Although there are different plastic extrusion processes, the fundamental principles remain the same. The type of extrusion plastic process depends on the die shape’s complexity and intricacy. Some types are better suited for dealing with complex designs better than others.
Are you interested in learning more about Extrusion Prototype Quality Control? Contact us today to secure an expert consultation!
Below are the 4 major types of this process manufacturers in the industry employ today;
Tubing extension follows the same general plastic extrusion process until the die section. This process is ideal when dealing with tubes and hollow items like pipes and long tubes. It is also ideal for producing drinking straws and medical tubing.
To produce hollow sections, an extrusion operator puts a mandrel or pin inside the die, followed by applying positive pressure to the internal cavities through the pin. In a situation that involves multiple holes, manufacturers place more than one pin at the center of the die. The number of pins is dependent on the number of holes desired.
Besides, air pressure for pins in this scenario is usually from a different source, making it easy to adjust the size of each hole.
The blown-film extrusion method is quite a popular method used for creating items like shopping bags. Like the tubing extrusion plastic method, the die is the major difference between blown-film extrusion and normal extrusion.
The blown-film extrusion die is an upright cylinder with a circular opening ranging from a few centimeters to over three meters in diameter. A pair of nip rolls pull the molten plastic upwards from the die for use in this process.
The nip rollers are often high above the die at a distance of four to twenty meters. The nip roll’s exact height depends on the amount of cooling needed. Furthermore, the speed of the nip rollers determines the wall thickness or gauge of the film. As the film travels upwards, an air ring around the die helps cool it down.
Want more information on Rapid Tooling For Injection Molding Molds? Feel free to contact us.
An air exit in the die’s center allows compressed air to be pumped into the center of the circular extruded plastic profile to produce a bubble. This results in some ratio expansion of the circular extruded plastics cross-section. This ratio, also called the blow-up ratio, ranges from a few percent to over 200 percent of the original diameter.
Finally, the nip rolls help flatten the bubble produced into a double-layered film with a width half the circumference of the bubble. This double-layered film has diverse uses, from cutting into different shapes to spooling or printing. It can also be sealed using heat to produce bags and other items.
This process is quite similar to blow-film extrusion, but the difference lies in creating the desired shape. In this extrusion type, a pulling and rolling process is the major requirement for attaining the desired shape. This includes determining the surface texture of the sheet as well as its thickness.
The rolling process ensures the product attains the desired shape and facilitates its cooling and permanent solidification.
This type of plastic extrusion is ideal for making insulation wires. The aim here is to give the material a plastic cover. Two major extrusion plastic tooling are used for coating wires: pressure and jacketing.
Both tooling types have their uses, but the one you use for coating wires depends on the intimacy required between the plastic material and the wire.
If intimate contact or adhesion between wire and material is necessary, then pressure tooling is ideal. But if intimacy and contact are unnecessary, jacketing tooling is best.
The major difference between these tooling types is the position of the pin to the die. When the pin extends to the flush with the die, it is jacketing tooling. On the other hand, the pin’s end stays inside the crosshead for pressure tooling. This means molten plastic covers the wire while still inside the die. Pressurization here occurs when both the wire and molten plastic exit the die.
If you are looking for more details, kindly visit Rapid Tooling For Automotive Prototypes.