Molding process of injection molding machine
·The granular plastic in the hopper of the injection molding machine falls into the feeding port of the feeding barrel, the heated barrel and the rotating screw generate shear heat, which melts the granular plastic into a viscous flow state, and continuously delivers it to the front end of the barrel from the feeding port of the barrel.
·Through the injection cylinder, the screw is pushed forward, so that the molten plastic at the front end of the barrel is pushed out and injected into the closed mold, which is filled with the mold cavity, and solidified into the shape given by the mold cavity after pressure maintaining cooling. After opening the mould, eject the products, and then take the products out of the mould. This is an operation process of injection molding.
·Cycle diagram of injection molding machine
Basic structure of plastic machine
Injection device, mold transfer device, heating and cooling device, electrical device, hydraulic system, protection and protection device.
1 injection device
1) The injection molding machine hopper is filled with granular plastic, which falls from the hopper to the feeding seat and enters the feeding port of the barrel. Driven by the rotating force of the hydraulic motor, the screw rotates, continuously pushing the molten plastic to the front end of the screw head, and then driven by the injection cylinder, the screw moves forward. The retaining ring, by the reaction of the injection force, moves backward to seal the screw slot and prevent the reverse flow of the molten plastic Move. Thus, the molten plastic is pushed out of the nozzle mouth and injected into the mold.
2) Name of injection device and main parts:
Injection device diagram
3) Connection position and function of main parts of injection device
The injection base is connected with a screw and a hydraulic motor, and the injection cylinder is installed on two sides of the feeding base, and is connected with the injection base. The screw is installed on the injection seat and connected to the transmission shaft of the hydraulic motor. The other end enters the barrel through the charging seat.
The charging seat is also equipped with a hopper, which is divided into a general charging hopper and a drying hopper. The drying hopper has a fan, which sends the air into the resistance heating chamber. After the cold air passes through the heating chamber, it sends out the dry hot air. The hot air flows from the lower part of the hopper to the air outlet above the hopper, so as to dry the granular plastic in the drying hopper from the bottom to the top.
The feeding metering scale is used to control the amount of pre molding and injection molding. The screw is composed of a screw body, a stop ring and a screw head. The screw is used to transport mixed plastic. The stop ring prevents the molten plastic from flowing back during injection. The hydraulic motor drives the screw to rotate and the injection cylinder pushes the screw forward and backward.
The nozzle head is connected to the barrel, the nozzle mouth is close to the mold gate by moving the oil cylinder forward, and the molten plastic is injected into the mold cavity through the nozzle to form products. Therefore, the main function of the injection device is to plasticize plastic particles, store the molten plastic and inject it into the mold through high pressure and high speed.
2 mold shifting device
1) The mould shifting device can load the mould for opening and closing, adjust and control the mould shifting distance according to the different thickness of the mould, lock the mould to bear the injection pressure, and has the functions of pulling and inserting the core and ejecting the products.
2) Drawing of mould shifting device and names of main parts:
Drawing of mould shifting device
Drawing of mold adjusting device
3) Connection position and function of main parts of mould shifting device:
The die closing cylinder is installed on the back template, which pushes the double elbow mechanism to pull the moving template forward and backward. The mould adjusting mechanism consists of hydraulic motor, gear driving mechanism, mould adjusting nut, etc. The rotation of the hydraulic motor drives the main transmission gear on the hydraulic motor to drive the big gear, and the big gear drives the adjusting gear, that is, the adjusting nut. The adjusting nut rotates on the pull rod thread to push the back and forth movement of the template, so as to change the distance between the front and back templates and meet the requirements of mold installation with different thickness.
The front formwork is fixed on the side near the nozzle head, the middle formwork is a movable formwork, the front formwork and the movable formwork are used to install the formwork, and the rear formwork is used to adjust the distance between the formworks. The pull rod connects the front and back formwork and the moving formwork to form a force closed system, which bears the injection pressure. The ejecting cylinder is installed on the moving formwork, which is used for ejecting products. The core pulling and inserting cutting plate is installed on the moving formwork, which plays the role of core pulling and inserting for the mold with core pulling and inserting.
3 heating and cooling device
1) Heating is to melt the plastic particles in the feeding barrel into viscous flow. Cooling is to cool the feeding seat, mold and oil temperature.
2) Heating is to install an electric heating ring on the outer wall of the barrel, set the plastic processing temperature through the computer operation display screen, the electric heating ring is electrified for heating, and the thermocouple on the barrel senses the actual temperature of heating to the computer operation display screen; The display shows the actual temperature of the barrel at that time. When the temperature is added to the range of the set temperature and kept warm for another 15 minutes, the pre molding and injection molding can be started. If it is not within the range of the set temperature, the pre molding and injection molding actions of the injection molding machine cannot be started.
After the plastic is heated and melted by the electric heating ring, press the pre plastic contact film key to pre plastic, the screw rotates under the drive of the hydraulic motor, and the plastic particles transported to the feeding barrel are pushed to the front end of the screw through the screw screw spiral groove continuously. Because the nozzle is blocked by the mold gate, the continuous pushing of the melting plastic produces extrusion pressure at the front end of the screw. This kind of extrusion pressure is called the pre plastic back pressure. The pre plastic back pressure can The volatiles, such as water vapor and air, in the plastics which are pre molded to the front of the screw are extruded out and discharged from the charging port of the barrel.
Because of the shear and extrusion pressure produced by the rotation of the screw, the molten plastic flows and rubs in the gap between the barrel and the screw, generating heat and accelerating the melting of the plastic. In addition, when injection molding, the screw moves forward to cause the molten plastic in the screw groove to flow, mix and remelt. Heat source of plastic melting: there are electric heating circle, shear heating during pre molding and shear heat generated by moving during injection;
3) Main parts and functions of the cooling device: the cooling device has a cooler and a heat exchanger, and the cooler is a cooling mold and a feeding seat