选择性激光烧结蒙脱土陶瓷粉末及聚合物纳米复合材料的工艺与性能分析

对蒙脱土陶瓷粉末及聚合物纳米复合材料进行了选择性激光烧结实验,通过改变不同烧结工艺参数,测试并分析了该复合材料的变化规律与影响程度。由于陶瓷材料和复合材料的应用前景广阔,因此这类研究具有很好的应用价值。

SOFTWARE SYSTEM FOR SELECTIVE LASER SINTERING

The advent of rapid prototyping & manufacturing techniques represents a major breakthrough in production engineering. This paper is concerned with the software system aspects of the selective laser sintering (SLS),i.e.the issues that deal with an external geometric CAD model to automatically control the physical layering fabrication process as directly as possible ,regardless of the source of the model. The general issues are described and some key methods are given in this paper.

Design and 3D Printing of Scaffolds and Tissues

A growing number of three-dimensional(3D)-print- ing processes have been applied to tissue engineering. This paper presents a state-of-the-art study of 3D-printing technologies for tissue-engineering applications, with particular focus on the development of a computer-aided scaffold design system; the direct 3D printing of functionally graded scaffolds; the modeling of selective laser sintering(SLS) and fused deposition modeling(FDM) processes; the indirect additive manufacturing of scaffolds, with both micro and macro features; the development of a bioreactor; and 3D/4D bioprinting. Technological limitations will be discussed so as to highlight the possibility of future improvements for new 3D-printing methodologies for tissue engineering.

Adaptive heating the powder bed for SLS system

The temperature of powder bed is very important for selective laser sintering system(SLS),because it directly affects the quality of part.Furthermore,the temperature of powder bed should alter according to the slicing section contour of model in order to ensure that the integration is successful and intelligent.Namely,the temperature of powder bed should change with shape of CAD model at different height.The paper illuminates how to distinguish the slicing contour loops from adjacent region.In this way,the temperature can be adaptively adjusted with altering of the sectional contours.

Synthesis of Polymer Nanocomposites for Selective Laser Sintering （SLS）

This paper presents initial development of polymer application. PNC materials containing a polyamide （PA） and nano to improve the mechanical properties. Commercial polyamide 6 nanocomposites （PNC） material for rapid manufacturing （RM） particles （5 wt%） were produced by solution blending with the aim （PA6） was dissolved in formic acid （HCO2H） together with two different types of nano particle materials： yttrium stabilised zirconia （YSZ） and Hectorite clay （Benton 166） and spray-dried to create powder, creating powder with particle sizes in the range of 10-40 μm. The materials were processed on a CO2 selective laser sintering （SLS） experimental machine. Mechanical properties of the PNCs were evaluated and the results were compared with the unfilled base polymer. Good dispersion of additives was achieved by solution blending, however the PA6 was degraded during the material preparation and spray drying process which resulted in the formation of porous structure and low strength. However the addition of 5 （wt%） nano particles in the PA6 has shown to increase strength by an average of 50-60%. Further work on powder preparation is required in order to fully realize these performance benefits.

Error rate of multi-level rapid prototyping trajectories for pedicle screw placement in lumbar and sacral spine

Objective：Free-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy,navigation or an alternative rapid prototyping drill guide template.In our study the error rate of multi-level templates for pedicle screw placement in lumbar and sacral regions was evaluated.Methods：A case series study was performed on 11 patients.Seventy-two screws were implanted using multilevel drill guide templates manufactured with selective laser sintering.According to the optimal screw direction preoperatively defined,an analysis of screw misplacement was performed.Displacement,deviation and screw length difference were measured.The learning curve was also estimated.Results：Twelve screws （17％） were placed more than 3.125 mm out of its optimal position in the centre of pedicle.The tip of the 16 screws （22％） was misplaced more than 6.25 mm out of the predicted optimal position.According to our predefined goal,19 screws （26％） were implanted inaccurately.In 10 cases the screw length was selected incorrectly：1 （1％） screw was too long and 9 （13％） were too short.No clinical signs of neurovascular lesion were observed.Learning curve was insignificantly noticeable （P=0.129）.Conclusion：In our study,the procedure of manufacturing and applying multi-level drill guide templates has a 26％ chance of screw misplacement.However,that rate does not coincide with pedicle perforation incidence and neurovascular injury.These facts along with a comparison to compatible studies make it possible to summarize that multi-level templates are satisfactorily accurate and allow precise screw placement with a clinically irrelevant mistake factor.Therefore templates could potentially represent a useful tool for routine pedicle screw placement.

New method of improving parts accuracy by adding heat balance support in selective laser sintering

In order to improve parts accuracy, a method of adding heat balance support （HBS） was proposed, and the detailed algorithm for generating HBS was developed. A number of experiments and a comparison between similar softwares, showed that the algorithm is efficient and feasible. Moreover, different features of riBS were studied for different kinds of materials, such as PS and nylon. The research findings indicate that automatically adding HBS can significantly improve the accuracy of the parts, and that the algorithm for generating HBS is efficient and precise.