抗震底座树脂模具强度研究

SLS技术处理后的烧结件用于模具时,为提高树脂模具的强度,对影响树脂模具强度的树脂混合液涂料质量、涂抹时间和涂抹后的固化处理工艺进行研究。试验表明,受树脂混合液涂料成分的影响,树脂混合液涂料应在45min内均匀涂抹在烧结件上;不同的烧结件所需要的树脂混合液涂料质量也有所不同;涂抹后的烧结件在常温下放置一段时间后再放入恒温干燥箱进行渐次升温固化处理可以明显提高树脂模具的强度。     

碳化硅零件的激光选区烧结及反应烧结工艺

为了获得高密度、高性能、复杂结构的碳化硅陶瓷件,提出采用机械混合法制备含有黏结剂和乌洛托品固化剂的碳化硅复合粉体,对复合粉体进行激光选区烧结（SLS）形成陶瓷素坯,并对素坯进行气氛烧结和渗硅处理,使其与基体发生反应烧结,最终形成复杂陶瓷异形件。实验证明：若激光功率为8.0 W、扫描速率为2 000 mm/s、扫描间距为0.1 mm、单层厚度为0.15 mm,获得的 SLS 陶瓷样品密度和强度最好。对SLS试样进行合理的中温碳化和高温渗硅,所得碳化硅陶瓷烧结体的抗弯强度最高可达 81 MPa,相对密度大于86%。     

氧化锆零件激光选区烧结/冷等静压复合成形技术

氧化锆陶瓷材料以其优异的性能在工业生产中具有极大的应用前景,但由于脆性大、硬度高等原因,复杂形状氧化锆零件往往难以成形和加工。为了获得复杂形状氧化锆陶瓷零件,通过溶剂沉淀法将粘接剂尼龙12覆膜至纳米氧化锆粉末的表面,然后对覆膜后的粉体进行激光选区烧结(Selective laser sintering, SLS)成形,并通过传统的冷等静压(Cold isostatic pressing, CIP)技术对SLS零件进行致密化处理,同时满足氧化锆初坯成形时形状复杂度和密度的要求。通过试验得出在激光能量密度为0.415 J/mm2时,获得的SLS陶瓷件密度较大,对不同激光能量密度制备的SLS陶瓷件进行保压压力为200 MPa的冷等静压致密化处理,根据热脱脂机理以及粘接剂的TG曲线,分别制定了SLS/CIP试样的热脱脂工艺,最后对脱脂试样进行高温烧结,在后续处理的各环节,氧化锆零件的密度仍受SLS成形的影响,但该影响逐渐减弱,SLS/CIP/FS成形件最大相对密度和维氏硬度分别达到了97%和1180 HV1,已接近“模压-烧结”的致密氧化锆陶瓷的性能,在试样断口的扫描电子显微镜(SEM)分析基础上,对氧化锆复合成形的微观演变进行了研究。虽然最终烧结件密度和硬度仍有待提高,但是提出了一种极具潜力的氧化锆零件近净成形工艺方法,为制造高性能复杂形状的陶瓷零件奠定了基础。     

激光选区烧结超高分子量聚乙烯工艺及性能

研究了激光选区烧结(SLS)成型工艺中不同工艺参数以及后续热处理工艺对超高分子量聚乙烯(UHMWPE)材料成型性能的影响。通过调整扫描间距、激光功率、扫描速度等不同工艺参数,描述了SLS成型UHMWPE零件的致密度、拉伸强度以及断裂伸长率,并对热处理前后的SLS成型UHMWPE零件的力学性能进行了比较。结果显示,致密度、拉伸强度、断裂伸长率总体上与激光功率呈正相关关系,与扫描间距、扫描速度呈负相关关系。经热处理后,SLS成型UHMWPE零件的力学性能有明显提高,致密度达到95.12%,抗拉强度达到24.08 MPa,断裂伸长率达到334.82 MPa。实验结果表明:SLS成型UHMWPE零件与模塑成型UHMWPE零件性能尚有差距,仅优化成型工艺不足以得到理想性能,但经热处理后,零件性能基本满足使用要求。     

一种新型材料3D打印性能及应用研究

本文提出了一种用于激光选区烧结(Selective Laser Sintering,SLS)成形的新型粉末材料KZF。研究了其适合进行SLS成形的粉末制备工艺,基于不同的激光加工工艺参数,得出了最优工艺参数。在最优工艺参数下SLS成形KZF粉生坯体具有较高的初始强度,得出了成形KZF生坯所需粘接剂的最低含量,和具有的强度值。研发了SLS成形的KZF生坯件的后处理材料、配方及工艺规范,研究了经确定最佳后处理规范后的KZF SLS成形件的力学性能以及微观组织的影响,确定了提高KZF生坯强度的材料及含量,经后处理后的KZF粉SLS成形件的弯曲强度提升幅度最大达273倍。本文为制造复杂形状的KZF成形件提供了一种新的思路与方法,并扩大了SLS成形材料的应用范围。     

室温快速固化高性能环氧树脂胶粘剂研究

为了提高胶粘剂在室温条件下的固化速度,并改善其力学性能,研究了固化剂含量、填料含量对环氧树脂胶粘剂固化速度和力学性能的影响.结果表明,当固化剂含量为95～100 phr,填料含量为60～ 80 phr时,胶粘剂的综合性能最好;该新型胶粘剂在室温12 min即可快速固化,剪切强度可达13.8 MPa,拉伸强度和弯曲强度分别达到了43.1MPa和83.2 MPa.     

SLS成形件的收缩模型和翘曲模型

快速成形的精度是快速成形技术发展和扩大其应用领域的关键,工艺误差是影响成形精度的关系之一,而成形件收缩和翘曲对其工艺精度起决定性的作用,通过建立SLS成形过程的收缩模型研究了SLS加工中成形件的收缩形式以及收缩规律,同时研究了收缩的不均匀性所引起的翘曲,建立了成形件的翘曲模型,发现烧结收缩与烧结程度密切相关,翘曲量与烧结收缩率成正比,与零件线尺寸成正比,这些研究结果为克服SLS加工收缩引起的误差和收缩补偿提供了依据,为减少翘曲变形提供了一种方法。     

SLS中支撑对零件精度影响的研究

针对选区激光烧结(Selected Laser Sintering,SLS)烧结件的精度问题,试验分析了支撑类型,支撑高度等对烧结件的精度影响,得出的结论是支撑对提高精度有着显著作用.并提出了现实可行的提高原型精度的工艺方法.     

一种新型材料3D打印性能及应用研究

本文提出了一种用于激光选区烧结(Selective Laser Sintering,SLS)成形的新型粉末材料KZF。研究了其适合进行SLS成形的粉末制备工艺,基于不同的激光加工工艺参数,得出了最优工艺参数。在最优工艺参数下SLS成形KZF粉生坯体具有较高的初始强度,得出了成形KZF生坯所需粘接剂的最低含量,和具有的强度值。研发了SLS成形的KZF生坯件的后处理材料、配方及工艺规范,研究了经确定最佳后处理规范后的KZF-SLS成形件的力学性能以及微观组织的影响,确定了提高KZF生坯强度的材料及含量,经后处理后的KZF-SLS成形件的弯曲强度提升幅度最大达273倍。本文为制造复杂形状的KZF成形件提供了一种新的思路与方法,并扩大了SLS成形材料的应用范围。     

SLS激光功率与烧结件弹性模量关系研究

为了研究利用SLS加工力学性能变化的功能件,首先分析了SLS成型机的粉床预热温度场,根据拉伸试验设计试样尺寸,烧结出9种激光功率下的试样;其次根据静力学拉伸试验数据,计算出了各种试样的弹性模量值;最后推导出SLS成型机激光功率与烧结件弹性模量间的数学模型。     

Direct Selective Laser Sintering of Hard Metal Powders: Experimental Study and Simulation

Direct selective laser sintering (SLS) technology can be used to produce 3D hard metal functional parts from commercial available powders. Unlike conventional sintering, it does not require dedicated tools, such as dies. Hence, total production time and cost can be reduced. The large shape freedom offered by such a process makes the use of, for example, sintered carbides components viable in domains where they were not applied before. Successful results have been obtained in the production of sintered carbide or hard metal parts through SLS. The investigation focuses on tungsten carbide–cobalt (WC-Co) powder mixture. This material is characterised by its high mechanical properties and its high wear resistance and is widely used in the field of cutting tools. This paper is devoted to the experimental study and the simulation of direct selective laser sintering of WC-Co hard metal powders.     

覆膜钼粉激光烧结成型件的高温烧结工艺研究

高温烧结是选择性激光烧结后处理工艺的关键问题之一，传统上高体积质量的合金烧结采用单一液相烧结法，但这种烧结方法不适用于保形性差的激光烧结件。通过对覆膜钼粉脱脂预烧结件进行真空固相烧结与还原气氛二步烧结，研究2种高温烧结件的组织及性能后发现，还原气氛对改善烧结体组织具有显著作用，二步烧结可以实现保持制件形状的液相烧结。     

A macroscale FEM-based approach for selective laser sintering of thermoplastics

A numerical approach to model the selective laser sintering (SLS) of polypropylene is proposed. A 3D thermal model was developed and thus enables the prediction of the temperature fields and the extension of the sintered area in the powder bed taking into account the phase change during multiple laser passes. Powder–liquid, liquid–solid and solid–liquid phase changes were modelled during the SLS and the subsequent cooling processes. Then, a 3D thermomechanically coupled model was set up based on the temperature results of the thermal model in order to predict the distortion of the produced parts after cooling down. Different pre-heating temperatures were considered, highlighting their influence on the final part properties.     

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Selective laser sintering (SLS) of a two-component metal powder layer on the top of multiple sintered layers by a moving Gaussian laser beam is modeled. The loose metal powder layer is composed of a powder mixture with significantly different melting points. The physical model that accounts the shrinkage induced by melting is described by using a temperature-transforming model. The effects of the porosity and the thickness of the atop loose powder layer with different numbers of the existing sintered metal powder layers below on the sintering process are numerically investigated. The present work will provide a better understanding to simulate much more complicated three-dimensional SLS process.     

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Selective laser sintering (SLS) of a two-component metal powder layer on the top of multiple sintered layers by a moving Gaussian laser beam is modeled. The loose metal powder layer is composed of a powder mixture with significantly different melting points. The physical model that accounts the shrinkage induced by melting is described by using a temperature-transforming model. The effects of the porosity and the thickness of the atop loose powder layer with different numbers of the existing sintered metal powder layers below on the sintering process are numerically investigated. The present work will provide a better understanding to simulate much more complicated three-dimensional SLS process.     

Research on manufacturing Cu matrix Fe-Cu-Ni-C alloy composite parts by indirect selective laser sintering

The property of alloy parts can be adjusted conveniently if alloy element powders are used for manufacturing alloy parts by indirect selective laser sintering (SLS), but there have been no reports in this field. Fe, Cu, Ni, C composite powders of two compositions were obtained through a 3D blending way in this paper. Green parts of above composite powder were manufactured by indirect SLS. Then, Cu matrix Fe-Cu-Ni-C alloy composites were produced after green parts had been depolymerized, high temperature sintered and infiltrated by molten Cu. The post-processing of green parts, microstructure and mechanical properties of alloy composites were investigated. The results show: Ni, Cu and C diffuse into γ-Fe when green parts are being sintered at high temperature and the distributing non-uniformity of alloy elements is eliminated basically; at room temperature, alloy composite microstructures are composed of lower bainite, α-Cu precipitated out of γ-Fe and Fe-Ni after they have been solution treated at 930°C and held at 350°C for 1 h later; the yield strength of alloy composites is near to 400 MPa and the elongation is under 3%. It can be used for manufacturing injection mold or other functional parts by indirect SLS.     

PA6粉末选区激光烧结多层应力分析

选区激光烧结成型过程中,激光束扫描时反复的加热、冷却带来不均匀的热应力,影响烧结过程和烧结件的质量。基于弹性变形原理,利用单轴应力作用下的变形梁的挠曲和应变与应力之间的关系,来分析烧结过程中的应力以及不同烧结层之间的相互影响,结果表明,在每个单层烧结时,烧结应力主要集中在烧结层的上表面和下表面的两端,且呈现为拉应力;在多层烧结时,烧结的热载荷对紧邻已熔接层的应力有直接影响,随着烧结层数增加,新烧结层对已熔接层的热影响逐渐减小,对应的随着温度变化较小,已熔接层的应力也较小且保持较低水平。     

Selective laser sintering of hydroxyapatite reinforced polyethylene composites for bioactive implants and tissue scaffold development

Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using composites of high-density polyethylene (HDPE) reinforced with hydroxyapatite (HA) with the aim of achieving the rapid manufacturing of customized implants. Single-layer and multilayer block specimens made of HA-HDPE composites with 30 and 40 vol % HA were sintered successfully using a CO2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS-fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products but also to produce appropriate features for their application as bioactive implants and tissue scaffolds.