Papers by Keyword: Metal Injection Molding

Abstract: Brackets fabrication should be done by a suitable process to produce great result. Processes commonly used are investment casting, machining, and metal injection molding. Investment Casting has a drawback in which the surface roughness is quite high for the standard of brackets and require further processing. Machining is done by removing unwanted part to get desire shape, whereas bracket shape requires a high accuracy and is quite complicated. In Metal Injection Molding, feedstock is injected into a mold where complicated shapes can be achieved with a better surface roughness. The weakness is the stages within the process are quite long. One of the problem is the efficiency of debinding stage. We conducted an experiment to enhance binder removal rate through solvent debinding with stirring and under vacuum condition. Sample use for this experiment is a cubic shape of 0.5 x 0.5 x 0.5 cm³. Experiment is done on magnetic stirrer and in vacuum furnace. The temperature is hold at 50°C. Drying process afterward is done in the vacuum furnace for 1 hour with temperature around 50°C. Amount of binder left is confirmed by STA and the particle morphology is seen by SEM. Results showed that stirring treatment enhances binder removal rate due to stirring mechanism that causes possibility of collisions between particles increases. Binder removal rate on the vacuum treatment has a mechanism similar to stirring, but with the addition of the solvent to be done on a regular basis due to decrease of solvent boiling point under vacuum. There were no cracks found on the surface with an increased rate of debinding. Stirring is use for experiment with sample of actual bracketorthodontic form. Debinding rate of the bracket sample is faster than the cubic sample. This result is affected by the dissimilarity on the volume to surface area.

Abstract: Generally, metal injection molding (MIM) method utilizes SS 17-4 PH as material for application of orthodontic bracket. One of the process of MIM is thermal debinding, which binder is eliminated by thermal energy. In this study, thermal debinding process is conducted with variation of temperature, i.e. 480, 510, and 540°C, holding time, i.e. 0.5, 1 and 2 hours, heating rate, i.e. 0.5, 1, 1.5, and 2°C/min.The effect of temperature shows that the increased temperature will result in the mass reduction percentage due to formation of oxide on the sample, which will be proven through TGA testing. The highest mass reduction was 6.4137 wt% which was obtained at 480°C. For the variation of holding time, the longer the holding time will result in increased mass reduction and the highest mas reduction was 6.255 wt% which was obtained during 2 hours of holding time. For the heating rate, the slower the heating rate will result in increased mass reduction and decreased the presence of crack formation. The best variable was obtained at heating rate of 0.5°C/min, which resulted mass reduction of 6.2488 wt% and less crack formation.

Abstract: Malocclusion is one of the common problems encountered in the teeth and mouth of Indonesian people. This country is also confronted with problems that the bracket have to been imported from abroad. The purpose of this study is to produce national orthodontic bracket by metal injection molding (MIM) process in Indonesia, particularly by using vacuum sintering for 17-4 PH stainless steel because it is a material commonly used for orthodontic bracket. Sintering conducted at four different temperatures, at 1320 °C, 1340 °C, 1360 °C, and 1380 °C. The results showed that there are inclusions in sintering products. The relative density increases with increasing temperature sintering because the area of porosity are reduced. In addition, the results of sintering at 1360 °C has optimal hardness, which is amounted to 395 HV and higher than commercial bracket.

Abstract: The metal injection molding (MIM) process allows the manufacturing of small and very complex metallic components. The metal injection molding processing combines the shaping capability of polymer injection molding with the large material variety of metals and ceramics. This paper discusses in detail the development of a numerical model capable of simulating micro-structural evolution and macroscopic deformation during sintering of complex powder compacts. A sintering model based on elastic–viscoplastic constitutive equations was proposed and the corresponding parameters such as bulk viscosity, shearing viscosity and sintering stress were identified from dilatometer experimental data. The constitutive model was then implemented into finite element software in order to perform the simulation of the sintering process. The numerical simulation methods being compared against results of the sintering experiments. The experimental data were obtained from sintering of 316L stainless steel powders.

Abstract: Powder injection molding (PIM) is a well-known process for the production of geometrically complex shaped parts at a high production rate. The possibility of recycling the raw material (feedstock) is economically necessary for industrial applications, especially when processing very expensive materials, such as rare-earth alloys. In this study, Nd-Fe-B magnets were fabricated by powder injection molding, in which the injection residues (gates, sprue and surplus green samples) were reprocessed, up to 6 times. Subsequently, samples underwent binder extraction by chemical and thermal procedures, being finally sintered under high vacuum. Physical characterizations were carried out and the magnetic properties were measured via B-H trace analysis in each batch to study the influence of the recycled feedstock on the magnetic properties of produced samples. It was concluded that the properties are significantly affected after the second reprocessing lot, mainly due to the contamination of the feedstock by organic elements by-products of the binder decomposition.