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Working principle of injection molding machine

Action procedure of injection molding machine
Mold closing → pre molding → backward shrinking → nozzle forward → injection → pressure maintaining → nozzle backward → cooling
Open die → eject → open door → take workpiece → close door → close die.
Operation items of injection molding machine
Operation items of injection molding machine include control keyboard operation, electrical control cabinet operation and hydraulic system
Three aspects of operation. Conduct injection process action, feeding action, injection pressure and injection respectively
Selection of speed and ejection form, monitoring of temperature, current and voltage of each section of barrel, injection pressure
Adjustment of force and back pressure, etc.
After the injection and cooling timer are finished, the pre molding starts. Screw rotation will
The plastic melt is extruded to the front of the screw head. Due to the function of one-way valve at the front end of screw, molten plastic
The material is deposited in the front end of the barrel, forcing the screw backward. When the screw retreats to the predetermined position (this
The position is determined by the travel switch, which controls the backward distance of the screw to realize quantitative feeding), pre molding
Stop, the screw stops rotating. Then there is the backward shrinking action, that is, the screw makes a small amount of axial force
Backward, this action can release the pressure of the molten material gathered at the nozzle, and overcome
The phenomenon of "salivation" caused by the imbalance of pressure inside and outside the cylinder. If it is not necessary to back down, it shall
Shrink stop, switch to appropriate position, let the pre molding stop. At the same time that the switch is pressed,
The retract stop switch is also pressed. When the screw moves backward to the press up stop switch,
Recoil stop. Then the injection seat began to move backward. When the injection seat moves back to the press up stop switch, the injection seat
Stop backing up. If fixed feeding mode is adopted, pay attention to adjust the position of travel switch.
1、 Working principle of injection molding machine
Injection molding is to use the thermophysical properties of plastics to add materials from the hopper into the barrel,
The outside of the barrel is heated by a heating ring to melt the material, and an external power motor is installed in the barrel to
Under the action of the screw, the material is conveyed and pressed forward along the screw groove
The material is plasticized, melted and homogenized gradually under the dual effects of external heating and screw shearing,
When the screw rotates, the material will melt under the action of the friction and shear force of the screw groove
The material is pushed to the head of the screw, at the same time, the screw moves backward under the reaction of the material, making the screw
The head forms the storage space, completes the plasticization process, and then the screw pushes the piston of the injection cylinder
Under the action of force, the molten material in the storage chamber is injected into the mold through the nozzle at high speed and high pressure
In the mold cavity of the tool, the molten material in the mold cavity is in the process of closing after pressure maintaining, cooling and solidification
Under the action of the die mechanism, open the die, and handle it through the ejector and handle it through the ejector
The shaped products come out from the top of the mould.
2、 Classification of injection molding machines
According to the configuration of mold closing parts and injection parts, there are three types: horizontal type, vertical type and angle type
(1) Horizontal injection molding machine: horizontal injection molding machine is the most commonly used type. Characteristic of the injection assembly
The center line is concentric or consistent with the center line of the mold assembly, and parallel to the installation ground. Its superiority
The point is that the center of gravity is low, the work is stable, the mold installation, operation and maintenance are more convenient, and the mold is opened
Large, small space, but large area, large, medium and small machines are widely used.
(2) Vertical injection molding machine: its characteristic is that the axis of the mold closing device and the injection device is arranged in a line
And perpendicular to the ground. The utility model has the advantages of small floor area, convenient mold assembly and disassembly, and easy insert installation,
Since the hopper falls into the material, it can be plasticized evenly, and it is easy to realize automation and automatic lines of multiple machines
Management and other advantages. The disadvantage is that the ejected products are not easy to fall off automatically, and they often need to be taken manually or by other methods
It is not easy to realize fully automatic operation and injection of large-scale products.
(3) Angle injection molding machine: the axes of the injection device and the mold closing device are mutually arranged vertically. according to
The relative positions of the injection assembly center line and the installation base surface are horizontal, vertical and horizontal
The injection assembly line is parallel to the base plane, while the center line of the closing assembly is vertical to the base plane
The center line of the injection assembly is vertical to the base plane, while the center line of the closing assembly is vertical to the base plane
Parallel faces. The advantage of angle injection machine is that it has both the advantages of horizontal and vertical injection machine, especially
The utility model is suitable for the mould of products with asymmetric geometry of side gate.
3、 Structure of injection molding machine
According to the requirements of injection molding process, the injection molding machine is a kind of machine with strong mechatronics,
It is mainly composed of injection parts, mold closing parts, fuselage, hydraulic system, heating system, control system
Charging device, etc.
(1) Typical structure of injection parts
1. Composition of injection parts
The working principle is: during pre molding, the screw in the plasticizing part is driven by the hydraulic motor
One end of the spindle is connected with the screw key, the other end is connected with the hydraulic motor key, and the screw rotates
During rotation, the material is plasticized and the plasticized molten material is pushed into the storage chamber at the front of the barrel, the same as this
When the screw moves backward under the reaction of materials, and the thrust seat moves backward through the thrust bearing
Pull the piston rod straight backward through the nut to complete the measurement. When injecting, the rod cavity of the injection cylinder enters
The oil pushes the piston rod through the bearing to complete the action, and the oil enters the rod cavity of the piston to push the piston rod and the screw rod
Complete the injection.
2. Plastic parts
There are two kinds of plasticizing parts: plunger type and screw type. Here is an introduction to screw type.
The screw type plasticizing parts are mainly composed of screw, barrel, nozzle, etc. the plastic in the rotating screw
During continuous propulsion,