Method for sinter molding plastic articles

Abstract

Molding is performed by directing streams of comminuted plastic material against surfaces of a heated form or mold, while repeatedly sweeping the form or mold across the streams, progressively depositing the material in one or more predetermined zones, so that the material assimilates progressively along the form or mold surfaces. Apparatus for so molding large receptacles, such as drum liners, includes a series of open molds supported on a turntable for rotation of the molds about their horizontal axes, with the open ends facing radially outward. The table is indexed relative to the various stations, at which successive steps of preheating, deposition, post-heating, cooling and stripping are performed. The deposition apparatus is on a carriage reciprocable radially of the table. A roll unit and several spray units direct streams of the material against the mold surfaces while the mold is rotated and maintained at a temperature suitable for incipient fusion of all the material substantially instantaneously upon impingement, so that the material adheres and fuses where deposited on the mold surfaces. When deposition is complete the mold passes through an arcuate oven overlying a sector of the table, for final sintering. The mold is then quenched, setting the material, whereafter the finished article is stripped from the mold.