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Technical Requirements for Four Parts of Plastic Unit of Injection Molding Machine
1. Shooting nozzle
Straight-through nozzle is widely used. Its characteristic is that the nozzle spherical surface contacts directly with the spherical surface of the main casting sleeve of the die. The arc radius and runner of the nozzle are smaller than that of the die. When injecting, the high-pressure melt is directly filled into the die cavity through the runner system of the die, which has the advantages of high speed, low pressure loss and convenient manufacture and installation.
Locked nozzles are mainly used to solve the salivation problem of through nozzles and are suitable for the processing of low viscosity polymers such as PA. The nozzle runner can be closed during pre-moulding to prevent melt salivation, and the melt can be opened under injection pressure to inject into the cavity.
2. Injection cylinder
The working principle is that the piston drives the piston rod and its bearing in the thrust seat to push the screw forward or backward when the injection cylinder enters the oil. Through the nut of piston rod head, the axial position of two parallel piston rods and the axial position of injection screw can be adjusted synchronously.
When the thrust seat is injected, the thrust seat pushes the screw through the thrust shaft to inject, while in the pre-plasticization, the screw is driven by the oil motor to rotate to achieve pre-plasticization.
3. Seat shift cylinder
When the seat moves oil into the cylinder, the forward or backward movement of the injection seat is realized, and the arc surface of the injection nozzle and the main casting sleeve of the mould is closely contacted, thus producing the injection seat pressure that can seal the melt.
4. Accuracy Requirements for Injection Parts
After the nozzle is assembled, the integral injection parts should be placed on the frame, and the nozzle and the main casting sleeve of the die must be closely joined to prevent spillover.
In order to ensure the matching accuracy between injection screw and inner hole of barrel, it is necessary to ensure the parallelism and symmetry of two injection cylinder holes and positioning central hole of barrel.
For horizontal machine, the parallelism and symmetry of the two guide holes of the seat-moving cylinder must also be guaranteed.