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
as this parameter relates to runner design as well as gate size, positioning
and configuration.
As with plastic injection molding, all tools have the requirement of parting
lines, gates and ejector pins. With ceramics, mold construction must also take
the shrinkage rate of the material to be molded into consideration.
Upon molding, the component has a consistency similar to a cake of soap thus
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 subsequent use
as a molding feedstock.
3. Molding
Molding is accomplished in a standard plastic injection-molding machine. 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 such time as it is sintered. This process
results in a porous body that creates the pathways for the remaining binder
ingredient to escape without damage to 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 in the order of 15% to 30%
as determined by the binder system and particular ceramic powder being
utilized. The fully sintered part retain the complex shape of the molded part
and close dimensional tolerances can be achieved.
For more information,
Introduction to CIM
CIM Design Guide
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