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13 Blow Molding

The document discusses extrusion blow molding and injection blow molding processes. Extrusion blow molding involves extruding a tube called a parison and then clamping it inside a mold and injecting air to expand it against the mold walls. Injection blow molding involves injection molding a preform and then clamping it in a blow mold to inject air and expand it to the final shape. Common materials used are polyolefins and considerations for molds include using aluminum for its lower strength requirements compared to injection molding. Blow molded parts are typically hollow shapes like bottles, barrels, and containers.

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suhas deshpande
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1K views21 pages

13 Blow Molding

The document discusses extrusion blow molding and injection blow molding processes. Extrusion blow molding involves extruding a tube called a parison and then clamping it inside a mold and injecting air to expand it against the mold walls. Injection blow molding involves injection molding a preform and then clamping it in a blow mold to inject air and expand it to the final shape. Common materials used are polyolefins and considerations for molds include using aluminum for its lower strength requirements compared to injection molding. Blow molded parts are typically hollow shapes like bottles, barrels, and containers.

Uploaded by

suhas deshpande
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPT, PDF, TXT or read online on Scribd
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Blow Molding

MFG 355
Extrusion Blow Molding
Basic Blow Molding Extrusion Head
Circular Blow Molding Machine
Extrusion Blow Molding

Parison

Mold Open

Mold Closed

Pressurization of
Parison

Mold Open

Cooled Part
Extrusion Blow Molding

Click frame to start video


Injection Blow Molding

Click frame to start video


Injection Blow Molding
• Preform is injection
molded
• Preform is placed in
the blow molding
machine
• Preform is heated
• Preform is
pressurized PET Preform
• Part is removed
Molds and Dies
• General die and mold considerations (for
injecting the preforms)
– Tool steel
– Multicavity
Preform Formation
• Material placement
• Stretch optimization
General Mold Considerations (for
the mold in which the part is blown)
• Blow molding is lower pressure that
injection molding
– Blow molding molds don’t have the strength
requirements
• Aluminum molds are most common
• Machined or cast
• Venting
• Symmetry
Preforms Placed in Mold
Formed Bottles
Other Blow Molded Parts

Photo Courtesy of Phillips Petroleum Company


Plant Concepts
• No extensive cooling needed
• Scrap removal and handling important

Needs to be
removed

Photo Courtesy of Phillips Petroleum Company


Material Considerations
• Most thermoplastics can be blow molded
(in theory)
– High melt strength is necessary
• Polyolefins are the easiest to process
• PVC is temperature sensitive
• Some materials require Coblow-Molding
Shapes
• Basically hollow
• Typically of a cubic or cylindrical shape
• Bottles, barrels, tanks, ducts, trash carts, flower
pots, double wall cases (for tools), and toys
• Care must be taken to not have corners that are
too thin
• Threads for caps are typically not of the highest
tolerance
• Handles can be made using pinch points in the
mold
Shapes

Mold Diameter
Blow Ratio=
Parison Diameter
Thank You

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