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Extrusion Blow Molding

Leshan blow molding machine

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. After the plastic has cooled sufficiently, the mold is opened and the part is ejected. Continuous and Intermittent are two variations of Extrusion Blow Molding. In Continuous Extrusion Blow Moulding the parison is extruded continuously and the individual parts are cut off by a suitable knife. In Intermittent blow molding there are two processes: straight intermittent is similar to injection molding whereby the screw turns, then stops and pushes the melt out. With the accumulator method, an accumulator gathers melted plastic and when the previous mold has cooled and enough plastic has accumulated, a rod pushes the melted plastic and forms the parison. In this case the screw may turn continuously or intermittently. Extrusion Blow Molding is the simplest type of blow molding. A hot tube of plastic material, called a parison, is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material "freezes" and the container now maintains its rigid shape.

Applications
Applications for extrusion blow molding are often similar to rotational molding. Extrusion blow moulding is normally a faster process, but rotational molding can sometimes allow for thicker wall sections. Tools are usually steel, but can also be made of aluminum or other materials.

Advantages
There are several advantages of Extrusion Blow Molding, one of which is lower mold costs compared to ISBM or IBM and the capability of forming handles. Another advantage of EBM is multi layer capability. In some instances, EBM bottles can have up to 7 layers of materials that include virgin plastic resin layers that encase a regrind (PCR) layer, barrier layer, and adhesive layers to bond the other layers together. Although specific capabilities differ from one manufacturer to the next - other capabilities unique to Extrusion Blow Molding includes IML (in mold labeling), window stripe on bottles, angled and offset necks, handleware, and multiple necks.In terms of logistics and cost benefits, EBM mold fabrication time is often shorter and relatively inexpensive compared to other blow molding methods, and many Extrusion Blow Molding manufacturers have interchangeable mold parts which allow the same bottle to be molded with different neck finishes, body, or embossment inserts. Since the inserts are interchangeable, the job change-over time are often relatively short.

Leshan machinery is the leading manufacturer of Extrusion Blow Molding in China We are completely committed to producing the highest quality blow molding machinery and making sure our customers know that they come first.

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