Common problems of plastic bag making machine

Bag-making processing is the last process in the production and processing of plastic flexible packaging. If the quality of the bag-making is unqualified or the consumption is too high, then the previous processes such as film blowing and composite printing will be used up, and the downstream customers’ claims will cause huge influence to the factory’s production and operation.

1. What should I do if the contents leak or deteriorate due to incomplete heat sealing of the bag making machine?
Reason: Poor anti-pollution heat-sealability of the film, mainly because the resin used in the inner sealing layer is not suitable.
Countermeasures: Use a film with good anti-pollution heat-sealability. Generally speaking, ldpe has medium anti-pollution heat-sealability. EVA has good anti-pollution heat-sealability when the VA content is large. Ionic resin and metallocene polymer It has excellent anti-pollution heat-sealability.


2.What should I do if the sealing of the bag making machine is brittle

1. Heat sealing temperature is too high;
2. Pressure is too high;
3. Heat sealing time is too long;
4. The edge of the upper part of the sealer is too sharp or the coated PTFE is damaged;
5. The bottom seal is Silicone rubber is too hard;
6, during the compounding and curing process, a part of the adhesive penetrates into the film, and the substrate is affected by the adhesive, the toughness (that is, impact resistance) has decreased, and the brittleness has increased;
7, plastic composite packaging bags After cooling and placing, the strength of the heat seal increases, and it also tends to become brittle.


1. According to the heat sealing characteristics of the inner sealing layer material, select the appropriate processing temperature, pressure and heat sealing time;

2. Improve the surface condition of the upper heat sealing knife to make the surface of the sealer flat;

3. Wrap with polyethylene cloth The covering is intact;

4. Choose a silicone rubber pad with appropriate hardness.


What should I do if the bag warps after being heat sealed by the bag making machine?
the reason:
1. The thickness of the composite film is inconsistent;
2. The heat sealing temperature is too high or the heat sealing time is too long.
3. In the longitudinal heat sealing knife part, the running track of the composite film is not straight,
4. Insufficient cooling.
5. The curing time is not enough.
6. The surface substrate film has poor heat resistance.
7. Improper control of the tension matching of the composite substrate during the compounding process results in residual stress after curing and setting, especially when the thickness of the composite film is thinner, such failures are more likely to occur.
1. Adjust the tension of the floating roller.
2. Use inner sealing base material with low temperature heat sealability.
3. Adjust the heat sealing temperature to an appropriate temperature.
4. Cool down sufficiently.
5. Make film fully mature.
6. Reselect the surface substrate film.
7. Adjust the tension of each part of the composite processing equipment, and try to make the two matching substrates have the same shrinkage.



What should I do if the outer contour of the heat-sealed surface of the bag making machine is not clear after heat-sealing? (The knife pattern is not clear)
the reason:
1. Short cooling time.
2. Poor contact of the cooling plate
3. As the silicone pad is heated, the edges melt
4. Unbalanced longitudinal heat sealing force
5. The edge of the heat-sealing knife is irregular and blunt.
1. Adjust the cooling time
2. Adjust the cooling plate.
3. Replace or adjust the heat sealing knife
4. Prevent the edge melting caused by overheating of the silicone pad.



What should I do if the heat sealing strength of the bag making machine is poor after heat sealing?
the reason:
1. The adhesive in the composite film has not been sufficiently hardened.
2. The heat sealing conditions are inappropriate.
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-sealability of the ink is not strong, resulting in a decrease in the composite strength of the film at the heat-sealed part.
6. Dust, spray powder and other substances adhere to the hot cover.
7. The composite strength is low or the composite strength of the heat-sealed place drops too much.

1. Promote the hardening of the adhesive (curing and curing) through heat preservation and aging, and improve the composite strength and heat resistance of the composite film.
2. Choose the best heat-sealing conditions (temperature, time and pressure) according to the structure of the film, heat-sealing state, etc., or improve the heat-sealing method, and cool down immediately after heat-sealing.
3. Check the shelf life and storage conditions of the heat-sealable film. If the heat-sealable film uses the old batch of film and the film that has been heat-sealed, special attention is needed.
4. Increase the thickness of the heat-sealable film.
5. Change the type and grade of the heat-sealable film and use a film with anti-pollution heat-sealability.
6. Check whether the grade of the adhesive meets the requirements (the exudation of low-molecular substances in the resin may sometimes affect the composition of the adhesive)
7. Improve the heat sealing performance of the heat seal layer, control the content of the slip agent, and use mlldpe film.
8. Control the monomer content of MDI in the composite adhesive.


What should I do if air bubbles or uneven surfaces occur in the heat-sealed part of the bag making machine?
the reason:
1. When heat-sealing is performed on a structure containing hygroscopic materials such as nylon film, the hygroscopic film will generate air bubbles when it absorbs moisture.
2. The heat-sealing knife or heat-sealing silicone pad is uneven.
3. Insufficient heat sealing pressure.
4. Using one-component adhesives, such as neoprene adhesives, when heat-sealing bags, the heat cover is prone to pits.
1. Keep the raw materials and semi-finished products properly to avoid moisture absorption.
2. Check or adjust the heat sealing knife and heat sealing silicone pad.
3. Replace the adhesive.

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