Color Picker

Here is some awesome colors.

  • info2@altolative.com
  • no.56-1,caijia,tongguang village,fengshan street,yuyao,zhejiang
  • Mon - Fri: 8:00 am - 7:00 pm

Ningbo Alever Technology Co.,ltd

Industry news

Design of extrusion blow molding mold for shampoo bottle

Design of extrusion blow molding mold for shampoo bottle

Design of extrusion blow molding mold for shampoo bottle


Hollow blow molding is a rapidly developing plastic processing method, which is divided into extrusion blow molding and injection blow molding. At present, it has developed into the third largest plastic product molding method after injection molding and extrusion molding. Shampoo bottle is a hollow part that can be seen everywhere in daily life. The structure is generally that the bottle mouth is much smaller than the bottle body. It cannot be molded in one time by injection molding method, and needs to be produced by hollow blow molding. Extrusion blow molding mold has the characteristics of simple structure, low cost, simple process and high efficiency.


1 Analysis of shampoo bottle structure


Because high-density polyethylene (PE-HD) container has good feel, light weight, non-toxic and odorless, it is suitable for shampoo packaging. The bottle body is made of PE-HD material with a density of 0.95 g/cm . The volume of the shampoo bottle is 450 mL and the wall thickness is about 1.0 mm. The customer requires that the molded product has no flash, the parting line should be combined and flat, without dislocation, and no obvious parting line traces.


2 Extrusion blow molding mold structure design

In the production of plastic hollow products, the quality and output of blow molded products are mainly affected by the blow molding mold structure and mold processing quality in addition to the accuracy and automation of the blow molding equipment. In terms of mold structure, the structure of the blank cutting mouth, the appropriateness of the exhaust system and the cooling system have a great impact on the quality and output of the product.


2.1 Overall structure of extrusion blow molding mold

The extrusion blow molding mold is mainly composed of two concave mold cavities (female molds). During blow molding, the mold should meet the following requirements:


(1) It can form hollow products with complex shapes;


(2) It can effectively pinch off the parison and ensure the strength of the product joint line;


(3) It can effectively and quickly exhaust;


(4) It can quickly and evenly cool the plastic product and reduce the temperature gradient in the mold wall to reduce the molding time and product warping.


Since shampoo bottles are relatively small and the production batch is large, the extrusion blow molding mold adopts a one-mold two-cavity structure from the perspective of reducing the manufacturing and processing mold cost and ensuring the mold accuracy. The overall design is completed with the help of Pro/E 4.0 software. In Pro/E 4.0, the design process of the whole set of molds is as follows: first, the original 3D model of the shampoo bottle is established according to the original size. Secondly, in the "Manufacturing" module, a new file is created with the subtype "Mold Cavity". The previously built 3D model is imported and the layout of one mold and two cavities is made. According to the "By Size" rule, the shrinkage rate of the reference model is set to 2%. The original model is appropriately enlarged to offset the shrinkage in size when the product is blown up and cooled. Then, the blank workpiece is created, the parting surface is designed, and the volume block is divided and the mold components are extracted using the parting surface. Then, the blank cutting mouth, residual material groove, exhaust system and cooling system are designed on the mold components. Finally, the processing design of auxiliary parts such as guide pillars and guide sleeves is carried out.


2.2 Selection of parting surface

Parting surface design is the first issue to be considered when designing a blow mold. The position of the parting surface should make the mold symmetrical, reduce the blow-up ratio, and facilitate product demolding. Therefore, the position of the parting surface is determined by the shape of the blow molded product. The shape of the shampoo bottle is similar to an ellipse. For an ellipse container, the parting surface should pass through the long axis of the ellipse. The blow mold is bounded by the parting surface and designed into two symmetrical half molds that match each other.


2.3 Design of the blank cutting opening and residual material groove

During the blow molding process, the excess material should be cut off when the mold is closed. Therefore, the bottle mouth and bottle bottom of the extrusion blow molding mold are equipped with blank cutting openings, which not only play the role of cutting off the residual material, but also play the role of clamping the closed parison in the mold before blowing. When designing the bottle mouth and bottle bottom inserts, the structure of the blank cutting opening and residual material groove should be mainly considered, which have an important influence on the molding and performance of the blow molded products.


The neck and bottom of the shampoo bottle are both designed with inserts. The blank cutting opening is located on the insert and made into a whole, which helps to cut off the neck excess material and reduce assembly errors. The die mouth part of the extrusion blow molding mold should be a sharp cut to cut off the parison. The width of the blank cutting mouth for cutting off the blank is about 0.5~2.5 mm. If it is too small, the thickness of the joint seam of the blow-molded product will be reduced, the joint strength will be reduced, and the blank may even be easily cut, resulting in the product being difficult or unable to be blown; if it is too large, the excess tail material cannot be cut off, and the mold cannot even be completely closed, resulting in obvious mold flash or bulging outward at the mold closing. The blank cutting mouth width is 1mm.


A residual material groove is opened behind the edge of the blank clamping mouth, which is located on the mold parting surface. The depth of the residual material groove has a great influence on the molding of blow-molded products, especially for blanks with large diameters and small wall thicknesses. Therefore, the groove depth of the residual material groove should be appropriately selected, and the depth of the residual material groove of each half of the mold is 90% of the wall thickness of the blank, that is, 0.9 mm.


2.4 Design of the exhaust system

Compared with injection molding, when molding hollow products with the same volume, the amount of air discharged from the blow molding mold is much more than that from the injection molding mold, and the pressure in the blow molding mold is very small, and the air is not easy to be discharged out of the mold. Therefore, the exhaust function of the blow molding mold is required to be high. Poor exhaust will lead to defects such as roughness, dents, unclear text or patterns on the surface of the product. In addition, it will prolong the cooling time of the product, resulting in uneven distribution of the wall thickness of the product and reducing the mechanical properties of the product. For PE-HD blow molded products, in order to make the product have a smooth surface, it is generally necessary to sandblast the surface of the mold cavity to make the surface of the mold cavity slightly rough, because this can provide a small mesh exhaust channel on the surface in the mold cavity, making the mold cavity easy to exhaust. The manufacturing material of this shampoo bottle is PE-HD, so the exhaust method adopted is: sandblasting the surface of the mold cavity and opening an exhaust groove on the parting surface. The exhaust groove is milled in the form of shallow first and then deep, narrow first and then wide. Since the appearance requirements of the shampoo bottle are high, the depth of the exhaust groove should be selected appropriately and should not leave marks on the product. For products with high appearance requirements, the width of the exhaust groove can be 5 to 25 mm. Therefore, the shallow groove designed near the inner cavity wall is only 0.02 mm deep, 13 mm wide and 1.5 mm long to avoid leaving obvious marks on the product; then the deep groove is expanded to 1.5 mm deep and 16 mm wide, extending to the outside of the mold for smooth exhaust.


2.5 Design of cooling system

Since the size of the shampoo bottle mold is relatively small, the cooling method used is similar to that of the injection mold. The cooling water channel is drilled directly in the mold wall in the longitudinal and transverse directions. Its characteristics are that the cooling water directly contacts the mold body for heat dissipation, the structure is simple, and the cooling effect is good. The cooling water enters from the bottom of the mold, and the outlet is set at the top of the mold. On the one hand, it can avoid the generation of air bubbles. On the other hand, because the cooling water at the outlet is higher than the inlet after heat conduction, the cooling water can flow in the direction of natural temperature rise, which is conducive to the uniformity of the mold temperature difference. Usually the diameter of the cooling water channel is generally 10~15 mm, and the aperture of the cooling water channel is 12 mm.


3 Conclusion

The extrusion blow molding mold for shampoo bottles with a general capacity of 450 mL adopts one mold with two cavities, the width of the blank cutting opening is designed to be 1mm, the exhaust groove is opened on the parting surface, and the cooling water channel is directly drilled in the longitudinal and transverse directions of the mold wall for cooling. After production verification, the blank cutting, exhaust system and cooling system of the mold have good effects, the quality of the molded products is good, the surface contour of the products is clear and smooth, and it has good economic benefits.