Everyone knows that the tie rods (green columns) of ordinary shaft type (machine hinge) injection molding machines of injection molding machines are easier to break than the fully hydraulic tie rods. Qingdao Jiaozhou injection molding machine shaft type design, due to the consideration of fragmentary rigidity, because the shaft type is based on rigid clamping force, so the diameter of the ordinary tie rod is large. But the strange thing is that its pull rod is easy to break, especially in some industries, such as consumer video cassette boxes, plastic fast food forks and other industries. Due to thin product walls, good data mobility, large molding area, and fast consumption speed, The breakage of the connecting rod (hinge) of the tie rod is very common, and even the template breaks.
First, the cause of the fracture of the tie rod
1. Overload breaking: As the shaft type obtains the clamping force by the deformation of the four tie rods, if the length of the four tie rods is different, the deformation is different. If one of the four is shorter, the shorter tie rod can Accepting a 1/4 clamping force far beyond what it should accept, incurring pull off.
2. Fatigue damage: The task process of the injection molding machine is the process of alternating stress, so any element that causes stress concentration can cause fatigue damage. Such as: 1. Defects in data 2. Short fillets, undercuts, etc. at transitions 3. Steps with large changes in shaft race 4. Thread surface roughness is too large 5. Surface flaws or processing threads may accidentally destroy the optical axis appearance 6 The improper heat treatment of the thread surface causes stress concentration. 7. The thread is compressed for a long time, which causes the surface to be damaged due to insufficient strength (at the adjusting nut).
3. Pull-out caused by composite strain: If the mold is uneven, the comprehensive error of the length of the connecting rod (hinge), the height of the bearing seat and the length of the tie rod is too large. When the connecting rod is crimped, the two sides are unevenly stressed. . Then: 1. After the template is formed, the tie rod is bent, and the tie rod is easily broken under the action of bending stress and tensile force. 2. The product flashes are formed. Operators who have experienced a short period of time will further increase the clamping force. As a result, the screw is overloaded and broken and the mold is overloaded and deformed.
4. Damage caused by instantaneous impact stress: Because the shaft type dared to release before mold opening, so: 1. The instant impact during mold opening caused the machine to vibrate and caused damage to the tie rod and other parts. 2. Due to the entire mold clamping part (including (Mold) Long-term adherence to stress conditions will lead to premature fatigue of parts.
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