Glossary

Thermoset

Duroplastics, also known as duromers, are plastics that cannot be deformed once they have cured. Thermosets are hard, glass-like polymer materials that are three-dimensionally cross-linked by main chemical valency bonds. Cross-linking takes place when precursors are mixed with branching points and is activated either chemically (isothermally) at room temperature with the aid of catalysts or thermally (exothermically) at high temperatures.

Deburring of thermoset parts / thermoset deflashing

The production of thermoset articles is always associated with the formation of burrs. On the one hand, these are raw materials which are heated during processing and in this state form a very low-viscosity melt. On the other hand, the corresponding moulds are composed of individual parts which inevitably form joints in the melt.

These burrs have to be removed because they are not only visually disturbing but, depending on the moulded part, can also impede the function and cause injuries during handling. All systems, injector, pressure jet and blast wheel are suitable for deburring. The blast wheel, due to its scattering range, is preferred. Such blast wheels are often installed in conveyor belt systems and thus the deburring process is automated.

Deburring of rubber parts

Burrs on rubber parts are created in a similar way as in the production of thermoset parts, in that the liquid raw material mass penetrates into gaps of compound moulds. A special feature is the production of O-rings which are manufactured in one piece, but then have to be separated from the webs (burrs), which corresponds to deburring in its mode of operation. The elastic property of rubber makes it impossible to remove burrs by blasting under normal conditions at room temperature. For this reason, rubber and other elastomers are cooled and cooled until embrittlement occurs. This so-called working temperature is between minus 20°C and minus 180°C depending on the type of rubber. This is also known as cryogenic deflashing.

Cryogenic systems, i.e. closed systems insulated against cold loss, are available for low-temperature deflashing. These are equipped with blast wheels and devices that circulate the parts to be deburred under the blast cone. The low temperature is achieved by using liquid nitrogen. Special demands are placed on the blasting media to maintain sufficient impact strength at these working temperatures.