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Common mold clamping device fault repair of plastic injection molding machine

2025/04/14 By Topstar

Clamping device of injection molding machine 1-2

The clamping device is one of the most critical components of the plastic injection molding machine during the molding process. The clamping device is essential for maintaining precise alignment, constant clamping force, and synchronous operation of the two halves of the mold during the injection cycle. When this system fails, it may cause problems such as insufficient clamping force, stuck or damaged second mold, mechanical failure, or unlocked mold creep. These failures not only affect the quality of the final product but also lead to increased downtime and rising maintenance costs. This guide will detail practical repair methods to deal with these challenges based on Topstar engineers’ experience.

Solutions to the insufficient clamping force of plastic injection molding machine

Insufficient clamping force is one of the most common problems of plastic injection molding machines. This failure occurs when the clamping force provided by the mold clamping device during the injection process is insufficient to close the two halves of the mold firmly. This will cause flashing and excess material to seep between the two halves of the mold. In more serious cases, it will cause defects in the molded parts, ultimately increasing scrap and rework rates. Improper machine settings, worn hydraulic components, or loose connections within the clamping system typically cause this problem.

To solve the problem of insufficient clamping force, the hydraulic system and mechanical fasteners need to be thoroughly checked. Vibration and continuous operation can cause fasteners to loosen over time, gradually reducing clamping pressure. In addition, wear or leakage of components can significantly reduce clamping efficiency. It may be necessary to replace worn parts or recalibrate hydraulic pressure.

So first check:

  • All screws, bolts, and fixtures are adequately tightened to ensure that the mold is firmly fixed to the clamping device.
  • Hydraulic seals and cylinders are carefully inspected and replaced in time if they are worn.

clamping force of plastic injection molding machine

The second mold is stuck, or the template is damaged

The second mold stuck, or template damage is also a common and troublesome failure in the clamping device. “Second mold” refers to the half mold that keeps moving during the molding cycle. When this portion of the clamping device gets stuck or releases improperly, it can cause mold parts to become misaligned or even physically damaged. Template damage usually manifests as bent or cracked edges caused by excessive force or uneven pressure distribution during clamping.

To solve these problems, the cause of mold sticking must first be diagnosed. These include:

  • Misalignment of the moving mold halves;
  • Obstruction of the clamping path;
  • Failure of the hydraulic system causing unsmooth operation;

Then, the wear and alignment accuracy of the moving parts will be checked. Simple adjustments, cleaning and lubricating the sliding surfaces, or realigning the mold can solve the sticking problem. Special attention must be paid to the guide pins or rails that ensure the correct movement of the second mold.

Damage to the mold plate usually requires a more detailed assessment, checking for signs of excessive pressure in the damaged area and recalibrating the clamping device to ensure that the two mold halves are correctly synchronized. If necessary, the damaged mold plate should be repaired or replaced, primarily if the damage affects the dimensional accuracy of the molded part.

Resolving mechanical failures in the clamping device

Mechanical failures in the mold clamping device of a plastic injection molding machine can seriously affect production quality and machine life. These failures may include:

  • Damage or wear of components such as hinges, locking mechanisms, or guide components;
  • Occurring due to long-term use, insufficient maintenance, or improper operation;

Failure of mechanical components usually leads to reduced clamping pressure, misalignment between the two halves of the mold, or even complete system shutdown, resulting in production delays and increased scrap rates. To repair mechanical failures effectively, the entire clamping assembly must be carefully inspected.

  • Check all moving parts for signs of wear, cracks, or deformation, and confirm that all connection points are firm and reliable;
  • The overall design of the mechanical system identifies any design defects;

In many cases, worn parts must be replaced to restore full functionality. For example, suppose the locking mechanism cannot engage properly due to wear. In this case, new parts that meet the specifications should be replaced. If there are problems with the overall design, optimizing the component geometry and replacing it with a higher grade material is recommended.

Resolving mechanical failures in the clamping device

Troubleshooting mold creep problems

Mold creep refers to the inability of the mold of the plastic injection molding machine to demold or accidentally slip during the mold opening and closing process, resulting in serious misalignment, resulting in part defects, increased wear of mold components, and other problems.

To solve the mold creep problem, first thoroughly evaluate the mechanical and automation components of the clamping system and carefully inspect the clamping components and guides. Generally speaking, loose mounting components or insufficient system tension will exacerbate such issues. In many cases, the creeping problem can be solved by simply tightening the screws and recalibrating the clamping device. In addition, the hydraulic system should be diagnostically tested to verify that it provides continuous and stable pressure. Inconsistent hydraulic pressure can also lead to incomplete unlocking or unexpected slipping during operation. Therefore, it is necessary to replace or repair defective hydraulic seals and ensure that the control valve is operating normally.

How to ensure the stability of the clamping device of the plastic injection molding machine?

Topstar’s plastic injection molding machines have highly wear-resistant copper sliding feet to ensure long-term operation even under high pressure. In addition, our machines are equipped with double sliding feet, which significantly facilitates the adjustment of the platen parallelism. This dual support maintains even clamping force across the entire mold, reducing uneven wear.

In addition, the full range of plastic injection molding machines is equipped with a one-touch mold adjustment system, which is standard. One-touch clamping significantly reduces mold adjustment time, allowing operators to quickly and easily readjust and calibrate the mold. One-touch mold adjustment improves production efficiency and consistency, ensuring more durability and reliability.

In summary

Common problems such as insufficient clamping force, second mold stuck or mold damage, mechanical failure, and mold opening creep can be solved by firmly installing, regularly tightening screws and hardware, and thoroughly checking hydraulic devices and mechanical systems. To avoid these failures, Topstar uses a copper slide, double slide, and one-button mold adjustment system to reduce common failure

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