Comparison between blow molding process and roll molding process

Blow molding and rotational molding are two common blow molding processes. What is the difference between blow molding and rotomolding? Which molding process is better?

First of all, let's understand the concept of blow molding process and rotational molding process. Learn about the difference between blow molding and rotational molding.

What is the blow molding process?

Also known as blow molding, the raw material is extruded or injected to form a plastic parison. Put it into the split mold while it is still hot, and after the mold is closed, compressed air is introduced into the parison, so that the plastic parison is inflated and adhered to the inner wall of the mold. After cooling, it is demolded to form various hollow blow molding products.

What is rotomolding process?

Also known as rotational molding, rotational molding, and rotary molding, it is a method of plastic hollow molding. The raw material is added to the mold, the mold is continuously rotated and heated along the two vertical axes, and the raw material in the mold is gradually and uniformly coated and melted and adhered to the entire surface of the mold cavity under the action of gravity and thermal energy, and is initially formed as required. The shape of the product is cooled and shaped into a corresponding rotomolded product.

Next, the difference between blow molding and rotational molding will be compared from different aspects.

Machine construction for blow and rotomolding

The hollow blow molding machine occupies a small area, has a simple structure, and is easy to operate. It only needs 3-4 people.

The rotomolding machine occupies a large area and has a simple structure, but the operation is more complicated and often requires a lot of labor.

Production efficiency in blow and rotomolding

Blow-molded products are generally made of high-molecular-weight high-density polyethylene resin, which is extruded and blown once. The molding process is fast and sufficient; the product is fully formed, and the internal quality and performance are stable.

Generally, the hollow blow molding machine can produce 18-20 plastic buckets per hour on average. For example, a 2000L bucket with a weight of 40Kg can produce 8-9 pieces per hour. 1-2 workers can be skilled in operation, and the automatic hollow blow molding machine is easy to operate, labor-saving and fast.

The processing speed of rotomolding is slow. For the same 2000L bucket, the output of rotomolding is only 1-2 pieces per hour.

In addition, rotomolding has high requirements on raw materials and less plastic material is available. In addition, large-scale rotomolding, 3-4 workers, is labor-intensive, long processing cycle, and high cost. Therefore, it is not suitable for large-scale assembly line production.

Production of multi-layer products for blow and rotomolding

The multi-layer blow-molded product uses a strong UV-stabilized outer layer, a black middle layer, and a virgin polymer inner layer that is in direct contact with drinking water. Multiple layers in the blow molding process can be formed at the same time, so the bonding between each layer is very tight

1. Introduction to the advantages and performance of hollow blow molding products

1. The product is light in texture, easy to handle, long-term use, durable, wear-resistant and anti-fall. Generally, it can have a multi-layer structure, and each layer is formed by melting the plastic melt at one time, and the defects caused by it are staggered, which greatly improves the impact resistance of the plastic barrel.

The multi-layer structure of the hollow blow-molded plastic barrel has multiple concepts: the outer layer is dark (blue), which can resist ultraviolet rays and light aging, and the inner layer is the natural color of the resin, which ensures the purity of the contents and makes it easier to use. The middle inner layer adopts recycled material, which conforms to the rules of recycling co-extrusion (RECO), which is beneficial to environmental protection, and the outer layer adopts new raw materials while ensuring the overall quality.

2. The hollow blow molding plastic barrel is made of high molecular weight high density low pressure polyethylene raw material, which has the characteristics of high rigidity, creep resistance, wear resistance and environmental stress crack resistance. Can be widely used in petroleum, chemical, pharmaceutical, food and other industries packaging.

In conclusion, the hollow blow molding machine adopts multi-layer die technology. Realize the production of multi-layer products. Improve material recycling rate, reduce material cost, and increase production efficiency accordingly.

In the rotomolding process, each layer needs to be added separately in each molding process, which will reduce the adhesion between each layer, cannot guarantee the quality of the product, and also cause a waste of manpower and time.

Which one is better quality and stronger about blow molded products and rotomolded products?

The answer, of course, is blow molding products.

The products produced by the blow molding process have good color, light weight, thick and uniform wall thickness, and good quality. In rotomolding, because the plastic is melted by fire and then cooled and formed, the factors affecting the quality of the product are difficult to control, and there are often quality problems such as uneven wall thickness of the product, large dimensional errors, and impurities on the surface of the product. In simple terms, blow molded products are more rigid than rotomolded products, and are more resistant to creep, wear and environmental stress cracking, and are more resistant to collisions and lower transportation costs.

In addition, in terms of energy consumption, blow molding is more energy-efficient than rotomolding.

At present, in the design and production of hollow blow molding machines, induction heaters are used for the die and extruder, which can save 40% to 50% of energy. The use of servo motors for the clamping device of the machine can save 40% of energy. The reduction in energy consumption also saves certain production costs.

Compared with rotomolding and blow molding, there is a lot more manual work. For example, in the production process of rotational molding, specialized workers are needed to open and close the mold. Opening and closing the mold is a heavy manual labor. This requires a lot of labor and labor costs.

The fuel used in rotomolding keeps the temperature at a high level that is dangerous for workers or the process of adding raw materials. Fuel combustion also produces gases that pollute the environment.

After the production of one product, in order to produce the next product as soon as possible, when the mold is still hot, it is necessary to pour cold water on it to cool it down, and the cost of fuel is very high, which results in a waste of resources.

This is a summary of the above. According to what we have said above, it should be seen that the cost of the blow molding process is lower, the blow molding requires less labor, high production efficiency, low material requirements, low material cost, Less energy consumption, etc.

The above is the process comparison between blow molding and rotational molding. In the long run, the blow molding process brings us a wider range of benefits. The blow molding process has so many advantages, and the advantages of the hollow blow molding machine using the blow molding process are beyond doubt.