Reciprocating screw blow molding machinery is characterized by the following sequence of operations in the making of a bottle:
- Plastic resin is melted by an extruder with temperatures ranging from 350F to 375F. As the screw rotates to melt the plastic, it also retracts, allowing molten resin to form a “shot” of resin in the front of the barrel.
- When enough plastic is melted, hydraulic pressure is activated to push the screw forward, forcing the shot of resin through flow heads and dies to form parisons.
- When the parison is fully extruded, which can happen in 1.8 seconds, the mold halves are closed under hydraulic pressure.
- Air enters the hollow parison, forcing it outward against the chilled mold halves. Air pressure is maintained until the plastic has cooled sufficiently to eject the part from the mold.
- Air pressure is relieved before opening the mold halves.
- The parts are removed from the mold. Parts may be released by gravity (with the aid of a part stripper) or removed using a part extractor. The parts are then ready for external trimming of "flash", or scrap plastic.
- Cycle time for a round gallon handle jug is 13.5 seconds.
Here is additional context for Altium's project:
- A reciprocating screw platform is used to manufacture monolayer parts, as intermittent processes are not well suited for coextrusion.
- Altium currently provides barrier solutions, using multi-layer constructions on continuous extrusion shuttle and wheel platforms in select locations.
- Having a monolayer barrier solution that runs on a reciprocating screw platform would provide a competitive edge to Altium due to the large number of these machines currently in operation throughout our North American network.