What's Injection Molding Machine Tie Bar

An injection molding machine tie bar is a component that connects the moving and stationary platen of an injection molding machine. These bars are typically made of steel and are responsible for keeping the mold securely closed during the injection molding process. This ensures that the molten plastic material is injected into the mold cavity with precision, resulting in a consistent product.

The tie bars play a critical role in the overall functionality of an injection molding machine. They help to distribute the clamping force evenly across the mold, which helps to prevent deformation and warping during the molding process. Additionally, they help to reduce the wear and tear on other components of the machine, such as the molding platens and the hydraulic system.

When selecting an injection molding machine, it is important to consider the size and strength of the tie bars. Machines with larger tie bars are capable of producing larger molded products, while those with stronger tie bars are better suited for producing products that require a high level of precision.

Injection Machine Tie Bar Material & Treatment

Tie Bar Production Procedure

The production process of injection molding machine tie bars typically involves cutting, machining, and heat treating high-grade steel bar stock to exacting specifications to ensure optimum strength, durability, and precision. These tie bars are then carefully installed and secured to the injection molding machine's frame to maintain the structural integrity and stability necessary for efficient, high-quality injection molding operations.

Typical Reasons for Injection Machine Tie Bar Broken

1. Fatigue damage of injection molding machine

The working process of an injection molding machine is a process of alternating stress, so any factor that causes stress concentration may lead to fatigue failure. For example:

1) Steps with significant changes in shaft diameter.

2) The transition lacks rounded corners and cutting grooves.

3) Surface scratches or accidental damage to the surface of the optical axis during thread processing.

4) The surface roughness of the thread is too large.

5) The thread is compressed for a long time, and due to insufficient surface strength, it causes compression damage at the surface adjustment nut. 6) Improper heat treatment of the thread surface causes stress concentration.

7) Defects in the material of the pull rod (Golin column).

2. Rod (Corinthian pillar) overload and breakage

Due to the elbow style, the locking force is obtained through the deformation of four pull rods. If the length of the four pull rods is different, their deformation will be different. For example, if one of the four pull rods is shorter, the shorter pull rod may bear much more than the 1/4 locking force it should bear, leading to tensile fracture.

3. Temperature strain causes tensile fracture

If four pull rods are of different lengths, such as one long and three short, then the longer pull rod will be constrained by the other three rods due to the thermal stress caused by rapid temperature rise or fall, and will be in a static and unstable state, which will cause the pull rod to fracture.

4. Tensile fracture caused by composite strain

If the plastic shell mold is uneven, the combined error of the length of the connecting rod (hinge edge), the height of the bearing seat, and the length of the pull rod is too large. When the connecting rod is straightened, the force on both sides is uneven. So:

1) Causing the back template to swing, the pull rod is bent, and under the action of bending stress and tensile stress, the pull rod is prone to breakage.

2) Causing product trimming, inexperienced operators usually further increase the locking force, resulting in rod overload, breakage, and mold overload deformation.

5. Damage caused by instantaneous impact stress

Due to the fact that the locking force of the elbow type can only be released before mold opening, therefore:

1) The instantaneous impact during mold opening causes machine vibration and damages the pull rod and other parts.

2) Due to the fact that the entire plastic mold closing component remains under stress for a long time, it can lead to premature fatigue failure of the parts.

How to Prevent Tie Bar from Broken

1. In design, it is necessary to avoid sharp changes in shaft diameter. At the step or cutting groove, large rounded corners should be used as much as possible for transition, and materials with better comprehensive performance should be selected. Special treatment should not only solve the surface hardness of the thread (wear resistance), but also try to reduce surface stress concentration, improve surface smoothness, and minimize stress damage.
2. To ensure machining accuracy, especially the length of the connecting rod, the height of the bearing seat, the accuracy of the crosshead, and the positioning accuracy of the bearing seat in the template.
3. Special attention should be paid to aligning the length of the four pull rods during assembly or after removing the adjusting nuts, and adjusting the distance between the adjusting nuts and the rear template.
4. When there are burrs on the plastic shell, the cause should be analyzed. Do not unilaterally increase the locking force. If the plastic mold is found to be uneven, it should be ground flat. If the length of the connecting rod is uneven, it should be corrected, including copper pads, paper sheets, etc., or adjusting the mold nut.