Reciprocating Screw (Intermittent Extrusion)

This is the most popular and cost effective method to produce lightweight dairy, juice and water containers. In this process the extruder feed screw reciprocates similar to an injection molding machine. The molds are stationary under the die head and simply open and close but do not shuttle. As the screw moves forward, the parison is pushed out into the molds for blowing. For lightweight containers, cycle times can be very fast with some under 5 seconds. Major machinery manufactures include Rocheleau and Uniloy.

PROS:

• Very fast cycle time capabilities
• Simple machine motions since clamps do not move
• Capable of 16 cavities small bottles or 8 gallons. Smaller models available
• Relative low cost per cavity
• Can easily run homo polymers and very low melt temperatures

CONS:

• Limited to monolayer applications
• Primary materials are HDPE and limited amount of PP
• Difficult to parison program

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