Study On Key Technology And Application Of Hollow Blow Molding

Extrusion blow molding is the main method of hollow products processing. Parison quality will directly affect the precision of products, product performance, molding cycle and cost, etc. So how to ensure the quality of parison become the key problem in extrusion blow molding process. Extrusion die is an important part of the parison forming, its traditional design method of "Try and Error" is cycle long and cost. Parison forming without thickness control system would easily lead to the final products of uneven axial wall thickness and material waste. Therefore in this paper, study the technology to ensure the quality of parison from two aspects of both design of extrusion die and realization of control system.As for extrusion die design, modern advanced CAD/CAE technology is applied in the design of extrusion die flow, firstly study on the method of numerical simulation of the head extrusion parison process, including building mathematical model comprised of control equations, constitutive equations, the initial value and boundary conditions and derivation its finite element method to solve. According to the foregoing principle analysis the extrusion processing of the 5 L double composite blowing bottle machine head, discussion the distribution of flow field, the performance evaluation of extrusion die based on the inlet pressure, the uniformity of the exit velocity, the distribution of high viscosity area and stability of coextrusion regional boundary surface. Optimal design the inner and outer layer of the head structure based on the principle of improving the uniformity of the melt exit velocity and avoiding the phenomenon of viscous with obvious optimization effect. Further analysis the influence of the inlet flow rate, material non-Newtonian index and entry the volume flow ratio between the inner and outer layer on the head extruding performance with certain practical guiding significance to the selection of process parameters.As for implementation of the wall thickness control system, applying electro-hydraulic proportional control technology and embedded technology, firstly analysis the composition of the head core position control system, discussion the rapidity, stability and steady-state accuracy of the system and study the influence of hydraulic parameters on the system performance. The fuzzy self-tuning PID control strategy has been put forward for its characteristics of nonlinear, time-varying, validation the control effect of the strategy, results showing that overshoot reduced, transition time shortened to unit step response and anti-jamming capability enhanced. Further Proposed design scheme of controller in control system composite hollow blow molding parison forming technology and embedded technology. The hardware part LPC2220 as the core of the overall design scheme is given, software part chooses μC/OS ?II as its operating system, research transplant method of μC/OS ?II on the LPC2220, and present the design method of the upper application system.