For the "Preform Engine": How to Scientifically Select the Right PET Preform Injection Molding Machine

Introduction: Preform Quality Determines Bottle Life

In the PET packaging industry chain, the preform is hailed as the "embryo" of the bottle—its quality directly determines the final blow molding's transparency, pressure resistance, and appearance. The preform injection molding machine is the core equipment for shaping this "embryo."

Faced with a dazzling array of brands and models on the market, many investors often fall into misconceptions: blindly pursuing high cavity counts, excessively focusing on price, and neglecting process compatibility. This article will systematically analyze how to scientifically select the right preform injection molding machine from three dimensions: technical parameters, process adaptability, and long-term operation, and will recommend a market-proven preferred model at the end.

I. Essential Lessons Before Selection: Clarifying Production Needs

Before contacting any equipment supplier, you first need a clear understanding of the project you are about to undertake. This is like describing your symptoms before seeing a doctor so that the doctor can prescribe the right treatment.

1.1 Preform Specifications

You need to clarify the following core data -4:

• Preform weight: From 5g small water bottle preforms to 60g carbonated bottle preforms, and then to wide-mouth bottle preforms weighing hundreds of grams, different weights correspond to different injection volume requirements.

• Neck size: Common bottle neck specifications such as 28mm, 38mm, and PCO1881 directly affect mold design.

• Daily production capacity target: This is the core basis for determining the number of mold cavities and machines.

1.2 Material Characteristics Understanding

PET material has unique processing characteristics: a high melting point (approximately 250-260℃), and the melt is prone to degradation and the production of acetaldehyde (AA) if it remains at high temperatures for too long. Therefore, a specialized PET screw design is required -10. Ordinary injection molding machines with excessively high screw compression ratios are prone to generating excessive shear heat, leading to PET thermal decomposition, yellowing of the preform, and decreased transparency -7-10.

II. In-depth Analysis of Five Core Technical Indicators

Choosing a PET preform injection molding machine is essentially solving a "matching problem"—a high degree of matching between equipment parameters and product requirements.

2.1 Screw System: PET-Specific Design is the Bottom Line

The screw is the "heart" of the injection molding machine. PET material requires the screw to have the following characteristics:

• L/D ratio ≥ 24:1: The longer screw length ensures sufficient melting and plasticization of PET crystalline particles -7. Ordinary plastic screws typically have an L/D ratio of around 18-22, while PET-specific screws must reach 24:1 or higher -7.

• Low shear design: Avoids excessive shearing leading to molecular chain breakage and increased acetaldehyde levels -10

• Special mixing section: Ensures uniform dispersion of color masterbatch, preventing flow marks or white fogging in preforms -8 Professional brands like Dekuma use PET-specific screws, which, through optimized compression ratio design and imported steel heat treatment processes, effectively control the AA value, ensuring high transparency and physical properties of the preforms -6-10.

2.2 Clamping Force: Scientific Calculation Avoids Waste

Clamping force is not necessarily better the higher it is—too high increases equipment costs and energy consumption, while too low leads to flash and scrap. The scientific calculation formula is as follows: Clamping force requirement = Finished product projected area (cm²) × Number of cavities × In-mold pressure (kg/cm²)

Where, the in-mold pressure of PET preforms is typically between 300-500 kg/cm². For safety, the machine's rated clamping force should be greater than 1.17 times the calculated value.

2.3 Injection Volume: Leave Sufficient Margin for Stability

The injection volume needs to be calculated based on the preform weight and the number of mold cavities, with a safety margin:

• The finished product weight should be within 75% of the theoretical injection volume.

• That is: Machine injection volume ≥ Preform weight × Number of cavities ÷ 0.75

For example, to produce a 20g preform with 48 cavities, the required injection volume is at least: 20 × 48 ÷ 0.75 = 1280g. This margin design ensures uniform plasticization and stable injection, avoiding material shortages due to batch differences in raw materials or temperature fluctuations. 2.4 Mold Dimensions and Mold Space

Smooth mold installation depends on three key dimensions-7:

• Tie rod inner distance: The width and height of the mold should be less than the tie rod inner distance, with at least one side being less than

• Mold thickness: The mold thickness must be within the machine's minimum-maximum mold thickness range

• Mold opening stroke: Should be at least twice the height dimension of the finished product to ensure smooth preform demolding. The Dekuma PETⅢ series specifically addresses the characteristics of PET molds by increasing the tie rod inner distance and maximum mold thickness, sufficient to accommodate large multi-cavity molds and effectively reduce product deformation-6.

2.5 Power System and Energy-Saving Configuration

PET processing requires high screw torque, thus necessitating a more powerful melt oil motor than ordinary machines-7-8. Simultaneously, servo energy-saving systems have become the mainstream choice—through electromelting technology and low inertia design, energy consumption during plasticizing and injection processes can be significantly reduced-6. The Dekuma third-generation PET machine has obtained Level 1 energy efficiency standard certification-6.

III. Mainstream Configuration Schemes Reference Depending on different production scales, mature configuration schemes are available for reference in the market: Small to Medium Scale Production (Startups or Trial Production Stage)

• Recommended Number of Cavities: 16-32

• Applicable Bottle Types: 5-30g water bottles, oil bottles

• Reference Cycle Time: 14-18 seconds (can be shortened to less than 12 seconds with a cooling robotic arm) - 5 Medium to Large Scale Production (Regional Brands or OEMs)

• Recommended Number of Cavities: 48-72

• Applicable Bottle Types: 20-60g water bottles, carbonated bottles, hot-fill bottles

• Reference Cycle Time: 12-15 seconds Large-Scale Production (Industry Leaders)

• Recommended Number of Cavities: 96-144

• Applicable Bottle Types: Large-scale standardized products

• Technical Threshold: Requires high-speed injection systems, in-mold labeling, and other automated integration

IV. Supplier Selection: More Than Just Equipment, Consider the Ecosystem

4.1 Professionalism Assessment

PET preform injection molding is not a simple extension of general injection molding. Professional suppliers should possess:

• An independent R&D team and product line for PET-specific machines

• Complete preform production line support capabilities (molds, robotic arms, auxiliary equipment, data platform)

• A rich library of industry case studies, providing successful examples similar to your project

4.2 After-sales service capabilities

For investors, equipment downtime means lost profits. When evaluating suppliers, pay attention to:

• Whether they have a service center or parts warehouse in the target market

• After-sales response time commitment

• Whether they provide operator training and process support

4.3 On-site Inspection Recommendations The ideal verification method is to visit the supplier's factory to observe the production process and quality control system.

1. Visit the customer's site and observe the actual operating status of the equipment (cycle stability, defect rate, energy consumption)

2. Request a trial mold and verify actual production on the target model using your molds and raw materials.

5.1 Application Case Reference Taking a common 28mm diameter, 20g water bottle preform as an example, paired with the EFFICIENT KEPT series and matching robotic arms, it can achieve:

• Stable production of 48 cavities per cycle

• Molding cycle can be controlled within 12 seconds

• Daily production capacity exceeds 340,000 preforms For those seeking high efficiency, stability, and low operating costs, this is a preferred model worth adding to your purchasing list.