With an extruder head, it can be basically divided into straight type and rotary type. In addition to some special
Most of the blow molding outside of the device (such as a horizontal blow molding system or a vertical extruder)
It is a downward-facing rotary nose.
Extruding the basic parameters of the preform The basic parameters of the preform are as follows.
1 Blow ratio: blow ratio is the maximum outer diameter of the blow molded product and the maximum outer diameter of the parison
Ratio. The blow-up ratio should normally be kept within ((2:1)) (3:1) but sometimes blown up
The ratio can be as high as (5:1) (7:1) or less than 1:1.
2 The difference between the actual outer diameter and the die diameter when the parison leaves the die,
After dividing by the die diameter and multiplying by 100%, the resulting ratio is called the parison expansion ratio. Its big
Small depends on the extrusion rate, cross-sectional area of the die, die pressure, type of extruded plastic, melt
Body temperature and the length of the straight portion of the die.
3 die shape in the case where the finished product section is circular or approximately circular
In the form of a die, the wall thickness distribution of the finished section in the circumferential direction is basically uniform. but
Yes, the 8-head material is generally medium carbon steel when the finished product section is rectangular or oval.
The wall thickness distribution is obviously not uniform.
The chamfer at the die 4 is for plastics with a higher metal viscosity, especially like poly carbonate
Ester and the like, in order to prevent the extrusion parison from being rolled up and stuck to the die, at the die
Design a 1-3 mm step.
5 Compression ratio (D), the maximum annular cross-sectional area (T) of the cavity in the head and the core
The ratio of the ring to the cross-sectional area between rods and dies. Generally choose between 2.5-4.
The length (L) of the 6-die setting section is approximately 8 times the gap width of the die.
7 Mold sag (S) Deformed when the parison hangs on the die under gravity