How Blasch casts complex ceramic parts close to their final shape, with very little shrinkage and no machining.
A forming process developed in Albany in 1979.
It casts ceramic parts so close to their final shape that they need no machining.
Net shape ceramic forming means making a ceramic part in its final geometry during forming, so it needs little or no machining after firing. The Blasch process does this by casting a ceramic slurry into a precise mold and setting it with a proprietary solidification step, using a binder system that leaves almost nothing to burn out. Parts shrink very little, hold a linear tolerance of about ±0.005 in (0.5%), and can carry threads, bends, tapers and changing wall thickness straight from the mold.
Most ceramic parts are pressed, extruded or cast oversize and then machined, because they shrink and distort as binders burn out and the part sinters.
The Blasch process starts from engineered ceramic powders mixed into a slurry. It is cast or injected into a machined mold and solidified there, so the part leaves the mold in its final shape with high green strength.
Because there is very little binder to remove, the part barely shrinks during firing. What comes out of the kiln matches the mold, every time, from the first part to the thousandth.
When the shape is fixed in the mold instead of the machine shop, complex geometry costs no more to repeat than simple geometry, and that changes which parts are worth making in ceramic.
| Property | Value |
|---|---|
| Linear tolerance without machining | ±0.005 in, about 0.5% |
| Surface finish as cast | 80 to 100 µm |
| Pore size | 3 to 5 µm, porosity and permeability adjustable |
| Part weight | 1 oz to 2 tons |
| Wall thickness | 0.06 in to 6 in |
| Quantity per order | 1 to about 1,000 |
Internal and external threads, bends, constant and transitioning wall thickness and mating surfaces can all be cast in. Parts can also be mortared into fired assemblies or delivered in an alloy or titanium shell, bonded or bolted, ready to install.
The size range runs from a matchstick to a sewer pipe, as Blasch puts it. Large and complex ceramic shapes
Thermal shock resistance comes from three properties built in during forming: engineered particle packing, the binder system and a continuous, interconnected porosity. The fine, even pores let the structure take up stress from fast temperature changes instead of cracking.
The same process makes 99%+ alumina that is neither fine grained nor fully dense nor sintered. It keeps the chemical purity a reducing atmosphere demands without losing the thermal shock behavior, which conventional high purity alumina struggles to combine.
High alumina, alumina mullite, mullite, fused silica, zirconia and zircon composites, aluminum titanate and silicon carbide in oxide, nitride, oxynitride, alumina and reaction bonded forms. Non-wetting additives can be included for parts in molten aluminum. Engineered ceramic materials
Interlocking StaBlox tunnel blocks with tongue and groove joints, hex head ferrules whose heads close into one surface at temperature, and degassing rotors with cast in threads all depend on geometry that would be costly to machine. For one-off shapes, see custom engineered ceramic shapes.
Forming a ceramic part directly in its final geometry, so that little or no grinding or machining is needed after firing. Near net shape allows a small finishing allowance on selected surfaces.
No. Both start from a slurry, but slip casting draws water into a porous mold and shrinks more on drying and firing. The Blasch process solidifies the whole casting in the mold and shrinks very little.
Blasch protects its technology with patents and with proprietary know-how that is not disclosed. The process was originally developed in 1979.
Yes. Orders range from a single part to about a thousand, so prototypes and spare parts are made the same way as series parts.
Send the part, its dimensions and where it runs. A Blasch engineer tells you whether it can be cast and in which material.
