PLC Technique-based Reconstruction Of Injection Molding Machine

As an important technology, the injection molding technology including the thermoplastic molding (hereinafter called plastic molding) and the thermoset molding (hereinafter called bakelite molding) has become a main technology of plastic production today.The injection molding machine is the main equipment of injection molding, its technical parameter and performance are closely related with the plastic property and its molding technology. The material with Polymers property in the process of plastic injection shows the totally differences in physical and chemical, rheological and thermal property, which bring forward some special requirement of injection molding technology, and then the special type of the plastic injection machine and the special machine are developed, the research object in the thesis is the plastic injection machine of thermohardening and the BMC bakelite molding machine.Through applying the PLC technology ,we successfully reconstruct the PLC electrical system of a second-handed injection molding machine from Japan, which included the control of the temperature ,the distance of the open-close and the sprue capacity in A/D module and the control of proportional pressure and flux in D/A module . On the basis of the reconstruction ,it is promoted in the reconstruction of the other aged injection molding machine , on one hand, we can lower the failure rate of the equipment ,and this will promote the productive efficiency , on the other hand , it will advance the machine utilization and control the molding parameter of the equipment precisely.According to the similarity of the equipment in the plastic molding, the bakelite molding and special BMC molding , through applying the PLC technology and the reconstruction of its relative parts of mechanical and hydraulic ,these three different types of plastic could be produced in a same equipment ,realizing the function of"three in one"in equipment.The flow of the plastic and the bakelite molding is almost the same,which have few differences in plastic heating and the technics of molding. The two types of molding equipment could be interconverted through changing the plasticizing equipment,adding the program of releasing gas in mold and converting the relative function .In the practical operation, two sets of feed-in organ and the screw barrel are prepared, due to the same dimension to install, it is convenient to change the parts of the equipment. In order to solove the different heating ways of the two types of equipment, the connection base connected with the electric heating control equipment near the screw barrel should be equipped ,which is convenient and drying facility with temperature control should be equipped. In the same theory ,when we convert into the bakelite molding, it is necessary to equip with the mould temperature controller and common feed-in organ without heating function in changing the screw barrel , that realize the conversion of its performance. The mold releasing gas module is a standby module in program writing of injection molding machine, we set a functional switch in the operation panel, which communicate with the mold releasing gas module ,when the thermoplastic is produced , the functional switch turns off and then turns off the releasing gas module ; when the thermoset is produced , the functional switch turns on and then turns on the releasing gas module, which makes the manual operation convenient.In the process of programming the PLC in injection molding machine, we consider the need of producing the special thermosetting BMC bakelite molding and develop some special programs, such as the vacuumizing control program, the cutting control program, the squeezing control program, the feed-in control program, and set switches for these related functions , when the BMC is not produced, all of these switches can turn off.Through a series of reconstruction of the mechanical parts , the electrical parts and the hydraulic parts in the equipment, all these three types of the equipment (the plastic, the bakelite, the BMC) be inter-used after changing some simple mechanical parts and its related hydraulic system and give them adjustment. , it make the equipment more flexible and promote the machine utilization rate, which saving the purchase cost of the equipment.