Causes and Solutions for the Unsmooth Surface of Blow-Molded Products


Today, let’s talk about the causes and solutions for the unsmooth surface of blow-molded products.
Do customers often ask why the products blown by the blow molding machine are not smooth, like sharkskin? So why does this strange shark skin phenomenon occur? The following editor will analyze the causes and solutions of this phenomenon from several aspects.

To find out the reasons and solutions for the unsmooth surface of blow-molded products, we must first understand the blow molding process:

hopper feeding material plasticization extrusion → blowing traction → air ring cooling → splint → traction roller traction → cooling treatment →The finished product is shaped.

However, we must note that the performance of blow-molded products has a great relationship with the production process parameters. In the process of blow molding operation, it is necessary to strengthen the control of technical parameters and standardize the operation process to ensure the smooth progress of production. , Produce high-quality blow molding products.

In the actual blow molding process, the following technical parameters need to be controlled:

First, adjust the temperature of the extruder. In actual operation, the extrusion temperature must be well controlled, and the temperature of the die must be uniform. If the extrusion temperature is too high, the resin is easy to decompose and become brittle, especially the longitudinal tensile strength is significantly reduced; if the temperature is too low, the resin Poor plasticization and inability to expand and stretch smoothly. The tensile strength of the product is low, and the surface gloss and transparency are poor, and even patterns like wood growth rings and unmelted crystal nuclei appear.

The second is to master the inflation ratio. The inflation ratio is one of the key technologies of the blow molding production process, which refers to the ratio between the diameter of the product after inflation and the diameter of the uninflated embryo. The inflation ratio is the transverse expansion multiple of the product. In fact, the product is stretched in the transverse direction. Stretching will have a certain degree of orientation effect on the raw material molecules, and the inflation ratio will increase, thereby increasing the transverse strength of the product. However, the blow-up ratio should not be too large. Too large can easily cause the product to be unstable, and the product surface is prone to wrinkles and unevenness. Therefore, the inflation ratio should be properly matched with the traction ratio.

The third is to master the traction ratio. The pulling ratio refers to the ratio between the pulling speed of the product and the extrusion speed of the embryo. The traction ratio is the longitudinal stretching multiple so that the product has a directional effect in the drawing direction. If the traction ratio increases, the longitudinal strength will also increase, and the thickness of the product will become thinner. However, if the traction ratio is too large, the thickness of the product will be difficult to control, and the product may even be broken, causing the fracture.

The above are the reasons and solutions for the unsmooth surface of blow-molded products.

Yankang Plastic Machinery specializes in the production of various blow molding machines, and the products produced have a smooth surface, no wrinkles, no bubbles, perforations, and cracks; no obvious black spots, crystal spots, and no unevenness on the surface of the product. The editor welcomes everyone to visit Yankang on the spot, and there will be unexpected gains.

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