Profile

To manufacture plastic pipe, industry uses a process known as Profile Extrusion. This process is used to manufacture plastic products with a continuous cross-section such as; drinking straws, plastic evestroughing, decorative molding, window trimming and a wide variety of other products polymer melt into the hollow mold cavity under high pressure.

The plastic is fed in pellet form into the machines hopper ( this machine is known as an Extruder ), the material is conveyed continuously forward by a rotating screw inside a heated barrel being softened by both friction and heat. The softened plastic is then forced out through a die and directly into cool water where the product solidifies. From here it is conveyed onwards into the take-off rollers, which actually do the pulling of the softened plastic from the die.

The die is a metal plate placed at the end of the extruder with a section cut out of its interior, this cutout, and the speed of the take-off rollers, determines the cross-section of the product being manufactured. A simple way to understand this concept is to consider squeezing a toothpaste tube, the product comes out in a solid rod because of the opening at the end of the tube, if that opening had a different cross-section than the product produced would take on that new cross-section.




Pipe is one of the more common types of plastic product we are familiar with. Pipe is produced by an extrusion process. Basically extrusion can be defined as forcing a material through a die orifice. This die orifice produces the final shape of the finished product. It is probably a bit of over simplification, but extrusion is somewhat analogous to squeezing toothpaste through a tube.

Plastic tube, sheet, wire and profile shapes are all also manufactured by this process. In fact, the plastic resin granules or pellets used for injection molding are produced by extrusion. A long strand or filament of extruded plastic is chopped or cut into pellet-sized pieces to produce plastic injection molding materials.

Extrusion produces an inherently strong finished product. More so than a molding process. This is one of the reasons that plastic pipe is rated at higher pressures than injection molded plastic fittings.

Blown Film

To manufacture Garbage bags, industry uses a process known as Blown Film Extrusion. This process is used to manufacture not only garbage bags but also items such as; vapor barrier, bread bags, grocery bags, or any one of thousands of different items that you would see packaged for resale.

The plastic is fed in pellet form into the machines hopper ( this machine is known as an Extruder ), the plastic is conveyed forward by a rotating screw inside a heated barrel and softened by both friction and heat. The softened plastic is then forced upwards through a circular die in a shape of a hollow tube.

This is a continuous process where the tube is expanded with air above the die, and collapsed by the take-off or nip rollors, the volume of air inside the bubble, the speed of the nip rollers and the extruders output rate all play a role in determining the thickness and size of the film.

The tube or "web" of film is then continuously rolled up by take-off rollers, or the web of film may be fed directly into a bag-machine in an in-line process. The tube is heat-sealed across its width to form the bottom of the bag and cut across further up the tube to form the opening.