Research On Sink Marks Of Injection Products Based On Moldflow

Injection molding is one of the main processing methods in plastic processing, but always there are many molding defects in the practical process. With the increase of industrial technology and public's living level, appearance quality of plastic products draws more and more attention, so, sink marks defects of appearance products often become the main reason for defective product.How to reduce the sink marks defects of plastic products is must be solved for engineers and technicians. However, only relying on the traditional experience and methods is time-consuming and labourious. That has more limitations. With the development of CAE technology, product design and mold design can be analysed and simulated, and the practical molding can be replaced by simulation test. CAE technology can predict potential design flaws, and can change the traditional engineering methods of repeated test mold and repair mold which only rely on the past experiences.Aming at the sink marks problem of Shanghai GM automobile door trim panel (external dimensions is 523mm×277mm×32mm)during test injection molding, the paper analysed the numerical simulation theory of injection molding, formation mechanism of sink marks and influencing factors, which discussed and determined the research methods of sink marks defects. The injection molding process of filling, pressure-keeping, cooling stages of numerical simulation analysis are done by using CAE analysis software Moldflow. Then, test programm is arranged by orthogonal test to get the influencing order of process parameters on sink marks. Finally, the molding process parameters optimal combination are preliminarily determined. To further study the influence degree of various factors on sink marks, single factor experiment simulation analysis for door trim panel is done for another time. The anlysis of various parameters change trend for sink marks, along with orthogonal test results, the paper ultimately determined the optimization injection molding parameters.Finally, on the basis of the aboved analysis, combined with pratical production, technicians modified mold structure and optimized the process parameters, then injected molding to test sink marks. Experimental results were satisfactory, the plastic parts had basically no sink marks, which proved the combination of CAE technology and orthogonal test is accurate.Numerical simulation and injection molding results of this paper show that: the optimization of process parameters can effectively reduce sink marks that injection molding generated; packing pressure and melt temperature is the main process parameters that influence sink marks, second is injection time and packing time. By contrast, mold temperature and cooling time have little influnce on sink marks; The method of orthogonal test design, combined with the CAE simulation technology is effective and reliable in solving sink marks problems of injection molding.Due to the reasons for sink marks of plastic products is various and complex, under the precondition of related requirement and reasonable economic benefit and feasible technical scheme, the paper choose reasonable materials, molding equipment and mold; with the orthogonal test and CAE technology, the paper optimize molding parameters and reduce the degree of sink marks.