Direct extrusion of the preform head, from the structural point of view, direct extrusion of the preform head can be divided into two categories:
Center feed type and side feed type. Center-feed preform heads can be divided into bracket heads and boosters
Stretch strength stent type two kinds. Lateral feed parison heads are: ring-branched parison heads,
There are three kinds of heart-shaped branch tube heads and spiral branch tube heads.
Storage type head storage type parison machine head. It is widely used before. The parison is stored in the head
Melt forming. During the recharging of the storage chamber, the melt in the head channel has time to relax.
Extrusion blow molding in industrial production now mainly uses storage type heads, see below.
Basic structure of storage type head
1 a movable sleeve; 2 a ring
Piston; 3 a storage tank head raceway set storage
The material chamber, directly fed by the extruder, ensures that the melt is advanced and discharged, and when the piston empties the material storage chamber,
The melt entering the storage tube first is first extruded from the nose. When the melt entering the head first has a long slack
During the downward movement of the piston, the shearing time it receives is shorter. In the head below,
Adjust the sleeve up and down to adapt the head to the plastic with different melt flow properties.
When designing storage type heads, the mechanical properties of the weld lines should be avoided as much as possible. Melted
The fork flow method can meet this requirement, which is also the basic method to improve the wall thickness uniformity of the product.