Principle of parison control of hollow blow molding machine.
The automatic control of blank wall thickness has axial control and radial control.As for the radial control technology, China is still in the research stage. In relative terms, the research on axial control is mature.In this paper, the axial control of the blank wall thickness is studied for the large-capacity hollow blow molding machine with more than 200L.The closed-loop control technology is adopted for the axial control of blank wall thickness.Users to finalize the design is set on the touch screen panel of wall thickness controller billet thickness curves of axial, PLC controller according to the curve of the corresponding voltage or current signal to the electro-hydraulic servo valve, controlled by electro-hydraulic servo drive servo cylinder center pole to move up and down, to change the nose mouth die clearance.
At the same time, connected servo cylinder rod in the center of the piston rod with sensor (maglev electronic scale), electronic foot perceived head mouth the size of the die clearance and feedback to the PLC controller, compared with standard signal within the PLC controller, and then the servo power amplifier is transmitted to the electrohydraulic servo valve, and then through the servo valve drive servo cylinder, cylinder drives the center pole, ultimately control mode of opening mouth, complete control of the parison wall thickness.The structure diagram of blank wall thickness control is shown in FIG. 2.In this paper, the slab wall thickness control system is a position control system composed of electro-hydraulic servo system.The core part of the control is the position of the center pole, and the control precision of the central pole position is the key to the control effect of the blank wall thickness.Therefore, the research focus of this system is the control precision of the center pole position, namely the control precision of the blank wall thickness and the response speed of the system.
The control method of blank wall thickness is to divide each blank forming process into several points, and control the wall thickness of these points respectively.The smaller the control points, the faster the response speed, but too few points, unable to reach the required wall thickness control precision, and formed a weld seam (ring grain) around the shape.Too many points will cause the system response time too long, the servo oil cylinder will not be able to respond to the received signal, the blank will be out.The traditional 200L plastic bucket wall thickness controller is 64 or 128.Based on 200 L double L ring drums are studied, through experimental verification, in meet the thickness control precision of plus or minus 1 mm, each point of the response time of 0.3 ~ 0.4 seconds under the premise of more appropriate chooses 256 wall thickness control.
The key technology of large capacity hollow blow molding machine is studied.The design of double - double helix is compared with other structural forms.The fusion is more uniform, the flow of melt is smoother, the theoretical joints are eliminated, and the strength of the products is improved.According to the function requirement, the optimization method is adopted to determine the technological parameters and the size, which lays the foundation for the optimization design of the large-capacity hollow blow molding machine in 200L.On the basis of the existing blank wall thickness control, the optimal control points and control points of 200L double L ring are studied, and the uniformity, precision and strength of the products are improved.