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Metal - Ceramic Injection Moldingmpounding

Similar to plastic injection molding, a molten polymer (called binder) plus ceramic or metal powder paste is injected into a mold. The part is removed when the polymer cools. The binder material is removed by either solvent extraction or controlled heating to above the volatilization temperatures. The volume (cubic inches) of the part is restricted to small components, and material properties such as yield strength are lowered.

Metal Injection Molding (MIM) is fine metal powders mixed with plastic binders. Some of the different methods that can be used to compact the powder include:

*Cold isostatic pressing (CIP)
*Hot isostatic pressing (HIP)
*Forging
*Rolling
*Extrusion
*Injection Molding
*Pressureless compaction.

This mixture is injected into molds similar to those used in conventional plastic injection molding. Metal injection molding is a technology that combines metal powder technology with capabilities of plastic injection molding. It allows complex shapes to be created by "reassembling" powder into a solid part through injection molding. Compounding of these metal powders with "binders" creates the feedstock. MIM is a viable alternative to the material limitations of plastic injection molding. This process is best applied to complex shaped, high performance components, where manufacturing cost is a key consideration.

Ceramic Injection Molding (CIM) is very well suitable for high volume production of complex design with tight tolerances like bonding capillaries is needed. It is an effective way of manufacturing complex precision components with highest degree of repeatability, and reproducibility.

CIM process is a combination of powder, injection molding, and sintering technologies. To obtain the necessary chemical and physical properties, powders are selected by size and shape and complemented with additives. Every particle of the powder is coated with an inorganic binder, which transports the powder for molding and gives the final form rigidity.


Molding

Once the feedstock is compounded it is ready for molding.
A standard injection-molding machine is employed utilizing standard injection tooling. At this stage the molded a part contains both the binder and powder.

Debinding

The determining characteristics of binder selection depends on applications economics, tolerance requirements, and geometrical size of the part. Because of different binder systems selected for the application, different debinding technologies are required. The different debinding technologies are catalytic, thermal or solvent.

After molding, the MIM part is debound and sintered at temperatures from 600 degrees F to 2,200 F or higher to fuse the fine powdered particles into a solid shape that retains all of the mold's features. Temperature depends on which process and actual materials you are working with. During this process, the molded part shrinks close to 20 percent. Sintering follows the process of compacting and shaping the powdered material. Sintering is the process of heating the material to a temperature below the melting temperature but high enough to allow bonding or fusion of the individual particles. Continuous sintering furnaces are used for most production.

Advanced sintering techniques are dramatically widening the design process for a broad range of engineered parts. Sintering is an important process for compressed powdered metal shapes, called the green compacts. After compaction, the density and strength of the material are low. Sintering, then, increases both properties of the material.

Metal and Ceramic Powder Injection Molding

Honeywell's PowderFlo Technologies technology exceeds traditional metal injection molding with the capability to produce larger, thicker components, usually associated with investment casting. In commercial applications PowderFlo has been used to fabricate automotive oxygen sensors and racing spark plugs.

The PowderFlo technology utilizes a water based binder system instead of a solvent-based binder system. Honeywell's PowderFlo is more environmentally sound, eliminates time consuming debinding processing steps, and makes possible larger, thicker, and more complex shapes than currently available.
Unlike the manual or CNC grinding technology, the finished product using the MIM or CIM process is molded net to shape. No need to do grinding or major external finishing process becuase of the superior surface finishing accomplished by the processes.