injection nozzle design

Injection nozzle design

The injection nozzle can be divided into straight through nozzle, locking nozzle, hot runner nozzle and multi channel nozzle

Straight through nozzle is a widely used nozzle, which is characterized in that the spherical surface of the nozzle is in direct contact with the spherical surface of the main pouring sleeve of the mold, and the arc radius and flow channel of the nozzle are smaller than that of the mold. During injection, high-pressure melt is directly filled into the mold cavity through the sprue system of the mold, with high speed, small pressure loss and convenient manufacturing and installation.

Locking nozzle is mainly used to solve the salivation problem of straight through nozzle, which is suitable for the processing of low viscosity polymers (such as PA). During pre molding, the nozzle flow channel can be closed to prevent melt salivation, and during injection, it can be opened under the action of injection pressure to inject the melt into the mold cavity.

The working principle of the injection cylinder is: when the injection cylinder feeds oil, the piston drives the piston rod and its bearing placed in the thrust seat to push the screw forward or backward.

Through the nut at the head of the piston rod, the axial position of two parallel piston rods and the axial position of the injection screw can be adjusted synchronously. When the thrust seat is injected, the thrust seat pushes the screw through the thrust shaft for injection; During pre molding, the oil motor drives the thrust shaft to drive the screw to rotate to realize pre molding.

When the oil is fed into the pedestal oil cylinder, the forward or backward action of the injection seat is realized, and the injection nozzle is ensured to be in close contact with the circular arc surface of the main pouring sleeve of the mold, resulting in the injection seat pressure that can close the melt.

Accuracy requirements for injection parts

After assembly, the integral injection part shall be placed on the frame, and the nozzle must be closely connected with the main pouring sleeve of the mold to prevent overflow. It is required to make the center line of the injection part concentric with the center line of the clamping part; In order to ensure the matching accuracy between 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 positioning center hole of the barrel and the symmetry of the center line;

For horizontal machines, the parallelism of the two guide holes of the displacement cylinder and the symmetry to its center must also be guaranteed, while for vertical machines, the parallelism of the two displacement cylinder holes and the positioning center hole of the barrel and the symmetry to the center line must be guaranteed.

The factors affecting the above position accuracy are the dimensional accuracy, geometric accuracy, manufacturing accuracy and assembly accuracy of the hole and shaft of the related parts.

Clamping part clamping part is one of the important parts of the injection molding machine. Its function is to realize the opening and closing movement, make the mold close, produce the system elastic deformation, achieve the mold locking force and lock the mold.

Requirements for clamping parts:

① The opening and closing die movement of the moving model shall be high-speed, stable and silent

② The clamping mechanism must meet the requirements of rated clamping force and reliably lock the mold;

③ The clamping parts have enough mold space and template stroke;

④ The moving model movement should be reliable and safe, protect the personal and mold safety, and set up double insurance;

⑤ The clamping parts and their molds have sufficient strength and rigidity.

The mold closing parts are composed of mold closing frame, mold closing mechanism, mold adjusting device, protection device, ejection device, etc