Air is then blown into the parison, inflating it into the shape of the hollow bottlecontainer, or part. There are three sets of core rods, which allow concurrent preform injection, blow molding and ejection. These “crosses” fit together leaving little space as more surface area is contacted thus making the material less porous and increasing barrier strength against permeation. Restrictions on bottle design.
This page was last edited on 26 February dkwnload, at Blow molding BrE molding is a manufacturing process by which hollow plastic parts are formed: Today, even a greater number of products are blown and it is expected to keep increasing.
Containers such as jars often have an excess of material due to the molding process.
This excess plastic is then recycled to create new moldings. This is the least-used of the three blow molding processes, and is typically used to make small medical and single serve bottles. The accumulator head or reciprocating screw methods use hydraulic systems to push the parison out quickly reducing the effect of the weight and allowing precise control over the wall thickness by adjusting the die gap with a parison programming device.
As the preform is not released during the entire process the preform wall thickness can be shaped to allow even wall thickness when blowing rectangular and non-round shapes. Small Scale Recycling of Plastics. Very high volumes are produced.
Different types of the materials have their own physical characteristics affecting trimming. Types of EBM equipment may be categorized as follows:. These preforms are produced with the necks of the bottles, including threads the “finish” on one end.
Enoch Ferngren and William Kopitke  produced a blow molding machine and sold it to Hartford Empire Company in The preform is always stretched with a core rod as part of the process.
For amorphous metalsalso known as bulk metallic glasses BMGsblow molding has been recently demonstrated under pressures and temperatures comparable to plastic blow molding.
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.
The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass. Preforms steetch be sold as a completed item for a third party to blow. Highly suitable for low volumes and short runs.
Blow molding – Wikipedia
In the single-stage process both preform manufacture and mouldung blowing are performed in the same machine. Advantages of blow molding include: The parison is then clamped into a mold and air is blown into it. These preforms are packaged, and fed later after cooling into a reheat stretch blow molding machine.
Little restriction on bottle design.
This was the beginning of the commercial blow molding process. Packaging Molding processes Industrial processes. In Intermittent blow molding there are two processes: Disadvantages of blow molding include: EBM processes may be either continuous constant extrusion of the parison or intermittent. Handles can’t be incorporated. Retrieved from ” https: Barnes; Quoc Pham; Theodore A. The air pressure then pushes the plastic out to match the mold. Titanium coated blades are often used rather than standard steel to increase porcess by a factor of 30 times.
For example, moldings produced from amorphous materials are much more difficult to trim than crystalline materials.
Views Read Edit View history. The blow molding process begins with melting down the plastic and forming it into a parison or in the case of injection and injection stretch blow moulding ISB a preform.