Abstract: In the production of thin-walled disposable casting patterns of expanded foamed plastic beads for the full mold casting method, difficulty is encountered in that the prefoamed preexpanded beads to be introduced into the pattern mold cavity with a bulk density of less than 20 g/l have a diameter of about 2 mm and consequently a reliable reproduceable complete filling of pattern mold cavities with a cross-section of less than 5 to 7 mm is not possible. It has been found that prefoamed and preexpanded beads nevertheless having adequate foaming agent content for the final foaming expansion in the pattern mold can be produced in that following prefoaming, evacuation of the steam-air atmosphere in the prefoamed chamber is effected and additional foaming agent is introduced.

Abstract: A full mold for casting contains a plastic foam material lost pattern. The plastic foam material is substantially sulfur-free and can advantageously be used to provide iron alloy-based full-mold cast pieces of high quality.