There are five steps to the Ceradyne CIM process.
- 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.
- 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.
- 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.
- 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.
- 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.