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Metal Casting Technologies : June 2007
www.metals.rala.com.au 34 applied in the electric control unit so operating staff can remotely monitor the working condition of CGCE. The flow control element is the key of CGCE pneumatic adjustment and it is also the main factor which influences pressure control precision. In the pneumatic adjustment unit the digital assembled valve system that we developed was applied as flow control part. As is shown in Fig. 3, the assembled valve system contains 8 electromagnetic valves, 8 manual valves and 8 throttles. Thus, the system can provide 256 different states, corresponding to 256 different filling rates, which are enough to perform all adjustment actions. It is important that the assembled digital valve system provides greater rapid adjusting rates than any other adjustors. The digital assembled valve system is driven by digital signals. Compared to the pneumatic membrane valve, which is driven by electric valve locator, the digital valve system has a much faster response speed. The response time between two different adjustment states is only 30ms. Therefore, the counter-gravity casting system is provided with better pressure tracing precision. 2.3 Controlling software All actions of the counter-gravity casting equipment are controlled by a computer with a self-designed program. The controlling software uses Windows desktop and is written with object-oriented Delphi. Every action is driven by external and internal events. Fig.4 and Fig.5 show parameter setup page and process monitor page of controlling software respectively. The parameter setup page offers abundant information necessary for casting production, including technical parameters, touch-point usage information, PID parameters, temperature field acquisition information, working-state information and parameters used to improve pressure-tracing properties. All information on this page can be saved or read. The process monitor page provides several action buttons where the operator can click to implement different actions e.g. opening air-in and air-out valves, locking mid- dividing board, and starting or stopping filling process, etc. Furthermore technicians can see the given pressure values, real pressure values acquired by pressure sensor, action state of different valves, pressure-tracing curves. If technicians want to obtain temperature field data during casting solidification, this page can also provide temperature-time curves of different positions by putting the necessary thermal couples at the corresponding positions. TECHNICAL FEATURE Fig. 3 Schematics of assembled valve Fig. 4 Parameter setup page Fig. 5 Process monitor page