Analysis and Solution of Insufficient Opening Force of Injection Molding Machine

【Summary】:

1. The area of the opening oil pressure ring is too small. The opening force = the area of the opening oil pressure ring × the opening oil pressure. Under the condition of determining the maximum pressure, you want to increase the opening force. You can increase the area of the mold opening hydraulic ring by increasing the diameter of the cylinder or reducing the diameter of the piston rod. 2. The gap between the mold opening and the oil is too small. In the opening section, due to the small clearance between the hydraulic buffer sleeve and the inner hole of the front cover of the cylinder, the pressure oil is slow or difficult to enter the cylinder opening cavity, so the maximum mold opening force cannot be provided. Increase the clearance between the hydraulic buffer sleeve and the inner hole of the front cover of the cylinder, so that the pressure oil can quickly enter the mold opening cavity of the cylinder and

1.The area of the mold opening hydraulic ring is too small

Mould opening force = Mould opening oil pressure ring area × Mould opening oil pressure

Under the condition that the maximum pressure is determined, the mold opening force can be increased. The area of the mold opening hydraulic ring can only be increased by increasing the area of the hydraulic ring opening the mold, or by increasing the diameter of the cylinder or reducing the diameter of the piston rod.

2.The gap between mold opening and oil is too small

During the opening of the mold, the clearance between the hydraulic buffer sleeve and the inner hole of the front cover of the cylinder is too small, which causes the pressure oil to enter the mold opening cavity of the cylinder slowly, so it cannot provide the maximum mold opening force. Increase the clearance between the hydraulic buffer sleeve and the inner hole of the front cover of the cylinder, so that the pressure oil can quickly enter the mold opening cavity of the cylinder and form a mold opening force with a certain impulse, which may cause a certain impact when the mold is opened.

3.After the high-pressure clamping mode, theta angle exceeds 90 °, which leads to reverse hinge

The design of the hinge parameters and the stroke and installation position of the clamping cylinder determine the end position of the small hinge during the final high-pressure clamping and form an θ angle. The designed θ angle must ensure that the machine installed within the cumulative tolerance tolerance of each part. The θ angle must be less than 90 °. Once the θ angle exceeds 90 °, the small hinge will appear reverse hinge. At this moment, when the mold is opened, the hook hinge and the long hinge are actually moved in a straight direction to produce a larger clamping force. The small mold opening force is not enough to overcome the deformation force generated by increasing the clamping force, so the mold opening cannot be completed instantly.

4. Excessive mold clamping pressure and flow lead to overload of clamping force, excessive deformation of the hinge, and mold opening force cannot overcome the excessive deformation.

When the hinge of the machine hinge is designed, the enlargement ratio of the hinge when it generates a predetermined clamping force has also been determined. Based on this, the thrust of the required clamping cylinder can be designed to determine the diameter of the clamping cylinder. The cylinder also needs to have sufficient mold opening force. If the mold opening force is sufficient, the larger the diameter of the cylinder is, the better, but the cylinder diameter is too large and the cylinder thrust during clamping is too large, which overloads the clamping force (bad mold adjustment) When), the deformation force of the hinge is too large, and the mold opening force cannot overcome the excessive deformation force, which makes it impossible to open the mold. In this case, you can usually prevent the clamping force from being overloaded by limiting the high-pressure clamping pressure and flow. Be patient while adjusting the mold, and use the lowest clamping pressure to adjust the clamping force as much as possible.

5. Low mold opening pressure and small flow, resulting in small mold opening impulse

Due to the low mold opening pressure and small flow, the mold opening impulse is small, and the deformation force of the hinge cannot be overcome, especially the first stage mold opening flow provided by the servo control system is small, the mold opening impulse is smaller, and it is more difficult to open the mold. This problem can increase the mold opening impulse by modifying the controller's PID and mold opening slope.

6. The temperature rises after the pressure test of the mold, which makes it difficult to open the mold.

After loading and testing for a period of time, the mold heats up and expands, and the clamping force increases, which makes it difficult to open the mold. Pay attention to adjust the mold capacity in time to return the clamping force to the original value and avoid mold opening failure.

7. The shutdown time is too long after mold clamping, which makes it impossible to open the mold.

The shutdown time after mold clamping is too long, which causes the lubricant film of the machine hinge to completely disappear, and the deformation of the machine hinge is further increased, which makes it impossible to open the mold. Downtime.

8, mold back pressure, resulting in insufficient mold opening impulse

Setting the mold back pressure in the mold opening section of the oil line also results in insufficient mold opening impulse. If this is found, cancel the mold back pressure.

9. The frictional resistance in the hinge is too large, which leads to the mold opening resistance. The frictional resistance of the large pin and steel sleeve in the hinge is too large, which requires a larger mold opening force to overcome its frictional resistance:

(1) There is no deburring on the edge of the oil groove in the steel sleeve, causing burrs to wear into particles and enter the mating surface of the large pin and the steel sleeve, causing the mating surface to wear or burn the mating surface. Deburr and smooth, check again during installation, clean all surfaces and apply grease after installation.

(2) If there is insufficient lubrication or lubrication failure, the friction resistance will be too large. At this time, you can check whether each lubricating oil circuit is normal and whether the lubrication pump is normal.