Design And Development Of A Control System For Vacuum Forming Machine

The vacuum forming machine is a kind of large equipment which manufactures the inner case of refrigerator using thermoforming craft. It involves knowledge of multi-subjects in the design and manufacture, such as control theories, thermoforming craft, materials, infrared radiation, heat conduction, bus communication, pneumatic and hydraulic transmission, mechanical transmission, and so on. The cross-integration of multi-subjects is embodied on the vacuum forming machines. Our designing level of plastic processing machinery has been inferior to that of developed countries all through, such as Germany, Japan, and the U.S.A. etc. We can do the designing and manufacture work of forming machinery. However, our products couldn't reach the level of developed countries on some indexes, e.g. automation level, stability, reliability, and producing speed. All those make the domestic market of high-level forming machinery be occupied by several foreign brands, and which results in the loss of foreign exchange of our country.Our government has called on people to construct an innovative society together, considering the situation that our country has complete industries, but low designing level. The government encourages to introduce advanced technologies into domestic industries, moreover, digest the technologies and innovate at last to change the current situation of complete industries but low designing level. The task is carried into execution under this environment.This paper mainly accomplished several tasks described as follows.(1) A good master of craft of the four stations vacuum forming machine, known the complicated logic relations well and realized them in program.(2) Chose appropriate PLC and set up the system and network according to the system requirements. Introduced PROFIBUS and distributed IO into our system according to the characteristics of the forming machine, which raised the data transmission speed greatly. Simplified and structurized the PLC program, so as to maintain the equipment conveniently later. Chose appropriate configuration software and programmed in order that the HMI become more practical and more friendly. (3) Improved the previous temperature control system and brought forward a new temperature control principle, introduced the two closed loop and cascade control into the temperature control system, so as to improve the heating performance of heater.(4) Analyzed the relation between heating rate of heater and radiant energy and the influence radiant energy on sheet detailedly through the theoretical research based on quantitative calculation.