Patent ID: 8540505

Claim:
A solid freeform fabrication system for producing a three-dimensional object comprising: a powder spreading system configured to spread a specified quantity of reactive powder; a dispensing system adapted to selectively dispense both a core binder and a shell binder onto said reactive powder, said dispensing system comprising a reservoir of said core binder and a separate reservoir of said shell binder, wherein said core binder is configured to react differently with said reactive powder so as to bind said powder with more flexural strength than said shell binder, and wherein said shell binder is configured to react differently with said reactive powder to as to provide a smoother surface finish than would said core binder; a curing system configured to cure said binder and reactive powder; and a computing device coupled to and configured to control said dispensing system and said curing system, wherein said computing device is programmed to selectively apply said shell binder to portions of said reactive powder which will be located at a surface of said three-dimensional object and to selectively apply said core binder to portions of said reactive powder that will be encased in a shell of said three-dimensional object that is formed by said shell binder.