Frequently, fiber sleeves are used in steel casting applications. These conventional sleeves contain, in addition to the fibers, rice husks that may lead to casting defects. Moreover, these slurry sleeves do not utilise their full volume for counteracting shrinkage defects, with the result that the effective yield is only 30%. The remaining 70% of the volume is used to maintain the heat in the 30% of the molten metal needed for feeding.
This is exactly where the cold-box bonded Exactcast KMV mini-risers come in, offering a fiber-free solution for steel casting. The volume at the riser can be reduced without loss to the feeding performance. The exothermic compound replaces the non-feeding material and maintains the metal in its molten state. The KMV mini-risers, therefore, present an efficient and reliable alternative to conventional slurry sleeves.
Exactcast Optima risers, available as a water-glass or cold-box version, noticeably increase efficiency in foundries. These mini-risers are fitted with a loose metal part in the bottom section (nozzle) and a rigid pin designed to achieve an exactly defined breaking point. They also reduce fettling costs.
A further benefit is the virtually frictionless sleeve and the integrated riser cap of the Exactcast Optima, which prevent crumbling particles from falling into the mould during the compaction process. Riser applications with rigid pins usually destroy the riser during compaction, and crumbling particles from the riser can fall into the mould, which needs to be purged with air afterwards. This can also happen when using spring pins under high compaction pressures. Exactcast Optima risers, by contrast, are fitted with a cover of non-friable material, preventing mould contamination and related casting defects and thereby raising the cycle times of the moulding systems.
Thanks to this saving, the foundry can produce more cast parts with a single furnace batch or even serve entirely new markets without investing in expanding the furnace capacity. The lower riser residue on the cast piece means that the reworking costs per cast piece are also lowered.