Effect Of Processing Parameters On Accuracy Of Extrusion Freezing Forming Of ZrO₂ Ceramic Paste

Because of its good biocompatibility and stable chemical properties,ZrO₂ has been widely used in bioremediation,especially dental restoration.Bioremediation is a kind of personalized manufacturing.It not only requires that the components havecertain mechanical property,but also produce kinds of different shapes components according to the different conditions of patients.It is difficult tomanufacture excellent products that can meet the individual needs of patients with the traditional and long cycle ceramic processing method.In recent years,a free form method based on ceramic paste extrusion freezing has been developed.This method can not only process any complex shape parts,but also shorten the processing cycle.However many factors influence the accuracy of ceramic paste forming with the method,therefore this paper aims to study the influence of process parameters to the extrusion molding precision of frozen free ZrO₂ ceramic paste from the view of control parameters.Main work and conclusions:Firstly,this paper researches the influence of model parametersincluding layer thickness,extrusion head diameter,extrusion head height to precision of extrusion stacking forming ZrO₂ ceramic paste,the aims of this part is to prepare final freezing conditions forming.This study shows that time of the same molding continuously decreased with the increase of layer thickness,it shows changes relationship between the two is the nonlinear reduction.Time is shorter between the same molding's two layer thickness.When the 3D parts are molded,the forming effect and the forming precision of the parts are the best in the range of ?h = 0.5 mm.When the extrusion head is smaller,the liquid phase migration is more likely to occur,resulting decrease of the liquid content in the late stage of extrusion molding.When the extruded wire breaks which leads to the difficult to mold.The forming effect of 0.84 mm extrusion head is in accordance with the require of the forming precision.When the height of the extrusion head is equal to or less than the diameter of the extrusion head,the formingaccuracy of the first layer of the sheet is higher than the height of the extrusion head is greater than the extrusion head diameter.Secondly,in order to ensure the smooth extrusion of ZrO₂ ceramic paste successfully under the freezing conditions,the influence of extrusion parameters on the extrusion precision of ZrO₂ ceramic paste extrusion was analyzed.The extrusion parameters were mainly scanning speed and scanning path and fill order.The resultshows that there is a certain matching relationship between the scanning speed and the extrusion speed.When the scanning speed is 2 mm / s,the dimensional accuracy is the best in the range of ± 0.2 mm.The choice of the scanning direction has little effect on the precision of the lamellar body for the single layer filling of the lamellar body.It means that the effectis small whether the x direction or the y direction filling.While the choice of the scanning filling method has obvious effect on the precision of the slice.The precision of the parallel line filling method is better,the precision of the edge lap filling is lower and the size span is larger.The precision of the layer is better if filling the outer firstly than the inner.Finally,this paper studies the influence of forming parameters to the forming ability and forming precision of ZrO₂ ceramic paste under the model parameters and extrusion parameters of the optimized parameters.It evaluated synthetically the effect of the process parameters on accumulation and forming accumulation of ZrO₂ ceramic paste through the molding of typical molded parts and the comprehensive evaluation of flexural strength and fracture morphology after sintering.The result shows that the size range is larger in freezingthan that at room temperature,and the maximum is in the range of +0.6 mm and the minimum is-0.4 mm.When the freezing temperature is-15 ?,the size of the molded part is better than that of other temperature.The smaller the thickness of the layer is,the greater the forming angle is,the better the forming thickness is 0.8 mm and the maximum forming angle is-35 ° when the thickness is 0.5mm.The greater the forming angel is,the worse the forming effect is with the same height of the parts model.The bending strength is the largest at the scanning speed of3 mm / s,however,the bending strength is the highest in the long and short size directions alternatelyat the same scanning speed,followed by the long dimension filling,and finally the short size direction.The cross section of the long-sized parallel-line filled sample is broken along the direction perpendicular to the long dimension,while the source of crack is mainly voids during the molding process.When the short-sized direction is filled,the fracture is along thebonding partsbetween the extrusionwires,and cross-section neat,long,short size alternately filled,fracture is along the short size directionin the middle layer.