What are the most common causes of welding defects and how can they be eliminated?

The most common welding problems and how to eliminate them

Faulty film seals can lead to leaking packaging, material loss and customer complaints. That is why it is so important to understand where sealing problems originate and how to eliminate them effectively.

Why do weld defects occur?

Film welding is a process that requires precision - even a small change in parameters can affect the quality of the joint. Below are the most common causes of defects and their practical solutions.

• Welding temperature too low

  If the temperature of the die or heat strip is too low, the film will not bond effectively. The weld may look closed, but it will separate when stretched slightly.

  Solution: Check the temperature settings and make sure heating is even across the width.

• Too high a temperature

  Excessive heating can lead to scorching, deformation of the film and puncturing of the material.

  Solution: Lower the temperature or shorten the welding time. Choose the right material to withstand higher temperatures.

• Inadequate pressure

  Too little pressure results in insufficient bonding of the layers, and too much pressure can crush or damage the film.

  Solution: Adjust the clamping force according to the machine manufacturer's recommendations and the type of film.

• Contamination on the surface

  Dust, grease or adhesive residues between the film layers hinder proper sealing.

  Solution: Keep the film clean and regularly clean the heating elements and guides.

• Uneven film guidance

  Crooked positioning or displacement of the film can result in partial seals or no seals at all.

  Solution: Use guides, centring rollers and position control sensors.

• Poor film quality

  Some films (e.g. recycled or low-quality raw material) are more difficult to seal.

  Solution: Choose reliable suppliers and test the new film before putting it into production.

• Inadequate welding time

  Too short a time prevents the layers from bonding, too long leads to burn-through.

  Solution: Set the sealing time according to film type and machine technology (impulse, constant heat, ultrasonic).

How to prevent welding defects?

A well-functioning sealing line is not only about settings, but also about taking care of the whole process.

• Regular maintenance of machines

  Contaminated or worn heat strips are one of the main causes of weld defects.

• Training of operators

  Knowledge of the film, its structure and the relevant welding parameters is the basis for proper operation.

• Testing and quality control

  Checking the strength of welds (e.g. tensile test) allows irregularities to be detected early.

• Adaptation of the machine to the type of film

  Different film - different settings. The use of setting memories on modern sealing machines avoids mistakes when changing material.

Summary

Seal defects are most often caused by inadequate temperature, time or pressure settings, as well as by poor film guidance and dirty tools. By eliminating these problems and using regular quality control, packaging efficiency and seal life can be significantly improved.