Papers by Keyword: Powder Injection Molding (PIM)

Abstract: With the capability of net shaping for complex 3D geometry, powder injection molding (PIM) is widely used for automotive parts, electronics and medical industry. In this study, an ultrasonic dental scaler tip produced by machining process was redesigned for the PIM process. An injection mold was designed and machined to produce the dental scaler tip by the PIM process. The mold design was aided by CAE analysis. A PIM feedstock was made of SUS316L powder and a wax based binder. The filling balance in the mold was checked by a short shot test with LDPE and the PIM feedstock. Production capability of the PIM process for the dental scaler tip was examined with the mold. Although there were minor problems such as a discoloration around the gate and a flashing at the air vent, the PIM process turned out to be an excellent substitute for machining process to manufacture the ultrasonic dental scaler tip.

Abstract: Powder Injection Molding (PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry. With this regards, design technology of dental scaler tip PIM mold, which has complex shape and a slim core pin of 0.6 mm diameter, with the help of computer-aided analysis for powder injection molding process was developed. Computer-aided analysis for dental scaler tip mold was implemented by finite element method with non-Newtonian fluid, modified Cross model viscosity, PvT data of powder/binder mixture. The core deflection analysis of dental scaler tip PIM mold during PIM filling process was also investigated. Compter-aided analysis results, such as filling pattern, weldline formation, and air vent position prediction were investigated and eventually showed good agreements with experimental results.

Abstract: This study is focused on the manufacturing technique of powder injection molding of watch case made from zirconia powder. A series of computer simulation processes were applied to the prediction of the flow pattern in the inside of the mould and defects as weld-line. The material properties of melted feedstock, including the PVT graph and thermal viscosity flowage properties were measured to obtain the input data to be used in a computer simulation. Also, a molding experiment was conducted and the results of the experiment showed a good agreement with the simulation results for flow pattern and weld line location. On the other hand, gravity and inertia effects have an influence on the velocity of the melt front because of the high density of ceramic powder particles during powder injection molding in comparison with polymer’s injection molding process. In the experiment, the position of the melt front was compared with the upper gate and lower gate positions. The gravity and inertia effect could be confirmed in the experimental results.

Abstract: Aiming to obtain components with higher density, this work evaluated the technical and economical viabilities to replace the pre-alloyed Fe49Co2V by an elemental powder alloy of iron and cobalt (Fe-50Co). Using an elemental alloy could increase the density of the final material due to the driving force created by the chemical gradient between the powders. The results showed that is possible to achieve higher densities in an elemental powder Fe-50Co alloy sinterized at the same temperature and in shorter times than the Fe49Co2V alloy. The analysis of economical viability showed that the replacement of the alloys have advantages as the pre-alloyed powder price is higher than the elemental.

Abstract: this paper describes the PADS process and equipment, which has been developed to produce PIM components. The use of a hybrid system of plasma discharge and Mo heating elements makes debinding and sintering PIM components in the same heating cycle possible. The use of an abnormal discharge between a cathode and anode under low-pressure provides reactive specimens that break the polymeric chains of the binder of the molded parts. By the combination of these features it was possible to use heating rates of 2,0º C/min during the debinding step. The hydrocarbons, resulted from debinding, are pumped out through vacuum pumps, without traps. The clean environment makes possible to sinter the parts in the same cycle, as well as execute a surface treatment during cooling. The results present short process times as 6 hours to Fe2Ni0,6C low alloy steel and 7 hours to 316-L stainless steel. Characteristics as density, carbon content and mechanical properties are similar to traditional PIM process. The reduction of energy and gas consumption and shorter lead-times are economic advantages of PADS system. The clean environment of PADS is also an ecological advantage.

Abstract: The use of AISI 316L stainless steels for biomedical applications as implants is widespread due to a combination of low cost and easy formability. However, wrought 316L steel is prone to localized corrosion. Coating deposition is commonly used to overcome this problem. Ceramic hard coatings, like titanium nitride, are used to improve both corrosion and wear resistance of stainless steels. Powder injection moulding (PIM) is an attractive method to manufacture complex, near net-shape components. Stainless steels obtained from this route have shown mechanical and corrosion properties similar to wrought materials. The literature on the use of PIM 316L steel, either coated or not, as implants is still very scarce. The aim of the present work was to study the corrosion behaviour of PIM 316L in two conditions: TiN-coated and bare. Electrochemical investigations were performed using EIS and potentiodynamic polarization techniques.

Abstract: Low-pressure powder injection molding was used to obtain AISI T15 high speed steel parts. The binders used were based on paraffin wax, low density polyethylene and stearic acid. The metals powders were characterized in terms of morphology, particle size distribution. The mixture was injected in the shape of square bar specimens to evaluate the performance of the injection in the green state, and then sintered. The samples were injected under the pressures of 0.4, 0.5 and 0.7MPa and at temperatures varying from 110 to 150°C aiming the optimization of the process. The results of the variation of injection pressure were evaluated by measuring the density of the green parts. Debinding was carried out in two steps: first, the molded part was immersed in heptane to remove the major component of the binder and then heated to remove the remaining binder. A second step debinding and sintering were performed in a single step. This procedure shortened considerably the debinding and sintering time.

Abstract: This study investigates the in vitro corrosion and cytotoxicity response of AISI 316L stainless steel produced by powder injection molding (PIM) technology in a solution that simulates physiological fluids (MEM) by electrochemical techniques and neutral red uptake cytotoxicity assay. The results were compared with those of AISI 316L produced by conventional metallurgy. Both steels showed high corrosion resistance and no toxic effect in the cytotoxicity test. The corrosion products were analyzed by instrumental neutron activation analysis (INAA). The surfaces of the alloys were evaluated before and after corrosion test by scanning electron microscopy and a passive behaviour was indicated supporting the results from other techniques.

Abstract: Manufacture of 2:17 Sm-Co magnets by powder injection molding was investigated. The binder of thermoplastic polymer was selected as the wax-based system including paraffin wax, stearic acid and high density polyethylene. Before mixing with paraffin wax and high density polyethylene, the powder of 5-8 µm was coated by stearic acid. The molding compacts were obtained under 200°C without deficits. Solvent debinding and thermal debinding were combined to remove the binder. The basic magnetic characteristics of the specimen were of the same level as those by powder metallurgy technique, which indicated that to fabricate 2:17 Sm-Co magnets by powder injection molding was feasible.

Abstract: Niobium and niobium-based alloys are used in a variety of high temperature applications ranging from light bulbs to rocket engines. Niobium has excellent formability and the lowest specific weight among refractory metals (Nb, Ta, Mo, W, and Re). Powder injection molding of niobium powder was investigated for efficiency of the process. The sintering of injection molded bars was conducted up to 2000°C in vacuum and low oxygen partial pressure atmosphere. This paper investigates the effect of sintering time, temperature and atmosphere on processing of pure niobium.