The structure of extrusion blow moulding equipment is relatively complex, mainly consisting of an extrusion system, transmission system, cooling and heating system, etc.

-Squeeze System

1. Screw: this is the most important component in extrusion blow moulding equipment, which directly affects the application scope and production efficiency of extrusion molding blow molding equipment. Generally made of high-strength metals with excellent performance.
2. Cylinder: It is generally a metal cylinder made of sturdy alloy steel or composite steel pipes that are resistant to high temperature, high pressure, and corrosion. The barrel and screw work together to crush, soften, melt, plasticize, exhaust, and compact plastic, and continuously and uniformly transport the rubber material to the molding system. Generally, the barrel should follow the principle of fully heating and plasticizing the plastic.
3. Hopper: The bottom of the hopper is generally equipped with a cutting device, which can adjust and cut off the material flow. The hopper of the blow molding equipment can also control the speed and quantity of plastic particle transportation according to the machine’s needs.
4. Head: The head of the extrusion blow moulding equipment and the head of the mold are composed of a carbon steel outer shell and an alloy steel inner sleeve. The head is equipped with a molding mold, which is used to transform the rotational motion of the molten plastic into parallel linear motion, to evenly and smoothly guide it into the mold sleeve and give the plastic raw materials necessary molding pressure. After the plastic is plasticized and compacted inside the machine barrel, it passes through a porous filter plate along a certain flow channel, passes through the neck of the head, and flows into the molding mold of the head. The appropriate fit between the core and sleeve of the mold should be made to form a continuously decreasing circular gap so that the plastic melt can form a continuous and dense tubular coating layer around the core wire. To ensure a reasonable plastic flow channel inside the extrusion blow molding equipment head, manufacturers often install diversion sleeves to eliminate dead corners of accumulated plastic and pressure fluctuations during plastic extrusion. Some manufacturers also set pressure-equalizing rings. To adjust and correct the concentricity of the mold core and sleeve, the head of the extrusion blow molding equipment is often equipped with a device for mold correction and adjustment. The external part of the machine head is also equipped with a heating device and a temperature measurement device.

-Transmission System

Driven by the transmission system, the screw begins to operate. The system of extrusion blow moulding equipment usually consists of structures such as electric motors, reducers, and bearings. When other conditions remain stable and unchanged, the design and manufacturing of a gearbox are often proportional to its external dimensions and weight, because the gearbox has a larger shape and weight, often consuming more materials, and using larger bearings, which will increase the energy and time required for design and manufacturing. When the screw diameter of the extrusion blow moulding machine is the same, the energy consumption of a high-speed and efficient extruder is much greater than that of a conventional extruder. The power of the motor will be doubled, and the reducer should also be correspondingly increased. But if the screw speed is high, it means that the deceleration is relatively low. Compared to those with high reduction ratios, reducers with the same weight and size have an increased gear module and a greater ability to withstand loads. Therefore, the increase in volume and weight of the reducer in the extrusion blow moulding equipment is not linearly proportional to the increase in motor power.

-Heating and Cooling Device

1. Nowadays, extrusion blow moulding equipment usually uses electric heating technology, including resistance heating and induction heating. Heating plates can be installed in various parts of the machine’s neck, body, and head. The heating device heats the inside from the outside to raise the temperature of the plastic inside the barrel, reaching the temperature required for subsequent extrusion blow moulding operations.
2. The manufacturer sets up a cooling device to ensure that the plastic can be within the temperature range required by the process. Specifically, it is to timely eliminate the excess heat generated by screw rotation, and shear friction, to avoid the high temperature of extrusion blow moulding equipment, which may cause plastic decomposition, scorching, prolonged cooling time, or difficult solidification and shaping. Barrel cooling can be divided into water cooling and air cooling. For general small and medium-sized extrusion blow molding equipment, manufacturers usually use air cooling, while for large equipment, water cooling or a combination of the two forms is often used; The cooling of the screw mainly adopting central water cooling, with the main purpose of increasing the conveying rate of solid materials, maintaining stable glue output, and improving the accuracy and quality of the product.