In cold isostatic pressing, the ceramic powder is stuffed into a rubber mould and pressed evenly from all sides with liquid pressure. This process generates a semi-finished product that is fairly close to the desired shape. This is then turned down to the desired shape by machining it while in the “raw shape”. Once machined, the workpiece is fired or sintered. This way, uniform properties are achievable throughout the workpiece.

We press large components up to 900mm in diameter and 2300mm in length at up to 150 MPa, and small components up to 120mm in diameter and 500mm in length at up to 150 MPa pressure.

Ceramic parts may also be manufactured by using the injection moulding and extrusion techniques, which are commonly used in the production of plastic parts. A thermoplastically mouldable mass is used as a matrix, into which a very high proportion of ceramic powder particles have been incorporated. In this case, in contrast to plastic production techniques, the organic matter is only used for plasticising and shaping the semi-finished item. Before the sintering process, the organic matter has to be removed from these raw parts by dissolution or decomposition processes, which currently limits the admissible wall thickness to a maximum of 8–10mm.

The main advantage of this process technology, however, lies in the very cost-efficient and repeatable production of near-net-shapes and of possibly geometrically complex components.

During pyrolysis / binder removal, the organic binder, which was temporarily required for the shaping process, is burned out of the ceramic preform without leaving any residue. The resulting carbonisation gases are rendered harmless via thermal exhaust gas afterburning (TNV).

Through pyrolysis or debinding, we remove the binder from components up to 800mm in diameter and 1,700mm in height at a maximum temperature of 650°C in standard air atmosphere, or up to 850°C in a controlled atmosphere with shielding gas.

Through one of a few different processes, ceramic preforms are first formed and turned into pre-structured raw-ware at room temperature from a raw mass, examples of which may be a granulate made from powder and binder, a slip made from powder and liquid or a “feedstock” made from powder and thermoplastic. The solid components with the material properties typical of ceramics are, however, only obtained after sintering at high temperatures.

Non-oxide ceramic materials must be sintered under vacuum or in the presence of a shielding gas, or else they burn or decompose. For this purpose, high-temperature systems, heated via resistance or induction, are used.

We sinter customer-specific components with a diameter of up to 700mm and a height of up to 1500mm at a maximum of 2400°C, under vacuum / shielding gas or at up to 1 MPa of gas pressure.

Powders, powder mixtures and granulates - metallic and non-metallic - can be compacted into plates and disc-shaped semi-finished products through the combined action of heat and uniaxial pressure.

In this way, materials and composites that would be too refractory or too adverse to sintering, in the case of pressureless or pressure-assisted sintering, and that would therefore sinter too loosely, can also be sinter-compacted.

At QSIL, we can produce components up to 400mm in diameter with a pressing force of up to 2500 kN as well as components up to 270mm in diameter with a pressing force of up to 1000 kN at a maximum temperature of 2200°C in a vacuum or under shielding gas (up to 0.1 MPa).

Ceramic slips (suspensions with a defined viscosity) can also be poured directly into plaster moulds. The plaster mould then pulls the water or solvent from the slip, so that over time the cast forms on the inside of the mould. This can then be dried and sintered into a ceramic part.

This shaping method is ideal for the cost-effective production of components with constant wall thicknesses (up to 8mm). QSIL also masters slip casting for the non-oxide ceramics Si3N4 and SiC, which are typically difficult to process using slip casting, as well as other manufacturing techniques for very large and heavy components.

Cold isostatically or uniaxially pressed raw parts and blocks made of pressed powder can also be pre-machined to near-net-shape components at QSIL using turning and milling processes. This makes it possible to create complex structures that are almost shaped to their final contour before sintering. This can help keep the intensity and costs of the subsequent grinding process within limits.

Hot isostatic pressing (HIP) gives components a higher density. The increase in density is achieved by applying an isostatic gas pressure.

We can (re)densify pre-sintered components or correspondingly encapsulated powders with dimensions of up to 280mm in diameter and 900mm in length. In this procedure, sintering temperatures of 2000°C and a gas pressure of a maximum of 200 MPa with N2 or Ar gases are possible.

After sintering, ceramic components often present a rough and imprecise surface, sinter skin and/or geometry. If the component-specific requirements for shape, dimensional accuracy, tolerance or surface quality cannot be met in the “as-fired” state, the component can first be manufactured oversize and then be finished by cylindrical, surface, cutting and 3D CNC-controlled grinding or polishing.

Since the high hardness of the ceramic requires the use of diamond grinding tools and long processing times, we determine all the surfaces and edges to be processed, all the processing steps and tolerances together with our customers on a component-specific basis.