Blow molding is a process specifically designed for mass production of hollow plastic containers. This issue will introduce Extrusion Blow Molding (EBM) in the blow molding process.

Process cost: Processing cost is moderate, and the cost per unit is low. Typical products: Chemical product packaging, consumer product packaging, and pharmaceutical packaging. Suitable production volume: Only suitable for large-scale production. Quality: High quality, with completely uniform wall thickness and suitable surface treatment options such as smooth, matte, or textured finishes. Speed: Fast, with an average cycle time of 1-2 minutes.

Blow molding can be divided into three categories:

  1. Extrusion Blow Molding (EBM): The lowest cost among the three categories, suitable for producing hollow plastic containers (PP, PE, PVC, PET) ranging from 3 ml to 220 liters.
  2. Injection Blow Molding (IBM): To be continued in the next issue.
  3. Stretch Blow Molding (ISBM): To be continued in the following issue.
The steps of Extrusion Blow Molding (EBM) are as follows:
Step 1: Pour the polymer particles into a rigid mold and continuously apply heat and pressure with a core rod to form a gelatinous, hollow cylindrical shape.
Step 2: When the hollow columnar prototype is extruded to a certain length, the molds on both sides start to close, and the top of the prototype is cut by a blade to the appropriate length for a single piece. Air is injected into the prototype through an inflatable rod, causing the prototype to adhere to the inner wall of the mold and cool and solidify, forming the desired shape.
Step 3: After waiting for the cooling to finish, open the molds on both sides and remove the part.
Step 4: Use repair tools to trim the edges of the part.
Example: Producing plastic laundry detergent bottles using extrusion blow molding.
  1. Polyethylene (PE) polymer particles are typically stored by color in industrial hoppers.
  2. “In this instance, blue PE (polyethylene) oligomer particles are continuously heated and squeezed to form a gel-like, hollow cylindrical prototype with the same wall thickness.”
  3. The molds on both sides are closed, and the upper end of the columnar embryo is cut to the appropriate length.
  4. The inflation rod is inserted into the bottle neck, and air is injected to make the glued embryo adhere tightly to the inner wall of the mold, forming the desired shape.
  5. The molds on both sides are opened, revealing the parts (connected to the inflation rod).
  6. The inflation rod is retracted, and the repair machine trims the laundry detergent bottle.
  7. Every laundry detergent bottle needs to undergo a pressure test.
  8. The filling machine fills plastic bottles with laundry detergent.
  9. The lids are assembled automatically by rotation.
  10. Labels are automatically affixed to the bottle body, completing the process.