Injection screw machine plasticizing unit requirements.

Update:31-01-2019
Summary:

The technical requirements of the four components of th […]

The technical requirements of the four components of the plasticizing unit of the injection molding machine.
1. Nozzle
The straight-through nozzle is a commonly used nozzle, which is characterized in that the spherical surface of the nozzle is directly in contact with the spherical surface of the main casting sleeve of the mold, and the radius of the arc of the nozzle and the flow passage are smaller than that of the mold. When the injection is performed, the high-pressure melt directly passes through the runner system of the mold. Filled into the cavity, the speed is fast, the pressure loss is small, and it is convenient to manufacture and install.
The locking nozzle is mainly used to solve the problem of the flow of the straight-through nozzle, and is suitable for the processing of low-viscosity polymers such as PA. In the pre-plasticizing, the nozzle flow path can be closed to prevent the melt from flowing, and when injected, it can be opened under the action of the injection pressure to inject the melt into the cavity.
2. Injection cylinder
The working principle is: when the injection cylinder is oiled, the piston drives the piston rod and its bearing placed in the thrust seat to push the screw forward or backward. The axial position of the two parallel piston rods and the axial position of the injection screw can be adjusted synchronously by the nut of the piston rod head.
When the thrust seat is injected, the thrust seat pushes the screw through the thrust shaft for injection; while in the pre-plasticizing, the thrust shaft is driven by the oil motor to drive the screw to realize the pre-molding.
3. Block moving cylinder
When the oil shifting cylinder enters the oil, the forward or backward movement of the injection seat is realized, and the injection nozzle is ensured to be in close contact with the arc surface of the main casting sleeve of the mold, thereby generating an injection seat pressure capable of closing the melt.
4. Precision requirements for injection parts
After the nozzle is assembled, the integral injection part is placed on the frame, and the nozzle must be tightly engaged with the main mold sleeve to prevent flashing.
It is required that the center line of the injection part is concentric with the center line of the mold clamping part; in order to ensure the matching precision of the injection screw and the inner hole of the barrel, it is necessary to ensure the parallelism of the two injection cylinder holes and the center hole of the barrel and the center line symmetry. degree.
For horizontal machines, the parallelism of the two pilot holes of the seat shift cylinder and the symmetry of its center must also be guaranteed.