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The Technology
he powder injection molding (PIM) process is a comparatively new process for the production of small, complex components in medium to large quantities. In recent years, PIM has established itself as a competitive technology for precision components whose production would be uneconomical with so-called machining processes such as milling, turning and drilling. The entire component is given its final geometry in just one work step, the filling of the injection mold. PIM is a special injection molding process, with which metal components (MIM: Metal Injection Molding) or ceramic components (CIM: Ceramic Injection Molding) are manufactured. MIM/CIM technology combines the design freedom of plastic injection molding with the material properties of metals and ceramics. A large number of components can be manufactured from metallic alloys ranging from steel and stainless steel to titanium, as well as from high-performance technical ceramics.
- MATERIAL PREPARATION
The finest ceramic/metal powder with a grain size ideally of 10-20 urn is mixed with binders (organic compounds, natural waxes, synthetic polymers) in a ratio of approx. 90% metal powder to 10% binder. The binder enables the production of a plasticized mass which is required for shaping- Mixing takes place at an elevated temperature so that the binder becomes malleable and can coat the powder particles. The homogeneous mass prepared in this way is granulated, resulting in the so-called feedstock, which can be further processed directly in an injection molding machine.
- MOLD DESIGN
Working with the customer, the data required for the injection mold are defined such as the injection point, parting line, required surfaces etc.
- FORMING THROUGH INJECTION MOLDING
The feedstock is heated, plasticized and injected under pressure into a negative form (mold) on an injection molding machine, thereby giving it its complex shape. The green part is the result.
- BINDER EXPULSION (DEBINDING/DEWAXING)
Next, the binder is removed from the green part. This is done either by catalytic debinding, thermal debinding (heating the green parts to melt, break down and/or evaporate the binder) or using solvents (the binder is dissolved by appropriate solvents and removed from the component). The brown part is thus created.
- COMPACTING THE MATERIAL BY SINTERING
The brown parts are sintered in a controlled furnace atmosphere (in a vacuum or a protective gas atmosphere) at high temperatures. The powder particles melt together and acquire the required material properties. The MIM component is created ready for use. The finished piece is approx. 20% smaller than the green part. This measurement factor must be taken into account when designing the mold.
- Great flexibility in design and shape/geometry
- High imaging accuracy - even the smallest contours can be rendered
- Material properties like those of compact material - By using the finest metal/ceramic powder with an average grain size of 5 to 20 u, density values of almost 100% can be achieved in the end product
- Wide range of materials (various stainless steels, titanium, high-performance ceramics, special steels and alloys, standard materials). Processing of difficult-to-machine high-performance materials is possible
- Wirtschaftliche Fertigung
- Free shaping - complex geometries are possible: undercuts, cross holes, internal and external threads, gear teeth, and surface structures as well as lettering and logos etc. can be integrated into the component without difficulty
- Material combinations are possible (connections between ceramics and metals as well!
- Components with thin walls can also be realized
- Narrow dimensional tolerances can be achieved {components can be manufactured in series with tolerances of 0.2% to 0.5% of the final dimension)
- No need for reworking (so-called net shape fabrication = ready-to-install products)
- Substitution of otherwise costly-to-make conventionally molded or machined parts, assemblies and joined parts
- Fully automatic process control during injection molding and computer-controlled debinding and sintering processes lead to high and reproducible process reliability
- High material efficiency, since 100% of the material flows into the molded part
- Surface finish can be adjusted for specific components