Blow molding product deformation analysis and solution

With the rapid development of the production and processing industry of hollow blow molding products, people have higher and higher requirements on the appearance and performance of blow molding products. Deformation is one of the common problems of hollow blow molding products. In view of this problem, Iyasu Xiaobian will share with you today the deformation analysis and solutions of plastic blow molding products.

First of all, what is blow molding product deformation?

Blow molding product deformation refers to its external shape deviated from the shape of the mold cavity, or convex or concave, or longitudinal or transverse, or local shape offset. It is one of the common defects of blow molding products, and it is also a comprehensive and difficult problem to deal with.

The degree of deformation and the excellent degree of performance are important indexes to evaluate the quality of blow molding products. The greater the degree of deformation of blow molding products, the appearance satisfaction and performance of the proportional decline, serious will lead to scrap products. The deformation of blow molding products is not only adverse to the quality of products, but also adverse to the output and production cost of blow molding products. Therefore, it is very important to solve the problem of deformation defect of blow molding products.

Blow molding product deformation analysis and solution

Thermal and physical characteristics of blow molding materials

(1) the use of cyanogen pigments in blow molding plastic processing formula will affect the crystallinity of polyethylene and lead to product deformation;

(2) the primary color blow molding products produced without adding any pigment are not easy to deform, which can improve the quality and output of products;

(3) the use of low melting point, good fluidity of plastic, because of its own shrinkage rate is small, cooling fast, not easy to deformation, can improve product quality and output.

Effect of wall thickness gap and cooling on blow molded products

(1) The structural design of blow molding products directly affects the wall thickness gap and cooling of products. The wall thickness gap is large, resulting in the cooling rate gap and deformation.

The wall thickness is small where the transition part of the product structure changes suddenly, whereas the wall thickness is large. Therefore, the structural transition part of blow molding products needs smooth transition, eliminate sharp corners and sharp edges. If the product structure is special, the wall thickness difference is large, should strengthen the cooling at the thick wall, and according to the cooling requirements to set the cooling circuit of the die;

(2) The larger the gap between the longitudinal wall thickness position and the radial wall thickness position of blow molding products, the easier it is to deform.The shrinkage of blow molded container products is more severe at the position of the die line than at the adjacent position,this is where the thicker area cools much more slowly than the surrounding area. Different cooling rate leads to different shrinkage and deformation.This defect is suggested to be solved by using servo longitudinal wall thickness control and servo radial wall thickness control simultaneously. To solve this problem, MEPER MACHINERYhas chosen to use MOOG wall thickness controller.

In addition, the radial wall thickness control can be replaced by trimming the head core die, but the effect is less satisfactory. For medium and small blow molding containers of flat and square shapes, the wall thickness difference of blow molding products can be reduced by slightly larger size configuration of mouth mold and core mold, so as to achieve shrinkage balance and solve deformation defects.

Molding process

(1) the barrel temperature, head temperature and mold temperature of blow molding machine extruder should not be too high. High temperature will lead to slow cooling and easy deformation of blow molding products;

(2) Forming cooling time is not enough, resulting in blow molding products after the mold is not uniform cooling and deformation;

(3) According to the product shape needs, fine adjustment servo wall thickness curve, make the product wall thickness as uniform as possible;

(4) Use a chiller to supply water to the mold for circulation cooling to improve the cooling effect;

(5) Improper adjustment of die opening stroke parameters will lead to the deformation of the product during die opening.

There are many factors affecting the deformation of blow molding products, only from the adjustment of blow molding production process parameters to solve is far from enough. We need to take different methods according to different deformation conditions. It must be comprehensively considered and reasonably solved. About blow molding products deformation analysis and solutions to share here, I hope you can use the actual blow molding production process, to produce high quality plastic blow molding products.