Lost foam casting is a green casting method with the characteristics of cleaner production. The white mold pattern with the same proportion as the casting is foamed and coated with fire-resistant coating is used for compact molding. Under the condition of negative pressure, the liquid metal is directly poured into the mold with white mold, so that the pattern is gasified and decomposed under the condition of high temperature, and then the liquid metal replaces the original pattern in the mold, After solidification and cooling, the required castings are obtained.
The surface roughness, dimensional accuracy and defects of lost foam castings are affected by the stiffness, strength and surface quality of burned white mold pattern. For specific pattern materials, optimizing the molding process and accurately controlling the pattern preparation parameters are the preconditions to ensure the quality and yield of lost foam castings.
At present, automatic pre foaming equipment with controllable pattern preparation parameters has been widely used in lost foam casting of complex castings. However, due to the high cost of such equipment, it is very necessary to develop a set of lost foam casting pre foaming equipment with easy to use, high performance and low cost.
(1) By studying the lost foam casting equipment, process and control requirements, a set of pre foam forming process control system with strong universality, easy operation and cost performance is designed by Using OMRON cj2m PLC. The pre foaming molding process is set online by the touch screen, the operation status of the pre foaming molding equipment is monitored through the sensor and I / O module, and then processed centrally by PLC to meet the parameters set by the process card. In terms of software, the control program and touch screen operation interface matched with PLC hardware are designed to facilitate the use of technicians and help to stabilize the forming quality of pre foaming pattern.
(2) The designed PLC control system can realize the automatic monitoring and control of complex pre foaming molding process and supporting equipment. Among them, the pre foaming / foaming temperature is automatically controlled by PID, and the cavity injection is controlled by the weight reduction signal of the ripening storage bin. Taking foaming temperature control as an example, through PID control, its steady-state fluctuation is less than the threshold defined by the process.
(3) The designed PLC system also takes into account the necessary software and hardware support required for subsequent function expansion and upgrading, allowing technicians to establish communication with PLC through Ethernet, export historical records, and optimize the pre foaming process parameters offline or online, so as to improve the pre foaming quality of patterns.
Therefore, by studying the lost foam casting equipment and process, the control system of pre foaming equipment is designed by OMRON cj2m PLC, the pre foaming process is controlled by PLC programming sequence, and the process parameters and I / O status of corresponding equipment are monitored. This is of great practical significance for optimizing the pattern forming process of lost foam casting and stabilizing the pre foaming forming quality.