The magazine: Hello. This highly successful technology offers a significant outlook for growth. Could you describe the manufacturing process? JCB: Of course. In simple terms, you must understand that this technology combines plastic injection and powder metallurgy and can be used to shape metal or ceramic parts exactly like plastic injection parts. The basic material is a very fine powder that is mixed with a thermoplastic binder to form a granulate that we call the feedstock. This composite is injected in a mould using a traditional plastic injection press. The molding process results in a green part, made up of powders coated with a thermoplastic binder. The magazine: Does this process include all the specific features of injection? JCB: Yes, provided that the volume remains smaller than or equivalent to that of a golf ball, any part that can be injection moulded can be made using PIM, which means that the complexity comes for free, like in plastic injection. The magazine: But how do you transform this part into a metal or ceramic structure? JCB: After injecting, the plastic, which is simply used for shaping purposes, must be eliminated. This unbinding operation is chemical, transforming the solid polymer into a gas. Once this step has been completed, the part is completely metal, but it has become very fragile. The part is then consolidated by sintering, which gives it the cohesion and microstructure that are typical of the final material, plus a controlled withdrawal. The magazine: It sounds like this is a crucial stage of the manufacturing process. Could you describe it in more detail? JCB: Yes, it is a very important step. Sintering is based on the atomic diffusion of solid phases. Above a given temperature, two bodies that are in contact will exchange atoms. If the correct temperature and pressure prevail, then the material is densified. Obviously, the conditions differ from one material to another, and what makes Alliance stand out is the fact that we command and control the homogeneity and the quality of the microstructures, so that the parts have the physical and chemical properties suited to our critical applications. The photo illustrates the different stages of the manufacturing process. The magazine: Our readers often ask questions about the quality of the metals made. Are they as good as metals made using traditional methods? And in particular, could you tell us more about the densities obtained. JCB: MIM technology is derived from powder metallurgy, but the use of spherical powders enables us to produce densities that are significantly higher and more homogeneous than conventional PIM. As a consequence, the properties of the alloys we make are identical to those made using traditional metallurgical methods. Alliance’s MIM parts can be polished, welded, machined and covered with any sort of galvanic or vacuum coating. Moreover, the microstructure is of the annealed type, which means that it is totally isotropic and guarantees identical performance in all directions. However, this technology cannot be used to fiberise the part, which is possible, for example, in a forge. The magazine: When we visited the factory, we saw several production lines, but other activities as well, such as the production of moulds. Can you explain why you decided to build such a large production plant? JCB: We have two types of competitor: other MIM companies on the one hand, plus conventional techniques, and in particular machining, on the other. In this case, customers are not used to footing a heavy bill for tools, which is the case with plastic, and they also want to receive their first parts reasonably quickly. A complex injection mould must be made for every PIM part and experience has shown us that outsourcing this activity, which requires significant skills and know-how, would be seriously detrimental to the competitive performance of the company. This is the reason why, in 1998, we decided to create our own design office and simulation facility, plus the complete production of all the tools. | | The magazine: The workshop we saw is very modern. Why make such a high capital outlay? JCB: The mould is the centrepiece. Without moulds, there would be no parts. Moreover, many customers are launching packs of tools for the same product and it is impossible to deliver a kit of parts for periods lasting longer than a few weeks. So we have to be very reactive, which is why we use the very latest CAD-CAM technologies. In order to produce the right mould at the first attempt and shorten the time to market, we simulate the injection using special software developed by the European "matlaw" project, in which we took part. The tools are then produced in-house using conventional techniques, plus the hard milling technology, which cuts lead times by doing away with the need to heat treat the tools. Each tool must only be used only once on each type of machine in order to achieve optimal quality and efficiency. Once the various parts have been made, they are adjusted by the technicians who also maintain the tools. The magazine: This is all very impressive. But what are these other machines used for? JCB: Our customers are asking for more and more finished parts or subassemblies that are ready to be assembled in the end product. For a few years now, Alliance has been capable of delivering this type of service with tight deadlines and top quality. Part of the re-work, like the heat treatment, is outsourced, but anything that impacts the precision of the parts is kept in house. These operations include the rectification or re-machining of the parts, and in particular of threaded holes, which cannot be moulded in small diameters. Finishing operations, such as polishing or shot peening, are also performed internally and the appearance of the product is checked on site in order to guarantee top quality and the quick reactivity that is required by the short deadlines strategy. Alliance can also propose complex assembly operations, including welding, some of which are robotized in order to achieve better global control of quality and deadlines. The magazine: Mr. Bihr, thank you for explaining this new technology, which demonstrates how technological innovation always bears fruit. |
