Injection molding process operating without opening the mold to airborne contaminants

A method for injection molding plastic articles within a moldset having a mold cavity having A and B sides on either side of a parting line which defines a first vertical plane, with opposing A and B partforming surfaces capable of contollably traveling between a first position and a second position in each molding cycle, comprising the steps of:

• a. closing the mold cavity to the first position to seal off an outside perimeter of the cavity from being in fluid communication with air external to the moldset, wherein the opposing A and B partforming surfaces being separated by a first distance;
• b. injecting molten plastic into the closed cavity while in the first position to form a molded plastic article and cooling the molded article until the molded article is solidified;
• c. moving one of the partforming surfaces to a second distance relative to the opposing partforming surface, the movement ending at the second position located at a second vertical plane, the second distance being greater than the first distance,
• d. transferring the molded article out of the moldset through an aperture in the mold cavity in the second position, the mold cavity having a closed outside perimeter except for the aperture which is in fluid communication with air external to the moldset only when in the second position, and the aperture is downward facing to prevent convective air currents external to the mold cavity from contacting the partforming surfaces therein.

A method for injection molding plastic articles within a moldset having a mold cavity having A and B sides on either side of a parting line which defines a first vertical plane, with opposing A and B partforming surfaces capable of contollably traveling between a first position and a second position in each molding cycle, and the cavity capable of being controllably supplied internally with pressurized filtered gas at least when in the second position, comprising the steps of:

• a. closing the mold cavity to the first position to seal off an outside perimeter of the cavity from being in fluid communication with air external to the moldset, wherein the opposing A and B partforming surfaces being separated by a first distance;
• b. injecting molten plastic into the closed cavity while in the first position to form a molded plastic article and cooling the molded article until the molded article is solidified;
• c. moving one of the partforming surfaces to a second distance relative to the opposing partforming surface, the movement ending at the second position located at a second vertical plane, the second distance being greater than the first distance, and pressurizing the mold cavity internally with pressurized filtered gas at least when the second position is reached, so as to create positive pressure higher than ambient air pressure external to the moldset;
• d. transferring the molded article out of the moldset through an aperture in the mold cavity in the second position, the mold cavity having a closed outside perimeter except for the aperture which is in fluid communication with the ambient air external to the moldset only when in the second position, and the aperture is downward facing to prevent convective air currents external to the mold cavity from contacting the partforming surfaces therein, and through the downward facing aperture the pressurized filtered gas is purged out of the moldset to prevent convective air currents external to the mold cavity from contacting the partforming surfaces therein.