The injection molding machine injects molten plastic into the mold and cools it into a product. It is very versatile and varies from plastic to plastic. The main body of the plastic extruder is a press machine, which consists of a pressing system, a transmission system and a heating and cooling system.

1, pressing system

The pressing system includes a screw, a barrel, a hopper, a head, and a mold. The plastic is plasticized into a uniform melt by a pressing system, and is continuously pushed out of the head by the screw under the pressure established in the process.

Screw: It is the most important part of the press machine. It is directly related to the application range and productivity of the press machine, and is made of high strength and corrosion resistant alloy steel.

Barrel: It is a metal cylinder. It is generally made of alloy steel with high heat resistance, high compressive strength, strong wear resistance and corrosion resistance or composite steel pipe lined with alloy steel. The barrel is matched with the screw to realize pulverization, softening, melting, plasticizing, venting and compacting of the plastic, and continuously and uniformly conveying the rubber to the molding system. The length of the general barrel is 15 to 30 times its diameter, so that the plastic is fully heated and fully plasticized.

Hopper: The bottom of the hopper is equipped with a cutting device to adjust and cut the flow. The side of the hopper is equipped with a sight hole and a calibration metering device.

Handpiece and mold: The machine head consists of an alloy steel inner sleeve and a carbon steel jacket, and the machine head is equipped with a molding die. The function of the machine head is to transform the rotating plastic melt into a parallel linear motion, which is evenly and smoothly introduced into the mold sleeve and imparts the necessary molding pressure to the plastic. The plastic is plasticized and compacted in the barrel, and flows into the head forming mold through the neck of the neck through a porous filter plate along a certain flow path. The mold core sleeve is properly matched to form an annular gap with a decreasing cross section, so that the plastic melt is in the A continuous dense tubular coating is formed around the core. In order to ensure the plastic flow path in the machine head is reasonable, and eliminate the dead angle of the accumulated plastic, a shunt sleeve is often placed. In order to eliminate the pressure fluctuation when the plastic is pushed out, a pressure equalizing ring is also provided. A mold correction and adjustment device is also mounted on the handpiece to facilitate adjustment and correction of the concentricity of the core and the mold sleeve. According to the angle between the flow direction of the machine head and the center line of the screw, the press machine divides the machine head into a bevel head (120o angle) and a right angle handpiece. The outer casing of the machine head is bolted to the fuselage. The mold in the machine head has a core sitting and is fixed to the inlet port of the machine head with a nut. The front of the core seat is equipped with a core, a core and a core holder. The center has a hole for passing the core wire; a pressure equalizing ring is arranged at the front of the machine head for equalizing the pressure; the forming part of the bag is composed of a die sleeve and a die sleeve, and the position of the die sleeve can be adjusted by the bolt through the support In order to adjust the relative position of the die sleeve to the core, it is convenient to adjust the uniformity of the thickness of the die layer. The outside of the machine head is equipped with a heating device and a temperature measuring device.

2, transmission system

The function of the transmission system is to drive the screw. The torque and speed required for the supply screw during the extrusion process are usually composed of a motor, a reducer and a bearing.

3, heating and cooling device

Heating and cooling are necessary conditions for the plastic extrusion process to proceed.

Nowadays, the press machine usually uses electric heating, which is divided into electric resistance heating and induction heating. The heating piece is installed in the fuselage, the neck and the machine head. The heating device heats the plastic in the cylinder from the outside to raise the temperature to achieve the temperature required for the process operation.

The cooling device is set to ensure that the plastic is in the temperature range required by the process. Specifically, it is to eliminate the excess heat generated by the shear friction of the screw rotation, so as to avoid the temperature being too high, so that the plastic is decomposed, scorched or shaped. The barrel cooling is divided into two types: water cooling and air cooling. Generally, small and medium-sized presses are suitable for air-cooling. Large ones are mostly water-cooled or combined with two types of cooling. Screw cooling mainly uses central water cooling to increase the solids transport rate. Stabilize the amount of glue and improve the quality of the product; however, the cooling at the hopper is to strengthen the conveying effect on the solid material, prevent the plastic particles from sticking and blocking the material due to the temperature rise, and the second is to ensure the normal operation of the transmission part.