Method for manufacturing monolithic hollow bodies by means of a casting or injection moulding process

摘要

A method for manufacturing a monolithic hollow body by means of a casting or injection molding process, the manufacturing method contemplating the steps of: producing at least one lost ceramic core that reproduces the shape of at least one internal cavity of the hollow body, introducing the ceramic core inside a first mold that reproduces in negative the external shape of the hollow body, feeding a molten material inside the first mold by means of a casting or injection molding process, letting the material inside the first mold solidify, extracting the hollow body from the first mold, and destroying and removing the ceramic core located inside the hollow body.

主权项

1. A method for manufacturing a monolithic hollow body by means of a casting or injection moulding process, the manufacturing method comprising the steps of:
producing at least one lost ceramic core that reproduces the shape of at least one internal cavity of the hollow body by forming the “green” ceramic core and successively heating the “green” ceramic core to a firing temperature; introducing the ceramic core inside the first mould which reproduces in negative the external shape of the hollow body; feeding a molten material inside the first mould by means of a casting or injection moulding process; letting the material inside the first mould solidify; and extracting the hollow body from the first mould; and destroying and removing the ceramic core located inside the hollow body; wherein producing the at least one lost ceramic core comprises the further steps of:
determining how the bending mechanical strength of the ceramic core changes as firing temperature varies;estimating in advance the mechanical stresses on the ceramic core when the ceramic core is handled and when the molten material is fed inside the first mould; andestablishing, as a function of the mechanical stresses on the ceramic core when the core is handled and when molten material is fed inside the mould and as a function of how the bending mechanical strength of the ceramic core changes as firing temperature varies, a firing temperature for the “green” ceramic core that allows the ceramic core to gain a mechanical strength that is higher, with a predetermined minimum safety margin, than the maximum mechanical stresses on the ceramic core when the ceramic core is handled and when the molten material is fed inside the first mould such that the ceramic core correctly resists in the casting or injection moulding process and, at the same time, has the minimum possible resistance to subsequent destruction and removal from inside the hollow body, andwherein heating the “green” ceramic core to a firing temperature comprises heating the “green” ceramic core to a firing temperature that is equal to the previously established firing temperature to give the ceramic core its final mechanical characteristics for utilization inside the first mould, wherein a ceramic material used to produce the ceramic core is constituted by 45% to 55% of quartz, 20% to 25% of clay and 25% to 30% of kaolin.