Shell moulding process
The shell molding process was developed by Johannes Croning (shell molding is also termed the ?Croning? process), who in February 1944 applied for a patent on the method in Hamburg.
Originally, the method only involved preparation of a powder resin - sand mixture with which a pattern could be covered to produce a shell.
The process was further developed in the fifties of the last century. Since then, the use of liquid resins to produce resin-coated sand by warm coating has also offered the possibility of fabricating shells and cores by shooting coated sand into coreboxes with compressed air.
In the sixties of the last century, the hot coating method evolved out of the warm coating technique. To produce precoated sand using this method, the molding material must be heated, causing the solid coating resin to melt and coat the sand during the mixing process.