MICRO MOULDING | ARTICLE
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CIM is ideal for high-volume production of complex, tight- tolerance components and offers significant advantages over conventional forming methods:
• Cost effective technique for complex designs • Ability to produce net or near-net shape parts • Very tight tolerance control • Low-cost, high-volume manufacturing runs
Ceramics are comprised of inorganic, non-metallic material. Explained simply, any solid material that is not a plastic or metal can be defined as a ceramic. In applications where plastic or metals won’t effectively function, ceramics have been the solution.
Limitations of Technologies Manufacturing small and complex shapes in volume before the advent of CIM had significant limitations and the obvious challenge for ceramics is the inherent fragility of parts prior to sintering and the hardness of the material, which makes machining processes difficult and expensive post sintering.
Dry pressing or extrusion are well-suited for high volume production, but they can produce only relatively simple shapes. For more complex shapes, tight tolerances and improved surface finish, secondary machining is generally required owing to which CIM came to the rescue and allowed for features such as re- entrant angles, multi-shaped blind holes, screw threads, surface profiles, perpendicular holes, undercuts and intricate cavities.
Ceramic parts are produced in the following variety of materials: 1) Alumina (from 96% to 99.9%): Applicable for parts that require good wear and corrosion resistance, such as in electrically insulating bodies, chemical operations, industrial machinery and the vacuum industry. Maximum Temperature of use is from 1200–1600°C.
2) Zirconia (YSZ): This is for demanding applications where the strength of alumina is insufficient and is available in white and black. The maximum temperature of use is 1200°C.
3) Zirconia toughed Alumina (ZTA): Applicable for parts with excellent surface quality requirements and reproduction of fine details. It delivers good wear resistance and high strength in applications such as biomedical, micro engineering, and fibre optics. The maximum temperature of use is up to 1200°C.
Ceramic Injection Moulding Process: Throughout the CIM process, the top priorities are to uphold quality and precision. Customer specifications are kept in mind before initiating the process.
The CIM process begins with very fine ceramic powders. The powders are compounded with polymer binders to produce a pelletised feedstock. During moulding, binders melt to form a liquid medium that carries the ceramic powders into the mould during the injection stage.
Using an injection moulding machine similar to that used in conventional plastic moulding, the feedstock is forced into a mould cavity forming a net shape part. Moulds can be single- cavity or multi-cavity configurations.
32 | commercial micro manufacturing international Vol 6 No.6
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