From Manual to Automatic: Energy-Efficient PET Blow Molding for China

The extrusion blow molding machine (PET blow molding machine) for producing hollow PET containers is the primary equipment for hollow container formation. Globally, 80% to 90% of hollow containers are formed using extrusion blow molding. In the development of hollow PET molding machines in China, extrusion blow molding machines have progressed the fastest and are the most well-developed, especially the rapid development of small-scale extrusion blow molding machines. Currently, several manufacturers in China can produce extrusion blow molding machines capable of shaping 1000L single-layer hollow containers.

1. Efficient and Energy-Saving Small Blow Molding Machines

There is still a significant portion of China using manual or semi-automatic bottle blowing machines for PET bottle production. With the current trend of labor shortages and increasing quality requirements for PET bottles, there is a shift towards fully automatic bottle blowing machines. Mainstream bottle blowing machine manufacturers in China use hydraulic mobile bottle blowing machine equipment, resulting in high prices and energy consumption. This not only increases user costs but also contradicts the national advocacy for energy conservation and emission reduction. Therefore, there is a need to develop low-energy, moderately priced fully automatic blow molding machines to meet the market's transition demands. Some domestic enterprises, like Hebei Cangzhou Zhongyi PET Machinery Co., Ltd., have introduced energy-efficient, cost-effective fully automatic rotary blow molding machines suitable for small PET bottles up to 1500 milliliters.

2. Multi-layer Co-extrusion Hollow PET Molding Machines

Multi-layer co-extrusion hollow PET molding machines have great development prospects. The proportion of multi-layer blow-molded high barrier hollow products in the field of hollow products is increasing. These products are rapidly growing not only in the food packaging industry but also in chemical, cosmetic, pharmaceutical, and other industrial packaging sectors. The development of multi-layer co-extrusion hollow PET molding machines is a weak link in the field of extrusion blow molding machines in China. In recent years, internationally, there has been rapid development and technological progress in multi-layer co-extrusion hollow PET molding machines. Some varieties have been introduced domestically, such as the HZ-CS6-38 three-layer co-extrusion double-station in-mold labeling hollow molding machine developed by HZM Mechanical Rubber and PET Machinery Co., Ltd. This machine uses a four-mold head double-station, equipped with a precise integrated PID temperature control system, real-time detection of each screw's extrusion pressure, automatic edge trimming, and precise Siemens full-computer control. It addresses the need for thinner inner and outer layers (0.03-0.05mm) without compromising the product's barrier properties.

2.1 Research Focus

The research on multi-layer co-extrusion hollow PET molding machines mainly focuses on three points:

• Researching co-extrusion heads (molds) within a certain range to meet different material, layer, and head diameter requirements.
• Researching a combined packaging system that can customize the number of possible combinations of heads based on different raw materials.
• Researching basic mechanical programs that can use different numbers of mold positions and platform sizes, including production speed and product design.

2.2 Key Development Areas for Product Varieties:

• Development of 0.2L1L cosmetic and household cleaning agent 23 layer co-extrusion hollow PET molding machines.
• Development of 4~6 layer co-extrusion hollow PET molding machines for automotive fuel tanks.

3. Injection Blow Large Hollow PET Molding Machines

Injection blow large hollow PET molding machines have developed based on extrusion blow large hollow PET molding machines and are suitable for shaping single-layer large hollow PET products. Injection blow large hollow PET molding machines combine the injection molding machine's injection PETizing mechanism with the extrusion blow molding machine's blow molding and mold closing mechanism to create a comprehensive hollow PET molding machine. This integration utilizes the strengths of both mechanisms, achieving high repeatability in preform weight, high PETizing capacity, short color and material change times, and high strength in the melt fusion seam zone. Generally, extrusion blow large hollow PET molding machines use accumulator-type die heads, which have complex internal structures and many components. Therefore, the inherent characteristics of accumulator die heads, such as long color and material change times and inaccurate metering precision, are unavoidable. The injection blow large hollow PET molding machine replaces the accumulator die head of the extrusion blow molding machine with an injection PETizing mechanism, simplifying the head structure. With a reasonable flow channel design, this fundamentally solves the problem of long color and material change times for extrusion blow large hollow PET molding machines, while not affecting the installation of the servo system for controlling preform wall thickness.

4. "One-Step" Injection Stretch Blow Hollow PET Molding Machines

"One-step" injection stretch blow hollow PET molding machines, mainly used for shaping PET carbonated beverage bottles and mineral water bottles in small and medium-sized machines and PC pure water bottles in large machines, efficiently carry out the processes of injection molding, heating molding, stretching molding, blow molding, and demolding on the same equipment. Currently, the injection stretch blow hollow PET molding machines used in China are mostly equipment from Aoki Corporation and Nissei ASB Machine Co., Ltd. of Japan. This situation deserves consideration from every hollow equipment manufacturer. Injection stretch blow hollow PET molding machines have their own characteristics that cannot be replaced by other bottle blowing machines. Foreign manufacturers see potential in the Chinese market. According to their estimates, the beverage packaging industry in China still needs more than 800 units of "one-step" injection stretch blow hollow PET molding machines for PET bottle production.

4.1 Analysis of Existing Problems in Research and Development

After nearly a decade of development, why haven't China's injection stretch blow hollow PET molding machines reached commercial levels? The main reasons are as follows:

4.2 Misguided Development Focus

Excessive focus on mainframe development and neglect of mold development. Injection stretch blow hollow PET molding machines are devices that combine the mainframe with molds. Considering the importance of both the mainframe and molds to the entire machine, the mainframe accounts for only 40%, while molds account for 60%. The success of mainframe development does not equate to the success of the entire machine. Only when both the mainframe and molds are successfully developed together can the injection stretch blow hollow PET molding machine be considered successful. The technical key to Japanese Aoki's "three-position" and Nissei's "four-position" machine models is the mold, and some PET machinery manufacturers in China developing injection stretch blow hollow PET molding machines do not correctly recognize the relationship between the mainframe and molds. They prioritize the development of the mainframe and neglect the more important development of molds, leading to failure.

4.3 Insufficient Mold Technology Level

The molds for injection stretch blow hollow PET molding machines differ from injection molding molds and have their own characteristics. In the molds for injection stretch blow hollow PET molding machines, the key is the mold for injection molding preforms. The material of the mold has special requirements for its performance, with a small coefficient of thermal expansion and contraction, high heat transfer efficiency, high thermal conductivity, and a mold structure in the form of a hot runner. From the current perspective of China's mold technology level, it cannot develop and manufacture molds for injection stretch blow hollow PET molding machines that meet quality standards

TAG:  Blow Molding Machine  PET Blow Molding Machine

                       

Update：Feb, 21 /2024

                       

Author：HZM Machinery

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