Extrusion blow moulding process step by step

The extrusion blow molding process is a manufacturing technique used to produce hollow plastic objects, such as bottles and containers.

Blow molding main is a two-step process in which first a hollow tube, normally referred to as parison or preform, is produced from molten plastics, then the second step of inflating it into desired shape is performed inside a mold. The inflated parison takes the shape of the mold and retains it upon cooling.

It involves several steps that I can describe to you step by step:

Step 1: Resin Preparation

The process begins with the preparation of the plastic resin, which is typically a high-density polyethylene (HDPE) or polypropylene (PP) material. The resin is heated and melted to a specific temperature suitable for extrusion.

Step 2: Extrusion

The molten resin is then fed into an extruder, which is a machine that consists of a heated barrel with a rotating screw inside. The rotating screw pushes the molten resin forward while mixing and homogenizing it. As the resin moves through the extruder, it becomes a continuous, cylindrical parison.

Step 3: Parison Formation

The parison is a tube-like structure of molten plastic with a hollow center. It is extruded from the extruder and shaped using a die head or a parison programming device. The die head shapes the parison according to the desired final product. Air is typically introduced into the parison to maintain its shape.

Step 4: Mold Clamping

Once the parison is formed, it is transferred to the blow molding machine’s mold area. The mold consists of two halves that are clamped together to create a cavity in the shape of the desired product. The parison is positioned between the mold halves.

Step 5: Blow Molding

In this step, the mold halves close around the parison, and air is blown into the hollow center of the parison. The air pressure causes the parison to expand and conform to the shape of the mold cavity. The molten plastic is cooled simultaneously, either by the mold or through external cooling methods, to solidify and retain the desired shape.

Step 6: Product Ejection

Once the plastic has solidified and taken the shape of the mold cavity, the mold halves are opened, and the newly formed plastic object is ejected. The excess plastic material, called flash, is usually trimmed or removed from the final product.

Step 7: Secondary Operations

Depending on the specific product requirements, additional secondary operations may be performed. These can include trimming excess material, adding labels or handles, and inspecting the finished product for quality control.

The above steps provide a general overview of the extrusion blow molding process. However, variations in equipment and techniques may exist depending on the specific machinery and requirements of the manufacturer.

What Are Typical Extrusion Qualities?

•    Bottles & Jars: Healthcare OTC, Household & Industrial Chemical, Personal Care and Food  ½ oz up to 2.5 gallon

•    Typical Resins: LDPE, HDPE, PP, PVC, extrudable PET(ePET), PETG, “soft touch” resins.

•    Standard Machinery: Bekum, Sabmann, Baker, Sig, R&B Plastics, B&W

•    Monolayer & multi-layer capable

•    Often multiple extruders for multiple bottle layers

SO the  Extrusion Blow Molding? In extrusion blow molding (EBM), plastic is melted and extruded into a hollow tube (a parison). This parison is then captured by closing it into a cooled metal mold. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container, or part.

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