Patent ID: 7318466

Claim:
A method of manufacturing a multilayer ceramic shell mould with at least one contact layer, one intermediate layer and several reinforcing layers, out of a master pattern, said method comprising the following steps: dipping said master pattern in a first slip containing ceramic particles and a binder to form a first layer, depositing sand particles onto the first layer and drying said first layer, in order to form said contact layer, dipping said master pattern in a second slip containing ceramic particles and a binder to form a second layer, depositing sand particles onto said second layer and drying said second layer, in order to form said intermediate layer, dipping said master pattern in at least a third slip containing ceramic particles and a binder to form a third layer, depositing sand particles onto said third layer, drying said third layer, in order to form a reinforcing layer, forming reinforcing layers being repeated until obtaining a shell mould of a set thickness, and baking the shell mould by heating up the shell mould to a temperature ranging between 1000 and 1150° C., wherein the ceramic particles of the slips comprise mullite or alumina, or a mixture of mullite and alumina, whereas no layer contains any zircon, and wherein said second slip comprises in weight percentage: a 50-75% mixture of alumina flour, a 5-20% mullite flour, a 20-30% colloïdal silica binder, 0-5% water, and a wetting agent, a liquefier and a texturing agent, wherein said sand particles are composed of mullite grains, wherein the sand particles are applied so that the shell mould exhibits an after-baking porosity ranging between 20 and 35%, and wherein the second and third slips comprise a mixture of alumina and mullite flours and mullite grains.