Today, let’s talk about the reasons and solutions for the soft bottom of the hollow blow molding machine.
The wall thickness of plastic blow molded products is one of the important factors affecting product quality. If we want to produce high-quality plastic blow-molded products, the wall thickness control of plastic blow-molded products cannot be ignored.
Let me share with you the reasons and solutions for the soft bottom of the hollow blow molding machine.

1. Adjust the gap of the die.
A groove is opened at the position of the die or mandrel of the extruder head of the blow molding machine to expand the gap of the die at the corner, thereby changing the thickness of the parison and obtaining a profiled parison to compensate for the inconsistent inflation ratio. The wall thickness of the blow molded product is uneven, and a blow-molded product with asymmetrical wall thickness is obtained.

2. Axial wall thickness control technology.
The function of the wall thickness control method of blow-molded products is to promote the extruded plastic parison to form different thicknesses along the axial direction according to the different blow-up ratios of different blow-molded products, thereby ensuring that the blow-molded products after molding have a uniform and stable thickness. This wall thickness control method is to change the opening of the engine according to the axial movement of the core rod or the die according to the preset position, so as to achieve the purpose of changing the wall thickness of the parison.

3. Radial wall thickness control technology.
Although the axial wall thickness control method can change the wall thickness distribution in the height direction of the plastic blow molded product, because the horizontal section of the extruded parison is still thick and round, if it is required to have a higher radial blow ratio The wall thickness control effect achieved by plastic blow molding products is not particularly ideal. Therefore, the radial wall thickness control technology has been produced. This technology can make the extruded parison show a non-circular cross-sectional change at the required position. The radial wall thickness program control technology has been developed so far, and two typical designs have been roughly formed, one is called the flexible ring type, and the other is called the lip repair form. Radial wall thickness control technology is an effective method to improve the quality of large plastic hollow blow molded products, and it can also reduce the quality of products. Take the 200L plastic blow-molded water tank as an example, at least 5-10% of raw materials can be saved.

4. The combination of axial wall thickness control and radial wall thickness control can obtain ideal plastic parisons, thereby obtaining plastic blow molded products with more uniform and stable wall thickness. If proper wall thickness control methods cannot be adopted during the blow molding process, the parison will be deformed, resulting in uneven wall thickness of the blow molded product, which is also the cause of the soft bottom of the hollow blow molding machine.

5. The deformation resistance of the parison can be expressed by viscosity, which is related to its temperature.
Therefore, during the extrusion process, cooling equipment must be used to forcibly cool the part where the parison has a relatively large blow-up so that the parison has a reasonable temperature gradient. The temperature of the part where the parison is relatively large in inflation is low, the viscosity increases, and the deformation resistance increases. In the free inflation stage, the parts with relatively large inflation are difficult to deform, and the number of deformation decreases, while the deformation of parts with relatively small inflation increases. When the part with a smaller amount of deformation is deformed and enters the stage of constrained inflation, the part with larger inflation will continue to deform until the part is inflated, so as to improve the uniformity of the wall thickness distribution of the plastic blow molded product.

In terms of wall thickness control, the Yankang plastic machine adopts a German wall thickness controller and corresponding wall thickness control technology, which solves the wall thickness problem of blow molded products more conveniently and simply. When the wall thickness of the product is too thin or the bottom of the product is soft, attention should be paid to the analysis and adjustment of the die gap of the die. The parison should not be skewed during extrusion; the mold and die should be consistent; prevent the parison from sagging during extrusion; the parison blowing ratio Can not be too large; adjust the position of the machine head or adjust the mold installation position so that the mold maintains a uniform temperature distribution.

The above content is the reason for the soft bottom of the hollow blow molding machine and the solution.