QuickSet^TM Injection Molding

QuickSet^TM is a novel, non-thermoplastic, injection molding process for the forming of ceramic and metal particulate bodies. QuickSet^TM uses low viscosity, highly dispersed suspensions of particles with volume fractions ranging from 15% to 70%. QuickSet^TM utilizes the science of collodial chemistry to provide uniform, well mixed and controlled dispersions of particles; the QuickSet^TM process has many advantages over thermoplastic injection molding processes.

'CPS licenses the QuickSet^TM  process to other companies for use in application areas outside of our areas of focus' 

Collodial Processing:

Colloidial processing yields a low viscosity feedstock material that is uniformly mixed.  Because it is a low viscosity the feedstock material can be easily mixed, pumped and monitored for density.  Additionally, entrained air (bubbles) are easily removed from the feedstock by applying a mild vacuum (de-gas).  Removal of bubbles is critical so that bubbles are not incorporated in the final product as a void.

Controlled Sintering Shrinkage:

A reproducible green density is the key to achieving uniform sintering shrinkage and tight dimensional tolerances on finished sintered product.  The low viscosity of QuickSet^TM allows the feedstock to be pumped through a density cell to directly measure the solids content, prior to being pumped to the injector system.  Adjustments to the feedstock can easily be made to achieve the correct density.  CPS has developed a process to control the solids content of most systems to +/- 0.2 vol%. This control has resulted in dimensional tolerances of +/- 0.010 on thickness and +/- 0.5 % on linear dimensions. The picture above shows a QuickSet^TM injection molded SiAlON pressureless sintered rotor (AGT-5).  Dimensional control on vane size and position is critical when you have to pass a 100K RPM spin test.

Control of the green density is important in a AlSiC composite system.  This is what ultimately determines the volume fraction of SiC (or other reinforcements) that gives the ratio for the composite properties.  Control is necessary to assure that there is little variance of these properties batch to batch, day to day, month to month, year to year.  The AlSiC microstructure above illustrates the uniformity achieved with the QuickSet^TM process even in systems that have multiple particle size constituents and multi-phase systems.

Low Pressure and Novel Binder System:

The low viscosity of the QuickSet^TM feedstock suspension allows for low pressure injection molding (<1000 psi).  CPS injection molds into cold molds to freeze the feedstock liquid component and the uniform particle dispersion (and controlled density).  CPS has chosen a carrier feedstock liquid that freezes near zero °C.  The frozen carrier acts as the primary binder of particles. The picture above shows molded SiC preforms from a multi-up cavity mold just after molding.

Binder Removal:

The binder (frozen carrier liquid) is removed by sublimation.  Sublimation is the phase transformation of a solid to its gaseous state without transforming into a liquid.  Particle rearrangement is avoided by never encountering the liquid state that can cause drying cracks, redistribution of particles and density variations.  This assures that the green body has a uniform green density and thus will sinter uniformly.  The added benefit is that this process is extremely rapid since binder removal does not rely on the percolation or pyrolization of liquid through the green structure.  Sublimation times are rarely over 3 hrs for most QuickSet^TM products as compared to binder burn out times for thermoplastic systems that range from 3 days to 3 weeks. The picture above shows Aluminum Nitride components as molded and as sintered (no machining). Clean and complete binder removal is critical in aluminum nitride processing since carbon residues degrade the thermal conductivity.  QuickSet^TM AlN products have thermal conductivity values of 200 - 230 W/mK.

In to the Fire:

After sublimation the product can be sintered (or infiltrated as in the case of SiC preforms).

Material Utilization:

It is important to note that up until the point of sintering all materials can be readily recycled.  Additionally the sublimated fluid is captured during the drying step on a condenser and is recycled for reuse. The picture above shows the green and sintered Aluminum Nitride heatspreader.  The sintered piece is 9.5 inches long 0.5 inches thick.  Material utilization and the capability to recycle is critical for components fabricated from expensive raw materials.

Material Capability:

CPS has applied the QuickSet^TM injection molding process to many material systems, both ceramic and metals, including: Alumina, Zirconia, Zirconia Toughed Alumina, Zircon-Zirconia, Aluminum Nitride, Silicon Carbide, Silicon Nitride, SiAlON, Stainless Steel, Copper, Copper Molybdenum, Nickel, Tungsten, Tungsten Carbide. The picture above shows a QuickSet^TM injection molded stainless steel rotor made using the same mold and very similar feedstock formulation (replacing SiAlON powder components with 316 Stainless Steel powder) as the SiAlON rotor above. 

Process Flow:

The QuickSet^TM process flow is outlined below: powder batching, mixing, de-gas, density verification, molding, sublimation and firing or infiltration.