How to design large-scale blow molding products

1. Introduction to Design

Large blow molded processed products are widely used in various industries, especially in the beverage and pharmaceutical packaging industry, and are also widely used in the toy industry, such as blowing baby bottles, hollow floating parts, Christmas lampshades, toy yachts, children's learning car accessories, and some large toys such as slide tracks, bases, etc.

With different product requirements, the focus of product design also varies. For blow molded toy products, more emphasis is placed on safety and physical testing (considerations of tension, torsion, throwing, and stress cracking), while for container products, more emphasis is placed on pressure resistance, corrosion resistance, and good impermeability requirements.  

1) Make an R transition at the edges and corners

Generally, the corners and edges of large blow molded products need to be made into R-transitions because the inflation ratio at sharp corners is relatively high, which can easily cause uneven wall thickness. In addition, sharp corners are also prone to pressure cracking. The R-transition of the product can make the wall thickness uniform.

2) Enhance structural design in terms of compression, tension, and torsion resistance

With different product requirements, some structural designs in terms of compression, tension, and torsion can also be added:

A. To increase the longitudinal compressive strength of the product, some reinforcing ribs can be designed along the direction of force;

B. To improve the anti collapse performance of the product, the surface can also be designed as an arc-shaped structure that is conducive to stress and supplemented with reinforcing ribs. The shoulders of bottle products should be inclined and not too straight;

Generally, the bottom of the bottle is made into a concave shape to increase strength and stability during placement. For example, the bottles we usually see containing edible oil often have some concave and convex shapes on the surface, which not only increase the strength of the bottle body, but also facilitate the labeling of trademarks.

Introduction to materials for large-scale blow molding processing

The development and application of large-scale blow molding technology are complementary to the development of blow molding materials. Blow molding materials have gradually evolved from LDPE, PET, PP, and PVC products to blow molding engineering plastics, rubber, and some composite materials.

A. Polyolefins

HDPE, LLDPE, LDPE, PP, EVA are generally used for blow molding industrial products, containers and toy accessories, storage containers for chemical drugs, etc.

B. Thermoplastic polyester

PETG and PETP are mainly used for blowing carbonated beverage packaging bottles, wine bottles, etc. They have gradually replaced PVC and are widely used. The disadvantage is that their cost is relatively high, mainly used for injection pull blow molding.

C. Engineering plastics (alloys)

ABS, SAN, PS, PA, POM, PMMA, PPO, etc. have gradually been applied in industries such as automotive, pharmaceutical, home appliances, and chemical, especially PC and its blended plastics, which can blow produce high-quality containers and automotive products (PC/ABS, etc.).

D. Thermoplastic elastomer

Usually, SBS, SEBS, TPU, TPE and other blow molded materials are used as rubber materials, while thermosetting plastics, vulcanized rubber and cross-linked PE cannot be processed by large-scale blow molding.