Four common problems in packaging bag making, and we have a solution!

I. Poor Heat Sealing Strength

Poor heat sealing strength refers to the strength of the sealed area being below the standard requirement.

1. Causes

1. The adhesive in the composite film has not fully cured.

2. Improper heat sealing conditions.

3. The distance between the heat sealing knife and the cooling knife is too long.

4. There is a problem with the inner sealing layer film.

5. The heat resistance of the ink is poor, resulting in a decrease in the composite strength of the film at the heat sealing part.

6. Dust, spraying, etc. adhere to the heat sealing surface.

7. Low composite strength or excessive decrease in composite strength at the heat sealing area.

2. Solutions

1. Promote the curing (maturation, solidification) of the adhesive through heat preservation aging to improve the composite strength and heat resistance of the composite film.

2. Select the optimal heat sealing conditions (temperature, time, and pressure) according to the structure of the composite film and the heat sealing state, or improve the heat sealing method, and cool immediately after heat sealing.

3. Check the shelf life and storage conditions of the heat sealing layer film. Pay special attention if the heat sealing layer uses old batch films and films that have undergone heat sealing treatment.

4. Increase the thickness of the heat sealing layer film or check the degree of treatment of the heat sealing surface.

5. Change the type and grade of the heat sealing layer film, and use an inner sealing layer film with anti-pollution heat sealing properties.

6. Check whether the grade of the adhesive meets the requirements (the exudation of low molecular weight substances in the resin sometimes affects the composition of the adhesive).

7. Improve the heat sealing performance of the heat sealing layer (substrate), control the content of the slip agent, and use MLLDPE film.

8. Control the monomer content of MDI in the composite adhesive.

9. Change the ink (preferably use two-component ink).

10. Change the printing pattern of the packaging bag so that the part with ink avoids the heat sealing part, or change the heat sealing method (pay special attention not to print metal ink on the sealing area).

II. Dimensional Errors

1. Causes

1. The length setting system of the bag making machine has excessive errors.

2. Inaccurate photoelectric tracking.

3. Influence of the plastic composite film bag making processing speed.

4. Operational factors, such as improper tension control, insufficient pressure setting of the film-feeding rubber roller pressure cylinder, etc.

2. Solutions

5. Adjust the length setting system.

6. Adjust the working state of the photoelectric eye.

7. Check for and adjust any cursor printing or spacing problems.

8. Check the tightness of the pressure-sensitive film ruler and whether the friction coefficient of the composite film is appropriate.

9. The pre-adjusted film feeding length (when adjusting the blank bag) should be as accurate as possible to the actual bag making size.

10. Reduce the bag making speed, and the adjustment of the bag making speed should be carried out slowly.

11. Adjust the pressure of the film-feeding rubber roller, the cylinder pressure, and the tension of each part.

III. Spots and Bubbles on the Cover

Spots and bubbles on the cover refer to unevenness on the sealing surface.

1. Causes

1. When heat sealing on materials with hygroscopic properties such as nylon film, moisture absorption will produce bubbles.

2. The heat sealing knife or heat sealing silicone pad is uneven.

3. Insufficient heat sealing pressure.

4. Using a single-component adhesive, such as chloroprene rubber adhesive, during heat sealing bag making, the heat-sealed cover is easily uneven with small pits.

2. Solutions

1. Properly store raw materials and semi-finished products to prevent moisture absorption.

2. Check or adjust the heat sealing knife and heat sealing silicone pad.

3. Change the adhesive.

IV. Misalignment of Upper and Lower Sheets

Misalignment of upper and lower sheets refers to the problem that the front and back sides are not aligned during bag making.

1. Causes

1. The composite film is uneven in thickness and has ruffled edges.

2. The tension of the double floating roller is too small.

3. Some rollers rotate unevenly.

2. Solutions

1. Adjust the tension of the double floating roller.

2. Check and adjust the relevant guide rollers (such as compensation rollers, deviation adjustment rollers, etc.).

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