contents and conclusions of this paper can be divided into the following sections.1. By analyzing the particularity of the gas flow measurement, D07-19B-type mass flow controller is used to control the gas flow of argon, silane and propane. In the choice of mass flow controller, we mainly focused on the the controller's input and output signal, range, accuracy and other factors. At the same time, as the gas mass flow rate greatly influenced by the pressure, it is necessary to pay special attention to the pressure of the controller.2. USB2831-type data acquisition card is used to monitor the gas flow. In the choice of data acquisition cards, we mainly focused on the number of channels of data acquisition card, range, sampling frequency, accuracy and other factors. In addition, because the data acquisition card is used to collect traffic generated by mass flow controller signals, the accuracy and resolution should be greater than the controller's accuracy and resolution.3. Because MFC class library of Visual C++ 6.0 is functional and easy to use, MFC is used to write data acquisition card procedures in this paper, to realize data acquisition, display, storage and other functions. 4. Let the data acquisition card collect the signal generated by a signal generator which is sine and then collect real-time display and store the signal. Simulation results show that:the data acquisition card can capture the signal properly, meet the traffic monitoring function.5. This monitoring system can collect and set the D07-19B-type mass flow controller's input and output traffic signals and complete the real-time display, storage and other functions.