Method of rotational molding

A method for a forming a part by rotational molding comprising:

• providing a mold formed from at least two mold parts and having an inside surface defining a hollow interior;
• introducing into the hollow interior a thermoplastic plastics material in particulate form;
• rotating the mold about two axes while applying heat to the mold so as to cause the plastics material to melt within the hollow interior and adhere to the inside surface;
• when the plastics material is fully melted and adhered to the inside surface, halting the application of heat to allow cooling of the plastics material to at least partial rigidity;
• and when the plastics material is cooled to at least partial rigidity, separating the mold parts to open the mold;
• wherein the improvement comprises providing an insulating member formed of a low heat transfer material at a selected location on the mold, the low heat transfer material being arranged to prevent the adherence of the plastics material to the mold at the selected location.

A method for a forming two separate molded parts each including an undercut portion by rotational molding comprising:

• providing a mold formed from at least two mold parts and having an inside surface defining a hollow interior;
• introducing into the hollow interior a thermoplastic plastics material in particulate form;
• rotating the mold about two axes while applying heat to the mold so as to cause the plastics material to melt within the hollow interior and adhere to the inside surface;
• when the plastics material is fully melted and adhered to the inside surface, halting the application of heat to allow cooling of the plastics material to at least partial rigidity;
• and when the plastics material is cooled to at least partial rigidity, separating the mold parts to open the mold;
• wherein the improvement comprises:
• providing an annular heat conduction member extending from an outer edge outside the mold through the junction between the mold parts to an inner edge inside the hollow interior;
• providing on the heat conducting member inside the mold undercut mold portions for molding respective undercut portions of two separate molded plastics components;
• provided on the heat conducting member a band of a heat insulating material around the junction between the parts which prevents the adherence of the plastics material at the band so that the mold molds the separate molded plastics components each separately from the other;
• and causing the heat conduction member to carry heat from the exterior to the undercut mold portions.