The importance of blow molding machine screw speed control
During the screw speed extrusion process of the plastic blow molding machine, the screw speed is high and the extrusion rate is fast, which can increase the output of the extruder and reduce the sagging of the parison. However, it is easy to cause the surface quality of the product to decrease, and it will also be affected by the shear rate. The increase will cause melt rupture of PE plastics and degradation of plastics with poor thermal stability such as PVC. Usually in the extrusion blow molding process, the screw speed should be controlled as fast as possible on the premise that it can extrude a smooth and uniform parison without overloading the extrusion transmission system. , but generally controlled below 70r/min. In order to control the screw speed below 70r/min, generally the hollow blow molding machine should choose a larger extrusion device.
Blow rate: The volume rate of air introduced during blow molding should be as large as possible to shorten the inflation time and make the product more uniform in thickness and better in surface quality; the air speed should not be too large, otherwise it may form at the air inlet. Low pressure will cause this part of the parison to sink in, or may break the parison at the die opening, making it impossible to inflate.
Blow pressure: The air used for blow molding should have sufficient pressure. Otherwise, it will be difficult to inflate the molded parts or the pattern on the surface of the product will not be clear. Generally, the pressure can be lower for thick-walled products, while thin-walled products and materials with high melt viscosity need to be used. Higher pressure, the general blow molding pressure is 0.2~1.OMPa.
The blow-up ratio refers to the ratio of the maximum diameter of the container to the maximum diameter of the parison, which is the multiple of the parison blow-up. The size of the parison and the blow-up ratio directly affect the size of the container. When the size and quality of the parison are constant, the greater the inflation ratio of the parison, the larger the size of the container. The inflation ratio of the parison is large and the thickness of the container wall becomes thinner. Although raw materials can be saved, inflation becomes difficult and the strength and stiffness of the container are reduced. If the blowing ratio is too small, the consumption of raw materials will increase, the wall thickness of the product will decrease, the effective volume will decrease, the cooling time of the product will be extended, and the cost will increase. Molding should generally be determined based on the variety and characteristics of the plastic, the shape and size of the product, and the size of the parison. Generally, the inflation of large thin-walled products is relatively small, taking 1.2 to 1:5 times; the inflation of small thick-walled products is relatively large, taking 2 to 4 times.
HUATAO provides blow molding equipment. Including:
Plastic Mold Equipment
Automatic Blow Molding Machine
Semi-automatic Blow Molding Machine
PS Foaming Machine
EPE Foaming Machine
PU Foaming Molded Machine
Horizontal lnjection Molding Machine
vertical lnjection Molding Machine
All-electric Injection Molding Machine
Thick Sheet Blister Machine
Thin Sheet Blister Machine
Color Plastic Masterbatch
Plastic Recycle Machine
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