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Common problems and solutions of hollow blow molding products

Views: 5     Author: HUAN Machinery     Publish Time: 31-10-2022      Origin: HUAN Machinery

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Common problems and solutions of hollow blow molding products

Hollow blow molding products are widely used in all walks of life, containers, drinks bottles, toys... It can be said that hollow products have been integrated into our life. Today, let's look at the common problems and solutions of hollow blow molding products.

First of all, the first problem with hollow blow molding products is usually large fluctuations in product weight.

The main reasons for this problem are as follows:

1. Abrupt change of type B embryo;

2. Uneven mixing of raw materials;

3. The feed section is blocked or bridged, and the extrusion is unstable;

4. The extrusion speed is unstable.

In view of the above problems, we can start from the following aspects:

1. Check and repair wall thickness control equipment to ensure that the mold is more stable;

2. Use appropriate material mixing equipment to properly extend the mixing time so that the raw materials are fully mixed;

3. Check whether there is blockage or other foreign matter blocking the entrance;

4. Reduce the inlet temperature appropriately to avoid "bridge" phenomenon;

5. Check whether the extruder is abnormal, whether the motor and gear box are loose or slip, and ensure that the screw speed is stable;

6. At the same time, we also need to check the electronic scale regularly to avoid the fluctuation of measuring instruments affecting the quality judgment;


Second, when the empty blow molding products are used to contain liquid, they often encounter unqualified capacity.

The main reasons for this problem are as follows:

1. The shrinkage rate of raw materials of different brands is different, and the cooling temperature of molds and blowing and molding solidification time are the reasons for excessive shrinkage of products. We need to analyze and solve the problem in a targeted way to make the product shrink within a controllable range;

2. In addition, the product wall thickness is too thick or uneven, resulting in deformation and depression. The product appearance does not meet the design requirements, the volume is not qualified.

We can also:

1. Repair and improve the mold, first meet the theoretical volume requirements;

2. Replace the raw material with smaller shrinkage rate, extend the blowing time, reduce the cooling temperature of the mold, and reduce the shrinkage rate of the finished product as much as possible;

3. Adjust the wall thickness controller to make the wall thickness evenly distributed and solve the concave shape and deformation problem of a single part;

4. Adjust the blowing time properly to make the product shape conform to the original design intention;

5. Or solve the problem by increasing the blowing pressure appropriately.

In addition, we found that the impact of weight on capacity is also critical. It's not a simple linear relationship where weight goes down by 1 kilogram and capacity goes up by 1 liter. The specific relationship between weight and volume requires a specific analysis of different barrel types.

The size problem is also a further extension of the volume problem. The size exceeds the standard category. The cause and solution are basically the same as the volume problem, and are not explained here. If the product control size can not be directly formed in the process of hollow blow molding, it can be solved by adjusting the appropriate process time, product wall thickness, selecting appropriate raw materials, and even using the external mold to control the quality requirements.

bus chair blow machine

In addition, the appearance of a product is the customer's first impression of product quality.

The black spots and black lines on the surface of the product are mainly caused by improper temperature setting of raw materials and carbonization; Carbides accumulated in the accumulator or head passage are removed; Foreign bodies are caused by foreign bodies.

For the above problems, we can check and solve the following methods:

1. Reduce the processing temperature appropriately;

2. Clean the runner system or reduce the injection pressure;

3, raw material purification, timely cleaning filter plate, magnetic frame and other measures, can effectively solve such problems;

4. In addition, by analyzing the location and characteristics of black spots, we can quickly find out the cause of the problem and improve the processing speed of quality problems.

The injection pressure was too high except the black spot and the black line. Wall thickness controller wall thickness tracking is not accurate; Problems such as blank die will cause the billet to encounter resistance during extrusion, resulting in horizontal streaks on the surface of the billet. Products.


Possible methods:

1. Reduce injection pressure appropriately;

2. Check the wall thickness controller or reset the wall thickness of the billet to reduce the fluctuation of wall thickness;

3. Solutions such as cleaning and polishing molds.

At the same time, there are foreign bodies in the mold; There is a rough edge or gap on the edge of the mold sleeve or core; A foreign body in the feeder or head may cause longitudinal streaks on the surface of the product. We need to clean the mold; When dressing the core mold cover, use or clean the core mold cover, usually pay attention to protection, so as to avoid personal injury; Clean the storage machine, head or increase the injection pressure, remove the foreign body with molten material and resolve. E it.

At the same time, product wall thickness is also one of the factors affecting product quality.


When the product wall thickness is uneven or too thin, the following reasons should be analyzed in time:

1. Improper adjustment of the clearance of the machine head mold, and the blank skew during extrusion;

2. The mold is not consistent with the center of the machine head;

3. The mold billet sags during extrusion;

4. Large length and large fluctuation of extrusion type billet;

5. The billet blowing ratio is too large;

6. Unreasonable mold design;

7. Mould temperature distribution is not uniform.

So we should:

1. Adjust mold clearance according to wall thickness distribution;

2. Adjust the position of the machine head or the installation position of the mold;

3. Appropriately increase the extrusion speed or die closing speed, select low melt flow of raw materials;

4. Check whether the hopper is blocked or bridged. If different grades of mixture are used, mix evenly as far as possible;

5. Appropriately reduce the inflation rate;

6. Re-improve the mold;

7. Adjust mould cooling temperature of different parts appropriately according to product characteristics to solve problems.


In addition, the ductility of the raw material in the molten state is also a problem that must be considered. Mass production should be avoided until the problem is fully resolved in order to avoid the expansion of quality problems.

Another problem is that the sealing performance of the product is one of the important quality control points. The compatibility of the sealing material with the contents and the fit between the sealer and the bottle mouth are important considerations.

Sealing is only a matter of degree.

At present, sealing methods mainly include inner cover sealing, sealing sealing and gasket sealing.

All three have advantages and disadvantages:

Inner cover sealing effect is slightly poor, but stable and durable; The gasket seal is good, but the repetition rate is slightly poor. The sealing performance of the sealing ring is good, but the design should pay attention to interference and friction.

In the selection of sealing methods, we must comprehensively consider materials, sealing capacity, sealing aging and other problems.

Common seal failure causes are as follows:

1. The plane or inner wall of the product seal is poor;

2. The sealing surface of the product has deviation before and after;

3. Chemical reaction between sealing material and contents;

4. Sealer and mouth do not match.

cooler box blow molding machine

We can:

1. Adjust the plane or inner wall of the seal to make it smooth;

2. Adjust the height deviation to make the height of the contact surface consistent;

3. Select appropriate sealing materials to avoid corrosion of contents;

4. Adjust the sealing machine and the mouth to solve the problem.

The study of sealing state is helpful to improve the prevention of sealing failure. In the process of research, we need to pay attention to practice is the way to test the theory. Too much faith in theory will make it difficult to produce qualified products, too much reliance on experience is not easy to find potential problems.

In the process of transportation, products will encounter stacking and transportation problems.

In the process of transportation, if the product accidentally falls from a height, it is easy to break.

Common causes of rupture are:

1. Wall thickness adjustment is not appropriate;

2. Molding temperature setting is not appropriate;

3. Unreasonable selection of raw material brand;

4. Unreasonable mold design and other reasons.

pallet blow molding machine-HUAN

We should:

1. Strengthen the wall thickness control of the force by readjustering the product wall thickness. It should be noted that the wall thickness is not as thick as possible, and sometimes the wall thickness of some parts will be reduced to improve the drop performance;

2. Reset molding temperature, too high will lead to too low decomposition of raw materials will lead to poor plasticization;

3. Re-select the appropriate raw material grade. Each grade also has different emphasis on raw materials. There is no good raw material, only the right raw material;

4. The method of improving the product structure can solve the problem of poor drop performance.

At the same time, if the wall thickness is not adjusted properly, the selection of raw material grade is not reasonable, and the mold design is not reasonable, it will lead to the poor stacking performance of products and affect the transportation of products.

By adjusting the wall thickness of the product, the wall thickness control of the force is strengthened, The suitable material grade is choosen again, The mould is improved, and the stiff eners are added according to the need, and the stacking performance of the product is further improved.

While improving the stacking performance, the hollow container is studied as a shell structure, which simplifies the research process. Generally speaking, when determining the product structure, the drop performance and the accumulation performance are complementary, and are opposed to each other. We need to find the right balance to meet the requirements of good stack performance and good drop performance.

Finally, with the different use conditions of products, the environmental stress crack resistance of products has been paid more and more attention. Improper selection of raw material brand; Mould design temperature is not appropriate, resulting in stress concentration and other reasons, will lead to the product environmental stress cracking performance is poor.



1. Select the appropriate grade of raw materials;

2. Improve the mold, especially in the sharp corner;

3. Setting appropriate molding temperature, adjusting wall thickness, avoiding stress concentration and other problems can be solved. Due to the particularity of environmental stress cracking, it is difficult to find environmental stress cracking in time in the production process, which may cause losses in the test. Therefore, this problem must be considered at the beginning of production.

When selecting materials, try to use materials with wide molecular weight distribution and high degree of branching. When designing the mold, try to avoid the sharp Angle and other structures with convenient force. Set appropriate temperature and cooling rate during process setting.

The F50 time of raw materials provided by most raw material manufacturers can effectively reflect the environmental stress cracking resistance of raw materials. However, in the actual production, the data can be used as a reference and should not be over-relied on.

Various situations may occur during the production of blow molding products. This time only select a few products that are prone to problems to discuss, and put forward a few solutions for your reference. All aspects and details of the production of blow molded products, such as raw materials, equipment, plasticization and molding, deserve further investigation.

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