Powder injection molding of pure titanium

An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.

Preparation of high nitrogen and nickel-free austenitic stainless steel by powder injection molding

High nitrogen and nickel-free austenitic stainless steel has received much recognition worldwide because it can solve the problem of ＂nickel-allergy＂ and has outstanding mechanical and physical properties. In this article, 0Cr17Mn11Mo3N was prepared by powder injection molding （PIM） technique accompanied with solid-nitriding. The results show that the critical solid loading can achieve up to 64vol% by use of gas-atomized powders with the average size of 17.4 μm. The optimized sintefing conditions are determined to be 1300℃,2 h in flowing nitrogen atmosphere, at which the relative density reaches to 99% and the N content is as high as 0.78wt%. After solution annealing at 1150℃for 90 rain and water quench, the 0.2% yield strength, ultimate tensile strength （UTS）, elongation, reduction in area, and hardness can reach as high as 580 MPa, 885 MPa, 26.0%, 29.1%, and Hv 222, respectively.

Microstructure and properties of nano-TiN modified Ti(C,N)-based cermets fabricated by powder injection molding and die pressing

Powder injection molding （PIM） and die pressing were employed to fabricate nano-TiN modified Ti（C,N）- based cermets. The shrinkage behavior, microstructure, porosity, and mechanical properties of the samples with and without nano-TiN addition fabricated by PIM and die pressing were analyzed. It is demonstrated that for either PIM or die pressing, the porosities are obviously reduced, the mechanical properties are significantly improved after adding nano-TiN, and the hard particles are refined; the rim phase thickness obviously becomes thinner, and the number of dimples in fracture also increases. Compared the samples fabricated by die pressing, it is difficult for PIM to obtain dense Ti（C,N）-based cermets. Due to the too much existence of pores and isolated carbon, the mechanical properties of the sintered samples by PIM are inferior to those of the sintered ones by die pressing.

Sintering Mechanism of Stainless Steel in Powder Injection Molding

Stainless steel samples were made by Powder injection Molding (PIM) process with-400 mesh powder in order to investigate the sintering mechanism in this system and develop the PIM of stainless steels. The process included mixing, injection molding, debin- ding and sintering. Neck growth model was used to analyze the sintering mechanism. The results show that lattice (volume) diffusion is the main mechanism in the sintering process, the products with higher density (>95%) and properties are obtained. At lower temperatures, grain boundary diffusion may play a role in the sintering densification.

Effect of annealing processing on microstructure and properties of Ti-6Al-4V alloy by powder injection molding

Ti6A14V alloy parts were prepared by metal injection molding. Brown parts were densified at 1 200-1 260℃for 2-4 h in vacuum atmosphere. The as-sintered specimens were treated through Hot-Isostatic Pressure(HIP) at 960℃and 140 MPa. Ti6A14V alloy compacts were annealed at 720-760℃for 1 h. The results show that binder in the parts can be removed by solvent debinding and thermal debinding process. Ti6A14V alloy has an uniform duplex microstructure with many equiaxedαgrains and a littleβgrains. When the annealing temperature is higher than 800℃, T16A14V alloy has lower mechanical properties.After solution treatment and aging, a typical martensite microstructure can be achieved.

Comparison of rheological analytic model with numerical simulation in powder injection molding filling process

Mathematical model of filling disk-shaped mold cavity in steady state was studied.And the mathematical model under vibration field was developed from the model in steady state.According to the model of filling disk-shaped mold cavity in steady state,the filling time,the distribution of velocity field and the pressure field were obtained.The analysis results from rheological analytic model were compared with the numerical simulation results using Moldflow software in the powder injection molding filling process.Through the comparison,it is found that it is unreasonable to neglect the influence of temperature when calculated the pressure changing with the time at the cavity gate,while it can be neglected in other situations such as calculating the distribution of the velocity fields.This provides a theoretical reference for the establishment of correct model both in steady state and under vibration force field in the future.

Micro powder injection molding——large scale production technology for micro-sized components

Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.

Analysis of Mechanical Properties of Injection Molded Short Glass Fibre (SGF)/Calcite/ABS Composites

Acrylonitrile-butadiene-Styrene (ABS), with and without calcium carbonate (calcite) particles,was used as the matrix for reinforcement with as-received short-glass fibres (were originallytreated by the manufacturer) and sized short-glass fibres with two amino-silane coupling agents.The calcite particle content is 0, 11.7 and 23.5 vol. pct for the matrices. The glass fiber contentis 0, 10 and 15 vol. pct. The matrix materials and corresponding composites were compoundedusing a twin screw extruder and dumbbell-shaped tensile bars were prepared with an injectionmolding process. The tensile and flexural properties as well as the unnotched and notchedCharpy impact energies of short glass fibre/calcite/ABS composites were studied in this paper.The effects of fibres, fibre surface treatments and particles on these mechanical properties ofthe composites were discussed in detail. An importarit information was obtained, which is thatthe tensile and flexural strengths of hybrid SGF/calcite/ABS composites are the same as thoseof corresponding fibre composites when the ratio of the interfacial adhesion strength betweenparticles and matrix to that between fibres and matrix is higher than certain value. otherwise theformer are lower than the latter.

Effect of film types on thermal response,cellular structure,forming defects and mechanical properties of combined in-mold decoration and microcellular injection molding parts

Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process.It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side.When polyethylene terephthalate(PET)films were applied,the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate(PC)and thermoplastic polyurethane(TPU)films.And the effects of film types on the cellular structure,forming defects and mechanical properties of IMD/MIM parts were also studied experimentally.The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts.Under certain film thickness,the offset distance of core layer was the largest with PET film used,while the offset distance was the smallest with TPU film used.And similar results were found for the warpage of the parts.However,an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.

The Banded Spherulites of iPP Induced by Pressure Vibration Injection Molding

Isotactic polypropylene（i PP） samples obtained by pressure vibration injection molding（PVIM） and conventional injection molding（CIM） were studied by polarized-light microscopy（PLM）, respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What＇s more, the banded spherulites were proved to be constituted of α-form crystal by hot stage polarized-light microscopy（HT-PLM） and wide angle X-ray diffraction（WAXD）. Morphology of the banded spherulites was also studied by scaning electronical microscopy（SEM）.

Rheological, mechanical and corrosive properties of injection molded 17-4PH stainless steel

The feedstock based on the binder 65%PW-30%EVA-5%SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1 380 ℃ for 90 min have the best mechanical properties and the good microstructure with homogeneously distributed pore structure and the moderate-sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over-sintered microstructure respectively. The compacts sintered at 1380 ℃ for 90 min have the density of 7.70 g/cm^3, the strength of 1 275 MPa, the elongation of 5%, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hardness increase, while the elongation decreases. The 17-4PH stainless steel has good corrosion resistance, showing an activation-passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, indicating a low anti-spot corrosive properties.

Mechanical and Antibacterial Properties of Injection Molded Polypropylene/TiO_2 Nano-Composites:Effects of Surface Modification

Polypropylene （PP）/titanium dioxide （TiO2） nano-composites were prepared by melt compounding with a twin screw extruder. Nanoparticles were modified prior to melt mixing with maleic anhydride grafted styreneethylene-butylene-styrene （SEBS-g-MA） and silane. The composites were injection molded and mechanical tests were applied to obtain tensile strength, elastic modulus and impact strength. Antibacterial efficiency test was applied on the injection molded composite plaques by viable cell counting technique. The results showed that the composites including SEBS-g-MA and silane coated TiO2 gave better mechanical properties than the composites without SEBS-g-MA. Antibacterial efficiency of the composites varied according to the dispersion and the concentration of the particles and it was observed that composites at low content of TiO2 showed higher antibacterial property due to the better photocatalytic activity of the particles during UV exposure.

EFFECT OF MELT TEMPERATURE ON THE PHASE MORPHOLOGY,THERMAL BEHAVIOR AND MECHANICAL PROPERTIES OF INJECTION-MOLDED PP/LLDPE BLENDS

The phase morphology and thermal behavior of various isotactic polypropylene （PP）/linear low density polyethylene （LLDPE） blends were investigated with aid of scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）, respectively. The effect of barrel （melt） temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that： first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.

内牙水管接头的注塑模具设计及CAE仿真

针对一端带有内螺纹和另一端为光孔的水管接头,设计了一套带有齿轮传动+抽芯液压缸的自动脱螺纹机构和斜导柱侧抽芯机构的三板式注塑模具。首先,结合塑件的结构特点,确定了点浇口进胶以及浇口位置和直流循环式的冷却回路,利用模流仿真分析软件moldflow对确定的模流分析模型进行注塑成型工艺过程模拟分析。结果表明,塑料熔体的充填时间、缩痕指数、气穴分布以及翘曲变形量等成型工艺参数都在合理范围之内,验证了浇注系统和冷却系统设计的合理性。其次,对模具结构进行设计,将主分型面取在塑件的轴心面上,其余两个分型面顺序分型实现浇注系统凝料的自动脱落。由于塑件为带内螺纹的管状零件,针对内螺纹脱模难的问题,设计了齿轮传动机构驱动螺纹侧型芯旋转和抽芯液压缸的直线移动的两套运动机构实施自动脱螺纹,塑件光孔部分的成型和抽芯采用斜导柱侧抽芯机构来实现。通过模流分析,验证了模具结构的合理性,并且缩短了模具设计的开发周期,有效地提高了塑件的成型质量。

基于模内组装的环式挂链多功能注射模具设计

结合某新款窗帘环式挂链6种组合状态塑件的注射成型要求,基于模内组装设计方法,设计了一副多功能三板注射模具,用作该环式挂链6种组装态产品的注射成型。模具中,模腔由6个独立的单环模腔构成,并且,两环之间的空腔形成90°垂直交叉型环套环状态,有利于通过对各独立模腔浇口的开闭控制,满足6种组装状态组装环挂链的生产要求。为实现对6个模腔浇口的独立开闭控制,设计了一种插板式浇口开闭控制机构,机构由6根插板、1个插座及1个压块组成,用6个螺丝对插板的停留位置进行锁紧。模具能满足单环、2环、3环、4环、5环、6环,共6种组装态的模内直接组装生产要求,具有较好的设计参考价值。

模内装饰技术在汽车外饰件上的应用

模内装饰技术已经在注射模中得到了很好的应用,而在模内装饰技术上融合电子电路是一项新工艺创新。对模内装饰与模内注射成型应用进行了介绍,以汽车侧门面板外饰件为案例阐述了嵌件加工工艺流程,着重介绍了导电银浆定义与导电银浆怎样做到嵌件上加工过程,及注射工艺情况。导电银浆应用于电子线路,电子线路并在模内装饰技术中应用,为拓展汽车外饰件功能的应用奠定了较好地基础。

汽车后大灯镜壳大型薄壁精密注塑模设计

根据汽车后大灯镜壳的结构特点,设计了一副大型薄壁精密注塑模具。模具采用定模成型内表面、动模成型外表面及动模侧向抽芯机构,有效地解决了成型塑件脱模困难问题;模具采用三级定位机构,显著提高了模具刚度和寿命;模具采用随形水路温度控制系统,成型周期降低了10%,成型塑件最大变形量下降了20%,成型塑件的尺寸精度达到了设计要求的MT3;模具采用推杆先复位机构,有效地消除了滑块和推杆汽相撞的风险,保证了侧向抽芯机构安全可靠。模具投产后运行平稳,成型塑件尺寸稳定。

小型电动汽车信号器外壳注射模设计

介绍了电动汽车信号器外壳的注射模设计。塑件成型材料选用科思创PC 2456,采用两板模进行成型。浇注系统中,使用2个扇形冷浇口对模腔进行浇注。塑件注塑工艺参数选定为,喷嘴出口料温为230~250℃;注射速度为200 mm/s;模具温度为80℃;注射时间为1~5 s,注射压力为80~100 MPa;保压时间为5~10 s,保压压力为40~60 MPa;背压为2~4 MPa;冷却时间为10~15 s。模具中,针对塑件外壁、内壁的脱模困难,设置了5个斜导柱滑块机构、1个3次抽芯复合机构、1个中抽式内收先抽芯滑块机构、3个斜顶机构、6个推管机构及多根顶针用于塑件的脱模。其中,3次抽芯复合滑块机构中,3个抽芯滑块组合在一起,先通过第一次开模驱动2个滑块联动抽芯,再通过第二次开模驱动3个滑块同步抽芯和移动,较为妥善地解决了塑件侧槽需二次抽芯脱模难题。模具机构选用恰当,紧凑合理,动作达标;与其它设计方案相比,制造成本约降低减少13%,工作效率约提高5%。

碎纸机塑件外壳大型注塑模具设计

以碎纸机塑件外壳为研究对象,设计了一副结构复杂的大型热流道塑胶模具。根据塑件的结构特点和使用要求,模具设计两点热咀进胶方式保证进胶的均衡性;采用1个油缸驱动的定模隧道滑块抽芯机构,1个天侧油缸驱动的滑块抽芯机构,1个地侧斜销驱动的滑块抽芯机构,滑块还包括延时弹针设计,5个斜顶抽芯机构,解决塑件所有倒扣的脱模难题。定模采用U形水路设计,动模采用水井均布的方式,滑块上单独水路冷却设计,使模具在实际生产过程中塑件的成型周期和品质均表现优异。模具顶出主要采用直顶块顶出机构的方式配合斜顶完成。

汽车油泵盖组合式抽芯机构注射模设计

采用POM材料对某燃油泵盖塑件进行注射成型。模具设计的难点为模腔充填困难、成型精度和尺寸稳定性要求高、难以脱模等。因此,采用1模1腔布局,保证尺寸精度达到MT3级,并且,精度稳定性较好;还需要开设直接浇口,模腔得到充分充填;主要成型件及滑块均设置Φ8mm的水路,模腔得到均衡冷却,保证尺寸精度的稳定性;除此以外,设计了8个滑块抽芯机构,用于局部复杂特征的脱模。机构中设计了一种二次抽芯滑块复合机构和一种复合式顺序抽芯滑块机构。二次抽芯滑块复合机构中,先由斜导柱驱动第一次抽芯滑块抽芯,再由油缸驱动完成第二次抽芯滑块的抽芯和2个复合滑块的移位,解决了外壁上交叉特征的脱模难题。复合式顺序抽芯滑块机构中,先由油缸驱动第一次抽芯滑块完成抽芯,同时解除第二次抽芯滑块的限位,然后,第二次抽芯滑块再完成抽芯,解决了塑件中交叉内孔的脱模难题。