Research On Filament Extruding Technique Of Bone Scafflod Rapid Protyping Machine Based On Fused Deposition Method

Bone tissue engineering is the future development direction of bone repair. Ituses degradable biomaterial to manufacturing the porous scaffold which has asimilar properties with bones both in shape and physical. The scaffold is a carrier forgrowing and reshaping of the new bone. The manufacturing of the bone scaffold isobviously important. There are many advantages to make bone scaffold using fuseddeposition modeling. This paper studied several of the problems relevant.Firstly, screw extruding theory was analyzed. The relationship between thescrew rotational speed and the filament extruding speed was deduced using theabove theory and polymer rheology. The formula to calculate the filament width wasdeduced based on the model of the cross section which was established. Themathematic model of the filament cooling process was established and solved.Secondly, a mini-screw extruder system was designed. The Simulink modelsrelevant to the filament extruding process were built, and POLYFLOW was used tosimulate the influence of the main screw parameters on the flow rate, stay time andmixing property. The design of the screw was optimized based on the result. Thetemperature changing during cooling process and its factors were simulated,including the influence of the flow rate, environment temperature on the filamentextruding temperature; and the influence of the fluid temperature flowed into thenozzle; cross section area, heat exchange coefficient, filament extruding temperature,fun speed etc. on the cooling time. Thus provide a guideline to decide and improvethe scanning speed.Finally, experiments were taken to measure the maximum force which thefilament feeder can provide, the filament width, die swell ratio and filamentdistortion during cooling process.