Analysis of the Causes of Injection Molding Machine Faults and Preventive Measures

Hinge edge fracture
A. Excessive locking force
The maximum pressure of a general injection molding machine system is 140 bar, and the maximum stress of the hinge edge is also calculated based on 140 bar. Under normal operating conditions, the hinge edge will have a lifespan of several years. If the system pressure is raised above 140 bar, the stress borne by the hinge edge will exceed the safe range, causing damage to the hinge edge.
B. Poor operation
During normal operation of the injection molding machine, the mold requires sufficient locking force to withstand the strong pressure generated by the injection molding. To prevent the product from producing burrs or defects. If the locking force is not adjusted enough or the mold is installed improperly, resulting in flash on the product, this situation not only affects the product quality, but also causes damage to the hinge edge. The reason is that the appearance of flash increases the stretching length of the Goering column, and the stress on the hinge edge correspondingly increases. Long term flash damage to hinge edges.
C. Insufficient lubrication
The machine hinge needs to replenish lubricating oil every day to reduce the friction between the hinge edge and the hinge, and maintain the normal operation of the hinge edge. If lubricating oil is not replenished in a timely manner, the hinge edge may be easily burned and broken due to increased friction. In addition, if lubricating oil is regularly replenished, the expected effect may still not be achieved, which may be due to the displacement of the hinge, causing the lubricating oil hole to be blocked; Or the hinge edge oil pit may be contaminated and blocked, causing the lubricating oil to not be replenished properly and losing its lubrication effect. Ultimately, it causes damage to the hinge edge. Choosing the right lubricating oil is also necessary, as too thin oil is prone to loss, but too thick oil also lacks fluidity.
D. Poor design
If the injection molded parts are unevenly distributed in the mold, it can cause flash and increase the extension of the Corinthian column, causing damage to the hinge edges.
Fault prevention:
A. If the mold pressure is too high, the system pressure should be maintained at 140 bar and cannot be raised on its own
Some customers often mistakenly perceive that the locking pressure is insufficient due to the pressure gauge displaying approximately 110bar during high-pressure locking, which leads to the misconception that the pressure is insufficient and the system pressure is increased by over 140bar. In fact, the locking force has already reached the highest standard. Currently, the general pressure gauge has a simple structure and cannot respond in a timely manner to rapid pressure changes. That is, when high-pressure locking is used, the high-pressure pressure rises and drops rapidly. Therefore, when adjusting the maximum locking force, the pressure gauge can only display a pressure of about 110bar.
B. Poor operation
1. When using an injection molding machine, it is necessary to first consider installing a suitable mold. The required locking force for the product should not exceed the standard specifications of the injection molding machine. The calculation of the locking force can refer to relevant calculation methods.
2. When adjusting injection molding parameters, it is necessary to avoid injection pressure exceeding the locking force, excessive material or mold temperature, and fast injection speed. Additionally, whether the parallelism and rigidity of the mold meet the standards, and whether it is tightly pressed during mold installation.
C. Insufficient lubrication
Arrange employees to regularly replenish lubricating oil on the hinge edges, and also regularly check whether there is sufficient lubricating oil in the lubrication pipe and hinge edges. It should be adjusted as much as possible to ensure that the oil distributor does not match the oil supply of the hinge. If dirt is found in oil holes, it should be cleaned in a timely manner. If it is found that the hinge edge often lacks oil and the lubricating oil supply is normal, it is necessary to check whether the through-hole on the hinge (steel sleeve) position has moved.
Golingzhu fracture:
A. The cause of Lin Zhu fracture is basically the same as that of hinge edge fracture
In the locking structure, the hinge edge of the Goering column withstands strong injection pressure during injection molding. According to the design formula, both the column and hinge edge of the Corinthians meet the standards. So under normal operating conditions, the lifespan of the Corinthian column and hinge edge can be guaranteed. However, if there are operational issues and the locking pressure is raised beyond the safe range, the Corinthian column will be damaged and its lifespan will be reduced.
B. External reasons can lead to the breakage of the Corinthian columns: the geometric tolerance of the template exceeds the standard, and if the parallelism and verticality of the template exceed the standard, the force distribution of the locking structure will be affected. As a result, the four Corinthian columns will have to bear different tensile forces and their lifespan will be shortened.
The reasons for causing parallelism or verticality to exceed the standard can be divided into the following aspects:
1. The parallelism or verticality of the mold used exceeds the standard;
2. Loosen the screws used for tightening the locking structure, causing the structure to deform;
3. Failure to properly install parts after maintenance, resulting in tolerances exceeding standards;
4. Improper installation after repairing the mold adjustment structure, and some mold adjustment screw nuts are too loose or too tight.
Fault prevention:
A. Maintain system pressure at 140bar and do not self increase
Pay attention to the operation situation, avoid product flash, and choose a suitable mold.
B. Does the geometric tolerance of the template exceed the standard
Regularly inspect and rectify any deviations found to exceed the standard. The screws inside the locking structure should be ensured to be tightened, and if there is any loosening phenomenon, they should be tightened immediately to avoid affecting the locking structure.
Maintenance of the locking part:
1. Check daily whether the central lubrication system, its oil distributor, and lubricating oil pipe are working properly, and whether the cylinder is clean
2. Keep the moving template slide clean and lubricated
3. Avoid using locking molds that approach or exceed system pressure
4. Control the shape and position of the mold opening and locking actions in the most appropriate position to ensure smooth mold opening and reduce impact.
5. Avoid using excessively large and heavy molds