Cause Analysis

solutions

The anti-contamination heat-sealing property of the film is poor, and the resin used for the inner seal layer is not suitable.

A film with good anti-pollution heat sealing properties is used. In general, LDPE has a moderate anti-pollution heat sealability, EVA has good anti-pollution heat sealability when VA content is large, LDPE also has good anti-pollution heat sealability, and ionic resin and metallocene polymer Excellent anti-pollution heat sealability.

Cause Analysis

solutions

（1）The heat sealing temperature is too high.

（2）over stressed.

（3）Heat sealing time is too long.

（4）The edge of the upper sealer is too sharp or the coated Teflon is damaged.

（5）The silicone rubber at the bottom seal is too hard.

（6）During the compounding and curing process, a portion of the binder penetrates into the interior of the film. The substrate is affected by the penetration of the binder, the toughness (impact resistance) is lowered, and the brittleness is improved.

（7）After the plastic composite packaging bag is cooled and placed, the heat sealing strength is increased, and there is also a tendency to become brittle.

（1）Depending on the heat sealing properties of the material of the inner seal layer, the appropriate processing temperature, pressure and heat seal time are selected.

（2）Improve the surface condition of the upper heat sealer and smooth the surface of the sealer。

（3）Covered with Teflon cloth.

（4）Choose a silicone rubber mat of the right hardness.

Cause Analysis

solutions

1）Composite film thickness is inconsistent。

（2）The heat seal temperature is too high or the heat seal time is too long.

（3）In the longitudinal heat sealing knife portion, 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 is inferior in heat resistance.

（7）In the compounding process, the tension matching of the composite substrate is improperly controlled, resulting in residual stress after the ripening and setting, especially when the thickness of the composite film is thin.

（1）Adjust the tension roller tension.

（2）An inner sealing substrate having a low temperature heat sealability is selected.

（3）Adjust the heat seal temperature to a suitable temperature.

（4）Cool down sufficiently.

（5）Fully matured.

（6）Reselect the surface substrate film.

（7）Adjust the tension of each part of the composite processing equipment, try to make the recombination rate of the two composite substrates equal。

Cause Analysis

solutions

（1）Cooling time is short.

（2）Poor contact in the cooling plate.

（3）Since the silicone pad is heated, the edge portion is melted.

（4）The longitudinal heat sealing force is not horizontal.

（5）The edges of the heat seal knives are not neat and blunt.

（1）Adjust the cooling time.

（2）Adjust the cooling plate.

（3）Replace or adjust the heat seal knife.

（4）Prevents edge melting caused by overheating of the silicone pad.

Cause Analysis

solutions

（1）The binder in the composite film has not been sufficiently hardened.

（2）The heat sealing conditions are not appropriate.

（3） The distance between the heat seal knife and the cooling knife is too long.

（4）The inner seal film has a problem.

（5）The heat-resistant sealing property of the ink is poor, resulting in a decrease in the composite strength of the heat-sealed portion film.

（6）Dust, dusting and other substances adhere to the hot cover.

（7）The composite strength is low or the composite strength at the heat seal is excessively reduced.

（1）The curing of the adhesive is promoted by curing (aging, curing), and the composite strength and heat resistance of the composite film are improved.

（2）According to the structure of the composite film, the heat-sealing state, etc., the best heat sealing conditions (temperature, time and pressure) are selected, or the heat sealing method is improved, and cooling is performed immediately after heat sealing.

（3）Check the shelf life and storage conditions of the heat seal film. If the heat seal layer uses the old batch film and the heat seal film, pay special attention.

（4）Increase the thickness of the heat seal layer film.

（5）The type and grade of the heat seal layer film are changed, and an inner seal film having anti-contamination heat sealability is used.

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

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

（8）Control the monomer content of MDI in the compound adhesive.

（9）Check the degree of processing of the hot cover.

（10）Replace the ink (preferably with two-component ink).

（11）Change the printed pattern of the package so that the printed portion avoids the heat-sealed portion or changes the heat-sealing method. (Special attention to metal inks should not be printed on the seal).

Cause Analysis

solutions

（1）When heat-sealing is performed on a hygroscopic material structure such as a nylon film, bubbles are generated when moisture absorption film absorbs moisture. (2) Heat sealing knife or heat sealing silicone padNot flat.

（3） The heat seal pressure is insufficient.

（4）With a one-component adhesive, such as a neoprene adhesive, the hot cover is prone to bumpy pits when the bag is heat sealed.

（1）Keep raw materials and semi-finished products in a safe place to avoid moisture absorption.

（2）Check or adjust the heat seal knife and heat seal silicone pad.

（3）Replacement adhesive。

Cause Analysis

solutions

1）Excessive corona treatment of the heat-seal substrate film results in partial breakdown thereof.

（2）High slip agent content in the film。

（3）The heat resistance of the substrate itself is poor or the content of the recycled material is too high.

For the commonly used blown film substrates, the heat sealability is affected by factors such as the extrusion temperature, the blow ratio and the draw ratio, the condensation line, and the recycled materials used, in addition to the influence of the resin grade.

The heat sealability of the inflation film will decrease as the extrusion temperature increases and the degree of oxidation increases.

A certain inflation ratio and traction ratio are beneficial to the improvement of the heat seal strength, but since the film inflation and traction actually cause the molecules entering the high elastic state to be oriented, accelerate and promote the crystallization, the result is the orientation strength of the film. At the same time, the heat sealability, that is, the heat seal fastness is reduced, and therefore, the excessive blow ratio and the draw ratio are not suitable.

The high condensation line indicates that the inflation is carried out in a liquid state. Inflation and traction do not produce molecular orientation, and the film can only be thinned, and the liquid free-moving polymer molecules are not oriented, and the produced film is close to the cast film. , has a good heat sealability. Conversely, if the condensation line is too low, the inflation is carried out in a high elastic state of the polymer, and the inflation not only makes the film thin. Moreover, the molecules are oriented under the action of the inflation force, and the crystallization of the polymer is promoted, resulting in deterioration of the heat-sealing property.

The recycled material used in the film undergoes multiple thermal degradations, and the heat sealing temperature is greatly increased.

（4）The adhesive has not yet fully hardened.

（1）Check the shelf life of the film for the main storage conditions, pay special attention when using the old batch number, slip agent content or heat treated film.

（2）Increase the thickness of the film.

（3）Check the type or grade of adhesive.

（4）Check the degree of treatment on the heat seal level and find that the problem is replaced in time.

Cause Analysis

solutions

（1）The curing temperature is high and the slip agent loses its effect at high temperatures.

（2）The adhesive penetrates into the surface of the inner layer, which affects the friction coefficient of the surface of the substrate film, especially in the case of thin film and excessive corona treatment.

（3）The film substrate itself is poor in slipperiness.

（1）Strictly control the curing conditions.

（2）Check the type or level of adhesive.

（3）Replace the substrate or use dusting.

Cause Analysis

solutions

Quality problems with films and adhesives.

Powder when making bags.

Cause Analysis

solutions

（1）The bag length of the bag mechanism mechanism is too large.

The method of lengthening the length of the bag can be divided into two categories, namely: mechanical fixed length and electrical fixed length. The mechanical fixed length is fixed length using an overrunning clutch plus a pneumatic or voltage trimming system. The fixed length of the electric appliance is fixed length using a stepping motor or an AC servo motor. These two types of fixed length systems are composed of a heat seal, a cutter linkage system and a film transport system, which are linked together by electric eyes. If the linkage or coordination produces an error, it will cause a dimensional deviation associated with the length of the bag.

（2）Electric eye tracking is not allowed.

When the electric eye cannot find or can not find the cursor continuously and stably, that is, when the tracking is not accurate, the bag length control cannot be discussed. The reasons for tracking inaccuracies are as follows:

① Electric eye problem: Photoelectric eye adjustment method and working condition are not properly selected.

First of all, to confirm whether the electric eye is adjusted, the electric eye reflection and the transmission selection are correct, and secondly to confirm the leading edge control or the trailing edge control, that is, the so-called polarity, and finally to confirm the tracking mode, such as: scanning type (that is, walking the fixed length first, Then scan the color mark), fixed length check type (that is, check whether there is a color mark after the fixed length, is too much or not in place).

②  Cursor printing or spacing problem

a. The cursor design is unreasonable, the available scanning area is too narrow, and the cursor is not obvious compared with the surrounding area.

b. The cursor spacing has changed. Due to the influence of stretching and shrinkage in the printing and compounding process, the distance between the actual cursors has been changed with respect to the original set size. At this time, the actual input size is changed according to the actual data. The uneven stretching caused by the compounding process, the frequent adjustment of the coloring of the printing process, the unevenness caused by the large temperature change, and the stretching also have a direct influence on the error related to the length of the bag. In addition, the thin film thickness of the composite film bag substrate and the ruffle edge will have a certain impact on this, and it is also one of the main reasons for the deviation of the finished bag. In general, the composite film processed by the dry composite process has a relatively high rate of bag making.

③   Film resistance: When the film resistance is too large (affected by the degree of compression of the film strip and the friction coefficient of the composite film), the film may not be in place or the cursor may be deformed, thereby affecting the scanning effect, resulting in the length of the bag. Relevant deviation.

④   Pre-adjusted film feeding length: Pre-adjusted film feeding length (when adjusting white bag) is too much error with actual bag size. When the scanning area does not cover the cursor, it can directly lead to tracking inaccuracy.

（3）The effect of plastic composite film bag processing speed

When the processing speed of the bag making is fast, the deviation related to the length control is obviously increased. The main reason is that the mechanical control is affected by the high speed inertia, and the actions of the cutter and the feed roller are affected to some extent. Since the degree of influence of the action of the heat sealing knife, the cutter and the feeding roller is different, the deviation of the bottom margin and the like is increased. However, for a bag making machine with a high manufacturing precision, it is possible to form a quantitative system error, which can be basically stabilized after adjustment.

In addition, when the process of speeding up and slowing down the film is too fast, due to the existence of inertia, it is easy to cause a large error in filming.

（4）Operating factor

①   The pressure setting of the film rubber roller pressure cylinder is insufficient.

②   The tension of each section is not set properly. Especially for thin composite films, when the tension is too large, the pitch may be changed, and the tension should be set carefully.

（1）Adjust the fixed length system.

（2）Adjust the working state of the electric eye.

（3）Check for cursor printing problems or spacing problems and adjust them.

（4）Check the degree of compression of the film strip and whether the friction coefficient of the composite film is appropriate.

（5）The pre-adjusted film feeding length (when adjusting the white bag) and the actual bag size should be as accurate as possible.

（6）Reduce the bag making speed, and adjust the bag making speed slowly.

（7）Adjust the pressure of the rubber roller, the cylinder pressure and the tension of each part.

Cause Analysis