There are five steps to the Ceradyne CIM process.
1. Tool Design and Manufacture
A key element in the success of the process is the ability to design tooling that is complimentary to
both the requirements of the finished part and the potential complications of the subsequent
manufacturing steps. Tool design must also consider the flow characteristics of the specific
powder/binder feed stock. This parameter relates to runner design as well as gate size, positioning
and configuration.
As with plastic injection molding, all tools parting lines, gates and ejector pins. With ceramics, mold
construction must also account for the shrinkage rate of the materia.
An as-molded ceramic component has a consistency similar to a cake of soap. The ejection system must
accommodate a delicate part.
2. Mixing
Sub-micron size ceramic powders are mixed thermo-mechanically with a proprietary multi-component blend
of binder constituents. The end result is a homogeneous blend of materials that is cooled and granulated
for use as a molding feedstock.
3. Molding
Components are molded in plastic injection-molding machines. The feedstock is gravity fed into the barrel
of the molding machine where it is heated and moved up to the nozzle by a screw rotating in the barrel.
The screw then plunges forward and rams the material through the nozzle into the cavity configured to the
required shape.
When the material in the cavity cools sufficiently to hold its shape, the machine opens the tool along
the parting line and ejector pins are activated to push the part out of the cavity. The machine then
closes the tool and the process is repeated.
At this stage of the process, the component is referred to as a green part. It is common for these
components to be produced in tools with multiple cavities thereby increasing productivity and reducing
unit component cost.
4. Debinding
Green parts are next treated in a proprietary solvent binder extraction process. All but one of the
binder ingredients are removed at this point.
The remaining binder ingredient is called the backbone and functions to hold the geometry of the green
part until it is sintered. This process results in a porous body that creates the pathways for the
remaining binder ingredient to escape without damaging the part during the sintering process.
5. Sintering
The green part is then placed in one of several high temperature furnaces. The firing atmosphere required
by the particular ceramic powder dictates the specific type of furnace utilized.
During sintering, the part will experience shrinkage ranging from 15% to 30%. This is determined by
the binder system and ceramic powder being utilized. The fully sintered parts retain the complex shape
of the molded part and close dimensional tolerances can be achieved.
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