The Process Parameter Optimizing For Injection Molding The Thin-walled Plastic Parts

Nowadays, the technology of injection molding thin-walled plastic parts has beengreatly developed. Compared with the conventional injection molding, the Thin-walledplastic injection molding process has higher forming efficiency and makes the plasticparts lighter and more beautiful，which catches the development trend of “light, thin,short” for producing today’s electronic products. But the molding performance ofthin-walled plastic parts is poor, and the parts quality could not be accurately controlled.Three problems generally occur in the thin-walled plastic parts injection molding process,such as the short shot, weld lines and warping deformation etc.The injection molding process of thin-walled plastic parts was simulated with theMoldflow software, and the simulation results of warpage were analyzed by orthogonaltest method. Thus the optimal molding process parameters were obtained. It has guidingsignificance for setting the process parameters in actual production. The main researcheshave been conducted in the following:1) After building the geometric model of the keyboard back cap in UG software, andcreating a new file in Moldflow, the geometric model was imported. Then the keyboardback cap was meshed and the finite element mesh was diagnosed and repaired till themesh matching rate basically met the requirements. After determining the optimal gatelocation, the gating system and cooling system were created. The PC, ABS, PC+ABSthree kinds of plastics were selected as the analysis material. The cooling+flow+warping analysis were completed with the default parameters, and the correspondinganalysis results, such as the filling process, the cooling process, weld line and warpage ofthe parts were obtained. Combined with the process parameters recommended bymaterials manufacturers, the injection molding parameter level values were set, and theorthogonal simulation test schemes were designed.2) The injection molding process parameters were optimized by orthogonalsimulation tests, and the optimum process parameters of injection molding PC, ABS andPC+ABS keyboard back caps were obtained. Their mold temperature were100℃,40℃and50℃, melt temperature were280℃,260℃and240℃, injection time were2.0s,1.0sand2.5s, pressure holding time were25s,15s and25s, respectively. Their holdingpressures all were110%the corresponding injection pressures. the minimum warpagedeformation of the keyboard back caps obtained by numerical simulations with theoptimal process parameters reduced by30%to50%than those obtained by the defaultparameters.3) Three plastic products, with same peripheral dimensions200mm×200mm and different thickness of0.6mm,0.4mm and0.2mm, were modeled respectively using PC,ABS, PC+ABS materials. Which were imported into Moldflow to study the influence ofthe melt temperature, mold temperature, injection pressure and injection rate on theplastic filling ratio of the different thickness and different materials plastic parts with thesingle factor analysis method (one variable parameter, the other three parameters were setconstant). The numerical simulation results showed that: in the above four processparameters, the influence of injection pressure on the filling ratio was the greatest andmore uniform, the injection rate had greater but uneven effect on the filling ratio, theimpact of mold temperature was the smallest.